BEC
Dec 19, 2002, 12:00 AM
<blockquote>Hello again, and again, it has been awhile. Oh well, let's get right to it!</blockquote>
<blockquote>I have one topic to cover first, and then it's on to trying to clear out some of the review backlog. I want to address some of the confusion about lengthening the wires on one end or the other of a controller, especially sensorless brushless units. Then this installment will review the MGM ComPro sensorless brushless controllers, and one item that is not a speed control at all, the Kool Flight Systems Ultimate BEC.</blockquote>
<p><big>The wires aren't long enough, and the instructions say don't lengthen them, so what do i do now?</p></big>
<blockquote>A recent topic of discussion on the EZone discussion boards of RC Groups has been what to do if the wires on an ESC just won't reach from where the motor is to where the battery is. In particular, this has been talked about when using sensorless brushless controllers. In general, the wiring on sensorless motors is pretty short, and the same is true for controllers. (Some motors, like the Model Motors minACs and the current batch of Mega 1615s have no wires at all). Furthermore, the instructions for several makes of these controllers caution against lengthening the wiring at all. </blockquote>
<blockquote>I have encountered this problem in a couple of my own planes, and at various times put have the question to speed control makers "if I need to lengthen the wiring on one end or the other, which is better?" What has been really interesting about this is that I've gotten different answers from different makers.</blockquote>
<blockquote><strong>First, here are the concerns about longer wires on either end.</strong></blockquote>
<blockquote>On the ESC-to-motor end of the controller, the concern seems to be primarily the addition of more resistance and inductance to the windings of the motor, which will make starting a sensorless motor more difficult. This is also an argument against having connectors between the motor and the controller. For either sensor-equipped brushless motors or conventional brushed motors, this does not seem to be an issue. Of course additional wire length and connectors do add to resistance losses and therefore result in less of the battery's power getting to the motor, but unless the connectors are really bad (such as the Tamiya type) or the wire is really long or undersized, this is a small concern.</blockquote>
<blockquote>On the battery-to-ESC side of the controller, the situation can be more severe. On this side of the controller, there is no diode or synchronous rectification to help smooth out the start-stop-start-stop of the electricity flow as the controller switches the motor on and off. Due to the small, but real, inductance of the wires that lead from the battery to the ESC, this current tends to try to keep flowing even during the "off" times. This induces a voltage spike in the wire. The more wire, the greater the inductance and resulting voltage spike. </blockquote>
<blockquote>Many ESCs, for both brushed and brushless motors, have a capacitor across the input side to help smooth out these spikes, but if the leads get too long, the voltage rating of that capacitor (or capacitors in some cases) can be exceeded. When that happens (and it can happen, I've seen it), the capacitor either smokes or even explodes! Afterward, the controller may still work, but now these voltage spikes are getting into the rest of the controller and sooner or later more smoke will leak out.</blockquote>
<blockquote>Therefore, while some makers have told me, "don't lengthen either end", and some have said, "it doesn't matter", most are of the opinion that if you must lengthen wires, it is better to do it between the motor and the controller, rather than between the battery and the controller. I think "Astro Bob" Boucher put it succinctly in an e-mail response to this question some time ago.</blockquote>
<blockquote>Bob wrote (in April of 2001), "The lead length to any brushless or brushed motor from the speed control is not important except for resistance losses. The inductance in the winding is higher than any leads. This is not true about the wire length between battery and control. These must be SHORT. The motor sees a PWM [pulse width modulated] voltage but a smooth current waveform. The battery sees an interrupted current waveform with one microsecond or smaller rise times [this would be true for anything other than a frame rate controller, and we don't use those any more, do we? - BEC]. This means big voltage spikes. The caps used on most controls are OK for 1 foot of wire. Add 3 feet and you have instant smoke. This is true of almost all speed controls on the market, brushless and brushed. At 30 Amps, a 3-foot loop will generate 20-volt spikes. Add this to the battery voltage and you are asking for trouble."</blockquote>
<blockquote>There are also considerations of having more wire to radiate interference, especially at higher power levels. This argues for keeping the wiring as short as possible all the way around.</blockquote>
<blockquote>However, it seems to me that the induced voltage spikes on the battery side are the biggest worry. That said, I routinely insert my Wattmeter between the battery and ESC when testing, adding about a foot of wire length. I've put more than 50 flights on my Big T with an MGM ComPro brushless controller with about a 9-inch extension on the battery side, and I haven't blown it up yet.</blockquote>
<blockquote>Regardless of what I might actually be flying, if you must lengthen wiring, and you have a choice, I recommend you do it on the motor end.</blockquote>
<p><big>Battery Eliminator Circuit on more than 10 cells - The Kool Flight Systems Ultimate Bec</p></big>
<blockquote>The convenience of being able to run everything in the airplane off of one battery that you know is freshly charged, even when the plane is big enough or powerful enough to carry a separate receiver battery, has driven many of us to use battery eliminator circuits (BECs) on higher and higher cell counts and with more than just two or three servos. The problem is that with the usual BEC designs that use linear regulators, the greater the voltage difference between the motor pack and the BEC output voltage (usually around 5V), the LESS current the regulator can supply without overheating. Look at the table provided by MGM ComPro in the TMM 35 extra review in the last column for a clear illustration of this.</blockquote>
<blockquote>Worse, when a BEC regulator overheats, it shuts down to protect itself, which immediately kills power to the radio system and usually this also kills the motor. What happens next is usually crash. I'm sure the story Steve Horney tells in his May 2002 Pitch, Roll and Yaw column of the PBY going dead in flight, then coming back to life again after hitting the ground is the result of a BEC regulator that overheated and shut down its output, then after cooling off a bit, coming back to life. In addition, I have witnessed at least one crash that was apparently due to an overheated regulator causing the motor and the radio to go dead.</blockquote>
<blockquote>While some speed control designers try very hard to arrange the thermal cutoff so that the motor is cut before the regulator overheats (Castle Creations, MGM ComPro, and Aveox come to mind), running the radio off of a drive battery of more than 10 to 12 cells has been impractical unless you're using a MaxCim brushless sensored controller, which has a unique approach to solving this problem. So up to now, for any power system other than one based on a MaxCim controller, running above 10 or at most 12 cells pretty much precludes running a BEC.</blockquote>
<blockquote>Some of you will say, "So what's the problem? Any plane that is running on 10 or more cells will never notice the weight of a receiver battery anyway!" and that is generally true. But I, for one, have witnessed (and participated in) far more model crashes due to a receiver battery that ran down before the pilot expected it to than those due to a BEC failure, even counting the BEC-related crash I saw that I mentioned a bit above. As I said at the beginning, there is the undeniable convenience factor of plugging in a freshly charged drive battery in the plane and then flying the plane without having to worry about checking the receiver battery or even having the receiver battery to maintain. So, if you want the convenience and reliability of BEC power in a larger electric model, what's the solution?</blockquote>
<blockquote>The answer is a BEC circuit that is not based on a linear regulator, but rather on a switching power supply. In this sort of a design, the voltage difference between the source battery and the output isn't just dissipated in heat, but the input power is converted to AC, the voltage is stepped down, and then turned back into DC for the output. Up until now, there have been two problems with the switching power supply approach, cost, and more importantly, radio interference generated by the switching power supply. In the past, I have tested a prototype add-on BEC based on a switching power supply that reduced my radio range to essentially zero. That unit never got into the air. There also have been several makers who looked at a switching BEC, and then dropped the idea because it would have been too expensive.</blockquote>
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<td width="100%" align="center"><a href="/articles/ezonemag/2002/dec/control/ubec_front1.jpg"><img src="http://static.rcgroups.com/articles/ezonemag/2002/dec/control/ubec_front1_t.jpg" border="2"></a></td>
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<td width="100%" align="center">This unassuming looking device is the solution - the Kool Flight Ultimate BEC</td>
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<blockquote>Jim Beck and Jeff Meyers of Kool Flight Systems have solved these problems. The resulting unit, called the Ultimate BEC, is a bit bigger than the unworkable unit that shall remain nameless, being about the size and weight of a 150-mAh NiCad receiver pack. Unlike that other unit, however, this one works without disturbing the radio system in the plane, and works well. Rated for an input voltage of up to 35V (with a bit of cooling) or 26 cells, and 3 continuous Amps of current (5A peak), it should bring the convenience and general reliability of BEC powered radio systems to all but the largest of electric powered models. At $30, it is not terribly expensive, either.</blockquote>
