FreeTrack Forum

Hey guys I decided im going to do the  Serial build with 5 volt USB. This will be mounted on a hat.

LED

Now the estimator tells me to use 5 Ohm resistor but the guide says to use 6.8 or 10, so the question is which do I use? Furthermore where the hell can I get a resistor that would match those specs?

PS: I don't know if its important but im going to use wireglue to make this since I don't have any solder gun.

Hi kithuni,
the value of the resistor depends on how much current you want to go trough your setup.If you use 5 ohm, the max current is 100mA

(powerersupply voltage - forwardvoltage of the 3leds)/resistor= current(going through your setup)

(5v-4,5v)/5ohm=0,1A
power dispensation is: 0,1 x 0,1 x 5= 50mWatt

I use SFH 485 P ir-leds in serie with a 10 ohm resistor.
(5v-4,5v)/10=50mA
power dispensation is: 0,05 x 0,05 x10= 25mWatt
With a 6,8 ohm resistor there will be a current flowing of 74mA, 37mWatt


Driven the leds at their maximum current will shorten the lifetime of them, therefore I use a 10 ohm resistor.And for freetrack there is no need to let them be so bright.As long as they are good visible.
Where can you buy them?It depends on where you live   .In the Netherlands you can buy them at
http://www.conrad.nl/ce/nl/?WT.mc_id=google&insert=8J&gclid=COSQhO6e8rYCFXMRtAodKGwA7A&WT.srch=1

Using wireglue should not be a problem.

greetz Stormrider