Controlling Interest - February 2001 - RC Groups

Controlling Interest - February 2001

Bernard discusses audible arming signals and what to do when your esc just won't go, plus he takes an in-depth look at three sport speed controls.

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It’s been quite awhile since my last column. All I can say is that my life continues to be "interesting", and sometimes that means other aspects of life getting in the way of the fun stuff. But, things are looking up (the back surgery was a success), and I have material and ideas for at least the next 4 or 5 columns. So, I hope that there will be shorter gaps between installments this year.

This time I’m going to spend a little time on a feature of many recent ESC designs that I have come to like a lot: an arming signal. Then we will look at three 30 to 40 Amp rated brushed motor speed controls, as a kind of sample of my next column, which will be the long-promised buyers guide to 30-40A controllers. This month’s units are the Kontronik Sun 4000 and Schulze slim-35be, both mentioned in my Electric Scout review, and the Great Planes ElectriFly C-30, which has been the subject of quite a bit of curiosity since it was announced a few months ago.

Arming Signals – Or, How Do I Know It’s Live?

In the days of analog electronic speed controls (ESCs) there was virtually no question that once you connected the drive battery to the unit or turned on your arming switch, when you advanced the throttle the prop would start to turn. With the advent of "safety power-up" features on microprocessor-based ESCs, that is no longer always the case. Depending on how the particular speed control designer and builder implemented that feature, you may or may not have power to the motor when you expect it. How many times have you carried your plane out to the runway, advanced the throttle, and had nothing happen? I don’t want to think about how many times it’s happened to me.

One response to this problem has been an LED on the ESC itself which is used to indicate set-points, or when full power is reached. The LED method (MaxCim, Aveox 60/160 series, Viper Models Mini and Speed Demons, and the new Great Planes C-20 and C-30, among others) is great for setting up the your model in the shop as you match the speed control’s response to the transmitter, but there are few ESC installations where you can see the LED at the field (though MaxCim provides a remotely-mounted LED option).

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An LED indicator on an ESC

More recently, a number of ESC makers have started providing audible indications of the state of the controller, including letting you know it’s armed and ready. I don’t know who pioneered the idea that a tiny burst of power to the motor would make it "beep", and that that could then be used as feedback to the user, though I first noticed mention of it in reading about some German-made units. Whoever came up with the idea, I am grateful, because I think this is a wonderfully simple way to give me very useful information about the state of the power system in my model.

A number of makers of ESCs have now adopted the audible feedback idea to not only let the user know the unit is armed, but also to signal where in the setup process they are. Here are a few examples of audible signals:

  • Current production Castle Creations controllers beep the motor once to let you know that power has been applied, then beep it twice to let you know that the unit is armed.
  • Schulze controllers use one, two or three beeps to indicate where in the mode-selection process you are. With them, a single beep indicates the unit is armed.
  • Jeti microprocessor-based units use a single beep to tell you it’s armed, and a continuous series of beeps to let you know of an error.
  • Kontronik uses a series of tones both to indicate the selected mode and to indicate that the control is armed. The Sun 4000, which has a single mode (called Auto Programming Mode or APM), gives three beeps of rising pitch to indicate that the unit is armed.
  • Gordon Tarling’s MicroStars beep twice to let you know they’re armed.

I’m sure there are others as well.

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A number of speed controls which use audible signals during setup and/or in regular use.

As I’ve said, this is one of my favorite little touches in today’s speed controllers. I hope more makers adopt audible feedback to let the user know all is well before he (or she) walks out to the flight line only to advance the throttle and have nothing happen.


But It Won’t Go! – Why?

This leads to – what are some of the causes for a controller not to arm when we expect it to? Well, most "safe power up" features are implemented in one of two ways: either there is a throttle position (as indicated by the duration of the control pulse being sent to the ESC) above which they will not arm, or they assume that the position of the throttle stick when everything is powered on is the "off" or "brake" position for the throttle, regardless of where that is. There are even a few that use both methods together, assuming that the initial throttle stick position is "off" or "brake" only if it is below a certain set value.