<blockquote>As received, the Kool Flight Systems Ultimate BEC is a flat package wrapped in heat shrink tubing about the size one would expect a 40A brushed speed control to be, and weighs 0.7 ounces. There are two generous (12 inch, 30cm) leads coming out of it. One, ending in a "universal" receiver connector (Hitec/JR type) is the output lead. It is plugged into either the battery port (or any spare port) of your receiver, or into the switch harness of your airplane where the receiver battery would normally plug in.</blockquote>
<blockquote>The input lead ends in tinned wires. These need to be connected to the battery side of your speed control so that power gets to the Ultimate BEC before it goes to your ESC. I put a JST connector on this lead, then made a little jumper cable with Powerpoles at each end, and then put a mating JST connector in parallel, so that I could still easily swap speed controls without having to get out the soldering iron. The JST lead is held parallel to the 13 gauge jumper wires for a short distance with some heat shrink tubing for strain relief as you can see in the photo below.</blockquote>
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<blockquote>I have used a similar arrangement in the past to power my Night Ops night lighting system, and to connect the power input wire on the MaxCim controller to the battery pack. If I didn't anticipate swapping speed controls, I'd just solder the input lead of the Ultimate BEC into the Powerpole contacts of the battery side of the controller along with the power wires, and then use the supplied heat shrink tubing for strain relief.</blockquote>
<blockquote><strong>Using the Ultimate BEC</strong></blockquote>
<blockquote>I've recently put a 14-cell power system in one of the planes that I've run on a 10-cell power system (and BEC-equipped speed controls) for over three years, and I really dreaded having to deal with the 270-mAh receiver battery that I was going to have to use. The plane can handle the extra weight without much notice, but just having to remember to check and recharge that little battery when all of my other active planes have no receiver battery at all was not something I was looking forward to.</blockquote>
<blockquote>Fortunately for me, I had already received the Ultimate BEC, and this became a perfect opportunity to put it to use. However, before I flew it, I had to see what effect it had on the radio system, since I'd had such a negative experience with a switching-regulator-based BEC unit before. Therefore, the first thing I did was put the 14-cell system on my test stand, hooked up the Ultimate BEC, and then ran it up using the old Ace ProStar receiver that was on the stand. I went so far as to lay the Ultimate BEC unit directly on the receiver's case. There was not a hint of a glitch in the throttle or the servos that are also hooked up to that receiver.</blockquote>
<blockquote>The next step, of course, was to put it all in the airplane, take it to the field, and then run range checks. I used a speed control for which I already knew the effect on range (schulze future-45Ko), so I knew the baseline range. The range check showed that the Ultimate BEC had no effect on the antenna-down ground range over running the radio system on a separate receiver battery. Therefore, with confidence, into the air it went. I have now flown the Ultimate BEC a number of times, both with the schulze controller and with a Hacker Master, and the radio link has been rock solid. The Ultimate BEC itself has been cool to the touch. Granted, I'm not yet pushing it very hard, as I'm running "only" 14 cells and using only three servos in the airplane, but applications are coming that will push things much harder. Based on what I've seen so far, I expect to be using one of these I any plane I fly that has a greater-than-10 cell power system, and no more little receiver batteries to keep track of for me.</blockquote>
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<td width="100%" align="center"><a href="/articles/ezonemag/2002/dec/control/ubec_vs_270s.jpg"><img src="http://static.rcgroups.com/articles/ezonemag/2002/dec/control/ubec_vs_270s_t.jpg" border="2"></a> </td>
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<td width="100%" align="center">The Ultimate BEC and the 270 mAh NiCad receiver battery it replaced in my LT-25</td>
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<blockquote>By the way, even though I've focused on using the Ultimate BEC with power systems of more than 10 cells, it can also be the answer when you have more servos to run than the BEC circuit in your speed control can safely handle. It is rated at 3A continuous and 5A peak. Even the most generous of in-controller BEC circuits I know of are rated at 5A peak but far less than 3A on a continuous basis, and I mentioned earlier, the continuous current limit for a linear regulator in an ESC's battery eliminator circuit goes down as the cell count goes up.</blockquote>
<blockquote>For example, if you have a complex scale or aerobatic ship that has two servos for ailerons, two for flaps and retracts as well as the usual elevator and rudder servos, you can use the Ultimate BEC to provide the power instead. Of course, if it used with a controller that has its own BEC circuit, the controller's BEC should be disabled according to the manufacturer's instructions. (Usually pulling the +ve pin out of the throttle connector and insulating it will do.)</blockquote>
<blockquote>The Ultimate BEC is available directly from Kool Flight Systems and several dealers including New Creations, E-Cubed, Model Electronics, EAM, Radical R/C, and Hobby Lobby. I even saw one in my local hobby shop recently!</blockquote>
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<td width="100%" align="center">MGM ComPro sensorless brushless controllers (40, 18 and 8A versions)</td>
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<blockquote>In my last column, I had a first look (for me, anyway) at controllers from the Czech firm of MGM ComPro. As you remember, I was very impressed with the operation and the construction of their TMM-35extra brushed motor controller, and noted several unusual features of the unit. As with some other controller manufacturers, MGM ComPro also makes brushless controllers. Their brushless line now consists of sensorless brushless controllers with three current ratings of 8, 18, and 40 amps, though I've recently seen some information that suggests they're expanding to higher currents and to cell counts beyond 16.</blockquote>
<blockquote>These brushless controllers all have the smart current limiting, lost signal protection, and a progressive rather than sudden low voltage cutoff. They also have the interesting on/off switch implementation that I wrote about last time. Therefore, rather than reiterate all of that, I will refer you to the <a href="http://www.ezonemag.com/cgi-bin/alist/jump.pl?ID=682">April 2002 edition of A Controlling Interest</a> for discussion about these features.</blockquote>
<blockquote>One feature I mentioned in that column but did not test on the TMM-35extra was the thermal shutdown. I did test this quite by accident with the TMM-40e-3ph in my Big T. I was doing a bunch of back-to-back flight testing while working with Ivan Pettigrew on the Big-T's balance, as described in the "A Balance Point Revelation" section of the <a href="http://www.ezonemag.com/cgi-bin/alist/jump.pl?ID=766">Big T review</a>. At that time, I had the controller installed in the nose of the airplane with no real air circulation around it. (Yes, I know, that's not the right way to do it, especially in a fuselage made from insulation foam.) Part way through one of the test flights, the motor went to about half throttle (while the airplane was inverted!) and would not go higher. I came around and landed, and once on the ground the system would not re-arm. Instead, I got a series of error beeps. I put my finger above the ESC and immediately knew what had happened. The controller got too hot. Instead of just cutting the motor off completely (which would have led to a crash considering where the plane was and in what attitude at the time), it cut the power back to reduce the heating while leaving enough controllable power to land safely. Very nice! I have now provided a little cooling air to the controller and have had no more thermal problems.</blockquote>
<blockquote>Another feature I have tested more thoroughly in the brushless versions, even though I didn't set out to, is the poor/lost signal filtering. Besides shutting down after a 1.5 second delay if the radio signal is lost or interfered with, they also will refuse to arm if they don't get a clean signal from the receiver. I ran into this while I had a GWS R6N receiver in my Switchback. From time to time, the 8A version it would not arm, especially if I did not complete the arming sequence shortly after powering up. (Instead, it gave out a steady beeping that indicated an error condition.) If this occurs, you have to turn it off and start the arming sequence again.</blockquote>
<blockquote>Now that I have a Berg receiver in my Switchback, I no longer have any errors while waiting arming. I have had some in-flight shutdowns (on both the 8 and 18A units) that were not accompanied by glitching of the control surfaces. If this happens, a quick return to "off" will rearm the control. Over the course of nearly 100 flights, I have only rarely had a similar experience with the 40A unit in the Big T. It has had the dual conversion 8-channel GWS receiver in it for the majority of its flying. Perhaps the bad or lost signal detection function in the software is a little too sensitive. I have also had this experience with early Jeti 06-3Ps when they first became available, but Jeti increased the delay before the motor was shut down due to a bad or lost signal, and I've had no more problems like this with their units.</blockquote>
<blockquote>Like the TMM-35extra, the -08, -18, and -40e-3ph all have a linear, rather than reverse exponential, throttle curve, which is lightly damped in response. Even though I like reverse expo better, the throttle "feel" in the air is good.</blockquote>
<blockquote>They also have one feature in common with the TMM-35extra (and several German controllers) that I don't like. You must program whether you want the brake on or off each time, you apply power to the unit. To select the brake off, you must switch on with the transmitter throttle stick high. This also sets the full throttle stick point. The motor will then beep twice, indicating the setting has been remembered. Pull the stick to low, the motor beeps once, the low throttle position is set, and the power system is now armed. To arm with the brake on, start with the throttle stick low. You'll get one beep. Advance the throttle stick to full. You'll hear two beeps and the high point is now set. Then pull back to low. There will be one more beep and the power system is now armed.</blockquote>
