I am currently designing a circuit that uses a 5V 2A power brick. The circuit requires a current source and I have seen good efficiency with Ohm's Law. The current is variable through a 2k potentiometer. However, now I need to design a circuit that gives the user the option of using the pot or using a current generator. This is what I had in mind for a very simple circuit:


simulate this circuit – Schematic created using CircuitLab

Is this a kosher way of doing this? The 5V is always on meaning current is always flowing through the resistors but is leaving the switch open (open circuit) good practice?

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    \$\begingroup\$ I don't know if there is a Jewish regulation for kosher circuit design. \$\endgroup\$ – JYelton Aug 12 '14 at 20:58
  • \$\begingroup\$ Unofficially, I think the illustrated circuit is both kosher and halal. Even shorting the output will not cause a problem because of the 1K resistor (don't leave it out, that would be trief/haram). \$\endgroup\$ – Spehro Pefhany Aug 13 '14 at 16:50

No, there is nothing wrong with floating the wiper of the potentiometer. You will simply "waste" 1.67mA of current through the upper part of the circuit.

Is this circuit really doing what you want? A current source designed using just Ohm's Law is extremely sensitive to changes in the load. If the resistance of the load changes, so will the current through the circuit. If your load does not change or is not sensitive to changes in current, then I guess you're ok. Do you mind explaining what this circuit is for?

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  • \$\begingroup\$ This is just a small RC circuit that I'm demonstrating to a friend of mine. He is having trouble understanding the basics and I wanted to given him a very very very basic way of achieving this. He has yet to learn active components, otherwise, I would just use an op-amp BJT combo circuit. Thank you for your response! \$\endgroup\$ – Ornusashas Aug 13 '14 at 14:23

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