Controlling Interest - May 2001 - RC Groups
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Controlling Interest - May 2001

Bernard Cawley presents his giant speed control comparison tables, plus a review of the Kontronik Star Line controllers.

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Well, finally, here is the long promised "buyers’ guide" to sport flyers’ speed controls for brushed motors. Included below are data for 17 individual speed controls, all in current production, which are aimed at electric sport flyers. With a couple of exceptions (which I’ll explain in a minute), they are all rated between 30A and 40A continuous, and from 5 or 6 to 10 or 12 cells. Most are BEC controllers, most have brakes, and most of the brakes can be disabled in hardware or software. As such, any of them could be suitable for anything from a geared speed 400 plane up to 300-400W power systems such as Astro Flight cobalt 15. None of them are all-out competition units and really aren’t aimed at that sort of flying, although the Kontronik Star series, this month’s featured controllers, have a "competition mode" – more on them a little later.

All but three of the 17 ESCs I have tested myself in my Electric Scout (7 cells, Velkom 24/12, APC 9X4.5 E-prop, about 28A at full throttle). Some, but not all, have also been flight tested in my Kadet LT-25 (10 cells, MEC Turbo-10GT, 5:1 gears, about 32A at full throttle) as well. The four I haven’t actually tested are all members of the same "family" as a controller I have tested. These are the Castle Creations Griffin 40 (similar to the Griffin 55), the Kontronik StarBEC 50-6-14 (similar to the StarBEC 40-6-12), the Tarling MicroStar 40 (similar to the MicroStar 20), and the Viper Models SD200B (similar to the SD202B). So, I feel pretty safe in expecting them to perform similarly to their other family members and including them here.

Some of the controllers in the tables below have appeared in prior issues of A Controlling Interest, so if you want more details about a particular one, look at the back issues. The others are being introduced here and will be covered individually in a future column (I hope!).

I have included two controllers which have ratings outside the 30A-40A continuous range. The first is the Kontronik StarBEC 50-6-14. It is there because it has a 5A peak rating BEC circuit and can be used on BEC up to 14 cells, which I thought would be of interest to some of you. It is otherwise similar to the other Star series models (two others are listed). The other is the Model Electronics Corp. MX-80, which is rated at 44A continuous. This is MEC’s only current controller (the MX-50 has been discontinued) and is otherwise close enough to be included as it’s clearly aimed at the sport flyer.

Weights and measures

I’ve been giving wire length measurements in this column for some time. In case anyone wonders, the diagram below shows what I mean by the length measurements I give in the physical data tables.

ESCdimensionsDiagram.jpg (10146 bytes)

The measured weights were done on a Pelouze PE-5R digital postal scale, which has 0.1 ounce precision (or about 3g). The "as received" weights include whatever wire and connectors (and, if present, a switch) as it comes out of bag or box. With only two exceptions these include no power connectors. The MEC MX-80 comes with Sermos (Anderson Powerpole) connectors installed. The Great Planes C-30 comes with the Tamiya type, which should be immediately removed and thrown away!. The ready-to-use weights in this group include Anderson Powerpoles on both the motor and battery side of the controller. For the controllers I didn’t have in hand, the ready-to-use weights are calculated.

The wire sizes given are from manufacturers’ supplied data, what is printed on the insulation of the wire, or, in a couple of cases, a guess on my part. There is a mix of metric sizes (in square mm) and American Wire Gauge, depending on the origin of the unit. A little internet research yields these rough equivalents for stranded wire:

AWG sq. mm
16 1.3
15 1.6
14 2.1
13 2.6
12 3.3

So, if the controller has 16 gauge wire, it’s about 1.3 sq. mm, and if it has 1.5 sq. mm wire, it's just a bit smaller than 15 gauge.


The data in the big tables that follow are based on my own measurements and tests (with the exception of the four units I mentioned above), and generally on only ONE sample of each. Most of them have been furnished to me for review purposes. Since these data are based on only one of each it is quite possible that you might, with another example of the same ESC model, see different results.

