Newsgroups: comp.robotics
Path: brunix!sgiblab!sgigate.sgi.com!olivea!hal.com!decwrl!netcomsv!netcom.com!nagle
From: nagle@netcom.com (John Nagle)
Subject: Re: Servos: How do I make it work?
Message-ID: <nagleCGs0HK.D6C@netcom.com>
Organization: NETCOM On-line Communication Services (408 241-9760 guest)
References: <1993Nov18.170703.15521@njitgw.njit.edu>
Date: Sat, 20 Nov 1993 05:56:06 GMT
Lines: 20

rxy5310@hertz.njit.edu (Rolan) writes:
>I recently received a servo and I'd like to find out how  
>to operate it.  It seems to be used for a RC car or airplane.
>There are 3 wires leading out of it- red, black, and white.
>Any info would be appreciated.

      Black is ground.  Red is +5 or so.  White is the control input.
The control input is a 60Hz or so square wave with a duty cycle of
about 0.5ms to 1.5ms on, 13ms or so off.  On time controls the servo
position.  On time should have no more than a few microseconds
jitter to avoid unwanted servo movement.  Off time can jitter several
milliseconds without harm.  Usually, a CMOS output is sufficient to 
drive the control input.  The power input can draw considerable current,
and may generate motor brush noise, so it should be isolated from logic
supplies.

      These things can be run nicely off of most microcontrollers with 
on-chip timers.

					John Nagle
