USB powered IR emitter for night vision webcam

Question

I had a spare webcam which i turned it into a night vision camera. I have to use IR emitters to be able to see with it ( http://www.instructables.com/id/Night-Vision-Webcam/?ALLSTEPS ) and i don't want to use a tv remote for that. I was wondering if i could power the emitters (4 emitters actually) with the usb port and cable of the webcam? Could you tell me how or give me a suggestion or a link or something? Thanks!

(Btw, i can do some basic soldering and stuff too)

Answer 1

• Your best bet is to buy these IR LEDs with 1.1 watts/sr @100mA @1.5V and use a string if 3 LEDS using 0.5V drop from 5V across a 5 Ohm 1/8W resistor. (verify current with a meter from V drop)
• If you can supply 200mA use two strings of 3 LEDs each with a 5 Ohm R.
• we call this an array of 3S2P.
• If not, then use slightly higher R. So buy a bunch of different R's like 5-10 Ohms or use 10's in combinations to make 7.5 Ohms and a dozen or more LEDs (cheap) .
• If you use the HDD connector 5V, you can add a switch to enable as many IR LED strings as you want and put them in a bundle to make a super strong 6 deg IR LED spotlight.
  • LED angles are always full angle while IR LEDs historically were half angle, but recently some disti's show full angle to avoid newbie confusion. So this LED is technically a 3 deg half angle and your bundle may spread this depending on alignment.
• doubling the angle will reduce the peak intensity in half approx. (except for lens loss with narrower angles)
• then intensity drops inverse squared with distance.
• warning , do not stare at the bundle up close