Some of my evaluations are somewhat subjective, especially opinions on how well the unit handles a loss of signal and motor-on range check results. Therefore they need to be taken as rough guides, not precision measurements. These range checks were all done in the Electric Scout, and as I noted in my last column, sometimes details of the installation matter a lot. In the Scout, the suggested equipment arrangement puts the receiver about 3/16 of an inch above and parallel to the motor battery, as shown in the picture below Note that the motor battery is immediately below the plywood plate to which the receiver is also attached For some controllers, this receiver location results in drastically shortened radio range with the motor running. Apparently switching noise is re-radiated by the battery and into the receiver. Being careful about the routing of the throttle-to-receiver lead helps, but for some ESCs that wasn’t enough.

slim_instl_better.jpg (27743 bytes)

Moving the receiver to the fuselage side, as shown below, both gets it further from the motor battery and changes its orientation so that the receiver’s circuit board is perpendicular to the battery rather than parallel. This improved the radio range greatly for all of the listed units that didn’t do very well with the receiver over the battery. These are noted as such in the throttle function data table.

Rx_on_side.jpg (20664 bytes)

Changing to a different receiver may also be an option in solving interference problems. I recently replaced the Airtronics receiver shown in the pictures with a Hitec 555 on the channel matching my new Multiplex Cockpit transmitter. Range checks with a known good combination (the Kontronik Sun 3000) resulted in slightly poorer results than with the Airtronics receiver, both motor on and motor off. So, in this airplane at least, a receiver swap did not change things significantly.

As always, range check any new airplane with both the motor off and running at part throttle, and don’t fly if the range is drastically reduced from one to the other. Also recheck every time you either change ESC or receiver, or relocate one or the other inside the airplane. Also, your motor off range should not be less than if the ESC isn’t there (though this is tough to check when using a BEC controller).

On another note, a couple of readers asked me to also include some units that are no longer in production in these guides, but this thing is already so late, I think I’ll save that one for later. I will note, in the descriptions below, significant differences between the current production version and earlier versions of some of these units, where I know them.

ESCs of the month – Kontronik Star-Line series

Before we get to the buyers’ guide, and to simplify some of the data presentation in the buyers’ guide, let’s have a separate look at the Star-Line series of ESCs from Kontronik GmbH in Germany. There are five members of the family: a 40A rated BEC-equipped unit (StarBEC 40-6-12), a 50A BEC unit (StarBEC 50-6-14), and opto-coupled units with 40A and 70A ratings (StarOPT 40-6-18, StarOPT 40-10-30, and StarOPT 70-6-18). They are all similar in size and except for the heavier gauge wire on the StarOPT 70-6-18, you could probably not tell them apart without their labels unless you removed the shrink wrap. The StarBEC 50-6-14, as I mentioned earlier, has the highest capacity BEC I’ve yet seen in a brushed motor controller, with a 5A surge rating and the ability to use BEC on up to 14 cells with 3 servos.

The Star-Line have a unique protection feature (so far as I know, anyway): they have reverse drive battery polarity protection. You can connect the drive battery to the Stars backwards for a short time without damaging them. If you do this, the motor in your plane will begin to run slowly but backwards. I have tested this and it works as advertised. They do caution that if your motor starts running immediately after you connect the battery to disconnect it again immediately. After a few seconds the controller can be damaged.

Physically the Stars are compact flat packages just about the same size as the Sun 4000 featured in the last column, but wrapped in red rather than yellow shrink tubing. Operationally, as received they operate pretty much the same way as the Sun 4000 as well, with variable start and endpoints learned each time when you first power up and advance the throttle to full, a pronounced reverse exponential throttle curve and a soft brake. They have the same variable frequency at low speed and overall smooth and responsive operation as the Sun 4000 as well. With 40, 50, and 70 amp ratings they start where the newly expanded Sun series ends, and they have the opto-coupled variants which work with up to 18 cells.

