Alt-BEAM Archive

Message #03379



To: westy civic83@execulink.com
From: Wouter Brok w.j.m.brok@stud.tue.nl
Date: Wed, 19 May 1999 14:22:01 +0200
Subject: [alt-beam] Re: phototropic bicore


Hello Shawn,

Let me see if I can answer your questions (If not then somebody else
probably will):

First have a look at
http://people.ne.mediaone.net/bushbo/beam/advnvnet.html and see if your
questions concerninng 'phototropic bicores' are answered, else just mail me
oke?

There are a couple of ways to limit motion of a robotic limp, two of which
you already mentioned:
- mechanical stops, are not such a nice solution of course,
- springs, which are sort of mechanical stops, but are more 'biological'
- end-switches: very practical, but kind of cruel (they just shut down the
power to the motor; it works alright)
- potmeters, mechanically connected to the turning part and implemented in
the bicore-circuit: you can make it such that the time constant (by means
of the resistor) is made smaller when the head is further away from its
centre position. This is a solution which creates a nice and smooth
behaviour of the head, the only problem is that you have to construct it,
which can be difficult, and you have to make something up so that the
timeconstant gets smaller in both directions away from the centre.
- maybe you can construct something which gets in front of one photodiode
when it turns too far. This results in turning the other way around because
there will be more light then, till it stops at a position such that both
diodes (on half covered or so) get the same amount of light.
- .....

Don't use 555's; they are really ugly IC's once you know about BEAM. Have a
look at the stuff which has been sent by Wilf a couple of days back. I
didn't have time yet to study the circuits, but if I remember well it can
also be used as pulse width modulation (PWM) .... I'm not sure though; have
to have a read through it.


Regards,

Wouter Brok.



> 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.
>
> I only need the head to rotate about 15 degrees either way of dead center,
>then stop turning. will the head do that automatically?, 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?
>
> 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???
>
> Thanks for any help.
>
>Shawn Westbrook
>civic83@execulink.com
>
>



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