Selfmade SMD speed-control for 6 to 12 cells.
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[translated from German by Josef Hoelzl]
[edited slightly by Eric Behr]

This is my first attempt to translate the german article from the magazine
ELECTROMODELL. Please excuse me if there are some things not described well.

This speed-control is mounted on a double-sided 51x30mm board and has the
following features:

- power-on reset
- soft start
- BEC
- thermal and low-voltage protection
- 2.5 kHz frequency 
- programmable stop and a fast EMK brake

Because  the speed-control is optimized, there are two R3/C3, and it was
possible to implement the EMK brake with fewer parts. The diode D8 cuts
off the peaks of motor induction voltage. The value of the Zener D5
depends on the MOSFETs (T4). With T4 of type SMP60N03-10L (30V), use ZF24
for D5. For a 50V or a 60V MOSFET use a ZF43 or ZF51.

Adjust stop-point with P1. R5 sets full throttle. If you have problems
adjusting full throttle you can change the value of R5 between 82k and
120k. C2 modifies the frequency. D7 is used for low-voltage protection.

The internal diode of the brake MOSSFET (T5) is used as a "free-run" diode.
Although this is acceptable, especially if the control often is used at
half-load, it may be better to use a fast diode BYV28 or a Shottky Diode
MBRD650 as D8. The power section (T4, T5 and the PTC thermistor) should be
mounted directly on the motor.

With more than 8 cells you should mount the voltage regulator IC2 on a
heat sink. Make sure that either IC2 or T4,T5 are insulated. If you don't
use thermal protection, connect the two soldering-points with a bridge.
Otherwise put the PTC thermistor on the heat sink, covering it with
varnish first for insulation.

For IC2 use LM2940(30V) or an LM4940(18V). With more then 8 cells use
LM78S05 (2A). For T4 (used three times) especially for low count of cells,
you should use the logic-level SMP60M03-10L mounted on a heat sink. Now
the circuit will withstand a current of 40A.

I wish you a lot of pleasure building the speed-control.

I hope I've translated the original of Milan Lulic well. To make sure read the
original in the scanned tiff-file.

Josef Hoelzl
Mail: 087422187-0001@t-online.de