Author Options:

24 LED strip Answered

Hello all,

I've got what i thought would be a simple project so i could take some impressive long exposure photos.
eg: www.flickr.com/photos/24528515@N05/2356088056/in/pool-lightpainted

Heres the materials i have: (also see pic)
1: 24 white led's soldered in series (yes i started without knowing what i was doing :P )
2: A small 4.5v battery pack.
3: A simple clicky switch.

Heres what i dont have:
1: A clue about resistors or where to add them.
2: I don't know what voltage the leds are as they were removed from a broken led lamp by my brother. (who also dumped the casing so i cant see what the circuit on it looked like)
3: Any more patience. :)

The third pic just shows one of the 24 leds being tested with a 3v battery. I've done this with all 24 to make sure that there are no dead ones.

Can anyone help my ignorance?


It looks much like a led strings. I have bought smd led strip from the hero led store, where they sent me instructions about how to choose power supply and how to hook them up to controller, very interesting.


 Put LED in the search box above.  Also search on Ironman Arc Reactor instructables that use multiple LEDs hooked up in a chain.  Good luck.

Hi caitlinsdad, thanks for your reply.

I've had a look at the ironman arc reactor and saw that one of the people that made one of the many copies of the arc reactor used a site called http://ledcalc.com.

I've tried to use this site but you have to know the voltage drop across led.
Would you happe to know how to find out that if i don't know what the voltage of the LED's are?

I'm not an electronics guy but if you tried testing the led with 3v or even one 1.5v battery, you could use those values if the LED seemed to light up bright enough without it seeming to burn out.  Maybe other LED instructables will have some insight to practical assumptions that work.  But it is fun to experminent and find out.

Fair enough,
From the various sites i've looked at the white LED's that i have could be 4v.
They're bright when powered by the 3v battery that i tested them with but i just tried powering 1 led off the 4.5v battery pack thats in the pic and it was very bright.

Any electronics gurus out there that feel like shedding some light on my query? 

Pun intended... :P

from the site LED BASICS we see that the LED voltage drop is safe enough to assume 1.7 volts for non-high-brightness red, 1.9 volts for high-brightness, high-efficiency and low-current red, and 2 volts for orange and yellow, and 2.1 volts for green. Assume 3.4 volts for bright white, bright non-yellowish green, and most blue types. Assume 4.6 volts for 430 nM bright blue types such as Everbright and Radio Shack. Design for 12 milliamps for the 3.4 volt types and 10 milliamps for the 430 NM blue. There ARE some higher voltage brands out there, as I have a single 12 v. LED (a monster sized thing, I have never found an actual use for yet....)

After some trial and error, i finished it. Powered with a 12v battery the leds are on two arrays of 4, attached to a 80cm pole and they're switched on and off by a momentary switch. Stay tuned to http://pix.ie/whatchamacallit for futher developments :) (last pic has nothing to do with the project, just happy that it works :) )

I couldnt figure out how to make a 24 led strip so i'm scaling it down to 8 leds instead because according to this site led.linear1.org/led.wiz

I can have 8 leds powered by a 12v battery and two 1 ohm resistors, see pic attached.

Any opinions?