Alt-BEAM Archive

Message #04371



To: beam@sgiblab.sgi.com
From: JVernonM@aol.com
Date: Wed, 9 Jun 1999 09:52:07 EDT
Subject: [alt-beam] Re: SE questions not found in the FAQ.


In a message dated 6/8/99 7:19:46 PM Eastern Daylight Time, bshannon@tiac.net
writes:

> Does anyone understand why the published circuits are shown this way?
Hi Bob,
I don't have the in depth knowledge of the separate components like you and
Wilf, but I have built a couple of these suckers, and have a comment or two.
First, I replaced the 150k pot. I found the circuit was too light sensitive
below 160k (I'm currently using 167k.) As the sun goes down the light level
decreases, but the circuit switches on too soon dumping it's load while it is
still fairly light out. This didn't work for my application (blinking 8
LED's). I raised the resistance, and it did better. You can take it to far
though. 200k caused the circuit to only partially come on during dusk and
bleed off the power from the cap before it got really dark, giving a very dim
show. One major problem I had was the cap trying to dump all of it's juice at
once, making a very bright, but very short display. Then fading down to a
dull blink for most of the discharge cycle. Wilf solved this by coming up
with a low drop out regulator that allows a more uniform discharge. I think
the circuit was originally designed to be simple yet still work. I can build
one in 5 minutes right on the leads of the cap. I think Wilf's D2 is a much
better design, although more complex.
By the way. Is there anyone out there who can take Wilf's designs and
translate them into component based schematics like what was done with the
BEAMant? There are several of these puppies now and it would be great if
someone could post them in the simpler to read format. I think many builders
out there would appreciate having the reference and would use the circuits
more if they were posted like the ones on Beam Online. I just find it easier
to try them if they are drawn out with the whole chip and pinouts rather than
just the inverters. The power Smart Head, D2, Low Drop Out regulator, etc.,
and many more, would be a great resource for new and old alike.
Jim

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