Alt-BEAM Archive

Message #11881



To: beam@sgiblab.sgi.com
From: "Dennison Bertram" dibst11+@pitt.edu
Date: Tue, 14 Mar 2000 22:39:32 -0800
Subject: [alt-beam] Re: FRED Componenet alternative



I'm not familiar with the FRED circuit, however I would likely lean towards
the answer: no. While the resistor change, from 2.2k to 3.3(k I assume) is a
reasonable substitution as they are close in value, the capacitor swap is a
different story. I would say it's highly unlikely that you could make such a
dramatic substitution. The difference between a 4700uf and 4.7uf is very
large. Whatever circuit you made a substitution like this in, it would alter
the behavior of the circuit dramatically. When makeing substitutions, try to
get close values, unless your selecting for something specific. But, as I
said I'm not familiar with 'FRED' and your unlikely to damage any components
in swapping them around so I would just say, try it and see what happens.

dennison


Sorry - one other question,

Is it possible to make some componenet changes in the FRED design. Have a
4700uf cap and 2.2k resistors instead of 4.7uf cap and 3.3 resistors?
______________________________________________________



11882 Wed, 15 Mar 2000 10:55:08 -0500 [alt-beam] Re: 1000k pots beam@sgiblab.sgi.com "Sathe Dilip" Try connecting a 110k ohm fixed resistor in parallel to the 1000k pot.
This will bring the effective pot value for the rest of the circuit to
(110 X 1000/1110 =) 99.099k. The adjustment part should also work ok.

CdS photocells are the same as light dependent resistors (LDR).

Dilip
--------------------------------------

Corey Centen wrote:

> Are 1000k pots too high to make a standard photovore? I couldn't find any
> small 100k's at radio shack, I think they were all out. Also, can
> photoresistors be used in the place of photodiodes? I got something at radio
> shack called cadmium photocells. I'm not sure if they are the same as the
> photodiodes or resistors? Any help would be appreciated.
>
> Thanks!
> ______________________________________________________
>


11883 Tue, 14 Mar 2000 22:49:37 -0800 [alt-beam] directional indicator for Bicore heads. "Dennison Bertram" Here's another one from the old files:

I have yet to test this idea, but back when I was working on bicore heads
with Depth Perception ablities, I was wondering how I could create a circuit
which would tell me the directional angle that the Head was turned in. So
here's the idea, which I'm curious to see what others think about it. Each
motor out line from the Bicore is connected, through a resister to a
Capacitor. When the motor out line is "high" It charges the cap, however
when it's "low" it discharges the cap. Now, if this was attactched to a high
frequency bicore head, you should be able to roughly judge the direction the
Head is pointing in by measuring the average voltage across the cap. The
voltage across the cap should represent a fucntion of the 'high' and 'low'
durations of the bicores outputs. The higher the voltage across the cap, the
more often the bicore output was in the 'high' state. The lower the voltage,
the more often the bicore output was in the 'low' state. I had thought of a
few applications for this type of circuit but never actually tried it. For
your perusal.

dennison

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