Re: from breadboard to hard wired

From: Terry Pinnell (terrypinDELETE_at_THESEdial.pipex.com)
Date: 08/03/04 

Date: Tue, 03 Aug 2004 17:24:15 +0100

Michael Eisenstadt <michaele@hotpop.com> wrote:

>Generous readers of this forum walked me through
>the building of a Pulse Width Modulator. This
>was earlier in the year in January.
>
>The project was to reduce the speed of a small
>12v DC motor which turns a 4 foot disk, in this
>case a painting on canvas mounted on a round
>laminated wooden stretcher, so fairly light.
>The point of the PWModulator is to conserve the
>batteries which power the motor whereas a voltage
>regulator would discharge the batteries faster.
>
>Other things intervened but having returned
>to the project I was pleased to see that the
>electronics work and that the speed of the
>motor can be adjusted to very slow.
>
>I now need to hardwire the components. As a
>total newbie, I am not even sure which side
>of the board the components are mounted
>on.
>
>The schematic of the PWModulator and pictures
>of the breadboard with components and of two
>sides of boards for hardwiring is at
>http://www.charlesumlauf.com/wiring.htm

You've got me puzzled. That circuit looks like a simple square wave
oscillator. Its duty cycle will therefore be roughly fixed. Yet you
say you can vary the speed of the motor? That's what the author claims
for his 'Pulse Width Modulation' circuit too. Surely, PWM keeps the
cycle period (and hence frequency) fixed, while changing the duty
cycle? adrift somewhere. Can someone clarify please?

-------

To build it, I'd use perfboard, with copper strips. The holes for the
MOSFET, and for the heavyish duty wires to the motor, will probably
need drilling out slightly (to maybe 1 mm). Use a 14-pin DIL socket
for the 4011. Drill holes in two corners of the small board if you
want to mount it in a small case. Alternatively, with such a compact,
light board, a piece of sponge will secure it adequately. A hole in
the case will accommodate your pot. 

-- 
Terry Pinnell
Hobbyist, West Sussex, UK

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