<blockquote>As for the specifically brushless aspects of these controllers, they acquit themselves pretty well. One way in which sensorless brushless controllers differ is in how well they start a variety of different motors. I have tried a number of motors on the TMM-40e-3ph, and I found that it starts most motors very easily and smoothly. It seemed to have the most difficulty with the Hacker B50L-13 that's currently in my LT-25. Starts of the Hacker were sometimes a little rough, but it never failed to start. Tests with Mega, Jeti, and Aveox showed quick and smooth starts with no need to advance the throttle suddenly or very far above "idle" to get a start. Oddly, the TMM-40e-3ph sometimes starts the Model Motors AXI 2820 in my Big T backwards. This is accompanied by some rather unpleasant sounds. When it happens, I immediately shut down, and when I try again, away it goes smoothly the correct direction. I corresponded with Ing. Dvorsky at MGM ComPro about this, and he sent me another TMM-40e-3ph with a slightly later software revision (2.31 vs. 2.23), but it does the same thing. I can't explain it, and neither can Ing. Dvorsky, it seems that once started the right way, it is fine on the ground and in the air.</blockquote>
<blockquote>So far, I've only run the Model Motors miniAC 1215/16 with the TMM-18e+3ph and the TMM-08e-3ph. (This motor is in my Switchback right now.) Starts are generally quick and smooth. Once in a while, you see a little of the prop waggling back and forth, which indicates it's trying to figure out which way to go, but this only happens for a second or so. Many folks are flying Mega Acn16/15 family motors with the 18A controller with good results too.</blockquote>
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<td width="100%" align="center">The TMM-18e+3ph controller's slim form factor lets it squeeze into tight places. You can just see it against the side of the fuselage, above and to the left of the battery in this picture of the inside of my Switchback.</td>
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<blockquote>Another area where sensorless controllers differ is in their minimum power setting. Here the MGM ComPro controllers work well, with a low enough "idle" that it isn't a problem getting airplanes to land (well under 5% of full power).</blockquote>
<blockquote>All three run fairly cool at full power near their rated currents, and don't heat up appreciably more at part throttle. As long as some airflow or even some space around them is available, (that isn't in insulating foam!), overheating them should not be a problem. Just be sure that the full-throttle current limits are respected.</blockquote>
<blockquote>Physically, the 40A version is about the same size as the Jeti 40-3P, weighs 1.6 ounces out of the bag, and 1.8 ounces ready to use. Connectors are not supplied for either the motor-side or the battery-side power leads. The 18A version is about the same size as its Jeti counterpart in length and width, but is only about half as thick. This helps it fit into tight places, such as alongside the drive battery in my Switchback. This one weighs 0.7 ounce out of the bag, with no connectors. The 8A is slightly smaller and weighs only 0.4 ounce out of the package, which is a bit less than the 6A Jeti. Until very recently, only the Castle Creations Phoenix 10 was smaller and lighter among currently available brushless controllers (more on that a bit later).</blockquote>
<blockquote>All three have a BEC on/off slide switch on a short lead. The switch supplied with the 40A controller is a redundantly wired DPDT unit. The ones supplied with the 8A and 18A units are miniature SPST types. Weights and measures are in the specification tables below.</blockquote>
<blockquote>My 8A and 18A units, which I purchased from Mega Motors USA, were supplied with electrolytic capacitors in the package. This, by the way, is the same input capacitor I was talking about in the discussion above about wire lengths. The instructions tell you to install these across the battery-side leads if you plan to run the units near their limits in current and voltage, or for extended periods at part throttle. I view this much like the motor diodes supplied separately with some inexpensive brushed motor controllers. If they are necessary, they should be installed at the factory. That said, I did not install the capacitor on either unit. When I was flying the Switchback on the 8A controller, propped for 7.5A, I encountered no problems, and the controller ran cool.</blockquote>
<blockquote>Ken Mizell of Megamotors USA has asked MGM ComPro to install the capacitors on subsequent orders, and Ken reports they are now coming that way. I also don't know about those sold by the other distributors such as EAM.</blockquote>
<blockquote>Despite some nitpicky problems, overall I think these units are a good value and work quite well enough for sport flying. If you're in the market for a relatively inexpensive brushless controller or one with some unique features, the MGM ComPro TMM xx-3ph family deserves consideration.</blockquote>
<p><big>A Look Ahead</p></big>
<blockquote>Brushless controllers continue to command my attention, and most of what I have to test are brushless. Pictured below are examples of two of the newest offerings from Jeti. The first is a member of the Advance series, which are just becoming available in 40 and 70A versions, both opto-coupled (for up to 16 cells) and with BEC for up to 12. The second is, as far as I know, the smallest brushless controller available to modelers today, the brand new Jeti 04-3P.</blockquote>
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<blockquote>I have been flying a prototype Jeti Advance 40-3P in the Big T the last couple of months, and it has been performing very well. I'll have more to say about it next time. The little 04-3P is a bit of a mystery to me right now, as I don't know of any brushless motor for which 4A is a reasonable upper current limit. Even the AstroFlight 010 is good to 5 to 6 amps, and perhaps more with the new EDF wind. Who knows, maybe by the time I get the next installment out I'll know what motor or motors Messers Jelen and Tinka had in mind when they created the Jeti 04-3P.</blockquote>
<blockquote>Also since my last installment, I have received samples of Kontronik Beat and Smile controllers (and a couple of Kontronik motors to drive with them), so they'll be going on the test stand and in the air.</blockquote>
<blockquote>Also in the package from Kontronik were a Rondo 300 and a Rondo 600 Pro. The Rondo 300 looks like a great controller for all the planes being flown on GWS EPS-300/370 systems including GWS's own Beaver and Zero, and planes like Mountain Models Switchback and MiniFlash. I intend to install this unit in one of those planes and find out.</blockquote>
<blockquote>It looks like it's going to be a busy winter's testing.</blockquote>
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<td width="100%" align="center"><strong>Specifications of Kool Flight Systems Ultimate Bec</strong>
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<a href="/articles/ezonemag/2002/dec/control/ubec_front1.jpg"><img src="http://static.rcgroups.com/articles/ezonemag/2002/dec/control/ubec_front1_t.jpg" border="2"></a><br><br></td>
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<li><strong>Type:</strong> High efficiency switching voltage regulator</li>
<li><strong>Rated Maximum Input Voltage:</strong> 35 V (there is also a 45V model available)</li>
<li><strong>Rated Minimum Input Voltage:</strong> 5.5 V (goes into bypass mode below 5.5 volts)</li>
<li><strong>Output Voltage:</strong> 5 volts</li>
<li><strong>Advertised Weight:</strong> 20 grams (0.7 ounce)</li>
<li><strong>Weight, Ready to Use:</strong> 0.8 ounce</li>
<li><strong>Rated Output Current:</strong> 3 amps continuous / 5 amps up to 5 minutes *</li>
<li><strong>Dimensions:</strong> 1 1/4 inches x 1 3/4 inches x 3/8 inch (32 x 44 x 9 mm)</li>
<li><strong>Input / Output Lead Lengths:</strong> 12 inches (30 cm)/ 8 inches (20 cm)</li>
<li><strong>Output Connector Supplied:</strong> Universal (JR/Hitec) servo connector</li>
<li><strong>Input Connector Supplied:</strong> None</li>
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<strong>*22 gauge wire and universal servo connectors are not designed for 5 amps current</strong></td>
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<td width="100%" align="center"><strong>Specifications of MGM ComPro TMM-08e-3ph</strong><br><br><a href="/articles/ezonemag/2002/dec/control/tmm08e.jpg"><img src="http://static.rcgroups.com/articles/ezonemag/2002/dec/control/tmm08e_t.jpg" border="2"></a><br><br>
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<li><strong>Dimensions:</strong> 1.1 X 1.0 X 0.2 inches (33 X 25 X 5.5 mm)</li>
<li><strong>Advertised Weight:</strong> 11g with wiring (0.4 ounce) 5.5g without wiring (0.2 ounce)</li>
<li><strong>Weight As Supplied:</strong> 0.4 ounce *</li>
<li><strong>Weight, Ready To Use:</strong> 0.5 ounce **</li>
<li><strong>Receiver Connector Supplied:</strong> Yes, JR/Hitec</li>
<li><strong>Motor Connectors Supplied:</strong> No</li>
<li><strong>Battery Connectors Supplied:</strong> No</li>
<li><strong>Throttle Function:</strong> Microprocessor controlled</li>
<li><strong>Cell Count Range:</strong> 6 to 10</li>
<li><strong>Rated Continuous Current:</strong> 8 Amps</li>
<li><strong>Rated Surge Current:</strong> Not stated. Current limiting prevents exceeding 8A</li>
<li><strong>Advertised On- Resistance:</strong> 20 milliohms</li>
<li><strong>Setup Method:</strong> Self-adjusting, variable start point, variable range</li>
<li><strong>High Rate Switching:</strong> 8 KHz</li>
<li><strong>Brake:</strong> Yes</li>
<li><strong>Can Be Disabled:</strong> Yes, select no-brake mode on power up (throttle stick high)</li>
<li><strong>BEC:</strong> Yes</li>
<li><strong>Stated BEC Rating:</strong> 2.0A peak, 1.5W continuous dissipation</li>
<li><strong>Radio On/Off Switch:</strong> Yes</li>
<li><strong>Low Voltage Cutoff:</strong> Progressive throttle limiting, based on initial conditions</li>
<li><strong>Cutoff Voltage:</strong> 5.3V or 0.7V per cell (calculated on power up)</li>
<li><strong>Motor Restart:</strong> Not applicable - motor is not completely cut off</li>
</ul>
<strong>Additional Features</strong>
<ul>
<li>Self-adjusting current limiting based on initial conditions</li>
<li>Over temperature protection by limiting throttle to 40% until landing</li>
<li>Soft loss-of-signal shutdown with restart</li>
<li>Audible signals for brake selection indication and arming</li>
</ul>
<p><strong>* Includes 2.7 inches of 0.5 sq. mm wire silicone jacketed wire for battery and motor connections, 5-inch receiver lead, BEC switch on 3.5-inch lead.
