[Cyborg] motor success, compass fail

Lamont Lucas lamont at cluepon.com
Mon Mar 23 13:52:49 PDT 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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