There is a very simple way of doing it with a generic NPN transistor, and a 10K resistor. Base current is insignificant, and that's all the master supply sees.
Basic diagram is basic; slave PS/on to the collector, grounds from both supplies to the emitter, and +5v from the master through the 10K resistor to the base.
If you want the LED, put the 5Vsb from the slave to the positive on the LED, and the other side to the grounds through a 1.5K resistor. If you want it only lit when the PS is operating, put the negative side (with the resistor) to the collector with the PS/on; when the transistor turns on, it gets ground along with.
I'm running this sans LED right now, and with up to 800mA available, I could easily stack several supplies.
Grounds MUST be commoned when paralleling supplies.
Basic diagram is basic; slave PS/on to the collector, grounds from both supplies to the emitter, and +5v from the master through the 10K resistor to the base.
If you want the LED, put the 5Vsb from the slave to the positive on the LED, and the other side to the grounds through a 1.5K resistor. If you want it only lit when the PS is operating, put the negative side (with the resistor) to the collector with the PS/on; when the transistor turns on, it gets ground along with.
I'm running this sans LED right now, and with up to 800mA available, I could easily stack several supplies.
Grounds MUST be commoned when paralleling supplies.
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