LMFAO Robot Head

[WTB360LABTOP]

I plan on making a LMFAO robot head for Halloween. I am planning on using a carboard box and putting packing foam on the inside so it is tight against my head. Then I'm cutting out a mouth a putting mesh over it (you see out of it) and for the eyes I am going to use 3 leds on each eye. How would I run 6 leds off of 1 battery?



I'm also thinking about putting 4 white super bright leds on the front near the bottom so I can see where I am walking.

[cross]

Hehe, sorry I used search function wrong.
If you find a AA battery pack from radioshark you can wire it up to some leds using a basic wiring. If its just for a night I have just slapped on a random resistor and it works fine (Use 220 ohm on a 3v line, thats how my Gameboy DMGs are allwired fine and thats with two led)

[WTB360LABTOP]

Question, i just read online that if you supply an led the exact voltage you don't need a resistor. Would it be possible to wire 6 3v leds in series (I think its series, might be the other) onto a two AA battery pack without a resistor?

[cross]

Well by that logic they would be underpowered. But if theyr the same voltage they should be fine, you power a PS1 with 7.2 volts from the battery which it asks for without it breaking, the leds will be the same

[jdmlight]

Question, i just read online that if you supply an led the exact voltage you don't need a resistor. Would it be possible to wire 6 3v leds in series (I think its series, might be the other) onto a two AA battery pack without a resistor?

That may or may not work.

i just need to power 2 3v leds and i am using 4 AA batteries. how should i aline them to power the 2 leds? i have them in a straight line right now but no power is getting to the leds. any help?

You need a resistor with LEDs, always. LEDs aren't so much concerned about the voltage, but rather the current. (to a point, you have to have at least the minimum voltage specified and there is a maximum) Typically you'd aim for around 20mA current. (.02A)

To calculate the resistor you need, take the voltage you have (4xAA = 6v), subtract the voltage that the LEDs take (6v-3v=3v), and divide that by the current. (3v/.02A = 150 ohm) You can pick a higher value resistor, but lower will probably burn out the LEDs. (higher value resistor = dimmer LED but also = less current drawn, which may be important for a portable) This isn't magic, it's just the V=I*R formula. (V=volts, I=current in amps, R=resistance in ohms)

In this case, you can't put the LEDs in series (straight line) because each takes 3v, so if you have two of them, you're trying to calculate the resistance necessary based on 0v, which ends up being infinity. Which is impossible.

tl;dr: Go here.

From here.

[WTB360LABTOP]

[jdmlight]

You need a resistor with LEDs, always. [snipped the rest of this]

tl;dr: Go here. LEDCalc will answer all of these questions.

[Turknatr12]

Here is one I made for my Homecoming:


I used 2 regular LEDs in each eye and also a 5 LED mini flashlight in each eye, mounted inside pop cans for reflectivity, and there's a switch to control it on the back.