DIY Wireless Speakers – Part 1: Transmitter

Welcome to my DIY wireless speakers tutorial. We will be building/modifying an FM receiver and FM transmitter to turn them into wireless speakers. First we’ll build the FM transmitter.

To do this, we’ll modify a car FM transmitter (available on eBay). These are a popular solution for cars without AUX connectors, you can connect an iPod’s headphone jack to the FM transmitter, and hear your audio over the radio.

To use this device, we’ll have to make a few modifications. First, I removed the 5V power supply circuitry, which wasn’t necessary anymore. Then I soldered an old USB cable to the output of the 5V supply. Now we can power the circuit over USB instead of car power.

To get the audio into the mix, I replaced the 3.5mm female port with the end of an old pair of headphones, so that we could plug it into the back of, say, a TV.

For aesthetics, I built the circuit into a black box, and cut out holes for the cables.

Now we have an FM transmitter, next we need the receiver. Stay tuned for part 2!

Useless Machine

A simple desk toy that switches itself off. While the idea is non-unique, the design and 3D print files are.

The lid and arm are meant to be 3D printed and fitted to a box of dimensions 7x7x14cm.

The two switches (main switch and reverse stop switch) are soldered to a PCB which is mounted to the enclosure by the nuts included with the main switch. Note: the main switch shown in the photos is red, switches available for purchase are blue. There is no difference.

The main driving arm is mounted to a 9G servo, and designed to hit the main switch at one extension, and hit the reverse stop switch at the other.


3D CAD File


  • Main switch – available from
  • Reversing switch – available from
  • Continuous rotation servo
  • PCB – order online or etch at home
  • Arm – 3D print online or locally
  • Lid – 3D print (as above) or make a simple lid from wood or a material of your choice (I used foam board)
  • Case – build a simple box out of your material of choice (I used foam board) to the dimensions specified above.

LCD Inverter Add-On

A micro-board add-on to an LCD screen inverter to allow for MoBo-less control.

A small (30mm x 10mm) PCB designed to be placed on top of a specific laptop LCD inverter board. This board is designed to fit within the footprint of the existing connector and ground screw pad. The board layout and schematic can be modified to fit other inverter models.

By using this design, one can reuse a laptop backlight for other purposes without needing the original computer’s motherboard. The board facilitates dimming and on/off functionality. Backlights can be used for cheap lighting, or for tracing images between pages.

EAGLE schematic and board layout can be found below, Arduino code as well.


  • 2x 6×3.5mm tact switches
  • 1x 0603 capacitor 10uF or 100uF
  • 1x 0805 resistor 10k
  • 1x AtTiny13a or AtTiny45/85 etc.
  • 1x SOT89 linear regulator 5V such as 78L05F


EAGLE Schematic: LCDInverterSCH-Rev1

EAGLE Board: LCDInverterBRD-Rev1

Board PCB: LCDInverterPCB-Rev1

Code: LCDInverterCode-Rev1