Alt-BEAM Archive

Message #05394



To: beam@sgiblab.sgi.com
From: "Pete McCarthy" dilbertpete@hotmail.com
Date: Fri, 23 Jul 1999 20:34:15 PDT
Subject: [alt-beam] Photopopper Woes


Hello Again BEAM Group,
I need help. When I was soldering my photovore, the transistors just broke
apart from each other. Does anyone know a strong glue that would survive
soldering??


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5395 Fri, 23 Jul 1999 22:37:29 -0500 [alt-beam] walker beam@sgiblab.sgi.com matthew landry hey
well i have been experimenting with some servos and a bicore and a
master/slave bicore, and some hacked servos. the thing that drives me
crazy is that the servos will turn more in one direction than the other,
how could this possible work for a walker if it's legs would turn all the
way around over a period of 10 steps?

my problem was diagnosed as noise from the motors, i have put .1 uf caps
across the motor terminals, and several .22uf and .1uf caps across the +v
and ground pins on the '240... what else is there to do, does one type of
240 work best for this high noise ( please let it be one of the kind i
ordered form digikey ;)

help, thanks

matthew

o and my URL is below, i have very little beam stuff, then again, i know
very little about beam!
feel free to surf around...
*************************************************************************
matthew landry stratguitar911@juno.com
http://www2.crosswinds.net/~stratguitar911/index.html
*************************************************************************

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5396 Fri, 23 Jul 1999 23:45:05 -0400 [alt-beam] Re: Solar cell v. doubler beam@sgiblab.sgi.com Bob Shannon

Wilf Rigter wrote:

> Well, surprise!
>
> Efficiency is not too shabby especially for the Bicore Charge Pump. About
> 70% with 3.4V in and 5.5V out @ 50 ma. I tested this with a 74AC04 and
> 1N4148 diodes so a 74HC/AC240 with Shottky diodes should give even better
> performance. An interesting feature of the fullwave charge pump is that it
> requires no output filter since it generates pure DC out. At 2.6V input, the
> tested 74AC04 Bicore Charge Pump easily drives a BG micro gear motor at over
> 4V out. How the efficiency of a system as a whole is affected is quite
> complicated. For example, I remember an article which demonstrated the
> overall efficiency of a solar cell battery charging system was increased by
> adding a dc to dc converter despite the converter losses, by loading the
> solar cell to operate at it's maximum power output point and optimizing the
> output voltage and current to match battery charging characteristics.
>
> enjoy

The trick here is to start and stop your charge pump based on the voltage from
the solar
cell. If you keep the load on the cell (a small cap) at the peak efficiency
point of the cells
V/I curve, you can easily overcome converter losses.

For polysilicon cells, you want to keep the solar cells output at .484 volts per
solar cell junction. By placing a small cap (220 uf) across the cell, and
starting and stopping the converter when the cell / cap voltage rises above /
drops below .484 volts per junction you will always get peak performance from
the cell regardless of light level and load.

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