volts, LEDs

[noop]

i should start by saying i know next to nothing about electricity

i want to make a night-light for my tank. i bought an LED today but it's way to weak on its own, so i'm gonna get a few more tomorrow and put them in series. the LED needs 3 volts. i have 2 AA batteries, 1.5 volts each. if i had 4 3-volt LEDs, would i still be ok with just these 2 batteries?

wish i'd paid more attention in physics class now

cheers
noop

 

[Lateral Line]

A LED is not like a light bulb. A LED drops voltage going through it, so you need to know the "Forward Voltage" of your LED's and the current they are designed to operate at. There should be a resistor in the circuit as well to limit the current. If you overload them, they will burn out.

The value of the resistor is dependent upon the voltage and the characteristics of the LED's but is easy to work out. The value of the resistor, R, is given by...

R = (VBattery - VLed) / ILed

... where VBattery is the voltage of the battery, VLed is the forward voltage of the LED, and ILed is the operating current.

Example, I'll assume your LED's have a forward voltage of 1.85V and operate at a current of 0.02 amps. I'll assume you have 3 LED's, and a 9 volt battery. The resistor value is then

9 - (1.85 + 1.85 + 1.85) / (.02 + .02 + .02) = 57.5 Ohms.

 

[ZX300SI]

Iam relly into cars and I got just put like 10 leds in my cars control pannle and they working nicly off 12 volts so I dont know if 3 volts is doing the job...