Wednesday, 30 January 2013

DIY RC Light controller pre-processor miniaturization

This blog post is a follow-up on "Pre-processor for the DIY RC Light controller"

It did not take long until it became necessary to shrink down the pre-processor for my DIY light controller.


The HobbyKing HK-GT2R receiver is significantly smaller than the HKR3000 the LANE Boys are using, especially in height. No way an old-fashioned micro-controller in a DIP (Dual Inline Plastic) package can fit in there!

We need to solve this...

WARNING: This and other DIY projects are purely "at your own risk". If you are at all uncomfortable or inexperienced working with electronics, please reconsider doing the job yourself.

Luckily it is easy to get tiny micro-controllers nowadays. I opted for a Microchip PIC12F1840 in a SOIC8 package, which while being only 5 x 6 mm is still reasonably handable by mere mortals.


To program the chip I had to temporarily solder on tiny wires. A converter socket we ordered on eBay is still in transit.


Conveniently there is an empty area on the bottom of the HK-GT2R circuit board were we can mount our chip. The area contains test pads for 3.3V and ground that we tap on to power our little computer. The signals are wired with 0.19 mm thick enamel wire.


Like in the HKR3000 we used the (unused) signal pin on the battery connector to output our light controller signal. The HK-GT2R has this pin floating so no modification was needed.


Everything works fine and is nicely concealed!

All articles in this series:
DIY car light controller for 3-channel RC
Pre-processor for the DIY RC Light controller
DIY RC Light controller pre-processor miniaturization
DIY RC Light Controller update
DIY RC Light Controller with WS2812B


  1. Where do i find the software code for this?

    1. Hi! The pre-processor code is part of the light controller firmware at

      The pre-processor for the PIC12F1840 is one of the make targets in Mk2:

      The Mk4 version with the ARM Cortex-M0 NXP chip can also be configured as pre-processor. That firmware is here:

    2. Thanks for that. I am a Mech/E trying to learn some coding and Electrical :)

    3. Great! A day where you learn something new is a good day :)
      If you need help don't hesitate to contact me at laneboysrc AT

  2. Hi! Will you be able to do a LED kit that will suit in a 1/28 rc car body such as mini z?

    1. Hi Tj, the tricky part with Mini-Z will be to tap into the steering and throttle signals. The Mini-Z integrates receiver and ESC on a single circuit board. It has a couple of connectors that could provide useful signals, but I am not familiar with the details.

      The size of the light controller itself should not be an issue. The LEDs and wiring will be fiddly, but the model railway guys have well established how to mount tiny SMD LEDs using "magnet wire" in miniature vehicles.