Those of the type which require the initial throttle stick setting to be below a certain set pulse duration (and sometimes to remain there for a certain minimum time) are the ones that seem to give the most difficulty. Here are things to check if you’re having problems getting an ESC to arm.:

  • Virtually all ESCs give increasing throttle with increasing pulse duration. Unfortunately, for some reason Futaba’s throttle channels by default work the opposite way, so check the throttle channel’s reversing switch. It should be in "reverse" for Futaba and "normal" for all other radios that I know of. Early Viper Models ESCs are the only exceptions to this I know.
  • If you have adjustable endpoints or travel at the transmitter, make sure the throttle channel is set to at least 100%.
  • If you don’t have adjustable endpoints, try pulling the throttle trim low and then try to arm the ESC again.
  • Don’t immediately throttle up to see if the motor runs – some controllers require a second or two of incoming pulses below the arming threshold before they will arm. Wait a bit and try again.
  • Some controls require you to sweep the stick from off to full power and back before they will arm – notably the new Great Planes ElectriFly units and the Model Electronics MX-50 and –80. They will not arm until you have finished this procedure.
  • If the controller has one-time programmable endpoints (Aveox H-60/160, Kontronik Star series in some operating modes), did you program the endpoints with the transmitter (or model memory) you are now using, and with the throttle trim where it is now? If not, it may need to be reprogrammed to match.

In any case, after you change something at the transmitter, it may be necessary to unplug the drive battery from the ESC for a few seconds to reset it so that it will "see" the change in reversing switch, endpoint or trim.

If you’ve tried all of these and the controller still won’t arm, I’d look for loose connections in the power circuit. I recently had problems with a fuse holder that made my Griffin 55 look as if it was having problems arming – but instead the power was not getting to it at all. Another thing to check for is an incorrect connection to the receiver (is it really in the receiver port corresponding to the throttle channel matching the transmitter?) or a receiver plug which is plugged in backward.

If all of this fails, then it’s time to start trading components in and out of the system to identify where the problem is. Getting help from another E-flyer, either locally or on the Internet, could help if nothing you do seems to work and you’ve tried all the things I’ve suggested above.


Featured Speed Controls:

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Kontronik Sun 4000, Schulze slim-35be, Great Planes ElectriFly C-30

This time we’ll cover three controls that fall into the 30-40A sport speed control category. Two are from German companies, and the third is a unit of Korean origin sold by the USA’s largest R/C modeling distributor. All three are self adjusting in some fashion, compact and easy to set up and use. Let’s look at them one by one.


Kontronik Sun 4000

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The Sun 4000 is Kontronik’s entry into the sport flyer’s 30-40A speed control range, and replaces the earlier Easy series. It is a 35 Ampere-rated ESC, with BEC/cutoff and brake, that is intended for you to simply install in the airplane and go fly, with no settings or adjustments to make. It succeeds in this objective very well. It is one of the more inexpensive units in this capability range, too. The US distributor’s (Northeast Sailplanes current price is $47.95 on their web site.

It is self-adjusting for both endpoints and range, with no separate programming steps required other than to run the motor up to full throttle briefly before you go fly. You can even dispense with this step if you advance the throttle to full on your takeoff run or before you hand launch.

If you have specific needs, such the need for more current capability (up to 70A), the ability to disable the brake, change the voltage cutoff level of the BEC/cutoff to suit different cell counts (or even have a progressive cutoff like the little JMP controls), or to dispense with the BEC altogether and have optical isolation between the power system and the radio system, there is a whole family of "Star" series controls with multiple programmable modes to address these needs. One Star even has a BEC rated at 5A and so should be able to handle 5 servos rather than the usual two or three. But I will cover some of the Stars in a later column

Getting back to the Sun 4000, as you can see in the picture above, it is physically similar to many controls these days, a flat package about 1 1/2 inches by 1 inch with the wires for the battery (red and black) and receiver coming from one end, the motor wires (blue and green) emerging from the other. It is covered in bright yellow shrink wrap. The label does not indicate which sets of wires do which. It comes in a small cardboard box with two short booklets describing how to connect it up and use it (one booklet in English, one in German).

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The Kontronik Sun 4000 with its box and instructions.

Both on the test stand and in the air, it is very smooth in operation, with just a touch of softness in the response – one of the best I have used. It has a strongly reverse exponential throttle curve, so almost the entire throttle stick throw provides meaningful power changes, yet you can have a lovely "tickover" idle if you want to. This makes it a pleasure to fly from full bore to low, slow fly-bys to touch-and-goes. It does have the odd characteristic of changing pitches at low throttle settings, so the switching rate must be variable.

