Alt-BEAM Archive

Message #05033



To: Bumper314@aol.com, beam@sgiblab.sgi.com
From: Bob Shannon bshannon@tiac.net
Date: Mon, 05 Jul 1999 09:26:44 -0400
Subject: [alt-beam] Re: Something funny with the 1382 voltage triggers?



Bumper314@aol.com wrote:

> > Has anyone notices a difference when using SMT components rather than thru-
> > hole
> > parts?
>
> yes...I have had this problem, twice, I have made 2 robots with SMD parts,
> and I have another SE from SMD's in my to-do tray, but I have the same
> problem with BOTH SEs. I dont know why, i corrected this by putting a 5k
> resistor in series with the motor/coil, and it worked fine, but i know this
> really lowers your power output, so you might just try putting a small value
> in series with the solar cell, i found that if you have it out side and its
> locked up, and you cover the cell for a second and uncover..it will fire, so
> try those and tell me what you get...i am anxious to see what others say.

Your exactly correct, if I cover the cell, and wait a long while then the SE will
begin to cycle again.

You say that you have had this problem with 2 out of 2 SMT SE's? Thats very
discouraging. Have you tried the same cells, cap and motor on a 'normal' SE?

Adding a resistor in series with the motors is a problem for me, I'm using these
SE's to drive a photovore thats got to carry around some extra cells and circuits,
so
I really need the power to the motors during the discharge cycle.

Wilf suggested either raising the resistor levels beyond 2.2k, to 4.7K.

I've often found (with these same motors and standard parts) that the SE's usually
work
better with a bit less than 2.2K, and I began using 1.8K. Now it seems that I've
got to
go the other way, and raise this value.

I'm thinking that rather than place a resistor in series with your motors, you
might do better
to place a resistor in series with the solar cell. Charge time will go up, but
you will still
have full motor current when it fires.

But I'm not at all sure just how sensitive this problem is to changes in the
charge current.

I'm thinking my next SE's will be PIC's, which dont have these problems at all!


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