Alt-BEAM Archive

Message #04259



To: beam@sgiblab.sgi.com
From: Evaristo Westplate evaristo@qctechnology.nl
Date: Fri, 04 Jun 1999 15:40:59 +0200
Subject: [alt-beam] Re: Bicore, wasting energy


Hi,

>How can this be done: if one output of the bicore is averaged (with a
>low-pass rc-filter) this signal can be fed to the V+ input of one opamp and
>to the V- input of another opamp. The other inputs of the opamps can be
>connected to the different parts of a bridge of wheatstone (those inputs
>should be fed with reference voltages to define the interval around Vcc/2 =
>50% dutycycle and this can be done with a couple of resistors in a
>wheatstone-like configuration ... will draw it sometime and send it).
>With the outputs of the inverters connected to an AND-gate (which can be
>made out of majority logic, like introduced by Wilf a couple of months
>back) we have a signal for
>stop.
>The rest of the signals: left, right and PWM we have already with the
>circuit I drew and posted at the beginning of this week.
>
>Part-count: two inverters in the bicore
> two opamps (in a single dual-opamp-chip) for the stop-signal
> one inverter for the majority logic
> one inverter for the left and right-signal
> one inverter for the PWM (like can be seen in the drawing)

Hmmm, a lot of components. It would be easy if you don't use a bicore. You
could simply put the two photo diodes in series with the power supply. The
voltage coming from the photo diodes will vary between Vcc and ground. Feed
this to a "window" comparator (2 op-amps) and you're ready. The outputs
from the op-amps will indicate: left, equal or right. Just thinking. What
if the voltage is sampled between the photo diodes in the bicore. Hmmm I
should measure it to know how it looks. It will probably be a charge
curve..... Have to look at it some more.

See'ya


Evaristo

Gizmo homepage: http://www.crosswinds.net/~evaristo



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