I have bread-boarded a constant current source using the attached schematic— the standard example.
My goal is a constant 100 mA source but when I tried to fine tune it by placing a 0-199 mA meter across the output and trimming the resistance, I got flickering readings from about 107 to 95 mA. Fearing to run down my battery (which is four Li-ion cells in series, all fully charged) I switched to trying a 10mA source by increasing the resistor. Same problem—flicker from just over 10mA to about 9. The flicker rate is about 2 or 3 Hz but I didn't measure it.
In desperation I tried connecting a 470 mfd capacitor from ground to everywhere in the circuit, one try at a time. No effect.
I tried a second LM 317 with no effect.
I tried a different power source with no effect.
My guess is that I'm doing something dumb but I sure don't know what.
Help appreciated. TIA
YES_SOMETHING DUMB--The power supply for the mA meter was low!!
Please don't reply to this stupit post.
My goal is a constant 100 mA source but when I tried to fine tune it by placing a 0-199 mA meter across the output and trimming the resistance, I got flickering readings from about 107 to 95 mA. Fearing to run down my battery (which is four Li-ion cells in series, all fully charged) I switched to trying a 10mA source by increasing the resistor. Same problem—flicker from just over 10mA to about 9. The flicker rate is about 2 or 3 Hz but I didn't measure it.
In desperation I tried connecting a 470 mfd capacitor from ground to everywhere in the circuit, one try at a time. No effect.
I tried a second LM 317 with no effect.
I tried a different power source with no effect.
My guess is that I'm doing something dumb but I sure don't know what.
Help appreciated. TIA
YES_SOMETHING DUMB--The power supply for the mA meter was low!!
Please don't reply to this stupit post.
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