diodes / caps on brushed motors

[humbug 36]

I have a few hot brushed motors that I would like to play around with.

In particular, I have a 15T modified motor with 3 tantalum caps soldered on the motor, however, with my am radio set, its still really glitchy. So I was guessing I need to solder on a big diode or cap onto my speed controller? I think I have a novak schottky diode, but I have no idea which way I stick it on or if it is even going to help me.

Any info would be greatly appreciated

[WillyChang 1814]

Schottky diode is only for use with NON-reverse (fwd only) ESCs.

It is connected "REVERSE" across the motor terminals,

ie it does *not* conduct when motor is powered forwards.

All it does is to zap the Back EMF spikes generated by motor

before they can travel back up the wire to harm the ESC's FETs.

(it helps reduce FETs' temperature a little bit)

Big cap on ESC battery leads is "power cap" giving more "punch".

Also helps with brownouts if battery isn't giving enough juice on high demand.

Tantalum caps on motor supress some EMF but more importantly

is the motor properly serviced? Won't help much if the comm is square

and the brushes are worn to a stump, brush springs are shot

= endbell lights up like an arcwelder.

If your AM radio set is glitchy, assuming its all working good... have you installed it right?

RX should be far away from ESC as possible, don't run motor wires near/over RX etc

If chassis is a big conductive plate (alloy, CF) then RX should be distanced from the plate

with several layers of servotape; also try mounting RX perpendicular.

[speedy_w_beans 4272]

A few things you can try.

1) Replace the ceramic capacitors on your motor with larger (higher value) ceramic capacitors; this will snub the noise a little better.

2) If the distance between the ESC and brushed motor allows for some slack in the wiring, twist the motor wires on the motor and ESC together like a peppermint stick, barber pole, twist tie, etc. By twisting the wires the loop area of the motor circuit is minimized, reducing noise emissions. Also by twisting the wires together each wire generates a field in opposing direction to cancel each other out.

3) Do the same (twist the wires) to the battery as well.

4) As Willy mentions, mount the receiver and run the antenna far away from the ESC and motor, spaced away from metal structure. Also make sure the motor is in top condition.

5) If all that fails, switch to a 2.4 GHz radio system -- they are much more resilient against interference.

-Paul