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FreeTrack Forum > FreeTrack : English Forum > Support : Tracking System > Need some input on a IR LED setup

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mutti_wilson #1 15/08/2008 - 08h10

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Im going to build a vertical clip setup with 3 IR LED's. My idea is to use a single AA @ 1.5v. Is this adequate or am I going to be running it down fast?

Here is the LED i'm thinking of using (i will be sanding it down for better angle)



I put the info from the specs on the LED and it told me 8.6ohm is ideal? Can somebody verify this for me? I just need to know what to buy! I know very little about this side of electronics, and I just need it explained to me.

Thanks alot guys, and can't wait to get started.
tristan68 #2 15/08/2008 - 20h57

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Hello mutti_wilson


Here is the LED i'm thinking of using



:blink: nothing ......

Can you try again ? thx


I put the info from the specs on the LED and it told me 8.6ohm is ideal?



Need to know the led characteristics to answer....  :dry:  So I'll wait your next message to answer  ^^


My idea is to use a single AA @ 1.5v. Is this adequate or am I going to be running it down fast?



It depends of what you call "fast" , what kind of battery you intent tu use , and how much current you'll need in each led......

IE :
lets imagine :
You're working with an unmodded webcam, so your leds will have to be bright enough to be clearly seen by the cam.......

You use 100mA leds , lets power them with 70mA. You'll have to use a parallel setup, so your entire setup will drain 3x70=210mA from your battery......

Your setup will usually stop working before the battery is totally drained.
(battery voltage remains roughly constant during the first part of its discharge cycle, then begin to drop when approaching end of lifespan

Lets imagine your battery is a 2000mah model.

It will be 2/3 drained in about  2000 * 2/3 / 210 = 6.3 hours so a little more than 6 hours continous play.

Now if you use an ir modded webcam , the current in your leds can be much lower, thus longer battery lifespan......

Caution : this is a very rough calculation, just to get an idea of the problem. don't take these values as real !!!!





Waiting for the led model to answer your other questions


cya
mutti_wilson #3 15/08/2008 - 23h08

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Weird, don't know how that link didn't come up.

http://www.radioshack.com/product/index.jsp?productId=2062565&cp=

I'm planning on modding my webcam (Logitech STX) so take that into consideration.

Thanks!

If I used the add link button the URL doesn't show up. If i just paste it in, it works.
tristan68 #4 15/08/2008 - 23h54

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Ok

These leds can work with a single 1.5v battery.

How did you get this 8.6 ohms value ?
I got 10ohms by using the wizard, and would rather use 12ohms (25mA)

Since it's a parallel setup , you'll need 3 resistors.

cya
mutti_wilson #5 16/08/2008 - 08h20

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I don't know, that's why im asking people who know.

Should look like this right?

           / Resistor - LED
Battery - Resistor - LED
           \ Resistor - LED

Thanks a bunch.
tristan68 #6 16/08/2008 - 10h02

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Yes that's it  :)

Here is an example of your setup :

Posted Image

With :

B = 1.5v Battery
SW = on/off switch
R = 12ohms resistor

cya

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