Alt-BEAM Archive

Message #04219



To: beam@sgiblab.sgi.com
From: Wouter Brok w.j.m.brok@stud.tue.nl
Date: Thu, 03 Jun 1999 19:45:51 +0200
Subject: [alt-beam] Re: Bicore, wasting energy


Hello,

Thank you for the suggestion.
First I have to mention that the in my mail a couple of minuted ago I
mentioned the three-state idea and forgot to tell that it wasn't my idea
(think it was Peter Low's idea ...)

The idea of using the energy if the head isn't turning to charge a battery
or so I like a lot ... have to have a look at the photovore-circuit since I
don't know by heart how it looks like.

I'll probably be away till monday .... hope you guys will surprise me with
a solution; meanwhile I'll keep thinking.

Regards,

Wouter Brok.


>How about using a photovore circuit that sends voltage to the bicore if the
>head is off-target, and sends voltage to some other component (a battery
>charger) if the head is on-target. Yes, I know, this is essentially the
>same thing as my tri-state photovore idea, but I suppose some of the
>brighter minds on the list could refine the theory.
>
>The triviality of the problem decreases with the addition of additional
>design constraints (bicore, only use X parts, etc). I guess this is my
>duct tape solution.
>
>Anyone know of a way of creating an off/on switch with a
>photoresistor/photodiode?
>
>
>At 04:55 PM 6/3/99 +0200, you wrote:
>>Hi,
>>
>>>Problem:
>>>The suspended bicore is a very, very nice little circuit, but using it in a
>>>typical light-seeking head application results in efficient light-seeking
>>>behaviour, which is paid for by a large, and in my opinion, redundant
>>>energy-consumption. This can be done better and I think this would make the
>>>bicore rise in its value for Beam.
>>
>>Ok lets analyze the problem. A bicore will be used to control the motor. A
>>special circuitry is needed to disable the motor ones the head is locked
>>into position. When the duty cycle of one of the outputs is around 50%, we
>>can say that the head is locked on the light source.
>>Here we go.
>>
>>- Reference pulse:
>>
>>When the head is locked, the outputs of the bicore will have a signal with
>>a duty cycle of around 50%. Comparing one of the outputs with a reference
>>signal can show if the duty cycle is 50%. Using an XOR function with a
>>filter can generate a good signal. Problem however is the cycle time of the
>>bicore, it isn't constant all the time. It depends on the light conditions.
>>So a fixed reference signal won't work.
>>
>>- Variable reference:
>>
>>Output 1 of the bicore can be used to generate a reference signal (for
>>instance charge a capacitor). Output 2 can be checked against this
>>reference signal (generated by output 1). The reference signal has to be
>>updated every time output 1 becomes active. This could work but will
>>require a lot of electronics to update the reference.
>>
>>Problem with above approach:
>>
>>Normaly the output signals turn the motor immediately. With the above
>>approach, it isn't real time anymore. First you check the duty cycle and
>>then you decide to power the motor. What will you use to switch the motor
>>on? The outputs from the bicore are gone when you finally know that it is
>>ok to switch the motor on. You could check the pulses once and then run the
>>motor on the bicore for a few cycles, then check the pulse again. It will
>>save some energy but not much (50% maximum if you check the pulses one
>>cycle and let the motor run the next cycle).
>>
>>Conclusion:
>>
>>This problems needs some serious thinking. Can't come up with an answer
>>right now. Maybe other people have an idea.
>>
>>
>>Evaristo
>>
>>Gizmo homepage: http://www.crosswinds.net/~evaristo
>>
>
>

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