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Adjustable Low Current Power Source. Need schematic.

Rory Starkweather

Nov 13, 2014
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I need to build a low voltage (Maybe 3.3 VDC) Low current source to test/calibrate some D'arsonvalle milliameters. It needs to be able to provide a stable output current of between 0 and 100 mA.

Does anyone have a circuit, or a link?
 

Arouse1973

Adam
Dec 18, 2013
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The LM317 is a dirt cheap, widely used voltage/current regulator. The datasheet has lots of regulation circuits you can tweak to your needs: http://www.ti.com/lit/ds/symlink/lm117.pdf check out page 21; just adjust the potentiometers to your needs

Yes but the control for current comes from the series resistor which carries load current This is ok for a battery charger but for calibration is it good enough, no I dont think so.
Adam
 

Arouse1973

Adam
Dec 18, 2013
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Adam, you're probably right. Still, it's a pretty badass circuit
Yes I have used this circuit many times, you right it makes a good general purpose current source. But the resistor that controls the output current should not be in the current loop. Thats just my opinion. But others seem to think otherwise, why am I not supprised :)
Cheers Adam
 

Rory Starkweather

Nov 13, 2014
77
Joined
Nov 13, 2014
Messages
77
The LM317 is a dirt cheap, widely used voltage/current regulator. The datasheet has lots of regulation circuits you can tweak to your needs: http://www.ti.com/lit/ds/symlink/lm117.pdf check out page 21; just adjust the potentiometers to your needs

I've been looking at the LM317 as well, but it is a linear regulator with all the efficiencies I've seen that go along with that.

The LT3902 might be a little more expensive, but it only requires 2 external parts.
 
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