edit: uploaded schematic: I am a novice, this diagram may not be correct but should convey the attempt.
I want to turn-on power to an arduino microcontroller when it is dark.
I white-boarded an example and uploaded the diagram below.
Using a photoresistor and a transistor, I plan to switch the high side that carries power to the arduino from a 5v dc adapter (eventually a battery pack).
- Arduino: https://www.arduino.cc/en/Main/arduinoBoardDuemilanove
- ARD_PWR: 5v regulated power input of arduino
- ARD_GND: ground port of arduino
- ARD_OUT_1: An output pin of the arduino, with 5v
- ARD_OUT_2: Another output pin of arduino, with 5v
I plan to control 5v power to the LED's through the arduino's output ports, and use 200Ω resistors to regulate the current on the ground side.
How do I determine the resistor values for R1 and R2. I'm new to EE and ohm's law, sorry.
Is my logic sound? Is this terribly inefficient?