It clearly indicates that the power system is armed by giving three beeps of increasing pitch (a little three-note musical tune) when you first apply power. These are quite loud and put enough power into the motor to cause the prop to turn just a little, especially on can motors like a Speed 600. I’ve armed it with the prop on a table so it couldn’t turn and it suffered no ill effects. Michael Franz at Kontronik advises that the prop doesn’t turn while "beeping" cobalt or Neodym motors.

It will arm regardless of where your throttle stick is when you power up (at least within the limits of my test equipment) That point will be considered "brake". As long as you have at least a 0.35 ms pulse duration increase from there to your full throttle point, you will get to full throttle (this is less than half the range most transmitters have available) and the ESC’s range will be auto-scaled between the endpoints.

It runs extremely coolly, even at part throttle – I noticed only slight warming either by running it at 75% throttle or by exercising several servos at once, or both – all while holding it in my hand and isolating it from any cooling air. So, it would be comfortable in an installation where little cooling air is available.

I have only a couple of slightly negative comments about it. First, I was surprised that it had a noticeable effect on the ground range of the radio system in the Scout (transmitter and receiver from Airtronics/Sanwa) when I checked it with the motor running at "idle". With the particular installation I have (you can see examples with a couple of other ESCs below) and testing at the particular field I tested it at, I get at least 150 backward paces of radio range with the transmitter antenna collapsed. This is about as far as I can go and still see the Scout’s rudder move. With the motor set to "idle" this range is reduced to about 90 backward paces. Perhaps I should try re-routing the receiver lead as described below in the Schulze slim-35be discussion.

Even so, this is still quite acceptable range, and I have flown most of the 56 logged battery charges through the Scout with this ESC and not had a single throttle glitch.

The second "complaint", if it is one, is that there is no radio on/off switch, and no provisions for one. I have not yet decided myself whether I prefer having a switch or not.

Overall, I gladly recommend the Kontronik Sun 4000. You put on the connectors you need, put it in the airplane, and go fly – what more could a sport flyer ask for?

Weights, measures, and many other specific details may be found in the tables at the end of the column.


Schulze slim-35be

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Schulze is the German firm best known (at least here in the US) for their world class (and very expensive) battery chargers, and also for being one of the leaders in sensorless controllers for brushless motors. They also seem to have a dizzying array of controller choices, each tailored to a specific application.

Their slim series (in all of their literature, the name is NOT capitalized) is their range of microprocessor-based controllers for conventional brushed motors. There are members of the family from the slim-08be for slowly/parkfly types through a 50A rated unit in two versions, one specifically for helicopters. The slim-35-be is a 35A rated unit with BEC for use with 6-12 cell drive batteries.

Physically it is just slightly bulkier than the Sun 4000. It is covered in a thick clear shrink tubing, with the label underneath the shrink-wrap. The battery wire end is clearly labeled "akku" and the motor side "motor" with the polarity also shown. In the bright pink box along with the controller is a small 36 page(!) booklet, 18 pages each in German and English. These instructions cover the entire "slim" family and also discuss their special 3.5mm connectors at some length.

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The Schulze slim-35be with its box and instruction book.

I also found that the JR/Graupner receiver lead supplied could not be made to plug into my Airtronics equipment by just switching the positive and negative leads as I can for a JR connector – the holes in the Rx connector body were just not quite large enough for the rectangular pins in old Airtronics servo extension cables. So, I had to change to a proper old-style Airtronics plug on the receiver lead. This will be of no consequence to anyone who is not using the older style Airtronics/Sanwa receivers and especially their servo extensions.

It can be used in all the same applications as the Kontronik Sun 4000, but it has a few additional tricks as well.. First of all, it has three different operating modes: one for direct drive planes with a fast acting (and very strong) brake. This is the "normal" mode. There is also a mode with the brake disabled, and a "gearbox mode" which is similar to the "normal" mode, but which both ramps the throttle up more slowly and applies the brake much more gently. You must select which mode you wish to use each time you power up the system. The selection is made by the position of the transmitter’s throttle stick when power is first applied to the ESC.

