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FreeTrack Forum > FreeTrack : English Forum > Support : Tracking System > Using no resistors with 1.5V battery and 1 LED?

RSS > Using no resistors with 1.5V battery and 1 LED?

Alexrey	#1 04/02/2010 - 12h49 Top
Class : Apprenti Posts : 20 Registered on : 24/04/2008 Off line	Hey guys, I'm heading back to university tomorrow morning and I really want to get my head tracking fixed up before I leave. My 3 LED model broke a few weeks ago and I've been unable to fly. I've only got 1 LED left so I thought I'd make the most of it and make a 2 DOF head tracker. Now my question is this: I want to connect a 1.5V battery to the 5mm IR LED, but I don't have any resistors. Would the current from the battery be enough to blow the LED or would it be fine without any resistors? Any help would really be appreciated. Thanks guys, cheers.
nadrealista	#2 04/02/2010 - 16h41 Top
Class : Habitué Posts : 84 Registered on : 13/01/2010 Off line	You didn't give enough info about LED. Here is answer to your question: http://tinkerlog.com/2009/04/05/driving-an-led-with-or-without-a-resistor/ I wouldn't run it w/o resistor. It will work, but less predictably because voltage drop while battery discharges (lower forward current, dimming LED brightness).
12AMS	#3 16/02/2010 - 23h25 Top
Class : Apprenti Posts : 2 Registered on : 17/08/2009 Off line	GOOD GOD, NO!! The LED will be burnt out almost immediately. Once the LED becomes biased, it is essentially a short. A resistor is required to limit the current. Regards, Rick
nadrealista	#4 17/02/2010 - 11h11 Top
Class : Habitué Posts : 84 Registered on : 13/01/2010 Off line	No, it wont Depending on voltage applied, LEDs pass through certain amount of current. In 485p case at 1.1V LEDs passes 0.001A, at 1.5V it passes 100mA, at 4V it "passes" 2A. Resistor shows voltage drop across itself. Resistor is "current limiter" in sort-of-speak meaning. But, when you try to calculate values in this circuit, resistor as "current limiter" is way to go. Battery can give maximum voltage of 1.5V. It is safe to have no R in this case (LEDs with V forward at 1.5V). With unregulated (even with some regulated, poorly though) PS you could have problem.

FreeTrack Forum > FreeTrack : English Forum > Support : Tracking System > Using no resistors with 1.5V battery and 1 LED?

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