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Re: Fertilizer pump fix...

>>I've picked up a cheap used IV pump that I want to convert for use as a
>>just open it up and disconnect it?  Can I somehow fool it into seeing the
>>flow?  Any ideas how this thing works?  Any ideas how to make it work?
>Hmm. Does the flow sensor detect the SHAFT ROTATION or the FLUID'S MOTION?
>There are basically three ways the sensor could be detecting motion of
>either the fluid itself or the shaft of the motor:
>1 - The fluid BLOCKS light from the detector, thus no light = flow
>2 - The fluid TRANSMITS light to the detector, thus light = flow
>3 - The fluid motion or shaft PULSES the light going to the sensor, thus
>BLINKING light = flow
>1 and 2 are easy to "fool". Use some black paper (or color some paper with
>a sharpy (beefy black marker that bleeds badly on paper) marker) and block
>the detector or emitter if (1), play with some aluminum foil acting as a
>mirror if (2), but (3) is tricky. A simply circuit could be build around a
>555 timer chip to fool a pulse-detector. You might also try shining an
>infrared remote control at the detector since it will generate a pulsed IR
>light output when active. Chances are that if you open up the unit you'll
>find the sensor is connected to a relay or other switching circuitry/device
>of some sort. If you bypass the switching part, you should be OK. Remember
>that many metering pumps are NOT CONTINOUS DUTY though, so be sure to cycle

Thanks for the insight...  here is some more information if it would help.
Its a FlexiFlow III Digital Peristaltic Pump used in hospitals for IV
pumping.  It has an adjustable range from 0-300ml/hr as well as a fixed
dose (0-999ml) setting.  The flow meter sensors seem to be contained in a
black box shaped clip.  Perhaps it is meant to contain a disposable in-line
plastic container, which makes me think further that its optical and sensed
fluid rather than shaft rotation.  I have already tried simply blocking the
sensors, but this didn't seem to work.  I'll bet your idea that its an
infrared sensor is spot on.  I've got all the parts at home to build a
555 based flasher, sans the infrared led (I'll bet rat shack has that).
test your theory with my vcr remote and if that doesn't work, some
mirroring with foil.  If its as simple as a flashing infrared led, I'm set.

As far as it not being continuous duty, this is counter to what I expected.
I honestly expected that a hospital IV pump would be continuous duty,
considering where and how its used.  Any idea what kind of duty cycle I
should expect?  What it looks like to me is a circuit controlling a stepper
motor connected to the pump head.  So, at 1ml/hr, the stepper motor duty
would be VERY low, and I would expect that the circuit itself would have no
duty-cycle problems.  OTOH, if I were to run it at 300ml/hr, the duty cycle
would be very high, and that might be a problem.  I'm assuming the stepper
motor duty cycle varies with its stepping rate, unless current is continuous
and used as a brake against reverse rotation.  Am I misunderstanding