Reactive LED Underglow Brakelights!

Just saw this on reddit and thought I would share (with permission of the creator). Go check out the full guide on

Anybody know how to make this work with a focbox?


Send a message to whoever makes/distributes the focbox and ask for a circuit map of the focbox so you can isolate the 2 resistor ends that carry the speed/brake signals and solder to them instead, everything else is the same

Alternative is to get a multi meter and poke every resistor you see and measure the voltage when you accelerate and brake

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Second approach seems like a great way to fry a DRV chip…

Please be careful!

A multi meter will not cause a short if you don’t connect anything high voltage

But make sure you don’t touch 2 adjacent points with the tip

Safer and guaranteed to work is to connect and arduino to the UART port and them you can do whatever you want

Make it speed based, make the color change based on how much power you are using, endless possibilities

The FOCBOX is a version of the VESC circuit and it’s digital, not analog. No such resistor exists.

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Are the Meepo ESCs analog? I though they had those resistors

Probably not, but I’m not really sure as I’ve never used one or seen one.

The output is certainly digital, and I can’t imagine the radio control being analog. Not sure what kind of gate driver system they use, but it’s highly unlikely.

Or you could get a module that specifically reads ppm data to manage lights, or you can put a small arduino to do the same thing…

Something like this


Would this just plug into the focbox directly? Or would some rewiring to a new connector need to be done.

You will need a Buck converter and to split the ppm cable so it also runs to the pcb


if I were to do it, I would just take signal from PPM.

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Just use an empty I/O on the STM32 on the VESC, set it to output when brake happens -> make a PCB that reads that signal and controls a LED, done. Repeat for turn signals for “left” and “right” (if you are more pro and have a nun-chuck obv,)

Bonus advanced: add a button to nunchuck to toggle headlight.

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Or just use a separate receiver so it’s not connected to the drivetrain.

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That’d be great except accessing those extra empty I/O are nigh impossible. Unless you want to remake the entire PCB.

your soldering skills needs improvement young padawan, but yes. Remaking the PCB would be ideal

Wait where else would you get ppm braking data if not from your original receiver?

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From a second receiver paired to the same remote.

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Which remote lets you pair two receivers at the same time?

Gt2b, Mini Remote for example :smile:

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