Electronic Speed Controls for Radio Controlled Models

A speed control takes a pulse-width modulated signal from an R/C receiver and converts it to an amount of power delivered to an electric motor. Here is my understanding of the way they work. The crucial part is a power MOSFET transistor (or a bunch of them, connected in parallel so they can deliver a greater current and present less resistance).

Several plans for speed controls appeared in hobby magazines. I am collecting them for my personal use, but since there are many others interested in building them, I decided to put some of the plans on this page. There are obvious copyright issues involved here. The plans are strictly for non-commercial use by individuals. I believe that this is in accordance with the "fair use" doctrine (as if you went to a local library, and made a Xerox copy). I tried to give proper credits and attribution to the authors.

If you have a speed control plan to contribute, or if you have built one and want to share your experiences, please send me e-mail, and we'll discuss the details. Please note that as a rule I will only be including links to sites which offer such information for free downloading (with rare exceptions made where I feel that the link can assist hobbyists in designing or building their own project).

As time allows, I will be adding more details: US parts equivalents, PostScript diagrams based on the TIFF files, etc. Please note that even though I'm doing my best to be accurate, I am not an electronics genius, nor a polyglot; I can make mistakes while interpreting the materials I have.


Most home-grown ESC plans are by design simple. This also means that they will be, as a rule, less reliable and more temperamental than commercial units. An ESC is supposed to detect pulses whose width is varying a little bit, and convert those variations to a big voltage swing which controls the FET. All this has to happen in a nasty environment: vibration, interference from the motor, etc. It isn't a trivial job.

If you are not experienced with debugging such electronics, if you don't have access to tools such as a good multimeter and a decent scope, or if your construction skills aren't great, take my advice: go to a hobby shop and buy a simple ESC for $40 or so. If you try to build one, you'll probably just end up wasting money, time, and feeling frustrated - not to mention possibly endangering yourself and others.

Important: as opposed to most commercial ESCs, most of the simple designs collected here do not have certain special safety features such as arming circuits or false pulse detection. It is common for them to turn on spontaneously when the power is applied, when the transmitter is nearby, or when some interference confuses the circuit. The moment you turn on the battery start behaving as if the motor were running - keep the prop away from anything it can damage (and you did dull that razor-sharp plastic prop with sandpaper, didn't you?)


This page expands chronologically towards the bottom, so the newest acquisitions are the farthest down.

Here are some comments about the designs, kindly provided by Søren Kjær Nielsen.

Off-site links

Personally I'm leaning towards digital designs using microcontrollers. They are likely to be more reliable and usually even simpler than the analog ones because a lot can be done in software. Here are some remarks about microcontroller chips in general, and about speed controls in particular. A nice design appeared in the Feb. 97 issue of Elektor Electronics; my copy has the author's name cut off, but it seems that the design is by Andreas Voggeneder (see links listed above). Andreas gave me his kind permission to put my own copy of his article online - here it is (but without the code). [added in August 2006] Thanks to Victor de Lang we finally have a PDF copy of the complete article from the Dutch Elektor.
[added in May 2004] Gustav Kuhn kindly sent me his 16F84A program for Voggender's ESC. Download (at your own risk) the assembly source or a compiled version. You may also want to look at the 16F84A header file used by that code and at some notes from Gustav.
[added in October 2009] Jason Markham sent me an updated version of Voggender's microprocessor control. Here's a zip archive of all the files. Thanks!

I recently decided to roll my own, and started writing up some of my experiences with trying to beat it into submission. But if you are looking for a working unit, check out Mike Norton's or Andreas Voggender's ESCs which are pretty close to what I was planning to achieve. I guess I'll never finish mine now! ;-(

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