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Re: Fertilizer pump fix... REDUX

Thanks for all the input and advice.  For others who may 
wish to try the same thing, here is my experience.

I opened it up, and sure enough it was a 4 winding stepper 
motor, 6V.  Checking the control wires, my meter told me 
they got a max V of just short of 4V.  Perfect for an 
infra-red LED.  I tied in an LED, and depending on if I 
powered it on the - or the + of the motor control signal, 
I could get different patterns of LED pulses.  (I can give 
you more info if needed, but basicly the motor controls 
wires are toggled from + to - in a specific pattern to make 
the motor step)  Everything looked great until I tried to 
position the IR LED such that it would fool the flow sensor.  
No matter what I did, I couldn't make it work.  It worked 
great if I pointed my VCR remote at it, and it worked great 
if I powered the LED constantly and waved it around, but I 
just couldn't get the flashing one to do anything useful.  I 
have no idea why.  Thats when I noticed a jumper on the 
controller board right below the sensor header, and sharing 
lines with the same chip.  On a whim, I checked it with a 
logic probe, and sure enough, every time the system decided 
the flow was bad, one of these lines would go high.  So, I 
started to wonder if this wasn't a test jumper for 
factory/service testing.  Figuring it was logic level and 
no damage would (hoping!) be done, I jumpered it.  Bingo!  
No more flow sensor.  Its been running non-stop at various 
speeds for about 4 hours now.  I'm calibrating it right now, 
and it looks like the tubing I'm using is about 20% larger in 
diameter than its calibrated for.  No biggie.  I'll leave it 
running slow (10ml/hr) over night and see what I get.  If that 
works, I'll leave it running for a few days at 1ml/hr and see 
how consistant it is.  As far as heat, even at full speed for 
over an hour, the motor doesn't seem to get hot at all.  
Perhaps thats because they are under-powering it somewhat.

So, I guess this used IV pump might just work out after all.  
Ain't ebay great?  :)