Help with simple LED circuit

[LEDnewb]

Hi there everyone, I'm new to the forum and electronics and hopefully with your help i will learn loads and get my LED circuit working.

I am currently starting work on a costume based on star lord from the new guardians of the galaxy film, but i thought it best to try and get my head around the eyes first. If anyone has seen the film they will know his helmet has two rings of LEDs in the eyes and i would like to recreate that. I have brought myself some 3mm LEDs which apparently run at 1.7v - 2v and at 20mA, and i have resistors and battery packs. I have already discovered that i can only run a few LEDs from a battery so what i would like someone to help me figure out is how to run lots of them.

I would like to make TWO rings of LEDs with each ring being made up of 12 LEDs, what i cannot work out is what power source i will need to run those and which resistor to use. I think i wont be able to mount the power pack in the helmet so size hopefully wont be a problem, but the smaller in size i can get it the better. I feel like there is some real simple solution to this that i cannot see, whether it be running lower numbers in series then linking each set up in a series of small circuits. (i can imagine some of you are cringing at my terminology, sorry i really am a newbie at this)

Anyway any help would be massively appreciated, if i can get this figured out then i can defiantly build the rest of the helmet

 

[Harald Kapp]

Welcome to our forum.

Have you read the ressource "Got a question about driving LEDs?" ? This should clarify all your questions. Feel free to ask if something is still unclear after reading the ressource.

 

[BobK]

You can run all 12 off two AA cells in series, by placing the LEDs in parallel.

At 20mA each, that would be 240mA, the batteries would last several hours. You could run them at 10mA with a little loss of brightness and longer battery life.

But, I would get super-bright LEDs and run them a lower current, a few mA. These can be quite bright at as little as 1 mA. And you would get much longer battery life, and run them off AAA cells.

Bob

 

[LEDnewb]

That's ace thank you. I've just read through a fair chunk of that and cannot wait to get home tonight and give it a go. I believe I can see where I have been going wrong so fingers crossed that has solved it for me

 

[LEDnewb]

Thank you so much for pointing me in the right direction. As you can see it works a treat. My next step will be to get some super bright LEDs and test from there.
Spot my mistake though. .......I had already soldered one side and couldn't be bothered to undo it.

Thank you again I feel like I've left and mile with this one

 

[Gryd3]

Glad you got it working.
Something to think about though. When you run the LED's in parallel like you just did, you need to add the current of each led together to determine if your battery can handle it.
Not a problem there... as 20mA x 12 is only 240mA.

This adds up fast when you use high power LEDs
(Solution, compensate with more batteries in parallel)

 

[LEDnewb]

I'll definitely take that into consideration so thank you. I'm going to do a load more tests to see what's going to work best. Least now I know I'm on the right track

 

[bigone5500]

I find this online resource valuable:
http://led.linear1.org/led.wiz

 

[kingofjong]

If you are looking for a power source you can use a battery to provide the power. On this website you will find a chart that will tell you how many volts different color LED's need. Each resistor is color coded and you can look up the amount resistance on google. Use ohm's law to figure out which is the correct resistance.