# looking for opinions on Capacitor placement



## Tesseract (Sep 27, 2008)

oniea said:


> ... most controllers schematics i see have a cap across the + to gnd of the battery *...*. I know this stops the spikes from back emf from the motor...


Nope - that capacitor has nothing to do with with motor; it is there only to decouple the inductance of the supply wiring and smooth out the input ripple that the buck converter produces from drawing current in pulses.



> ...but what i have in my set up is a cap across the motor....


That would probably be an unmitigated disaster (for the capacitor, anyway). A small (sub-1uF) capacitor with a low ohm value resistor in series - in other words, an RC snubber - can be effective at reducing RFI and spikes when placed across the motor, but not a plain capacitor.


----------



## oniea (Jul 29, 2009)

thank you very much for your reply


----------

