Subject:
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fwd: high currents kill handyboard?
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Newsgroups:
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lugnet.robotics.handyboard
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Date:
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Mon, 18 Feb 2002 04:29:24 GMT
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Viewed:
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6805 times
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From: "Tanya Tickel" <sti398@merle.it.northwestern.edu>
Date: Sat Feb 16, 2002 10:47:20 AM US/Eastern
Subject: high currents kill handyboard?
Hi,
If this could be forwarded to the LUGNET group, I'd be grateful.
as of yet I haven't gotten permission.
I am the TA for a Mechanical Engineering course which uses the
Handy Board. We used a grounded scope to look at the PWM outputs
of the motor drivers, and shorted the ground when we commanded
motor(x,negative). Since then, even with new motor driver chips
(replacement really wasn't necessary) We have not been able to
drive nearly as much current as before--the board freezes at
varying levels of current output.
(We have one board which can drive only one coil of a stepper
motor (~24 ohm terminal resistance) or two at 50% power;
one board which can only drive coils at about 10% power;
and a third which resets whenever a motor command is given
at all, without even lighting the LED's.)
From previous posts, I suspected that voltage supplies were dying,
but with all chips save U2 out, both of them were powered, and
maintaining acceptably near 5V.
When I command motor pulses without the H-bridges plugged in, the
only pins (on the U10/U11 sockets) which carry a pulse are the
'enable' pins. Everything else (besides chip outputs which aren't
connected) is either high or low. (I don't know if that's the way
the drivers were programmed..I thought cs would go high and the
inputs would pulse.)
I'm desperate for help. Our students start building projects next week.
Best regards,
Tanya Tickel
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