So I built a prototype with what I had lying around.

• 1 TTP223
• 1 Zener Dioder 5.1V
• 1 2k2 Resistor
• 1 1k5 Resistor
• 1 BD137 Transistor

Panelized Design 6 x 12V TTP223 Touch Controller

First the schematic. I also included a flyback diode in the design, so you can also directly control a relay. The TTP223 chip has the same components as on the small original board. As on that, the 22pf capacitor is optional and is used to control the sensitivity of the touch controller. An FMMT617-625 comes into play as the transitor. You can also use another one. However, according to the data sheet, this one delivers 18V 3A. But I won’t go over 2.5A, just to be on the safe side :)

Panelized Design 6 x 12V TTP223 Touch Controller

• 1 TTP223 SOT23-6 Chip
• 1 Q1 FMMT617-625 SOT23 Transistor or equivalent
• 1 D1 1N4148W SOT123 (optional)
• 1 BZX BZX84 4.7V or 5.1V SOT23
• 1 R1 Resistor 2k2 1206
• 1 R2 Resistor 1k5 1206
• 1 C1 Capacitor 100nF 1206
• 1 C2 Capacitor 22pF 1206 (optional)

8 days after ordering, the prototype PCBs finally arrived. They look simply great.

ow do I make my stencil? First I laminate a white or black sheet of paper or thin cardboard into the foil. The paper is for visibility afterwards, so that you can position the holes better. Then I put the whole thing through the laser cutter and it’s done.

Most of the time, this works quite well.

First I built a PCB holder.
The PCB can be flush with the surface. This simplifies the application of the soldering paste. I have added a small notch to make it easier to remove the pcb. (red arrow)

After the soldering paste is applied and all components are positioned with the help of tweezers, the whole thing goes into my unmodified 15€ pizza oven for +-10min.

Here is the finished PCB after cooling down. 5 on 6 without problems.

After soldering on the slipped diode,, I checked the solder joints again with a microscope. Everything looks good so far.

After separating the boards, I connected a 1m long Led strip with 120 LEDs. The current consumption is a little more than 800mA. The board works as I imagined it would. Although the switching transistor can handle 3A, I still wouldn’t switch more than 2A, otherwise it gets a bit too hot during continuous operation.

As on the original board, there are also solder points A and B. These are used for programming the TTP223.

I have left out the diode on the circuit board, as it is only needed when you want to switch a relay. The 22pf capacitor can also be left out to increase the sensitivity of the switch, for example to install it behind a thin wooden or plexiglass panel.

I hope that some of you can use these instructions. As I said, all the data including the Gerber files can be found here: https://github.com/awall9999/Capacitive-Touch-Switch-12V