Alt-BEAM Archive
Message #03378
To: westy civic83@execulink.com, beam@corp.sgi.com
From: Dennison dennlill@buffnet.net
Date: Wed, 19 May 1999 08:12:00 -0400
Subject: [alt-beam] Re: phototropic bicore
Well, bicore is a variation of the Microcore. And it's simply a control
circuit. No bicore is 'phototropic'. A head can be made phototropic by
altering the time durrations of the pulses. IE: Playing with the resistors.
So to make a phototropic head, instead of resistors, use either cds cells or
photodiodes.
> Hello, I was wondering if anyone can point me to info on phototropic
>bicores, I have the schematic from beam-online, but have a question about
it.
>
What?
> I only need the head to rotate about 15 degrees either way of dead center,
>then stop turning. will the head do that automatically?,
no, it will keep turning, unless it's phototropic, in which it will turn
untill it point to the brightest source of light.
there are
>mechanical stops that will prevent it from turning past that, but the
>bicore will still try turning the motor, which I can see burning something
>out eventually? I was thinking of limit switches singnaling that the end
>of travel has been reached. Any ideas?
You may be right, you may not. Anyway, limit switches are a very good idea,
and will do the job fine. Wilf and I discussed this problem in the past and
he suggested that the HEAD be attached to a spring.
>
> Also, any ideas for a curcuit that controlls the speed of a motor
>proportional the the amount of light falling on a cds cell, I was thinking
>of a 555 circuit of some sort, using the cds cell to vary the resistance
>causing the timing of the 555 the vary???
Sure that would work, Just attach the output of the 555 timer to the enables
of the the 74hc245 driver chip.
>
> Thanks for any help.
>
sure!
Dennison
>Shawn Westbrook
>civic83@execulink.com
>
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