Wiring up eight LED's

Hello,

I'm not very smart electronically. I can solder, so I guess that helps a little. I need a little help on a new project.

What I need to do is wire up eight BLUE LED's to three AA batteries. If this isn't possible, then any type of common battery type is okay. I will be using about 1m of wire, wether or not it effects the voltage or flow I don't know.

A diagram and parts list (if possible) would be GREAT.

Thanks in advance.

3 AA alkaline battery cells in series make 4.5V when they are new and the voltage drops to 3V when they are dead.
Blue LEDs need at least 3.2V to 3.5V so they would be bright with a new battery then they will dim as the battery voltage runs down.

Use 4 AA cells then the voltage is 6V when they are new and the voltage drops to 4V when they are dead and the dimming won't be so severe.

3 AA alkaline cells will last about 5 hours and the LEDs will dim a lot.
4 AA alkaline cells will last about 7 hours.

audioguru said:

3 AA alkaline battery cells in series make 4.5V when they are new and the voltage drops to 3V when they are dead.
Blue LEDs need at least 3.2V to 3.5V so they would be bright with a new battery then they will dim as the battery voltage runs down.

Use 4 AA cells then the voltage is 6V when they are new and the voltage drops to 4V when they are dead and the dimming won't be so severe.

3 AA alkaline cells will last about 5 hours and the LEDs will dim a lot.
4 AA alkaline cells will last about 7 hours.

Click to expand...

Would I need any resistors or anything like that?

You should be able to hook them up in parallel, and they would light up for a little while. Might consider a series resistor for each LED to protect. 20 mA X 8 LEDs = 160 mA.

**broken link removed**

Suggests 82 ohm resistor for 4.5 volt supply, 3.0 volt/ 20 mA LED...

Drift Noob said:

Would I need any resistors or anything like that?

Click to expand...

Click on my attachment to see the value of the resistors.

The maximum allowed current for an ordinary LED is 30mA.
AA alkaline battery cells can supply up to 330 times more to blow up LEDs that don't have a current-limiting resistor.

I made some blinking flashlights with 3.5V blue LEDs. I blink them on for a very short duration then their max allowed current is 100mA. Their voltage at 100mA is about 4.5V. Look at the datasheet for your LEDs.

Drift Noob said:

Hello,

I'm not very smart electronically. I can solder, so I guess that helps a little. I need a little help on a new project.

What I need to do is wire up eight BLUE LED's to three AA batteries. If this isn't possible, then any type of common battery type is okay. I will be using about 1m of wire, wether or not it effects the voltage or flow I don't know.

A diagram and parts list (if possible) would be GREAT.

Thanks in advance.

Click to expand...

You could use the link Harvey posted and a 6V lantern battery to get usable life out of it, if you don't have to carry it around. Otherwise, you might be able to hack the Joule Thief idea (**broken link removed** ) and your layout together to work. Another link to something like the Joule Thief that I have used (and which contains more information) is at http://www.cappels.org/dproj/ledpage/leddrv.htm, but it would also require some changes to do what you want.

What exactly are you trying to do? Do you have to carry it around? Leave it installed somewhere? Knowing that would help us decide what a "reasonable" solution might be.


Torben