How do I set up a single LED to be turned on by a battery? (like a square 9 volt, or other small battery)?

Question

How do I set up a single LED to be turned on by a battery? (like a square 9 volt, or other small battery)?

Answer 1

If you have the specs of the LED, it is easy to figure it out.  If not, you can assume the voltage drop is about 2 volts, and the forward current required is about 10 milliamps.  So with a 9-volt battery, you need (9-2) / .01 = about 700 ohms.  Most LED's can take about 20 milliamps without any problem, and most of the newer ones will operate at 5 milliamps or less and still be bright enough for an indicator light.  If you want to use one of the high-intensity LED's (like for a flashlight), it may need 100 ma. or more, and a 9-volt battery won't last long at that high a current.

Answer 2

just use a 1k ohm resistor in series.

Answer 3

If you are using the superbright LED, it needs about 3V to light up. 9V is sufficient to get the LED light up but you need to add in the resistor. the lowest or I would say it is safeter to use >500ohm in series with your LED.