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Aimtrak IR LEDs?
drventure:
Anyone have any ideas what the specs are on the Aimtrak IR LED's used in the ir module?
I picked up several from radio shack a while back (actually before I came across an aimtrak, thanks NeverendingStory!) and they work, but if I hold the gun even at three foot distance, the aimtrak indicates it's a weak IR signal and gets a bit jumpy.
The LED's I've got are 1.2v forward voltage, 100ma, with a 45deg viewing angle, and a wavelength of 940nm
I'm using a slightly higher resistance resistor than the LED calculator recommends (it says 39ohm, I'm using 47ohm cause it's what I've got) so that could very well be the issue.
Yeah, I suppose I +could+ just buy the ultimarc IR board, but I already had all these LED's and the whole things gotta go in this swing arm copper and brass hinged tube thing I'm welding up, so it seems silly to buy one just to hack it up ;)
Anyone know the specs or resistor values from the board? I can't make it out from the pictures on the site.
Neverending Project:
Ahem. Atreyu is from Neverending Story. ;)
The LED board has one LED on the right (D6) and five on the left (D1 to D5 left to right). The LEDs are in three parallel chains of 2 LEDs in series. D6 and D5 have a 75 Ohm resistor, and the other two legs have 47 Ohms. Maybe this is so the single LED is not as bright as the group of 5. I drew up a quickie schematic.
What voltage source are you using?
Andy, if this is not OK with you, please let me know and I will remove it ASAP.
drventure:
:-[
Oops. Neverending +Project+! doh!
Looks like I do have too much resistance on them. 5v power supply (I figured as much from the direct USB hookup).
Thanks for the info. It'll likely take a comment from Andy to verify the LED wavelength, but I'm guessing I'm good, since my test board DOES actually work, it's just showing to be dim unless I'm within 2 feet or so.
I'm just stoked to be getting to play with an aimtrak and my nerf guns!
Neverending Project:
I'm not sure you have too much resistance. If you were to put two in series, you want want a 27 Ohm resistor. That would give you about 116 mW dissipated by the LEDs. But Andy is using a 47 Ohm resistor, which cuts the power in half (66 mW). If you are using a 47 Ohm resistor on a single LED, you should still have around 97 mW, which is more power than Andy's board.
I am wondering if making the single LED even more dim than the group of 5 is the solution?
drventure:
Hmm, I could try that. I've got some larger resistors lying around, just not any smaller ones.
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