Alt-BEAM Archive
Message #01910
To: Jonathan D Rogers chessmaster14@juno.com
From: Steven Bolt sbolt@xs4all.nl
Date: Wed, 31 Mar 1999 10:17:14 +0200 (CEST)
Subject: [alt-beam] Re: Phtotovore senors
On Tue, 30 Mar 1999, Jonathan D Rogers wrote:
> Hey, I'm really having trouble finding the BPW41 photodiodes the Suneater
> 4 photovore is supposed to use.
SunEater_IV is just a kind of Solar Engine, intended for
SunEater_V, which is basically a miniature version of SunEater_III
in SMT, with very tiny pager motors and micro-cassette rubber
rollers as wheels. Still on the drawing board for lack of time...
> I have some photocells,though, so is there a way I can substitute
> them?
Not without changing the (presumably SunEater_III) circuit, and an
elegant way to do that isn't obvious to me.
> If not, where do I get the photodiodes?
A suitable photodiode should not be too difficult to find. You might
try the BPW34.
Looking at the circuit, the photodiodes are selected to give a full
swing from Vcc to gnd within as few degrees of turn (of the
SunEater_III) as possible. Their output must be able to swing a
reasonably low input resistance, to maintain adequate signal/noise
despite the metal feelers which are connected to the same input.
The BPW41's achieve a full swing in about 5 degrees of turn.
(SunEater_III/Photovore motion is shown on
http://www.xs4all.nl/~sbolt/e-fotovoor_beweging.html)
If you want to test other photodiodes, then measure the swing using
a good voltmeter (10M or better input resistance) at the connection
between them. In SunEater_III, de diodes and their (2K7) resistor
are connected to the pulse generator to avoid wasting current. When
measuring the swing, connect the resistor to +.
If all else fails, you could buy a Dutch fl 10 banknote from your
bank (about $5) and mail it to me. That gets you two, perhaps three
BPW41s in return :)
Best,
Steve
----------------------------------------------------------------------
# sbolt@xs4all.nl # Steven Bolt # popular science monthly KIJK #
----------------------------------------------------------------------
------------------------------------------------------------------------
eGroup home: http://www.eGroups.com/list/alt-beam
Free Web-based e-mail groups by eGroups.com
Home