</strong></p>
<p><strong>** As above plus 3-pin Deans on motor side and 2-pin Deans connector on battery side</strong></p>
</td>
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</table>
</div>
<br>
<hr>
<br>
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<td width="100%" align="center"><strong>Specifications of MGM ComPro TMM-18e+3ph</strong><br><br><a href="/articles/ezonemag/2002/dec/control/tmm18e.jpg"><img src="http://static.rcgroups.com/articles/ezonemag/2002/dec/control/tmm18e_t.jpg" border="2"></a><br><br></td>
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<td width="100%" align="left"><ul>
<li><strong>Physical Dimensions:</strong> 1.5 X 1.1 X 0.2 inches (38 X 27 X 5.5 mm)</li>
<li><strong>Advertised Weight:</strong> 19g with wiring (0.7 ounce) 10g without wiring (0.4 ounce)</li>
<li><strong>Weight As Supplied:</strong> 0.7 ounce *</li>
<li><strong>Weight, Ready To Use:</strong> 0.8 ounce **</li>
<li><strong>Receiver Connector Supplied:</strong> Yes, JR/Hitec</li>
<li><strong>Motor Connectors Supplied:</strong> No</li>
<li><strong>Battery Connectors Supplied:</strong> No</li>
<li><strong>Throttle Function:</strong> Microprocessor controlled</li>
<li><strong>Cell Count Range:</strong> 6 to 12</li>
<li><strong>Rated Continuous Current:</strong> 18 Amps</li>
<li><strong>Rated Surge Current:</strong> Not stated. Current limiting prevents exceeding 18A</li>
<li><strong>Advertised On- Resistance:</strong> 10 milliohms</li>
<li><strong>Setup Method:</strong> Self-adjusting, variable start point, variable range</li>
<li><strong>High Rate Switching:</strong> 8 KHz</li>
<li><strong>Brake:</strong> Yes</li>
<li><strong>Can Be Disabled:</strong> Yes, select no-brake mode on power up (throttle stick high)</li>
<li><strong>BEC:</strong> Yes</li>
<li><strong>Stated BEC Rating:</strong> 3.0A peak, 2.5W continuous dissipation</li>
<li><strong>Radio On/Off Switch:</strong> Yes</li>
<li><strong>Low Voltage Cutoff:</strong> Progressive throttle limiting, based on initial conditions</li>
<li><strong>Cutoff Voltage:</strong> 5.3V or 0.7V per cell (calculated on power up)</li>
<li><strong>Motor Restart:</strong> Not applicable - motor is not completely cut off</li>
</ul>
<strong>Additional Features</strong>
<ul>
<li>Self-adjusting current limiting based on initial conditions</li>
<li>Over temperature protection by limiting throttle to 40% until landing</li>
<li>Soft loss-of-signal shutdown with restart</li>
<li>Audible signals for brake selection indication and arming</li>
</ul>
<p><strong>* Includes 3 inches of 1.0 sq. mm wire silicone jacketed wire for battery and motor connections, 7-inch receiver lead, BEC switch on 3-inch lead.</strong></p>
<p><strong>** As above plus 3-pin Deans on motor side and cut-down Anderson Powerpoles</strong></p></td>
</tr>
</table>
</div>
<br>
<hr>
<br>
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<td width="100%" align="center"><strong>Specifications of MGM ComPro TMM-40e-3ph</strong><br><br><a href="/articles/ezonemag/2002/dec/control/tmm40e.jpg"><img src="http://static.rcgroups.com/articles/ezonemag/2002/dec/control/tmm40e_t.jpg" border="2"></a><br><br></td>
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<tr>
<td width="100%" align="left"><ul>
<li><strong>Physical Dimensions:</strong> 2.3 X 1.2 X 0.5 inches (58 X 30 X 12 mm)</li>
<li><strong>Advertised Weight:</strong> 44g with wiring (1.6 ounce) 30g without wiring (1.1 ounce)</li>
<li><strong>Weight As Supplied:</strong> 1.6 ounce *</li>
<li><strong>Weight, Ready To Use:</strong> 1.8 ounce **</li>
<li><strong>Receiver Connector Supplied:</strong> Yes, JR/Hitec</li>
<li><strong>Motor Connectors Supplied:</strong> No</li>
<li><strong>Battery Connectors Supplied:</strong> No</li>
<li><strong>Throttle Function:</strong> Microprocessor controlled</li>
<li><strong>Cell Count Range:</strong> 6 to 12</li>
<li><strong>Rated Continuous Current:</strong> 40 Amps</li>
<li><strong>Rated Surge Current:</strong> Not stated. Current limiting prevents exceeding 40A</li>
<li><strong>Advertised On- Resistance:</strong> 5 milliohms</li>
<li><strong>Setup Method:</strong> Self-adjusting, variable start point, variable range</li>
<li><strong>High Rate Switching:</strong> 8 KHz</li>
<li><strong>Brake:</strong> Yes</li>
<li><strong>Can Be Disabled:</strong> Yes, select no-brake mode on power up (throttle stick high)</li>
<li><strong>BEC:</strong> Yes</li>
<li><strong>Stated Bec Rating:</strong> 3.0A peak, 2.5W continuous dissipation</li>
<li><strong>Radio On/Off Switch:</strong> Yes</li>
<li><strong>Low Voltage Cutoff:</strong> Progressive throttle limiting, based on initial conditions</li>
<li><strong>Cutoff Voltage:</strong> 5.3V or 0.7V per cell (calculated on power up)</li>
<li><strong>Motor Restart:</strong> Not applicable - motor is not completely cut off</li>
</ul>
<strong>Additional Features</strong>
<ul>
<li>Self-adjusting current limiting based on initial conditions</li>
<li>Over temperature protection by limiting throttle to 40% until landing</li>
<li>Soft loss-of-signal shutdown with restart</li>
<li>Audible signals for brake selection indication and arming</li>
</ul>
<p><strong>*Includes 303 inches of 2.5 sq. mm wire silicone jacketed wire for battery and motor connections, 7.5-inch receiver lead, BEC switch on 4-inch lead.</strong></p>
<p><strong>** Same as above, plus 3.5mm female bullets on motor side and Anderson Powerpoles battery side</strong></p></td>
</tr>
</table>
</div>
<blockquote>I have one topic to cover first, and then it's on to trying to clear out some of the review backlog. I want to address some of the confusion about lengthening the wires on one end or the other of a controller, especially sensorless brushless units. Then this installment will review the MGM ComPro sensorless brushless controllers, and one item that is not a speed control at all, the Kool Flight Systems Ultimate BEC.</blockquote>
<p><big>The wires aren't long enough, and the instructions say don't lengthen them, so what do i do now?</p></big>
<blockquote>A recent topic of discussion on the EZone discussion boards of RC Groups has been what to do if the wires on an ESC just won't reach from where the motor is to where the battery is. In particular, this has been talked about when using sensorless brushless controllers. In general, the wiring on sensorless motors is pretty short, and the same is true for controllers. (Some motors, like the Model Motors minACs and the current batch of Mega 1615s have no wires at all). Furthermore, the instructions for several makes of these controllers caution against lengthening the wiring at all. </blockquote>
<blockquote>I have encountered this problem in a couple of my own planes, and at various times put have the question to speed control makers "if I need to lengthen the wiring on one end or the other, which is better?" What has been really interesting about this is that I've gotten different answers from different makers.</blockquote>
<blockquote><strong>First, here are the concerns about longer wires on either end.</strong></blockquote>
<blockquote>On the ESC-to-motor end of the controller, the concern seems to be primarily the addition of more resistance and inductance to the windings of the motor, which will make starting a sensorless motor more difficult. This is also an argument against having connectors between the motor and the controller. For either sensor-equipped brushless motors or conventional brushed motors, this does not seem to be an issue. Of course additional wire length and connectors do add to resistance losses and therefore result in less of the battery's power getting to the motor, but unless the connectors are really bad (such as the Tamiya type) or the wire is really long or undersized, this is a small concern.</blockquote>
<blockquote>On the battery-to-ESC side of the controller, the situation can be more severe. On this side of the controller, there is no diode or synchronous rectification to help smooth out the start-stop-start-stop of the electricity flow as the controller switches the motor on and off. Due to the small, but real, inductance of the wires that lead from the battery to the ESC, this current tends to try to keep flowing even during the "off" times. This induces a voltage spike in the wire. The more wire, the greater the inductance and resulting voltage spike. </blockquote>
<blockquote>Many ESCs, for both brushed and brushless motors, have a capacitor across the input side to help smooth out these spikes, but if the leads get too long, the voltage rating of that capacitor (or capacitors in some cases) can be exceeded. When that happens (and it can happen, I've seen it), the capacitor either smokes or even explodes! Afterward, the controller may still work, but now these voltage spikes are getting into the rest of the controller and sooner or later more smoke will leak out.</blockquote>
<blockquote>Therefore, while some makers have told me, "don't lengthen either end", and some have said, "it doesn't matter", most are of the opinion that if you must lengthen wires, it is better to do it between the motor and the controller, rather than between the battery and the controller. I think "Astro Bob" Boucher put it succinctly in an e-mail response to this question some time ago.</blockquote>