  • If the stick is at low throttle when everything is initially turned on, "normal" (or "brake") mode is selected, and the unit will beep once only almost immediately, telling you it is armed. It determines the high throttle position and the range based on the first advance of the stick – which must be done quickly and stopped where you want "full throttle" to be. When the full throttle point is "learned" the ESC very momentarily interrupts the running of the motor to give an audible indication of this (a sort of reverse beep).
  • If the stick is at high throttle when you power up, the "no brake" mode is selected, and this position becomes the full throttle point. It will beep twice to tell you this has taken place. When you pull the stick back to low and the unit beeps once, it is armed. As before, the range is scaled between the set endpoints.
  • If the stick is in the MIDDLE of it’s throw when you power up (1.35-1.65 ms pulse duration), the unit will beep three times, indicating selection of "gearbox mode". When you then pull the stick back to low it will beep once, and this becomes the "off" point. The high throttle point is calculated to be 0.6ms above the low point. So, in this mode it has a variable start point but a fixed range (like the FMA Direct controllers, but with twice the range).

If I were in charge of the Schulze software design department (rather than Mr. Herder), I’d exchange the first and third modes so that the default mode would have the soft start and brake (and a range scaled to the endpoints selected) and I'd put the hard brake on the fixed-range mode. But, I’m not…..

This mode selection by transmitter stick position also means that you need to be aware of what brand of ESC is in your plane when you go out to fly more so than with most others. By the way, the future series of sensorless brushless controllers (at least in the form I have seen them) also have the same three modes, selected the same way. This may be changing, however.

Another unique feature of the Schulze controller is that the motor power connectors are attached directly to the ESC’s circuit board and the mating connectors (3.5mm gold bullet types) are supplied preinstalled in the onboard sockets. Simply pull them out and solder them to your motor leads, or make up short jumpers to make the controller compatible to the rest of the wiring in your plane (as you will see I did in the photos). Extra 3.5 mm connectors – both halves – are, of course, available from Schulze and their dealers.

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Two views of the supplied motor-side connectors. The first shows both jumpers I made removed from their sockets. The second shows one of the supplied plugs installed (motor +) and one removed (motor -).

Finally, the receiver lead and a jumper into which an on/off switch can be fitted all plug into the controller’s circuit board on the opposite end from the motor connections. This is supposed to make it easier to move the ESC from one airplane to another without having to mess with the Rx-to-throttle connection at the receiver itself.

On the test stand it is fairly well behaved and smooth, with no discernable steps. There is a bit more switching noise (the part throttle "whine" you hear from the motor is both louder and coarser) than from the Sun 4000 but it is quieter than, for example, the Jeti JES350, which is another unit which switches at 1 kHz. None of this makes any real difference in the air, however.

It also runs quite cool in my part throttle test and BEC exercise test and so should be fine in any installation that allowed even a small amount of air circulation around it (as long as the full throttle current of the system is 35A or less).

In flight it is quite satisfactory. It has a linear throttle curve, making the lower half of the throttle stick motion of little use. I found that I prefer powering it up in the "no brake" mode because the brake application in "normal" mode is so sudden and strong.. I expect someone using one of these in a mini-hotliner would have no problem with the prop folding RIGHT NOW when the throttle was pulled off. As I say, I’d really prefer the softer throttle response and brake of the "gearbox" mode to be the default.

I also noted that after a short time the brake releases again. The instruction sheet says this period is 8 seconds long.

When I first did the radio range check on the slim-35be I got a puzzle. I did the test at the same place and just a few minutes time away from the one described above for the Sun 4000, and so used the same 150 backward paces as my baseline motor-off range. I found that with the motor running at "idle" in the airplane I had control of the rudder and elevator to virtually the same range as with the motor off. However, I couldn’t seem to control the motor (get it to change speeds) until I got to well more than half the distance back to the plane. Yet I had had no in flight difficulties with it at all.

When I mentioned this to Matthias Schulze, he suggested that I should be careful to run the Rx lead as far as possible from the drive battery leads and above them. I tried this, and sure enough, a second range check showed a ground range, motor on and motor off, of the control surfaces and the motor as far as I could see the control surfaces move and the prop turn – about 150 paces. In the first picture below, you can see my initial installation, with the excess length of the receiver lead pushed down between the battery tray and the fuselage side. This put the receiver lead right next to the drive battery cables and the battery itself.

