Newsgroups: comp.robotics
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From: nagle@netcom.com (John Nagle)
Subject: Re: Servo control...
Message-ID: <nagleD4D3EE.BKG@netcom.com>
Organization: NETCOM On-line Communication Services (408 261-4700 guest)
References: <1995Feb21.015352.194775@zeus.aix.calpoly.edu>
Date: Tue, 21 Feb 1995 18:01:26 GMT
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cmayer@harp.aix.calpoly.edu (Chad Erich Mayer) writes:
>Hi--I've been wanting to build a simple servo control using a 555 or 558 
>IC timer so that I can directly control a servo with a potentiometer but 
>I wanted to know if anyone has already done this and know exact resistor 
>and pot ohmage values and capacitor values so I don't have to experiment 
>a million times to find them out. I don't know the exact pulse length or 
>time. I wanted to use a 558 because I could then control pulse width and 
>time pretty simply. I would rather use a 555 because of its convenience 
>and price but I don't know how to configure it so that a specific pulse 
>can be generated. (The length and duration of pulse). If anybody can help me 
>with any ideas-

      We just answered that question yesterday.  Read before you post.

      Assuming you mean a model R/C servo, the drive requirements are
+5 or so to power (red), black is ground, and the other lead is a pulse
train; 0.5ms to 1.5ms ON, about 13ms OFF.  The ON pulse width controls
the position.  Put a big filter cap between power and ground at the servo.

      Radio Shack sells a little Forrest Mims pamphlet on 555 timers
that should answer your questions.  Or read "The Art of Electronics".
Or get the data sheet for the thing.

					John Nagle