<blockquote>Bob wrote (in April of 2001), "The lead length to any brushless or brushed motor from the speed control is not important except for resistance losses. The inductance in the winding is higher than any leads. This is not true about the wire length between battery and control. These must be SHORT. The motor sees a PWM [pulse width modulated] voltage but a smooth current waveform. The battery sees an interrupted current waveform with one microsecond or smaller rise times [this would be true for anything other than a frame rate controller, and we don't use those any more, do we? - BEC]. This means big voltage spikes. The caps used on most controls are OK for 1 foot of wire. Add 3 feet and you have instant smoke. This is true of almost all speed controls on the market, brushless and brushed. At 30 Amps, a 3-foot loop will generate 20-volt spikes. Add this to the battery voltage and you are asking for trouble."</blockquote>
<blockquote>There are also considerations of having more wire to radiate interference, especially at higher power levels. This argues for keeping the wiring as short as possible all the way around.</blockquote>
<blockquote>However, it seems to me that the induced voltage spikes on the battery side are the biggest worry. That said, I routinely insert my Wattmeter between the battery and ESC when testing, adding about a foot of wire length. I've put more than 50 flights on my Big T with an MGM ComPro brushless controller with about a 9-inch extension on the battery side, and I haven't blown it up yet.</blockquote>
<blockquote>Regardless of what I might actually be flying, if you must lengthen wiring, and you have a choice, I recommend you do it on the motor end.</blockquote>
<p><big>Battery Eliminator Circuit on more than 10 cells - The Kool Flight Systems Ultimate Bec</p></big>
<blockquote>The convenience of being able to run everything in the airplane off of one battery that you know is freshly charged, even when the plane is big enough or powerful enough to carry a separate receiver battery, has driven many of us to use battery eliminator circuits (BECs) on higher and higher cell counts and with more than just two or three servos. The problem is that with the usual BEC designs that use linear regulators, the greater the voltage difference between the motor pack and the BEC output voltage (usually around 5V), the LESS current the regulator can supply without overheating. Look at the table provided by MGM ComPro in the TMM 35 extra review in the last column for a clear illustration of this.</blockquote>
<blockquote>Worse, when a BEC regulator overheats, it shuts down to protect itself, which immediately kills power to the radio system and usually this also kills the motor. What happens next is usually crash. I'm sure the story Steve Horney tells in his May 2002 Pitch, Roll and Yaw column of the PBY going dead in flight, then coming back to life again after hitting the ground is the result of a BEC regulator that overheated and shut down its output, then after cooling off a bit, coming back to life. In addition, I have witnessed at least one crash that was apparently due to an overheated regulator causing the motor and the radio to go dead.</blockquote>
<blockquote>While some speed control designers try very hard to arrange the thermal cutoff so that the motor is cut before the regulator overheats (Castle Creations, MGM ComPro, and Aveox come to mind), running the radio off of a drive battery of more than 10 to 12 cells has been impractical unless you're using a MaxCim brushless sensored controller, which has a unique approach to solving this problem. So up to now, for any power system other than one based on a MaxCim controller, running above 10 or at most 12 cells pretty much precludes running a BEC.</blockquote>
<blockquote>Some of you will say, "So what's the problem? Any plane that is running on 10 or more cells will never notice the weight of a receiver battery anyway!" and that is generally true. But I, for one, have witnessed (and participated in) far more model crashes due to a receiver battery that ran down before the pilot expected it to than those due to a BEC failure, even counting the BEC-related crash I saw that I mentioned a bit above. As I said at the beginning, there is the undeniable convenience factor of plugging in a freshly charged drive battery in the plane and then flying the plane without having to worry about checking the receiver battery or even having the receiver battery to maintain. So, if you want the convenience and reliability of BEC power in a larger electric model, what's the solution?</blockquote>
<blockquote>The answer is a BEC circuit that is not based on a linear regulator, but rather on a switching power supply. In this sort of a design, the voltage difference between the source battery and the output isn't just dissipated in heat, but the input power is converted to AC, the voltage is stepped down, and then turned back into DC for the output. Up until now, there have been two problems with the switching power supply approach, cost, and more importantly, radio interference generated by the switching power supply. In the past, I have tested a prototype add-on BEC based on a switching power supply that reduced my radio range to essentially zero. That unit never got into the air. There also have been several makers who looked at a switching BEC, and then dropped the idea because it would have been too expensive.</blockquote>
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<td width="100%" align="center"><a href="/articles/ezonemag/2002/dec/control/ubec_front1.jpg"><img src="http://static.rcgroups.com/articles/ezonemag/2002/dec/control/ubec_front1_t.jpg" border="2"></a></td>
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<td width="100%" align="center">This unassuming looking device is the solution - the Kool Flight Ultimate BEC</td>
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</table>
</div>
<blockquote>Jim Beck and Jeff Meyers of Kool Flight Systems have solved these problems. The resulting unit, called the Ultimate BEC, is a bit bigger than the unworkable unit that shall remain nameless, being about the size and weight of a 150-mAh NiCad receiver pack. Unlike that other unit, however, this one works without disturbing the radio system in the plane, and works well. Rated for an input voltage of up to 35V (with a bit of cooling) or 26 cells, and 3 continuous Amps of current (5A peak), it should bring the convenience and general reliability of BEC powered radio systems to all but the largest of electric powered models. At $30, it is not terribly expensive, either.</blockquote>
<blockquote>As received, the Kool Flight Systems Ultimate BEC is a flat package wrapped in heat shrink tubing about the size one would expect a 40A brushed speed control to be, and weighs 0.7 ounces. There are two generous (12 inch, 30cm) leads coming out of it. One, ending in a "universal" receiver connector (Hitec/JR type) is the output lead. It is plugged into either the battery port (or any spare port) of your receiver, or into the switch harness of your airplane where the receiver battery would normally plug in.</blockquote>
<blockquote>The input lead ends in tinned wires. These need to be connected to the battery side of your speed control so that power gets to the Ultimate BEC before it goes to your ESC. I put a JST connector on this lead, then made a little jumper cable with Powerpoles at each end, and then put a mating JST connector in parallel, so that I could still easily swap speed controls without having to get out the soldering iron. The JST lead is held parallel to the 13 gauge jumper wires for a short distance with some heat shrink tubing for strain relief as you can see in the photo below.</blockquote>
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<td width="100%" align="center"><a href="/articles/ezonemag/2002/dec/control/jumpers.jpg"><img src="http://static.rcgroups.com/articles/ezonemag/2002/dec/control/jumpers_t.jpg" border="2"></a> </td>
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<blockquote>I have used a similar arrangement in the past to power my Night Ops night lighting system, and to connect the power input wire on the MaxCim controller to the battery pack. If I didn't anticipate swapping speed controls, I'd just solder the input lead of the Ultimate BEC into the Powerpole contacts of the battery side of the controller along with the power wires, and then use the supplied heat shrink tubing for strain relief.</blockquote>
<blockquote><strong>Using the Ultimate BEC</strong></blockquote>
<blockquote>I've recently put a 14-cell power system in one of the planes that I've run on a 10-cell power system (and BEC-equipped speed controls) for over three years, and I really dreaded having to deal with the 270-mAh receiver battery that I was going to have to use. The plane can handle the extra weight without much notice, but just having to remember to check and recharge that little battery when all of my other active planes have no receiver battery at all was not something I was looking forward to.</blockquote>
<blockquote>Fortunately for me, I had already received the Ultimate BEC, and this became a perfect opportunity to put it to use. However, before I flew it, I had to see what effect it had on the radio system, since I'd had such a negative experience with a switching-regulator-based BEC unit before. Therefore, the first thing I did was put the 14-cell system on my test stand, hooked up the Ultimate BEC, and then ran it up using the old Ace ProStar receiver that was on the stand. I went so far as to lay the Ultimate BEC unit directly on the receiver's case. There was not a hint of a glitch in the throttle or the servos that are also hooked up to that receiver.</blockquote>
