>            Very interested to hear about the PIC being used for the speed
>controller or perhaps soft start.  I am very interested in electric flight,
>I was even at the 94 F5B world champs and saw Tal Nizri fly, really
>something to see. I think he is still flying and selling the CLASH, a real
>nice plane.
>Do you have any info on the circuit for a PIC based unit or is it the
>British one.  I have only seen ads for the British one, the author doesn't
>seem to be interested in sharing the design.
>Re the PIC based unit, myself and a friend (who is a bit of a PIC whiz) have
>kicked the idea around of making a multiconfigurable unit but any help you
>could give would be most appreciated.
>Thanks  Kim Turner.

As I'm always working ... I don't have so much time to do something else ...
I build glider, developp some programs ... and electronics cards ...
My last research on the "DC motor control subject" shows there are'nt
difficulties to build an electronic unit to drive motor.
I don't know if we talk about the same British PIC based unit, I saw the Ken
HEWITT schematic.
Anyway, I have done some experience with a SPEED600 (DC MOTOR for R/C
plane), a 7 elements battery pack and 3 MOSFET STP60N06. No problem for
thermal dissipation, loose voltage on MOS-FET is low, less than 0,2V, DC
current is about 12A.
STP60N06 have the following characteristic:
        RDS_on = 0,02 OHM
        ID (at 25degree) = 60 A
        ID Max (pulse) = 240 A
        Max POWER dissipation at 25 degree = 150W
        VDS Max = 60V
This MOS-FET is available from: Radio Spare Componnent or FARNELL Components
in FRANCE.
If you decide to use another, there is no problem. You must be carrefull
about the RDS_ON parameter wich is the most important.
- To avoid reverse voltage, you must connect a fast diode, like TV Diode:
BYT xxxx or something else.
- to drive MOS-FET as fast as possible, it's necessary to use a MOS-FET
driver like:
        EL 7242 or EL 7252  from ELANTEC (available from Radio-Spare Components)
     or EL 7202 or EL 7212  from ELANTEC (available from Radio-Spare Components)
These drivers have TTL/MOS interface and needs only 5V to run.
- If you want to use this controller for a plane, it's better to put a break
circuit inside: means to put a MOS-FET directly on the motor to stop-it when
there is no more power. This seems to be a little bit dangerous, because you
must avoid to have at the same time:
        - the power MOS-FET ON
        - the break MOS-FET ON
In that case you risk a lot of smoke !!!
- PWM frequency to make a soft start seems to be around 2KHz as some
measurement on commercial unit shows it.
- In addition, you can make a PWM regulation of power to drive the motor, I
mean:
        - MOTOR can be drove only at 7,2V for example (SPEED600 case)
        - Battery voltage is 14 x 1,2V = 16,8V
To double the POWER time (normally a SPEED600 with 7 elements pack is about
3 minutes), and not destroy the motor by to high voltage and current, it's
possible to make a PWM regulation.
- getting and separate R/C signal is easy with interrupt possibilities (use
PIC16C71)
I already wrote code for 16C57 to get R/C signal.

Such a design seems to be not so hard to do, just a little bit long to
experiment. As I tell you, I don't have so much time and prefer to spend a
lot of money to buy a ready-to-plug unit (to put inside a glider). In
addition a little computation shows the commercial cost is lower than the
do-it-yourself cost, but making electronics board is not to earn money ...
only to have fun!

Regards,
        Philippe.