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Re: Fertilizer pump fix...

>I'm pretty sure this is stepper motor based, though I haven't opened
>it up yet.  The pump head moves a very small amount, maybe a few degrees
>each "pulse".  The frequency of the pulse depends on what I set the digital
>control to.  Lower the ml/hr, the less frequent the pulse occures.

That sounds like a stepper motor. Steppers work by moving a specific number
of degrees (commong numbers are 1.8 and 3.6 degrees) each time a winding is
activated. A sync motor will usually only have 2-3 wires, a stepper will
have at least 4, and usually in the 5-8 range (most steppers I've seen are
4-phase, and thus need at least 5 wires -- one per phase + a common).

>Here is what I have figured out for the benifit of any one else who might
>try this...  I'm 99% sure its infra red, since pointing my vcr remote at >the
>sensor windows keeps it from tripping.  Blocking the sensor does not work,
>foil doesn't seem to work (probably just didn't get it right).  So, a 555, 

Before you try making the pulses, try just setting up the IR LED to just
run. It's possible the emitter is just broken, and it is very easy to make
an LED just light and stay on. A 1k ohm resistor (brown-black-red color,
read starting at the end FARTHEST from the metallic (gold/silver) band that
indicates the tolerance of the resistor), while not exactly right, is close
enough to light a typical LED from a 9-12v source OK.

It might also be possible to use the stepper motor's pulses to pulse the
LED. Most steppers are 6-24 volts, with common values being 6v, 12v, and
24v. If that works it saves you the trouble of building the 555 circuit and
lets you make the unit self-contained within the pump.


Waveform Technology
UNIX Systems Administrator