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Class : Apprenti
Posts : 2
Registered on : 21/03/2008
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Im getting ready to make my Track IR. I have 3 IR LED's, forward voltage is 1.2v, forward current 100mA. Im using a 6v 300mA power adapter. The best match I found for the resistor was a 47Ohm 1/2 watt with 5% tolerance. Will this work?
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Class : Apprenti
Posts : 10
Registered on : 10/03/2008
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i am not sure if you got the right resistor... using your 6v power adapter, and the leds voltage and current, I came up with much lower numbers for the resistor.
did you use the LED calculator? I can't say for sure, because I haven't had enough experience, but I think that you are way overboard on that resistor.
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Class : Electronicien en chef
Posts : 651
Registered on : 10/07/2007
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Hello Snipcod.
I checked your values , and :
- about the resistor value (47ohms)
everything seems OK.
Depending of the "real" voltage value of your power adapter, you should get a bit less or about 100mA, so it's OK
Remember it's often of no use to reach the led max power, because your leds will usually be brigth enough at 1/2 max power already.
- about the resistor power allowance (1/2w)
According to the led wizard, you'd dissipate about 0.4w in your resistor. I's a bit close to the max value of your resistor (0.5w). I'd recommend using a bigger resistor (about 1w), just to be sure.
Cya
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