Sanity check please

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1

All,

The problem I am trying to solve is I want to create an IR beacon that can be used with IR detectors on my robot so it can zero in on my charging station when the batteries are starting to go. 

My question is how to wire up multiple leds in a circuit.  I googled and found a formula on instructables.com but it comes up with a very low resistor value which I just don't trust.  I have a 9V wall wart which puts out about 10V with no load.  I have 3 IR leds which are rated 1.6V forward voltage and can pull a continuous 100 mA.

With the formula I found it is (10V - (3 * 1.6V)) / 0.3 A = 17.33 ohm resistor.  That value doesn't seem right, but I will bow to the electronics gurus who cruise this site.

Thanks for the sanity check.

Regards,

Bill

2

Just to add to what OddBot suggested,

he mentions a 1 watt resistor. That was calculated by 10v @ .1A. Power (watt) = Voltage (in V) * Current (in A) = 10 * .1 = 1 Watt

3

Good point. I will have to

Good point.  I will have to check the rating on what I have. 

Thanks.

Regards,

 

Bill