Use of 4x AA and resistor or circuit

[Weylan]

I have a bunch of kids toys I was thinking of moding. So that my kid has a flashlight as well as a toy. Since the toys generally have 4x AA. I have had the formula for picking the resistor needed so we don't burn up a Lux 1 or White LED somewhere. But does anyone have what the value of what the resistor should be? I moved and don't have any of my notes handy and can't find the formula to calculate it.



I know that ideally 3x AA's work great or best. And you get better performance and less waste from 3x AA's. But I would really like to cheaply convert the toys to lights since sometimes both my son and I need a light and if the toy has batteries already, this should work. A cheap circuit could work too, but simpler is better, without sacrificing life of the LED too much.

 

[danielo_d]

Here's the link to Metku's Led Calculator.

http://metku.net/?sect=view&n=1&path=mods/ledcalc/index_eng

Good Luck. Let us know how it turns out.


Danno

 

[danielo_d]

Oops, double post. :huh2:

See previous post.

 

[Doug Owen]

120 Ohms should give you about 20 mA with a typical while 5mm part. 12 Ohms would give about 200 mA with a LS (which is a lot of current from AA cells....).

Doug Owen

 

[HarryN]

120 Ohms should give you about 20 mA with a typical while 5mm part. 12 Ohms would give about 200 mA with a LS (which is a lot of current from AA cells....).

Doug Owen

It is also a surprising amount of light. I made a small 2xCR2 with resistor light to my 10 YO daughter set for 100ma, and it is surprisingly useful. I actually borrow it fairly often. Lately, she has been telling me to "get my own".