<blockquote>The next step, of course, was to put it all in the airplane, take it to the field, and then run range checks. I used a speed control for which I already knew the effect on range (schulze future-45Ko), so I knew the baseline range. The range check showed that the Ultimate BEC had no effect on the antenna-down ground range over running the radio system on a separate receiver battery. Therefore, with confidence, into the air it went. I have now flown the Ultimate BEC a number of times, both with the schulze controller and with a Hacker Master, and the radio link has been rock solid. The Ultimate BEC itself has been cool to the touch. Granted, I'm not yet pushing it very hard, as I'm running "only" 14 cells and using only three servos in the airplane, but applications are coming that will push things much harder. Based on what I've seen so far, I expect to be using one of these I any plane I fly that has a greater-than-10 cell power system, and no more little receiver batteries to keep track of for me.</blockquote>
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<td width="100%" align="center"><a href="/articles/ezonemag/2002/dec/control/ubec_vs_270s.jpg"><img src="http://static.rcgroups.com/articles/ezonemag/2002/dec/control/ubec_vs_270s_t.jpg" border="2"></a> </td>
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<td width="100%" align="center">The Ultimate BEC and the 270 mAh NiCad receiver battery it replaced in my LT-25</td>
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</table>
</div>
<blockquote>By the way, even though I've focused on using the Ultimate BEC with power systems of more than 10 cells, it can also be the answer when you have more servos to run than the BEC circuit in your speed control can safely handle. It is rated at 3A continuous and 5A peak. Even the most generous of in-controller BEC circuits I know of are rated at 5A peak but far less than 3A on a continuous basis, and I mentioned earlier, the continuous current limit for a linear regulator in an ESC's battery eliminator circuit goes down as the cell count goes up.</blockquote>
<blockquote>For example, if you have a complex scale or aerobatic ship that has two servos for ailerons, two for flaps and retracts as well as the usual elevator and rudder servos, you can use the Ultimate BEC to provide the power instead. Of course, if it used with a controller that has its own BEC circuit, the controller's BEC should be disabled according to the manufacturer's instructions. (Usually pulling the +ve pin out of the throttle connector and insulating it will do.)</blockquote>
<blockquote>The Ultimate BEC is available directly from Kool Flight Systems and several dealers including New Creations, E-Cubed, Model Electronics, EAM, Radical R/C, and Hobby Lobby. I even saw one in my local hobby shop recently!</blockquote>
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<td width="100%" align="center"><a href="/articles/ezonemag/2002/dec/control/mgm_family1.jpg"><img src="http://static.rcgroups.com/articles/ezonemag/2002/dec/control/mgm_family1_t.jpg" border="2"></a> </td>
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<td width="100%" align="center">MGM ComPro sensorless brushless controllers (40, 18 and 8A versions)</td>
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<blockquote>In my last column, I had a first look (for me, anyway) at controllers from the Czech firm of MGM ComPro. As you remember, I was very impressed with the operation and the construction of their TMM-35extra brushed motor controller, and noted several unusual features of the unit. As with some other controller manufacturers, MGM ComPro also makes brushless controllers. Their brushless line now consists of sensorless brushless controllers with three current ratings of 8, 18, and 40 amps, though I've recently seen some information that suggests they're expanding to higher currents and to cell counts beyond 16.</blockquote>
<blockquote>These brushless controllers all have the smart current limiting, lost signal protection, and a progressive rather than sudden low voltage cutoff. They also have the interesting on/off switch implementation that I wrote about last time. Therefore, rather than reiterate all of that, I will refer you to the <a href="http://www.ezonemag.com/cgi-bin/alist/jump.pl?ID=682">April 2002 edition of A Controlling Interest</a> for discussion about these features.</blockquote>
<blockquote>One feature I mentioned in that column but did not test on the TMM-35extra was the thermal shutdown. I did test this quite by accident with the TMM-40e-3ph in my Big T. I was doing a bunch of back-to-back flight testing while working with Ivan Pettigrew on the Big-T's balance, as described in the "A Balance Point Revelation" section of the <a href="http://www.ezonemag.com/cgi-bin/alist/jump.pl?ID=766">Big T review</a>. At that time, I had the controller installed in the nose of the airplane with no real air circulation around it. (Yes, I know, that's not the right way to do it, especially in a fuselage made from insulation foam.) Part way through one of the test flights, the motor went to about half throttle (while the airplane was inverted!) and would not go higher. I came around and landed, and once on the ground the system would not re-arm. Instead, I got a series of error beeps. I put my finger above the ESC and immediately knew what had happened. The controller got too hot. Instead of just cutting the motor off completely (which would have led to a crash considering where the plane was and in what attitude at the time), it cut the power back to reduce the heating while leaving enough controllable power to land safely. Very nice! I have now provided a little cooling air to the controller and have had no more thermal problems.</blockquote>
<blockquote>Another feature I have tested more thoroughly in the brushless versions, even though I didn't set out to, is the poor/lost signal filtering. Besides shutting down after a 1.5 second delay if the radio signal is lost or interfered with, they also will refuse to arm if they don't get a clean signal from the receiver. I ran into this while I had a GWS R6N receiver in my Switchback. From time to time, the 8A version it would not arm, especially if I did not complete the arming sequence shortly after powering up. (Instead, it gave out a steady beeping that indicated an error condition.) If this occurs, you have to turn it off and start the arming sequence again.</blockquote>
<blockquote>Now that I have a Berg receiver in my Switchback, I no longer have any errors while waiting arming. I have had some in-flight shutdowns (on both the 8 and 18A units) that were not accompanied by glitching of the control surfaces. If this happens, a quick return to "off" will rearm the control. Over the course of nearly 100 flights, I have only rarely had a similar experience with the 40A unit in the Big T. It has had the dual conversion 8-channel GWS receiver in it for the majority of its flying. Perhaps the bad or lost signal detection function in the software is a little too sensitive. I have also had this experience with early Jeti 06-3Ps when they first became available, but Jeti increased the delay before the motor was shut down due to a bad or lost signal, and I've had no more problems like this with their units.</blockquote>
<blockquote>Like the TMM-35extra, the -08, -18, and -40e-3ph all have a linear, rather than reverse exponential, throttle curve, which is lightly damped in response. Even though I like reverse expo better, the throttle "feel" in the air is good.</blockquote>
<blockquote>They also have one feature in common with the TMM-35extra (and several German controllers) that I don't like. You must program whether you want the brake on or off each time, you apply power to the unit. To select the brake off, you must switch on with the transmitter throttle stick high. This also sets the full throttle stick point. The motor will then beep twice, indicating the setting has been remembered. Pull the stick to low, the motor beeps once, the low throttle position is set, and the power system is now armed. To arm with the brake on, start with the throttle stick low. You'll get one beep. Advance the throttle stick to full. You'll hear two beeps and the high point is now set. Then pull back to low. There will be one more beep and the power system is now armed.</blockquote>
<blockquote>As for the specifically brushless aspects of these controllers, they acquit themselves pretty well. One way in which sensorless brushless controllers differ is in how well they start a variety of different motors. I have tried a number of motors on the TMM-40e-3ph, and I found that it starts most motors very easily and smoothly. It seemed to have the most difficulty with the Hacker B50L-13 that's currently in my LT-25. Starts of the Hacker were sometimes a little rough, but it never failed to start. Tests with Mega, Jeti, and Aveox showed quick and smooth starts with no need to advance the throttle suddenly or very far above "idle" to get a start. Oddly, the TMM-40e-3ph sometimes starts the Model Motors AXI 2820 in my Big T backwards. This is accompanied by some rather unpleasant sounds. When it happens, I immediately shut down, and when I try again, away it goes smoothly the correct direction. I corresponded with Ing. Dvorsky at MGM ComPro about this, and he sent me another TMM-40e-3ph with a slightly later software revision (2.31 vs. 2.23), but it does the same thing. I can't explain it, and neither can Ing. Dvorsky, it seems that once started the right way, it is fine on the ground and in the air.</blockquote>
<blockquote>So far, I've only run the Model Motors miniAC 1215/16 with the TMM-18e+3ph and the TMM-08e-3ph. (This motor is in my Switchback right now.) Starts are generally quick and smooth. Once in a while, you see a little of the prop waggling back and forth, which indicates it's trying to figure out which way to go, but this only happens for a second or so. Many folks are flying Mega Acn16/15 family motors with the 18A controller with good results too.</blockquote>
