Alt-BEAM Archive
Message #09698
To: beam@sgiblab.sgi.com
From: cactus@dynamite.com.au
Date: Wed, 2 Feb 100 06:25:02 GMT
Subject: [alt-beam] Motorised Trimpots
I found a motorised trimpot at DSE the other day and I thought it might have
some BEAM applications. These are the things that they use in stereos with
analogue remote control volume. A little motor actually turns the volume dial.
The motor runs on only 40 to 50 mA (50 at "stall" - the motor doesn't stall,
just the trimpot output shaft. A friction device lets the motor continue
running) but requires about 4.5V. It's about the same size as a pager motor
and I think you could easily replace it with one (if I had any, I'd try it).
The gearbox uses two wormdrives (ie totally non compliant) to give a gear ratio
of (from memory) about 500:1. The output shaft turns at about 6 rpm. Since
some pager motors run at about 11000 rpm, you could probably get the output
shaft up to about 22 rpm by replacing the motor.
Of course, a trimpot is already built in so you could easily use one of these
in Wilfs' one motor walker/crawler (Wilf, am I right in thinking that with
feedback from the trimpot you no longer need a compliant gearbox?), though even
at 22 rpm, it would be a bit slow.
At 6 rpm, you could attach a couple of these to some large (say 10cm diameter)
wheels and get good ground clearance at a reasonable speed.
You could also make a very slow turbot.
Those are about the only ideas I've had for how to use one. I'd be interested
to hear other peoples' suggestions.
The DSE website is http://www.dse.com.au/cgi-bin/DSE.storefront
and you can see
the trimpot by searching for cat no R7830
It costs A$8.95.
Simon.
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