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Installation of the slim-35be in the Electric Scout with the Rx lead near the battery cables and motor battery. This arrangement limited the ground range of the system.

In this second picture you can see the re-routed receiver lead, laid out above the battery tray, about 1 cm from the receiver itself and with the excess length gathered back by the servos. With this arrangement the antenna-down radio range was very much improved, as I described just above.

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Installation of the slim-35be with the receiver lead re-routed. This arrangement gave much better ground range check performance.

Bottom line: I can recommend this one as well, especially if you want the flexibility of the multiple modes, and/or your airplane is already wired with Schulze 3.5mm bullet connectors. The current price from the US distributor, RC-Direct is $54.95. But take special care with the wire routing and do a thorough range check, both motor off and with the motor running slowly, before flying. This is good practice after installing ANY speed control.

Weights, measures, and many other specific details may be found in the tables at the end of the column.


The Great Planes ElectriFly C-30

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In just the last few months, Great Planes Model Manufacturing Company, which I think is the largest distributor of R/C model airplane-related merchandise in the US, has released a line of items for electric flight under the "ElectriFly" brand. Some of these are just rebadged products that have been around awhile, such as the Mabuchi 550 motor that used to be called the Goldfire, and is now the ElectriFly S-600. But included in that line are four Korean-made speed controls, rated at 5 A, 10 A, 20 A, and 30 A continuous current, and named, not surprisingly, the ElectriFly C-5, C-10, C-20, and C-30. The actual maker of them is not identified.

When their ads first started appearing, there was a great deal of curiosity about them on the E-flight mailing list. Based on some of the electric flight products we’d seen distributed by Great Planes over the past 10 years or more, there was quite a bit of skepticism expressed about how good these new controllers would be, especially at an advertised price of $39.95 US for the C-30.

Thanks to our esteemed editor, I was able to obtain one of each. They are compact units of the usual flat, heat-shrink tubing covered sort, each packaged in a nice plastic box (like some servos and receivers). The label on the front of the unit clearly shows which wires go to the battery and which to the motor, and indicates their polarity.

Also in the box are a double sided 8 1/2X11 instruction sheet, and in the case of the C-20 and C-30, three capacitors and a diode which may be installed on the motor you will be using, if needed. The C-20 and C-30 both come with a Tamiya-style plug on the battery leads, a Futaba-J style plug on the receiver lead, and a small radio on/off switch. This is a single pole single throw radio on/off switch similar to that seen on some other inexpensive controllers such as those from FMA Direct. The C-30 is physically smaller than either of the two German units discussed above. However, it is also rated for only 5-10 cells at 30 A maximum, rather than the 6-12 cell, 35 A ratings of the others.

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The ElectriFly C-30 in its box with capacitors, diode and instruction sheet.

The instructions are clear and straightforward, and cover the usual "which wire goes to which connection" sort of thing, and how to use a bit of Velcro to mount the unit in your airplane. They also cover such things as has how to modify the supplied Futaba J-style receiver plug to work with your radio if needed (like the Schulze above, if you’re a user of the older-style Airtronics/Sanwa equipment, I’d really recommend replacing the plug altogether), and how to change the supplied Tamiya-style battery plug (please do!), how to set up and range test your power system, how to disable the BEC and why you might want to do this, and a troubleshooting guide. I found one error in the original instructions (about setting reversing switches on the throttle channel of your transmitter – as mentioned earlier this is usually only necessary for Futaba transmitters). The error has been fixed and correct instructions are available for download from .

OK, so they are packaged nicely enough – how do they work? What follows is based on testing of the ElectriFly C-30, but since the C-20 is very similar, I expect that most of what I have to say will apply to it as well.

On the test stand it proved to be of the variable start, variable endpoint (and therefore scalable range) variety. The transmitter stick position when you first power up is presumed to be "brake" (almost regardless of where this is) and the on-board LED lights steadily. You then sweep the stick to the full throttle position and hold it there for a couple of seconds (the on-board LED then starts to blink, letting you know the upper point has been set), then you bring the stick back to off and the LED goes out. The unit is now armed. You must sweep the stick from off to full and back again each time you power up in order to arm the unit. This is similar to the Model Electronics Corporation MX-50/80 controllers.

