Society of Robots - Robot Forum

Software => Software => Topic started by: Chris_Balls on May 20, 2009, 07:03:16 AM

Title: Drive voltage for servo????
Post by: Chris_Balls on May 20, 2009, 07:03:16 AM

I've built the 50$ robot and would like to know if any body could help me with the outputs from pd0 pd1 which drive the servos. I'm getting very low outputs at the moment in the terms of milli volts surely this cannot be right?? Any help would be greatly appreciated

Title: Re: Drive voltage for servo????
Post by: Webbot on May 20, 2009, 12:03:43 PM

You are probably trying to measure with a volt meter.

The signal sent to the servos is a pulse. For 'center' it is a 1.5ms pulse every 20ms. So its only high for 7.5% of the time. So if you are using 5v then 7.5% is about 0.375v (forgetting about mean vs RMS etc).
So it is expected that you would see a small voltage.

The difference between full-reverse and full-forward is only 0.5ms either side of this. So the voltage on meter will only vary by a very small amount.