Arduino battery backup v2

477

07:14:49

Automatically switch to a 9v battery on power outtage. Now includes transition smoothing capacitor, and a connection to monitor battery health via an analog input. Lamp represents Arduino, and the volt meter represents an analog input pin.

published 9 years ago

BillyT

9 years ago

You can do away with the transistor and resistor, it's just another voltage drop and not required. http://everycircuit.com/circuit/5229466640449536

mngosselin

9 years ago

How do you figure the tansistor isn't needed.? Clearly it is needed for the circuit.

mngosselin

9 years ago

The bipolar transistor opens the circuit to allow the 9v current to flow when the 12 v current is lost.

BillyT

9 years ago

The secret is that the battery is at a lower voltage than the main power supply thus it's diode is reverse biased and no current can flow from it. Basically that is how the transistor is working also, so with the transistor, the diode is not really needed.

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