Question on servo and electrical noise

Most of the better servos have bycaps caps on the motors and other techniques that filter noise pretty well. After all, the average R/C airplane has 3-4 of these things, and it wouldn't do to have noise interfering with the receiver, and bringing the whole thing out of the sky.

In any case, because you need to move the servo to a given position in order to take a reading, you'll actually be stopping the servo to take that reading. (You can sweep open loop, or you won't know where the sensor is pointing as it fires off.) If you remove the pulses after the servo has reached its transit point then the motor will be effectively off, and no noise will be generated.

What most folks do is sweep a degree or two, wait a pre-determined time to let the servo settle, then take a reading on the servo. This isn't a process that, at least when using name-brand servos, appears to generates a lot of interference noise.

-- Gordon

They shouldn't interfere via RF hash. But check for interference via the power leads. The sonar and the servo should be on separate regulators, and the sonar needs a big capacitor (100ufd, at least) to absorb the spikes it puts into the power rail.

Get hold of a scope, and filter until you see no spikes on the power or ground lines bigger than 100mV.

John Nagle

John Nagle wrote in news:ofhte.860$ snipped-for-privacy@newssvr13.news.prodigy.com:

Gordon,

Guess I just wasn't thinking about the sonar being motionless when firing. Makes sense. Thanks.

John,

Thanks for the tip, I'll dust the scope off.

Joe