IR-LED Array

[turel777]

Hi, I'm currently working on my MSc games programming dissertation and the program I'm writing uses infrared light detection. At the moment I'm trying to make a couple of simple 2x2 IR-LED arrays but I have no idea how to lay the, out on stripbaord.

Could anyone help me out with the layout please? I'm a complete noob when it comes to electronics.

I used an LED array wizard to work out what I needed. It came up with this:

Solution 0: 1 x 4 array uses 4 LEDs exactly
+----|>|---/\/\/----+ R = 15 ohms
+----|>|---/\/\/----+ R = 15 ohms
+----|>|---/\/\/----+ R = 15 ohms
+----|>|---/\/\/----+ R = 15 ohms


I'd have to add a switch to this as well. This arrangement is a bit of a problem for me since the layout really needs to be 2x2. Previously I was using a single LED but it wasnt bright enough which is why I want 4 of them arranged in a tight square.

I'm using IR LEDs with a forward vltage of 1.6V, a forward current of 100mA and I'm usign a 3V battery. The site I used was: **broken link removed**


Any help or advice you could give me would be much appreciated!

 

[MikeMl]

In the long run, will you be multiplexing (pulsing) the IR emitters? If so, you could use row/column scheme where each LED is connected at the row/column intersection. This is the way large arrays (eg 10x10) are layed out.

 

[turel777]

Nah, I jsut need them to stay on constantly. I'm makign a head-tracking game so All I need is a 2 small clusers of LED (two 2x2 squares shoudl be enough) which I cna place either side of someones head, probably jsut taped to a baseball cap.

Previously I tried to use single IR LEDs in a pair of safety goggles, jsut replacing the original white LEDs. This worked but a single LED wasnt bright enough to be detected at distances of over a meter or 2.

 

[MikeMl]

How long do you think your 3V battery will last if you are drawing 4x100mA?

Why dont you connect the four LEDs in series, then use only one resitor and a higher battery voltage. Much more efficient.

 

[turel777]

To be honest, I have no idea. I'm kinda clueless when it comes to electronics and didnt think I'd need to be doing anything like this in my project. Would having 4 LEDs running on a single battery drain it particularly quickly then? At the moment I'm using 3V watch batteries and I can quite happily add more as needed, I'm not sure what kidna resistor I'd need for 4 in series though. My main problem is I've never made anything using a stripboard before, my first attempt at this is rather large because I've made the whole thing with just segments of wire connecting all the ocmponents

 

[MikeMl]

The battery voltage has to be greater than 4*Vf + the drop across the resistor.
The resistor value = (Vbat-4*Vf)/Iled

A watch battery wont even come close to supplying 100mA, let alone 400mA. I'd go with a 9V alkaline. It will still only last a few hours at 100mA.

(9-4*1.6)/0.1 = 26Ω, so use standard value of 22Ω or 27Ω

 

[turel777]

ok, I'll give that a try, thanks very much for the advice! =)