Sun_4Stars.jpg (27129 bytes)
Kontronik Sun 4000 and four members of the Star-Line

Where they are really different is that the self-adjusting "Automatic Programming Mode (APM)" is only one of 6 different operational modes. The mode programming is done through the use of a jumper plug.  When in place when you power up and then removed after the "armed" three tones or 5 seconds, it starts the mode programming process. This jumper can be seen on the left side of the StarOPT 70-6-18 in the picture just above. In addition to the APM mode (mode 1), there are the following five possibilities:

Glider Mode (2) – which allows you to program and have remembered the motor-on point, the full throttle point, and, if desired, a separate brake-on point. These set points are retained until you go through the programming sequence again or switch to APM mode. The brake is activated after a 0.3 second delay, and the motor cutoff is set to 0.8V per cell. Over-temperature and over-current protections are active, and the throttle curve is reverse exponential.

Motor Plane/Boat Mode (3) – which allows you to program and store the start and full throttle points, and disables the brake. Instead of a hard motor cutoff, the ESC reduces the throttle automatically once the battery voltage falls to 5.5V in order to maintain the battery voltage at that level or higher. This is a little rough in operation – the motor pulses a little bit – but overall it works very well indeed. Over-temperature and over-correct protections are active, and the throttle curve is reverse exponential. This is the mode I used for test flights.

Helicopter Mode (4) – which has a special speed governor function called "balancing of battery voltage or BOB. This increases the throttle to maintain a constant voltage out to the motor at a given throttle stick setting, in order to keep the rotor head speed constant at that throttle setting. Kontronik recommend using a channel on the Tx which is controlled by a slider and using the throttle stick for collective pitch and mixing the two at the transmitter. Both the under-voltage cutoff and the over-temperature cutoff are DISabled in Mode 4, and the throttle curve is linear.

Competition Mode (5) – this mode allows programming and storing the start and full throttle points as in modes 2 and 3. The brake is set to come on instantly and the instructions caution that the airframe must be strong enough to resist the resulting forces (!). Both the under-voltage cutoff and the over-temperature cutoff are DISabled in Mode 5, and the over-current limit is set to its maximum. Note that this mode could allow you to run the drive battery low enough that the BEC function (in the StarBECs) could shut down.

Car Mode (6) – provides a proportional brake and a current limiter set to provide a form of traction control. Over-temperature protection is enabled. The manual says the throttle "characteristic is optimized for cars". I don’t know if this is a linear curve, a reverse exponential curve as used in the airplane modes (1, 2, 3, 5) or something else.

So, you see that Kontronik is trying to cover a wide range of applications in addition to the sport fixed-wing airplane flyer with the Star-Line. I will leave it to someone else to evaluate the helicopter and competition airplane modes, as well as the car mode. I can say that I really like the combination of features provided in Mode 3. See the Kontronik Star table below, which summarizes the controller characteristics in the various modes.

This ability to tailor the characteristics of the controller to your application, along with the reverse polarity protection, make the Kontronik Star-Line unique in the market for conventional brushed motor controllers. If you need any of the special capabilities provided by the Star-Line, or if you just need a 50-70A controller, they are well worth considering. I am impressed.

OK, finally, on to the buyers’ guide tables. Only a few more things to say.

Sharp-eyed readers will see that the Kontronik Sun 4000, reviewed in the last column, isn’t in the tables below. This is because Kontronik has discontinued it in favor of three new Sun series controllers: the 18A Sun 1000, the 30A Sun 3000, and the 40A Sun 4001. The latter two are in the table. These are all a little smaller and lighter than the Sun 4000, and have a brake disable function that operates the same way as that in the Schulze slim-35be reviewed last time. To disable the brake, power up with the throttle stick high rather than low.

This method of disabling the brake is also used by another German unit, the Orbit Control30. So, even though I don’t really like the idea of having to remember to power up with the stick high for some controllers, this method seems to be becoming more common.

Finally, these tables will also be available in Adobe Acrobat format for downloading, as they are very wide and will probably be difficult to print satisfactorily from here.

As always if you have any feedback I may be reached at either ABCawley(at) or abc_quiet_flight(at)

View HTML table or download Apr2001DataTable1_rev1.pdf

View HTML table or download Apr2001DataTable2.pdf

View HTML table or download Apr2001DataTable3_rev1.pdf


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Jul 08, 2007, 04:24 AM
Registered User
BEC's Avatar
Those e-mail addresses for me are out of date. Send me a PM or email from my profile.

Also, it seems the links to the HTML versions of the data tables are broken. The .pdfs still work, though.

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