Dark Sensing LED Light

ldrled

This is a Dark Detecting LED light schematic I found here

LED Light that turns on at night(dark)

Few Questions(As I'm new to electronics),

  1. Can I use this circuit with a 6v input ?
  2. When there is light on the LDR(Photo-resistor) curent will flow
    through R2 and PH1 (LDR) right ? So when there is light power will
    be wasted ? If so, how many Ma(Mili-amperes)?
  3. What to change if I want to use a 5v led(70ma @ 5v while input is 6v as stated in question No.1. It's 4Leds removed from a torchlight) ? (The resistor values)

Edit : I edited the questions after "Peter Bennett" answered.

Edit: I (Peter Bennett) edited my answer after the OP's edit.

Best Answer

  1. I expect that the supply voltage is not very critical - 6 volts should be fine.

  2. You can determine using Ohm's Law, that the maximum current through R2 will be about .05 mA.

  3. An LED advertised as "5 volt" will be a bare LED with a suitable resistor or current limiting circuit so that it can be operated from 5 volts with no additional current limiting components. (I believe the highest voltage bare LEDs are blue (or white, which is just blue with a white phosphor) which have a forward voltage of 3.0 - 3.5 volts)

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