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RSS > 9 V battery what resistor

wiechu	#1 10/01/2018 - 19h31 Top
Class : Apprenti Posts : 2 Registered on : 09/01/2018 Off line	Hi all Im building my first free track and Im complitely noob when its comes to watts , volts , ohms etc. I have those 3 led http://uk.farnell.com/osram/sfh485p/ir-emitter-880nm-5mm-radial/dp/1212738 a nd I would like to connect them to 9v battery so any one know what kind of resistor should I use. I found one resistor in my drawer and its a 30 ohm 1/4 watt and im just wondering if thats enough . Thank You
Stormrider	#2 14/01/2018 - 14h29 Top
Class : Légende du Forum Posts : 466 Registered on : 02/01/2013 Off line	this setup will only work for a very short time and will end in smoke.With that resistor there will flow a current of 300mA.For those leds it is to much.A current between 50mA and 75mA is what you need.If you want to stick wihh that 9v battery you need a resistor value between 180 ohm( 450mW) and 120 ohm(675mW). Just make it easy for yourself and take a look at this. http://forum.free-track.net/index.php?showtopic=1856#11461

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