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<td width="100%" align="center"><a href="/articles/ezonemag/2002/dec/control/full_sb.jpg"><img src="http://static.rcgroups.com/articles/ezonemag/2002/dec/control/full_sb_t.jpg" border="2"></a> </td>
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<td width="100%" align="center">The TMM-18e+3ph controller's slim form factor lets it squeeze into tight places. You can just see it against the side of the fuselage, above and to the left of the battery in this picture of the inside of my Switchback.</td>
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<blockquote>Another area where sensorless controllers differ is in their minimum power setting. Here the MGM ComPro controllers work well, with a low enough "idle" that it isn't a problem getting airplanes to land (well under 5% of full power).</blockquote>
<blockquote>All three run fairly cool at full power near their rated currents, and don't heat up appreciably more at part throttle. As long as some airflow or even some space around them is available, (that isn't in insulating foam!), overheating them should not be a problem. Just be sure that the full-throttle current limits are respected.</blockquote>
<blockquote>Physically, the 40A version is about the same size as the Jeti 40-3P, weighs 1.6 ounces out of the bag, and 1.8 ounces ready to use. Connectors are not supplied for either the motor-side or the battery-side power leads. The 18A version is about the same size as its Jeti counterpart in length and width, but is only about half as thick. This helps it fit into tight places, such as alongside the drive battery in my Switchback. This one weighs 0.7 ounce out of the bag, with no connectors. The 8A is slightly smaller and weighs only 0.4 ounce out of the package, which is a bit less than the 6A Jeti. Until very recently, only the Castle Creations Phoenix 10 was smaller and lighter among currently available brushless controllers (more on that a bit later).</blockquote>
<blockquote>All three have a BEC on/off slide switch on a short lead. The switch supplied with the 40A controller is a redundantly wired DPDT unit. The ones supplied with the 8A and 18A units are miniature SPST types. Weights and measures are in the specification tables below.</blockquote>
<blockquote>My 8A and 18A units, which I purchased from Mega Motors USA, were supplied with electrolytic capacitors in the package. This, by the way, is the same input capacitor I was talking about in the discussion above about wire lengths. The instructions tell you to install these across the battery-side leads if you plan to run the units near their limits in current and voltage, or for extended periods at part throttle. I view this much like the motor diodes supplied separately with some inexpensive brushed motor controllers. If they are necessary, they should be installed at the factory. That said, I did not install the capacitor on either unit. When I was flying the Switchback on the 8A controller, propped for 7.5A, I encountered no problems, and the controller ran cool.</blockquote>
<blockquote>Ken Mizell of Megamotors USA has asked MGM ComPro to install the capacitors on subsequent orders, and Ken reports they are now coming that way. I also don't know about those sold by the other distributors such as EAM.</blockquote>
<blockquote>Despite some nitpicky problems, overall I think these units are a good value and work quite well enough for sport flying. If you're in the market for a relatively inexpensive brushless controller or one with some unique features, the MGM ComPro TMM xx-3ph family deserves consideration.</blockquote>
<p><big>A Look Ahead</p></big>
<blockquote>Brushless controllers continue to command my attention, and most of what I have to test are brushless. Pictured below are examples of two of the newest offerings from Jeti. The first is a member of the Advance series, which are just becoming available in 40 and 70A versions, both opto-coupled (for up to 16 cells) and with BEC for up to 12. The second is, as far as I know, the smallest brushless controller available to modelers today, the brand new Jeti 04-3P.</blockquote>
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<td width="100%" align="center"><a href="/articles/ezonemag/2002/dec/control/newfromjeti.jpg"><img src="http://static.rcgroups.com/articles/ezonemag/2002/dec/control/newfromjeti_t.jpg" border="2"></a></td>
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<blockquote>I have been flying a prototype Jeti Advance 40-3P in the Big T the last couple of months, and it has been performing very well. I'll have more to say about it next time. The little 04-3P is a bit of a mystery to me right now, as I don't know of any brushless motor for which 4A is a reasonable upper current limit. Even the AstroFlight 010 is good to 5 to 6 amps, and perhaps more with the new EDF wind. Who knows, maybe by the time I get the next installment out I'll know what motor or motors Messers Jelen and Tinka had in mind when they created the Jeti 04-3P.</blockquote>
<blockquote>Also since my last installment, I have received samples of Kontronik Beat and Smile controllers (and a couple of Kontronik motors to drive with them), so they'll be going on the test stand and in the air.</blockquote>
<blockquote>Also in the package from Kontronik were a Rondo 300 and a Rondo 600 Pro. The Rondo 300 looks like a great controller for all the planes being flown on GWS EPS-300/370 systems including GWS's own Beaver and Zero, and planes like Mountain Models Switchback and MiniFlash. I intend to install this unit in one of those planes and find out.</blockquote>
<blockquote>It looks like it's going to be a busy winter's testing.</blockquote>
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<td width="100%" align="center"><strong>Specifications of Kool Flight Systems Ultimate Bec</strong>
<br><br>
<a href="/articles/ezonemag/2002/dec/control/ubec_front1.jpg"><img src="http://static.rcgroups.com/articles/ezonemag/2002/dec/control/ubec_front1_t.jpg" border="2"></a><br><br></td>
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<td width="100%" align="left">
<ul>
<li><strong>Type:</strong> High efficiency switching voltage regulator</li>
<li><strong>Rated Maximum Input Voltage:</strong> 35 V (there is also a 45V model available)</li>
<li><strong>Rated Minimum Input Voltage:</strong> 5.5 V (goes into bypass mode below 5.5 volts)</li>
<li><strong>Output Voltage:</strong> 5 volts</li>
<li><strong>Advertised Weight:</strong> 20 grams (0.7 ounce)</li>
<li><strong>Weight, Ready to Use:</strong> 0.8 ounce</li>
<li><strong>Rated Output Current:</strong> 3 amps continuous / 5 amps up to 5 minutes *</li>
<li><strong>Dimensions:</strong> 1 1/4 inches x 1 3/4 inches x 3/8 inch (32 x 44 x 9 mm)</li>
<li><strong>Input / Output Lead Lengths:</strong> 12 inches (30 cm)/ 8 inches (20 cm)</li>
<li><strong>Output Connector Supplied:</strong> Universal (JR/Hitec) servo connector</li>
<li><strong>Input Connector Supplied:</strong> None</li>
</ul>
<strong>*22 gauge wire and universal servo connectors are not designed for 5 amps current</strong></td>
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<td width="100%" align="center"><strong>Specifications of MGM ComPro TMM-08e-3ph</strong><br><br><a href="/articles/ezonemag/2002/dec/control/tmm08e.jpg"><img src="http://static.rcgroups.com/articles/ezonemag/2002/dec/control/tmm08e_t.jpg" border="2"></a><br><br>
</td>
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<td width="100%" align="left">
<ul>
<li><strong>Dimensions:</strong> 1.1 X 1.0 X 0.2 inches (33 X 25 X 5.5 mm)</li>
<li><strong>Advertised Weight:</strong> 11g with wiring (0.4 ounce) 5.5g without wiring (0.2 ounce)</li>
<li><strong>Weight As Supplied:</strong> 0.4 ounce *</li>
<li><strong>Weight, Ready To Use:</strong> 0.5 ounce **</li>
<li><strong>Receiver Connector Supplied:</strong> Yes, JR/Hitec</li>
<li><strong>Motor Connectors Supplied:</strong> No</li>
<li><strong>Battery Connectors Supplied:</strong> No</li>
<li><strong>Throttle Function:</strong> Microprocessor controlled</li>
<li><strong>Cell Count Range:</strong> 6 to 10</li>
<li><strong>Rated Continuous Current:</strong> 8 Amps</li>
<li><strong>Rated Surge Current:</strong> Not stated. Current limiting prevents exceeding 8A</li>
<li><strong>Advertised On- Resistance:</strong> 20 milliohms</li>
<li><strong>Setup Method:</strong> Self-adjusting, variable start point, variable range</li>
<li><strong>High Rate Switching:</strong> 8 KHz</li>
<li><strong>Brake:</strong> Yes</li>
<li><strong>Can Be Disabled:</strong> Yes, select no-brake mode on power up (throttle stick high)</li>
<li><strong>BEC:</strong> Yes</li>
<li><strong>Stated BEC Rating:</strong> 2.0A peak, 1.5W continuous dissipation</li>
<li><strong>Radio On/Off Switch:</strong> Yes</li>
<li><strong>Low Voltage Cutoff:</strong> Progressive throttle limiting, based on initial conditions</li>
<li><strong>Cutoff Voltage:</strong> 5.3V or 0.7V per cell (calculated on power up)</li>
<li><strong>Motor Restart:</strong> Not applicable - motor is not completely cut off</li>
</ul>
<strong>Additional Features</strong>
<ul>
<li>Self-adjusting current limiting based on initial conditions</li>
<li>Over temperature protection by limiting throttle to 40% until landing</li>
<li>Soft loss-of-signal shutdown with restart</li>
<li>Audible signals for brake selection indication and arming</li>
</ul>
<p><strong>* Includes 2.7 inches of 0.5 sq. mm wire silicone jacketed wire for battery and motor connections, 5-inch receiver lead, BEC switch on 3.5-inch lead.
