Hi guys can some please help me out, I wanted to know how I can connect 4 White LED's to a LDR the simplest way possible I don't know that much about electronics so please tell me dummy terms. I want it to turn on the LED's at night and off at day and I will have it hooked up to a 9volt battery. I will really appreciate anyones help.
A 9V alkaline battery will be dead in about 8 hours with a 40mA load. 7V of the 9V is wasted in heating the resistors.
If four AA alkaline battery cells are in series making 6V then they can power 40mA for about 40 hours.
A 9V alkaline battery will be dead in about 8 hours with a 40mA load. 7V of the 9V is wasted in heating the resistors.
If four AA alkaline battery cells are in series making 6V then they can power 40mA for about 40 hours.
I just realized that you are lighting 3.5V white LEDs instead of 2V red LEDs.
The voltage does not matter since 5.5V of a 9V battery is wasted heating the resistors instead of lighting the LEDs. 6V is better since not as much voltage is wasted and the LEDs will still light when the 6V battery drops to 4v when it is almost dead.
AA cells are almost 5 times bigger than the tiny AAAA cells in a 9V battery so they provide the current for almost 5 times longer.