DIY: Tracer Unit

In this video, I am going to show you how to modify your hopup to be a tracer unit.

"Alright, if anyone wants to do this in the future and get it right without any experimentation listen up.
An LED has a forward voltage drop of around 1.5 volts. If you're not sure, read the package.
An LED needs between 18-22 milliamps to light up. If you're not sure, read the package. If you want it brighter or darker, you can increase or decrease the advertised current value by a 15 percent fudge factortm.
Now do this math:
(Supply Voltage - Forward Voltage Drop)/(Current) = Resistor Value in Ohms
Now don't eff up your polarity and everything is groovy.
Special Note: Don't do LEDs in parallel. They're kind of funky when it comes to parallel, in that you need a resistor on each LED or they won't distribute current well.
If you do multiple in series, add up the voltage drops and subtract them from the source voltage."

Difficulty: Medium
Tech skill needed: Minor
Time: 10-15 minutes
Cost: worst case $25, best case $10

Materials needed:

Hopup unit
super glue
wiring with connectors of choice
dremel
3mm drill bit
soldering iron
solder
150-200ohm resistor (Radio Shack)

Comment and I will answer as fast as I can.

[Minerva_Devi]

Nice Gorillaz instrumental :D Done this a bunch before, works relatively well, especially in conjunction with a more standard tracer.

[legionvpdixie]

Hmm is this the tracer bb video you were talking about on insta

[CSquaredPlaysGames]

You know you can calculate the right resistance, right? V=IR, where V is voltage, I is current and R is resistance. Since we want R, rearrange to R=V/I, and feed in your figures. V is source voltage minus LED supply voltage, current is the listed current on the LED. The danger with giving people a range to choose from is that it's completely different for different LEDs and certainly if someone uses a 12v battery rather than 9v, or 5v, or whatever. There's a level of variance, sure, since you choose the resistor value that's closest to what you calculate, but the range you give could easily blow LEDs if someone chooses the wrong end for their supply.