Quote:
Originally Posted by dgr
Pedcab,
For those of us that don't have a regulated powersupply to provide 14V for the calibration procedure, do you have an alternative suggestion
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You may be able to put two 9 volt
radio batteries in series to get 18 volts, and then use a variable resistor to knock the voltage down to where you need it. To do this you will need to remove the lamp that acts as the dump load because that will be too much of a load for those small batteries, but they will power the 741 opamp just fine.
Quote:
Originally Posted by dgr
Pedcab,
Have you measured the parasitic amperage draw on this when it isn't doing anything? It looks like all that would be pulling current is the LM741 and the series of resistors that includes the variable resistor. If I am reading the spec sheet correctly on the LM741, it only looks like it draws 2 milliamps and the series of resistors would draw another 2 milliamps
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It looks to me like the combination of R5/D2(led 2) will draw some current. It looks like that LED is used as a power-on indicator.
The voltage divider network of R1, R3 & R2 will draw some current.
The combination of R4, D1 will draw some current.
And of course the LM741 istelf will draw some current.
I don't really know what the total draw would be (maybe 6 or 8 milliamps??), although not very much really, you wouldn't want to leave it connected to your batteries when not in use for extended periods of time.
Quote:
Originally Posted by dgr
Pedcab,
Why did you pick 2.3V for the cutout voltage?
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I really don't see where you are getting that number from? sorry. I hope I helped.