Using the AstroFlight WhattMeter on my test stand, I found the C-30’s throttle response to be linear, not reverse exponential. It is smooth, with no noticeable steps. The initial run up to full throttle is fairly soft, but once there, it responds quickly to throttle stick changes. It shuts down fairly cleanly with signal loss.

I also found that the "optional" diode was indeed optional, at least for the combination of equipment I tested. This is very unusual in that up until now any time there has been a diode in the package with an inexpensive controller it was there because there was not one on the controller itself. This loose diode had to be installed on the motor you were going to be using the controller with – or across the controller-to-motor connector as I have done before (for example, see the FMA Mini-20 review in my February 2000 column In this case, however, the instructions said it could be installed to gain a slight bit of efficiency and decrease the heating of the unit at part throttle or it could be left off. More on this in a bit.

One of the interesting things I learned when checking it with my Ace Datamaster is that C-30 will arm with the initial throttle setting as high as 1.65 ms pulse duration (which is much above half throttle on most radios) and the full throttle point is set wherever you stop moving the stick on that initial sweep above the start point, as long as the pulse duration is greater than 1.68 ms. This means you can go from brake to full power in almost no stick travel at all, if for some reason you wanted to (though I can't imagine why anyone would). It also means that regardless of how short your transmitter's throttle stick throw is, chances are you will be able to get the ElectriFly C-30 to arm and to reach full throttle without fussing with trims or having to modify mechanical stops as has been a problem with some ESCs and some inexpensive transmitters.

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My Ace Datamaster, with which I can measure controller endpoints and span, and see whether they are variable or fixed, among other things.

My Ace Datamaster draws a constant 250 mA (thank you Astro Micro WhattMeter for giving me that data) and this constant draw was enough to noticeably warm the BEC regulator. Putting two servos in constant motion warms it a similar amount, but the temperature stabilizes quickly.

The C-30 also gets noticeably warmer at part throttle than either of the German units discussed above, but not so hot as, say, the FMA Mini-30. I would strongly recommend that cooling airflow be available to it in use, especially if the plane you put it in will spend a lot of time around 3/4 throttle and/or you use long-running batteries like RC2400s or P3000s.

One other item of concern, at least for the particular sample I received, is that the motor is not cut off by the BEC/Cutoff function until the drive battery voltage falls to 4.1V, rather than the stated 4.8V. The output to the receiver at this point is about 3.95V. Neither my test stand receiver nor the one in the Scout seem to suffer any ill effects by brief drops to this voltage, but this would be worth checking in your installation. This would be especially true, I suspect, if you were using one of these newer receivers that is microprocessor-based.

I attempted to evaluate the effect of the optional diode by soldering one end of it to the old Goldfire motor I use on my test stand and then holding the other end in contact with the other motor terminal while the C-30 was running at part throttle. I heard no increase in RPM (so I concluded there was no efficiency gain) and I could not feel any change in the amount of heating. Perhaps if I somehow instrumented and isolated the controller from cooling air I could find a difference in performance due to the diode, but during this admittedly crude test there was no noticeable change. It would also become much more necessary if the motor timing was not right for the load – especially if you took a standard motor and then fitted a gearbox requiring the rotation to be reversed but without retiming to match. Here fitting the external diode could be very necessary.

In test flights in my Scout, even those behind the Velkom 24/12 (nearly 30A at full bore) the control was cool upon landing - but there is a plenty of airflow through the airplane (and air flowing through the plane isn't all that hot in the Seattle area this time of year either!). In flight it handles very well for a linear throttle and I have no problem modulating it to any desired point from full bore down to an approach-steepening "tickover". Shooting touch and goes with the airplane were not complicated by the throttle’s characteristics. That Velkom motor, by the way, is a beauty and sounds like a smooth running turbine. But I digress again….

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The Velkom 24/12 in the nose of the Scout. It is a drop-in replacement for the S600-type motor installed previously.

In test flying I found that the C-30’s brake, which comes on fairly softly, stays on once it is set, unless you advance the throttle again.

