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Circuits
designed by David Johnson, P.E.
Last Updated on:
Monday, December 25, 2017 02:05 PM
Master Category List - Dave's Circuits
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David A. Johnson, P. E. -- ALL Rights Reserved.
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Constant Current /
Current Sink
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1 Amp Current Injector Circuit
designed by David A. Johnson |
| I designed and built this thing many
years ago. I published the hobby circuit in the now defunct “Radio Elecronics”
magazine back in 1992. The electronic circuit injects a precise 1 Amp of current into
any unknown resistor, up to about two ohms. Two alkaline C cells power the complete
circuit. |
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voltage booster provides the current control circuit with a higher voltage, to insure the
electronic circuit operates properly, even as the battery voltage drops. A single
LED provides both power monitoring and a low battery indicator. The current source is
activated when a pushbutton switch is pressed. |
| With a good digital
voltmeter, you can use this device to measure resistances down to less than one micro
ohm. That is 0.000001 ohms. I often use it to measure contact resistance of a relay or
the resistance of big chunk of heavy gauge wire or the resistance of a copper trace on
a circuit board. You can also use it to measure the voltage drop of a power diode,
when conducting one Amp of current. |
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Click on Drawing Below to view PDF version of Schematic |
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Constant Current / Current
Sink
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