Alt-BEAM Archive
Message #01569
To: TurtleTek@aol.com
From: Steven Bolt sbolt@xs4all.nl
Date: Wed, 17 Mar 1999 09:24:53 +0100 (CET)
Subject: [alt-beam] Re: More Photovore problems
On Tue, 16 Mar 1999 TurtleTek@aol.com wrote:
> That same photovore (the photophobic one) is having some other
> problems also. When I put it under a bright light, it
> [sometimes] doesn't move and I hear a wierd high-pitched sound.
All published Solar Engine circuits I've seen - except the
SunEaters, especially -II and higher, and variations on
that theme like Ben's `Alf' - are rather prone to oscillation.
That's what you hear. At lower light levels there isn't enough
power to keep the oscillation going, so you don't or hardly notice
the problem there.
> I guess this sound might be the 1381's. This might help: the
> 1381's are the "g", they trigger at about 2.4v.
The 1381 is innocent, as it doesn't even try to latch the on-state.
When it triggers, a circuit behind it has to latch and keep the
motor switched on until either the supply voltage drops below a
certain level, or a timer runs out. It's the latch that is causing
you trouble, together with the motor. It switches power to the
motor, the voltage drops, the 1381 lets go, and the latch fails to
latch. The motor stops before it started, the voltage immediately
rises (caps have a spring-like quality due to their internal
resistance), the 1381 triggers, the latch switches, the voltage
drops... And so on, many times a second.
If you are building a circuit that is known to work, make sure you
use the right parts and that they are connected as they should be.
Best,
Steve
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# sbolt@xs4all.nl # Steven Bolt # popular science monthly KIJK #
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