My range test on this unit also gave me a surprise, but this time it was a good one. I could see NO discernable loss of radio range between motor off and motor at "idle" with this unit in the airplane.. I made no special accommodations in the wire routing and still, as far away as I could still see the airplane's rudder move, I had full control of the rudder, elevator, AND motor. This is among the best such performances I've ever seen on a BEC-equipped speed control.

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C-30 installation in the Scout

My summary on this one: If I were "Consumer Reports" magazine (a US magazine that buys, tests and rates all sorts of consumer products from canned soup to computers to automobiles), I would have to rate this one a "Best Buy". It is compact and it works well. I even like having the little on/off switch. I do wish it ran cooler at part throttle, and I would rather have an audible arming signal (you're not likely to see the LED unless the unit's in something like one of Tom Hunt's Clearfilm covered Stik Series planes). And, of course, I've mentioned before that I prefer a reverse-exponential throttle curve on any throttle. These are still pretty rare, however.

But if you're looking for an inexpensive but functional choice, the ElectriFly C-30 deserves a good look. However, be sure that you don’t load it beyond its 30 Amp rating, as it seems to have less "headroom" than the other two units featured this month. It will also have the advantage for many folks in the US of being available at most any local hobby shop (as long as they get stock from Great Planes). I like it.

As I mentioned above, weights and measures and more in tables below.

Physical Characteristics

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Manufacturer or Distributor



Great Planes


Sun 4000


ElectriFly C-30

Length X Width X Thickness

1.5 X 1.0 X 0.22 inches

1.7 X 1.0 X 0.4 inches

1.3 X 0.7 X 0.3 inches

Advertised Weight

0.5 oz., 1.0 oz. with wiring

0.4 ounces, 0.8 ounces with wires

0.7 ounces with wires

Weight As Received

1.0 ounce

0.9 ounces

0.8 ounces + optional diode, capacitors

Ready to Use Weight*

1.2 ounces

1.3 ounces

1.0 ounce

Motor Lead Length

3.5 inches

None supplied

4.5 inches

Motor Connector?

None supplied

3.5 mm gold bullet type

None supplied

Battery Lead Length

3.0 inches

3.8 inches

4.5 inches

Battery Connector?

None supplied

None supplied

Tamiya type

Receiver Lead Length

11 inches

11 inches

5 inches

Receiver Connector?

JR type

JR type

Futaba-J type

Radio on/off switch type


None, but provisions for one


Switch lead length



4 inches

Special Features

Quick plug in connectors for motor and receiver leads on board. Mating 3.5mm bullet connectors for motor supplied.

Three capacitors and Schottky diode supplied. Diode installation is optional (and I saw no effect of its use)

US "street" price




* Ready to use weight includes Anderson Powerpoles installed for both motor and battery connections. All supplied wiring is left full length. Schulze weight includes 2 inch motor leads.


!Throttle Function

Manufacturer or Distributor



Great Planes


Sun 4000


ElectriFly C-30

Digital or Analog?




Continuos Current Rating




Surge Rating

45A/ 15 sec.


Not Stated









Operating Switching Frequency

High rate, variable

1 kHz

1.5 kHz

Stated On-Resistance

Not Stated

2.3 milliOhms

Not Stated

Off/Start Point




How Start Point Set?

Initial throttle stick position

Low throttle stick position

Initial throttle stick position (<1.65 ms pulse width), LED on

Full Throttle Point

High throttle stick position if greater than 0.35 ms pulse width above initial throttle stick position

Varies depending on mode - see separate table

High throttle stick position (>1.68 ms pulse width), LED blinks

Set Once or Continuous Update?

Set once per power-up

Set once per power-up

Set once per power-up

Range from low to high

Variable, minimum 0.35 ms pulse width

Varies depending on mode - see separate table


How Range Set?

Scales from initial endpoint settings

Varies depending on mode - see separate table

Scales from initial endpoint settings

Arming Mode

Armed on power up

Varies depending on mode - see separate table

Turn on switch, sweep throttle stick to full for about 2 seconds, return to off. Unit is then armed.

Arming Indication?

Three beeps of rising pitch

One beep

LED goes out

"Safe start" feature?

Initial stick position is assumed "brake"

Varies depending on mode - see separate table

Initial stick position is assumed "brake"

Throttle Curve

Reverse exponential



Part Throttle Heating

Very low



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