Help controlling a 4x9 LED matrix and identifying components

Hey guys, haven’t posted in a while (my last project never got finished). But I need your help again!

Basically, I’m building a large ‘light panel’. Here’s a crappy diagram:
The red area is the lit area.

The first problem I have is identifying what LEDs I have. I am taking these from 4 headtorches i had laying around.
They are powered by 3x AA batteries. Here are some photos:



My main question is, what do I need to do to turn this bundle of LEDs (i’m going to remove them from that lame PCB and wire them to wire and spread them out.
I imagine there is some magic way you guys can tell me what power these LEDs use, what resistors i’m going to need etc.

I want to be able to individually control the brightness of any of the LEDs, so i’m guessing i’ll need PWM Multiplexing? (What ever the hell that is).

So what chips am I going to need, and how am I going to hook them up? :stuck_out_tongue:

(I realize I ask a lot, and I will be googling to try answer some of my questions, figured I’d ask though :))

After much research it appears I am going to need a MAX7219 chip.
From a little bit of math it appears the LEDs I have are 20ma? and the resistor on the current board is 2.2ohms.

Not quite sure what I’m gonna need from here. by the looks of it, i’m going to need the MAX chip, 2 caps (what kind?) and a resistor (what kind?)

Then I think i could follow the tutorial on the arduino MAX7219 page.

Also, i’ve heard about the MAX7221 chip. The thing I am building is designed to be sat basically next to a pair of speakers and a 400w amp. Is the 7219 sufficient, or am I going to need the 7221?

Your cheap headlamp has a very poor circuit: 9 LED's in parallel and only one current limiting resistor. There is no guarantee that the curren through the resistor is shared evenly. You can measure the voltage drop across the LED's to get that. Subtract that from 4.5V (the supply voltage) and divide by 2.2 to get total current (in Amps). Divide again by 9 to get the (intended) current through each LED. That will give you the two values you need to design any LED circuit: forward voltage drop and current.

johnwasser: Your cheap headlamp has a very poor circuit: 9 LED's in parallel and only one current limiting resistor. There is no guarantee that the curren through the resistor is shared evenly. You can measure the voltage drop across the LED's to get that. Subtract that from 4.5V (the supply voltage) and divide by 2.2 to get total current (in Amps). Divide again by 9 to get the (intended) current through each LED. That will give you the two values you need to design any LED circuit: forward voltage drop and current.

OKay, so I'm going to have to grab myself a multimeter and measure it. Any guides or tutorials for howto measure this? Never really used one :p

I gave up on this idea and decided to buy this instead:

http://www.ebay.co.uk/itm/Waterproof-5M-LED-RGB-300Led-3528SMD-Strip-24Key-IR-Remote-Power-Adapter-/330654864014?pt=UK_HomeGarden_Lighting_Lamps_Lighting_SM&hash=item4cfc90d28e#ht_2345wt_1206

Now I plan to 'simulate' the IR signals from the remote using the arduino, I think I found a nice guide on howto sniff IR signals and it shouldn't be hard to just push data directly to where the IR receiver diode 'was' (i plan to unsolder it and wire directly to it).

Is this wise? I'll be following up with more details as I proceed.