Driving servo on pure DC

akio123008 · December 3, 2019

Hello everyone,

A servo is usually connected to some power source, and also to a PWM signal source (such as an arduino), where the duty cycle of that signal determines how much the servo moves. As far as I know, most servos map a duty cycle to a position of 0 to 180 degrees.

Ok so far, so good, but here's what I'm wondering; if I connect a DC source directly to the signal wire, that's technically a 100% duty cycle, so it should turn to 180 degrees right? Or would this destroy the servo somehow? What I'm planning to do is to attach a servo straight to a switch so that when you flick the switch it'll turn 180 degrees. Would this work?

Nene · December 4, 2019

Probably not. Servos are looking at the timing of the PWM signal, from 1000 µS to 2000 µS out of 20 ms interval pulses.

That puts you firmly into the Undefined Behaviour realm.

Why not use one of the servo testers you can get?

akio123008 · December 4, 2019

10 hours ago, Nene said:

Probably not. Servos are looking at the timing of the PWM signal, from 1000 µS to 2000 µS out of 20 ms interval pulses.

That puts you firmly into the Undefined Behaviour realm.

Haha yes indeed, but this project requires the amount of electronics to be absolutely minimal, so I thought perhaps it'd work. But if there's no way to be sure what it'll do I guess it's not such a good idea.

10 hours ago, Nene said:

Why not use one of the servo testers you can get?

This is an extremely good idea. I guess I can just set the tester to 180 degrees and then switch it on using a simple power switch. Thanks a lot for the great suggestion!