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msxer	#1 15/12/2007 - 21h36 Top
Class : Apprenti Posts : 4 Registered on : 08/12/2007 Off line	I built a 4 point cap with IR leds, it worked nice for some... hours. I think I burnt the leds with the 2 AA batteries. So I ask which resistor I should use to connect the 4 leds properly to 2 AA batteries?
tristan68	#2 16/12/2007 - 11h01 Top
Class : Electronicien en chef Posts : 651 Registered on : 10/07/2007 Off line	Hello msxer. Sorry to hear it.... Did you power the leds directly on the batteries , or use a resistor in your first attempt ??? To help you , i need to know : - your batteries characteristics (1.5 or 1.2v) - your led characteristics (led forward voltage and led forward current , or led model) Since resistor model depends on these values... Once you have them, just reply or use the led wizard on the website frontpage. cya Edited by tristan68 on 16/12/2007 at 11h02.
msxer	#3 17/12/2007 - 03h04 Top
Class : Apprenti Posts : 4 Registered on : 08/12/2007 Off line	I ingenuously powered the leds directly on the batteries. The batteries are in series and the leds in parallel. My batteries are 1.2v. That's all the information I have. I don't know the informations about the led. I just know that they're 5 millimeter diameter IR leds. Can you help me with only these informations?
tristan68	#4 17/12/2007 - 11h11 Top
Class : Electronicien en chef Posts : 651 Registered on : 10/07/2007 Off line	Hello msxer bad news : chances are you effectively fried your leds. Now about your setup : Leds characteristics or model are mandatory to get a proper setting. However, you can try to use a "conservative" setting, by using the minimal standard values. This setting would use : Power supply : 2.4v (your 2 batteries, serial mounting) led forward voltage : 1.5V (common value for red and IR leds) led forward current : 20 mA (every led accepts at least 20 mA, so if unsure, its the secure value) To get this , you'll need 3 x 47 ohms resistor and use the following schematic : You can try this but again, it's only a second best setting, you should try to get the led characteristics at your electronics shop. Cya. Edited by tristan68 on 17/12/2007 at 11h15.

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