can i get away without a polyswitch fuse? Powering it with a usb wall charger.

should i also consider the dissipated power and tolerance of the resistor?

Hi, sorry for the late response, I'm not really active here anymore and I didn't get a notification. The fuse is not strictly required, I just had one on hand so I used one. Resistor tolerance isn't too important here either, just make sure to check the datasheet of your IR-Leds for the max current rating and don't exeed that. Once you know the current you can calculate the dissipated power of the resistor as follows: (5V-3*Vf)*I=Pd. So if you would use the same SFH485P IR-Leds without a fuse I'd suggest using a 8.2Ohm resistor, this would give you a current of around 61mA. the dissipated power of the resistor would be around 31mW so a regular 1/4W resistor is fine.

I built this project the other day and it went well.  The only issue was with the 3D clip.  The design of the two angled IR holes was too tight to put in the LEDs.  I had to file out a fair amount of material to get them in.  It would be nice if the angled ends had a small box on the backside to allow for a bit more room to pout in the LEDs.

I am following your tutorial but I am unsure about the resistor, what do I have to look for in max voltage, amps etc?  Do you have a link to the one you used so I can find similar?
 My build will be: LED: 1.35v x3, 50ma using the XTHI30W LED.  I was going to use a 22ohm resistor and put the LEDs in series on a USB plugged into my computer but I would like to protect my computer but am totally confused as to resistor.

R1 in my schematic is to limit the current that flows throught the IR-LEDs. In your case you probably don't wanna go over ~45mA for the XTHI30W. Because 50mA is the absolute maximum current the LED can handle, so you want to stay a bit under that max rating.

Then you can just calculate your R1 value: (5V - 3 * 1.35V) / 45mA = 21Ω -> 22Ω is fine.

And Power dissipation: (5V - 3 * 1.35V) * 45mA = 43mW -> Just get a common 0.5W resistor.

Now for the polyswitch fuse, something like a TRF250-110U might be fitting. 110mA hold current should be plenty for this. I only went with 300mA because that's what I had laying around at the time.

What you have to keep in mind though, is the series resistance of the fuse. In this case the polyswitch has between 5-9Ω. So your combined resistance would at least be 27Ω, which would give you a current of ~35mA. Hope that helps!

Thank you for your reply, and sorry for waiting so long.  I got my tracker built following your tutorial but without a fuse, just a resistor.  I run it through my USB hub which has a fuse built in.