Alt-BEAM Archive

Message #02706



To: "BEAM Mail" beam@corp.sgi.com
From: "Nigel Joyce" nigel.joyce@qr.com.au
Date: Wed, 28 Apr 1999 10:23:12 +1000
Subject: [alt-beam] FLED Photopopper Question



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Hey everyone,
Sorry to annoy you with another debug question =

but here goes. I breadboarded up a FLED photopopper circuit =

using the design supplied by Nik

=

Now I used 2.2k resistors off the base of the 3906's, =

3906 and 3904 transistors, 5mm Green FLED's, 5mm
Photodiodes, two pager motors, a 4700uF cap and a =

2433 solarcell. (on the diagram I put the FLED's =

closest to the transistors, does it matter?)

Because I used new matched components, I didn't
see the need to use a trimpot between the photodiodes
and gnd. (is this assumption correct, or do I still need
resistors between the photodiodes and gnd?)
Now, it doesn't work. I have a multimeter although =

I don't know how to work it properly yet, I watched =

the voltage across the cap rise up to 3.25v in full sun, =

don't know about the capacitance though, measured =

the voltage across the FLED go up to 2.45v and the =

voltage across the photodiode go to 0.7v (should I be =

measuring the resistance across these to debug?) =

anyway I sat there for about 15 Min waiting for it to fire =

and nothing. =


Do you guys have any suggestions about how I can get =

it to work? What I am doing wrong? The only thing =

different between the above diagram and my circuit is
the trimpot, I just have the diodes in series to gnd.

Any help would be appreciated, Thanks in advance.

Blue Skies
---Buzz---
nigel.joyce@usa.net


------------------------------------------------------------------------
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>
=3D0 =

src=3D"cid:013c01be910d$4d408930$8d3e580a@qrail.com.au">
Now I used 2.2k resistors off the base of the 3906's, =


3906 and 3904 transistors, 5mm Green FLED's =

size=3D2>, 5mm

Photodiodes, two pager motors, a 4700uF cap and a =


2433 solarcell.
size=3D2>  (on the diagram I put the T =

size=3D2>FLED's

closest to the transistors, does it matter?) V>
 

Because I used new matched components, I didn't<=
/DIV>
see the need to use a trimpot between the =

photodiodes

and gnd. (is this assumption correct, or do I still =

need

resistors between the photodiodes and gnd?) >
Now, it doesn't work.  I have a multimeter althoug=
h =


I don't know how to work it properly yet, I watched =


the voltage across the cap rise u=
p to =

3.25v in full sun,

don't know about the capacitance =
though, =

measured

the voltage across the FLED go up=
to 2.45v =

and the

voltage across the photodiode go to 0.7v ze=3D2> =

(should I be

measuring the resistance across these to debug?)=

size=3D2>

anyway I sat there for about 15 Min waiting for it=
to =

fire

and nothing. 

 

Do you guys have any suggestions about how I can get =


it to work?  What I am doing wrong?  The only=
thing =


different between the above diagram and my circuit =

is

the trimpot, I just have the diodes in series to =

gnd.

 

Any help would be appreciated,  Thanks in =

advance.

 

Blue Skies
---Buzz---


href=3D"mailto:nigel.joyce@usa.net">nigel.joyce@usa.net





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Groups.com/group/alt-beam

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Attachment: FLEDPV.gif

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