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FreeTrack Forum > FreeTrack : English Forum > Support : Tracking System > 940 nm from Radio Shack

RSS > 940 nm from Radio Shack, Will these work?

marcheenek	#1 22/01/2012 - 06h07 Top
Class : Apprenti Posts : 1 Registered on : 22/01/2012 Off line	Will 940 nm LEDs from Radio Shack work for 3-point setup with USB power? Thanks!
Steph	#2 23/01/2012 - 11h58 Top
Class : Moderator Posts : 656 Registered on : 16/11/2007 Off line	Do you have a data sheet for them or a link?
dewey1	#3 23/01/2012 - 13h31 Top
Class : Habitué Posts : 191 Registered on : 25/06/2010 Off line	Yes they will work. The LEDS will probably need to have the lens sanded and polished to increase beam angle. Series circuit with USB power: 1.28 x 3= 3.84 5.0-3.84=1.16 1.16/.05=23.2 Ohms for 50 mA Use a 1/2W 5% resistor in the range of 20 Ohm to 22 Ohm. 20 Ohm will be 58 Ma current. 22 Ohm will be 53 Ma current. You could use 10 Ohm resistors and series wire for 20 Ohm. http://www.radioshack.com/product/index.jsp?productId=2062565
kloppenberg	#4 04/02/2012 - 08h21 Top
Class : Apprenti Posts : 25 Registered on : 26/06/2008 Off line	This is what I use. I sanded the tips flat with 300 grit and power them via USB. Make sure you fuse it so you don't short out your USB controller or worse. This worked fine with a MS webcam, and my current PS3 Eyetoy. Edited by kloppenberg on 04/02/2012 at 08h22.
Steph	#5 04/02/2012 - 20h20 Top
Class : Moderator Posts : 656 Registered on : 16/11/2007 Off line	I wouldn't use USB Power even with fuse. Because: Some non-standard USB devices use the 5 V power supply without participating in a proper USB network which negotiates power draws with the host interface. These are usually referred to as USB decorations. The typical example is a USB-powered keyboard light; fans, mug coolers and heaters, battery chargers, miniature vacuum cleaners, and even miniature lava lamps are available. In most cases, these items contain no digital circuitry, and thus are not Standard compliant USB devices at all. This can theoretically cause problems with some computers, such as drawing too much current and damaging circuitry; prior to the Battery Charging Specification, the USB specification required that devices connect in a low-power mode (100 mA maximum) and communicate their current requirements to the host, which would then permit the device to switch into high-power mode. Reference: Wikipedia

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