[Cyborg] motor success, compass fail
Lamont Lucas
lamont at cluepon.com
Mon Mar 23 20:52:49 UTC 2009
Hi guys, sorry to miss the meeting this weekend, entertaining
girlfriend's parents. I'll also miss next sunday, due to travel, but
after that should be back and looking forward to more discussions and
projects. Please don't count me out.
I got an assortment of pager motors from goldmine-elec and found one I
liked better than the one Rachel so kindly gave me:
http://www.goldmine-elec-products.com/prodinfo.asp?number=G16777
it's crazy tiny, has nice leads to solder onto, and buzzed up a storm at
just 1v. I'll mount a capacitor across it and experiment with PWM
control later this week. I don't think I can safely run it from a
microcontroller's output pins directly, but TI's TPIC6B595 8 bit high
power shift register can do 150 mA per channel and has a built in
voltage clamp on the outputs to protect against the inductive kick of
the motor turning/shutting off. Plus it's DIP for easy prototyping. My
plan is to PWM the enable pin (the /G) while shifting in the bit I want
for the one motor I'm turning on.
As covered in the earlier mail, I was unable to get the HMC1052L working
out of the box. I'd hoped I could just use a differential amp across
the wheatstone bridge outputs and maybe ignore the set/reset pulse, but
the readings were mostly useless and too faint to play with easily. (I
got at most 1.6 mV across OUTA+ and OUTA-, but I have not yet done the
set/reset)
I'll keep trying with the h-bridge to do the set/reset pulse, but I may
ignore the analog solution and go for the i2c controlled HMC5843 if we
can figure out a way to mount it.
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