Alt-BEAM Archive
Message #00922
To: Justin jaf60@student.canterbury.ac.nz, beam@corp.sgi.com
From: "George Rix" rix.g@bmts.com
Date: Wed, 24 Feb 1999 10:48:48 -0500
Subject: [alt-beam] Re: (bicore photovore)
> If you've been following my ongoing attempts, most of this won't be
> news, but however:
>
>> Okay, I made myself a bicore-powered photovore last night (well, I
>> breadboarded it anyway) and I was wondering:
>> Is there any way I can make it solar-powered without using the PM1 SE,
>> anyway easier, I mean?
>
> The schematic at
> http://www.geocities.com/SoHo/Lofts/1121/beam/bivore.gif
> has a very efficient solar engine (Alf/SuneaterII style) build on the
> same chip as the bicores, but the schematic is out of date, as I'm
> trying to get the rest of it more efficient. (The schematic shown draws
> around 200mA, and so far I've made changes on my breadboard that have
> got the circuit down to about 70mA, but I still want less (down't quote
> that out of context :-))
Well, I got a source for 1381s and 2N7000 MOSFETs, so since that was the
only barrier, I'll use the PM1 SE anyhow. Sorry =)
> This method of solarising it might or might not be easier, depends on
> you and what you want :)
> You can also go for a simpler, smaller, and less efficient solar engine
> (and fit it and the bicores on a 14-pin IC insetad of 10) by ditching
> the pulse generator part of the SE, but I havn't got a schematic of that
> online ATM.
>
>> Also, it works, but it isn't very sensitive to light. I predicted
>> (correctly, by my dad's estimate) that it would turn towards the light but
>> VERY slowly. I'm using two 1.8 meg resistors with my photodiodes, and no
>> trim pot. Should I take away one of the resistors, add a trim pot or what?
>
> How does your bicore direct the bot?
> Eg, is it driving a steering wheel? or do you have a bicore for each
> motor? or one bicore triggering both motors, and triggering one more
> often depending on light?
The last one. Just like the photopopper.
> Lower the resistors, or remove them if you can, (perhaps replace them
> with pots and fiddle until it's doing what you want it too, then measure
> the resistance of the pots and swap them for similar resistors,
> preferably of the same value :).
Hey! It works!
> If you're looking at a photopopper style of vore, you might want to
> consider the sensor arrangement noted in the schematic I indicated. It
> makes the bot pivot to face light, then go forward when it is facing the
> light. It also allows easy addition of tactile-sensor induced pivoting
> and reversing.
I like it the way it is now, so, since I'm mainly making it to prove a point
to my dad, I'll leave it like this for now.
>> Also, where should I attach tactile sensors, assuming I make them?
>
> You can short them across a photodiode, (depending on your resistor set
> up, you might want have to add one to the tactile sensor as well, but
> I'm assuming that's not the case). If you want the tactile sensors to
> continue to reverse the bot after they've connected and opened again,
> you'll need some sort of timing circuit. I've worked out one
> http://www.geocities.com/SoHo/Lofts/1121/beam/bireverser.gif
> That works fine. Ideally, I'd like to get rid of that transistor, but I
> havn't found a way to do that without influencing the bicore. Another
> timing circuit can be added accross the remaining photodiode for a
> sensor for the rear, or for a somewhat useless "I'm being attacked by
> something - run!" sensor :-) (Have the cap trigger a transistor over the
> other bicore's sensors as well to produce a blind march forward :)
That makes good sense. Thank you VERY much for telling me all this, I've got
it working, so I just have to make the tactile sensors before I solder it
all together.
Thank you everyone!
Signing off,
Rob Rix
'If anything can possibly go wrong, it probably already has'-Murphy's law
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