Alt-BEAM Archive
Message #01115
To: beam@corp.sgi.com
From: Justin jaf60@student.canterbury.ac.nz
Date: Tue, 02 Mar 1999 07:17:35 +1300
Subject: [alt-beam] pocket motor-tester / BEAM multi-meter
I might be heading off to a bigger city for a while, and thinking off
things like surplus stores, I thought of quickly throwing together
something with which to test potential BEAM hardware, and double as a
useful tool when building.
My idea so far;
- Build a PM1 solar engine (schematic at BEAM Online), as this is simple
but can also drive non-inductive loads.
- Put a tiny cap on it (say 330uF), just enough to run an indicator LED.
- Put a little volt meter on it (not strictly necessary, but I like to
be able to see what the circuit is doing, and it's _very_ useful when
you're charging BIG caps).
- Put a little 2.7V sunceram cell on it to power it
- Wire the cap up to a DIP socket, with all the left legs wired to one
lead, and all the right leads wired to the other.
- Put some alligator clips or similar on the outputs
- Perhaps a row of dip switches which add more caps to the SE
Thus you can test caps and combinations of caps (using the DIP socket),
you can see if and how well they'll run a motor, you can likewise test
bicores etc as you work (in some situtations I don't want to use
batteries), and so on.
However, the main purpose of this is to test motors in the store, (hence
dip-switches to change capacatance rather than taking a handful of caps
for swapping in the DIP socket), but while it shows how well the motor
is going to run, I get the distinct impression that a whole lot more
functionality could be added. Ideas?
Hmmm, I think it might be a much better idea to use a suneater or
suneaterII circuit as this would allow you to add a dial which sets the
trigger voltage. Yes, that would be very useful.
A more far-fetched idea would be to put a little gear-box in the unit,
with some sort of rubber grommet or something such that you could just
poke the motor shaft into it to run the gearbox, which goes through a
few worm gears (yes - they do have a use :) and rotates a dial on the
front panel. With it geared down sufficiently, a 4700uF discharge would
get you about a 270 degree revolution on a good motor, thus giving you a
visual guide and comparison to how many revolutions a prospective motor
gets from the charge, and thus presumably, how efficient it is. Except
this doesn't measure torque, and is already a lot of work...
At this stage, I'm not sure its usefullness merits the hassle of putting
it together. Any suggestions appreciated.
In the meantime, I think I'll head off to the FAQ's and find out if you
can work out much via things like motor internal resistance.
Seeya
Justin
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