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DPRG: library display case books

Subject: DPRG: library display case books
From: sluggy slugmusk at alias.flash.net
Date: Thu Jan 29 19:39:03 CST 1998

>Yep, the only problem is that we don't have power.  We could run
>off batteries, but It'd have to be a really big battery to
>last an entire month.  Except for something like a 3909 blinker
>circuit that'll last a year on a AA, will a hc11 or an 8051 and
>an LCD last for a month on one gel cell?  If it will, I'm all for

I can see it now!  A bank of solar cells to trickle charge the battery and a
low power CPU that goes into a standby mode outside of library hours and a
optical sensor that turns on the display when somebody steps up to the case
during the day.  We could run it at a very low clock rate to further
conserve power... Obviously, everything would be CMOS and LCD (no
power-hungry LEDs in this project)

I see a domino sized robot with a titanium foil chassis and aluminum-on-mica
circuit boards and non-encapsulated ICs.  It moves photolythographically
machined tracks powered by electostatic micromotors.  It would pick up power
and commands from an induction system imbedded in the platform.

It should have a small manipulator arm and it could be programmed to
assemble, disassemble, move to a random location and reassemble a pyramid
made of small balsa wood blocks.

Any volunteers?

Seriously, though, in my (admittedly narrow) experience, gel cell batteries
tend to have a short shelf life without charging.  They are really made to
be charged and discharged fairly regularly and never discharged below a
certain level before recharging.  A marine type wet cell battery can be used
to provide fairly high current for an extended period of time.  Lithium
batteries tend to be pretty high priced per AH, but they are clean, very
small (especially in a watts per cubic inch rating) and are easily
obtainable.  I picked up a couple of very thin Ultralife lithum batteries.
I understand AH and discharge rates and the like to a decent degree, but
real world experience seems to work best for me.  I put a bank of three LEDs
on it (to reach a draw of 30mA) and ran them for a week before deciding that
the lithium batteries would do what I need!  During that week, voltage
tapered of from 3.03 to 2.97.  

Speaking of things powerful, does anyone know why DC-AC inverters tend to
use SCRs and capacitors instead of transistors to dump pulsating DC into a
transformer?  I recently salvaged parts from a 7.5KVA UPS that had a fried
transformer. (the transformer weighed 318 pounds)  The SCRs were fuse
protected and work fine, at least as far as I can test them.  I haven't
looked up ratings on them yet, but they are stud mounted devices and the
wire on the anode is about AWG 6, so it seems to be a serious current
switching device.  



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>My employer won't claim these opinions so I'm giving them away for free.
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