Newsgroups: comp.robotics
Path: brunix!news.Brown.EDU!noc.near.net!howland.reston.ans.net!usc!cs.utexas.edu!csc.ti.com!tilde.csc.ti.com!mksol!strohm
From: strohm@mksol.dseg.ti.com (john r strohm)
Subject: Re: DC motor speed control
Message-ID: <1993Sep12.181816.2468@mksol.dseg.ti.com>
Organization: Texas Instruments, Inc
References: <dkj-110993093923@kip-87.apple.com>
Date: Sun, 12 Sep 1993 18:18:16 GMT
Lines: 13

In article <dkj-110993093923@kip-87.apple.com> dkj@apple.com (Dave Johnson) writes:
>Speak to me of motor speed controllers, please, for little toy DC motors.
>In the past I have rolled my own PWM with a 555 and a power transistor. Now
>I want to control the speed with an analog voltage rather than a pot, and
>I'm sure I can build a circuit do it (eventually), but I'll just bet
>there's an easier way. I know there are PWM chips out there. Anybody used
>these? Are they exceedingly cheap? (a definite requirement). Am I wasting
>my time with 555's? E-mail or post, please.

Actually, a 555 can do PWM from a control voltage.  One of the input pins
is for just such a purpose.  Usually it is bypassed to ground.  Check a real
databook (National Semiconductor Linear databook, if you have it.) for the
gory details.  It is either pin 4 or pin 5, I think pin 5, on the 8-pin DIP.
