LED with 2 supply voltage

Hey guys!

Just asking if it’s possible to power an led with 2 supply voltages–battery and solar
The point is, it doesn’t turn off; when both supplies are present, both supplies will power the led or when the solar power is off, only the battery will power it and so on.

Sure: Source 1 - Diode - | - LED - Resistor - Gnd Source2 - Diode - |

Anodes to the left, cathodes to the right.

What kind of diodes are needed? Will the changing of supply affect the brightness of the led?

I believe that the response assumes identical supply voltages from separate sources, otherwise there would be a need for two different resistors. If the supply sources have different voltages, then changing source will change the LED's brightness, in the current circuit. This could be fixed by using two separate resistors, one on each source, sized so that the current through the LED is the same for both sources.

arduinoTime: What kind of diodes are needed? Will the changing of supply affect the brightness of the led?

In addition to joshuabardwell's comments, it wil also depend on the ability of the solar cell or panel to supplythe current for the LED.

You could also put a voltage regulator between the diodes and the LED. Probably not worth it for a single LED, though.

I would a 20mA constant current chip to power the LED then it dosn't matter what the voltage is. Again use the diodes.

Thank you guys! +1 Karma :)