</strong></p>
<p><strong>** As above plus 3-pin Deans on motor side and 2-pin Deans connector on battery side</strong></p>
</td>
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<td width="100%" align="center"><strong>Specifications of MGM ComPro TMM-18e+3ph</strong><br><br><a href="/articles/ezonemag/2002/dec/control/tmm18e.jpg"><img src="http://static.rcgroups.com/articles/ezonemag/2002/dec/control/tmm18e_t.jpg" border="2"></a><br><br></td>
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<td width="100%" align="left"><ul>
<li><strong>Physical Dimensions:</strong> 1.5 X 1.1 X 0.2 inches (38 X 27 X 5.5 mm)</li>
<li><strong>Advertised Weight:</strong> 19g with wiring (0.7 ounce) 10g without wiring (0.4 ounce)</li>
<li><strong>Weight As Supplied:</strong> 0.7 ounce *</li>
<li><strong>Weight, Ready To Use:</strong> 0.8 ounce **</li>
<li><strong>Receiver Connector Supplied:</strong> Yes, JR/Hitec</li>
<li><strong>Motor Connectors Supplied:</strong> No</li>
<li><strong>Battery Connectors Supplied:</strong> No</li>
<li><strong>Throttle Function:</strong> Microprocessor controlled</li>
<li><strong>Cell Count Range:</strong> 6 to 12</li>
<li><strong>Rated Continuous Current:</strong> 18 Amps</li>
<li><strong>Rated Surge Current:</strong> Not stated. Current limiting prevents exceeding 18A</li>
<li><strong>Advertised On- Resistance:</strong> 10 milliohms</li>
<li><strong>Setup Method:</strong> Self-adjusting, variable start point, variable range</li>
<li><strong>High Rate Switching:</strong> 8 KHz</li>
<li><strong>Brake:</strong> Yes</li>
<li><strong>Can Be Disabled:</strong> Yes, select no-brake mode on power up (throttle stick high)</li>
<li><strong>BEC:</strong> Yes</li>
<li><strong>Stated BEC Rating:</strong> 3.0A peak, 2.5W continuous dissipation</li>
<li><strong>Radio On/Off Switch:</strong> Yes</li>
<li><strong>Low Voltage Cutoff:</strong> Progressive throttle limiting, based on initial conditions</li>
<li><strong>Cutoff Voltage:</strong> 5.3V or 0.7V per cell (calculated on power up)</li>
<li><strong>Motor Restart:</strong> Not applicable - motor is not completely cut off</li>
</ul>
<strong>Additional Features</strong>
<ul>
<li>Self-adjusting current limiting based on initial conditions</li>
<li>Over temperature protection by limiting throttle to 40% until landing</li>
<li>Soft loss-of-signal shutdown with restart</li>
<li>Audible signals for brake selection indication and arming</li>
</ul>
<p><strong>* Includes 3 inches of 1.0 sq. mm wire silicone jacketed wire for battery and motor connections, 7-inch receiver lead, BEC switch on 3-inch lead.</strong></p>
<p><strong>** As above plus 3-pin Deans on motor side and cut-down Anderson Powerpoles</strong></p></td>
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</table>
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<td width="100%" align="center"><strong>Specifications of MGM ComPro TMM-40e-3ph</strong><br><br><a href="/articles/ezonemag/2002/dec/control/tmm40e.jpg"><img src="http://static.rcgroups.com/articles/ezonemag/2002/dec/control/tmm40e_t.jpg" border="2"></a><br><br></td>
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<td width="100%" align="left"><ul>
<li><strong>Physical Dimensions:</strong> 2.3 X 1.2 X 0.5 inches (58 X 30 X 12 mm)</li>
<li><strong>Advertised Weight:</strong> 44g with wiring (1.6 ounce) 30g without wiring (1.1 ounce)</li>
<li><strong>Weight As Supplied:</strong> 1.6 ounce *</li>
<li><strong>Weight, Ready To Use:</strong> 1.8 ounce **</li>
<li><strong>Receiver Connector Supplied:</strong> Yes, JR/Hitec</li>
<li><strong>Motor Connectors Supplied:</strong> No</li>
<li><strong>Battery Connectors Supplied:</strong> No</li>
<li><strong>Throttle Function:</strong> Microprocessor controlled</li>
<li><strong>Cell Count Range:</strong> 6 to 12</li>
<li><strong>Rated Continuous Current:</strong> 40 Amps</li>
<li><strong>Rated Surge Current:</strong> Not stated. Current limiting prevents exceeding 40A</li>
<li><strong>Advertised On- Resistance:</strong> 5 milliohms</li>
<li><strong>Setup Method:</strong> Self-adjusting, variable start point, variable range</li>
<li><strong>High Rate Switching:</strong> 8 KHz</li>
<li><strong>Brake:</strong> Yes</li>
<li><strong>Can Be Disabled:</strong> Yes, select no-brake mode on power up (throttle stick high)</li>
<li><strong>BEC:</strong> Yes</li>
<li><strong>Stated Bec Rating:</strong> 3.0A peak, 2.5W continuous dissipation</li>
<li><strong>Radio On/Off Switch:</strong> Yes</li>
<li><strong>Low Voltage Cutoff:</strong> Progressive throttle limiting, based on initial conditions</li>
<li><strong>Cutoff Voltage:</strong> 5.3V or 0.7V per cell (calculated on power up)</li>
<li><strong>Motor Restart:</strong> Not applicable - motor is not completely cut off</li>
</ul>
<strong>Additional Features</strong>
<ul>
<li>Self-adjusting current limiting based on initial conditions</li>
<li>Over temperature protection by limiting throttle to 40% until landing</li>
<li>Soft loss-of-signal shutdown with restart</li>
<li>Audible signals for brake selection indication and arming</li>
</ul>
<p><strong>*Includes 303 inches of 2.5 sq. mm wire silicone jacketed wire for battery and motor connections, 7.5-inch receiver lead, BEC switch on 4-inch lead.</strong></p>
<p><strong>** Same as above, plus 3.5mm female bullets on motor side and Anderson Powerpoles battery side</strong></p></td>
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</table>
</div>