Alt-BEAM Archive

Message #05031



To: bshannon@tiac.net, beam@sgiblab.sgi.com
From: Steven Bolt sbolt@xs4all.nl
Date: Mon, 5 Jul 1999 10:56:56 +0200 (CEST)
Subject: [alt-beam] Re: Something funny with the 1382 voltage triggers?


On Sun, 4 Jul 1999, Bob Shannon wrote:

---8<---
> The problem is lock-up under full sun. The problem does not
> happen with indoor lighting unless the photovore is held abut 5
> cm from a full spectrum desklamp.
>
> Trouble shooting with a scope gave me a supprise or two. First,
> the SE is not oscillating.
> Secondly, the lock up condition happens at low cap voltage,
> rather than just before the trigger point.

The 1381 plus 2-transistor latch type SE needs the voltage to drop
to less than about 0.7V before the latch unlatches and recharge is
possible. If the load (motor) draws insufficient current at low
voltages (or the solar panel supplies too much), this low level
isn't reached.

The best remedy is to use a time constant rather than a voltage
level to switch off the SE. This principle is illustrated by
SunEater_IV and _V. Both switch on when a voltage level is
exceeded, and switch off after a certain time.

Linkname: SunEater_IV
URL: http://www.xs4all.nl/~sbolt/Other/suneaterIV.html
Linkname: SunEater_V
URL: http://www.xs4all.nl/~sbolt/Other/suneaterV.html

---8<---
> Last question, what is the limit of a photopoppers ability to
> climb over obstacles?

With direct drive, about nil.
However, if you put the direct drive on top of rubber-tyred idler
wheels, performance improves a lot - especially if you use decent
small recorder motors instead of pagers!

Linkname: SunEater_III
URL: http://www.xs4all.nl/~sbolt/Other/suneater.html

Best,

Steve

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# sbolt@xs4all.nl # Steven Bolt # popular science monthly KIJK #
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