Hi I am trying to make an LED 3.5V 0.02A run in a circuit that will turn it off when visible light comes on. I have a cadmium sulfide photocell I took out of a night light. The power input is 12V 250mA. I understand I need to use a transistor as a switch for the LED and I know how to calculate the resistor for the LED. I am having trouble figuring how to calculate and place resistors for the photocell parallel so that the current turns on the transistor to the LED. Any tips on where to start or formulas? Im getting about 4V on after the photocell when lights are on if that helps. Thank you!!!