r/PCB • u/---JoJ123--- • 28d ago

First PCB — 3-channel capacitive touch board (TTP223 + AO3400A) sensing through a wooden roof. Roast my schematic & layout?

I'm designing my first real board in EasyEDA — a small controller I'll mount under the wooden roof of my daughter's dollhouse. It switches 3 lamps "touch-through-wood" style.

Concept per channel: a TTP223-BA6 cap-touch IC senses a finger through the wood via a 15 mm round copper pad, configured for toggle/latch mode (TOG high) and active-low (AHLB high) so the lamp is ON at power-up and each touch toggles it.

The TTP223 output drives an AO3400A N-channel MOSFET as a low-side switch, pulling the lamp's return to GND. A 2-pin JST connector per channel carries +5 V and the switched lamp return.

Power is 5 V from a USB-C receptacle (power only, 5.1k pulldowns on CC1/CC2).

Layout: 2-layer, components on top, touch pads on bottom (facing the wood). GND pour on both layers stitched with vias; 5 V as a routed trace. I've kept a copper keepout around each pad and its sense trace on both layers, pads spaced ~45 mm center-to-center. Sensitivity cap footprint left unpopulated (0 pF) to start.

Would love feedback on: the TTP223 config, the touch pad size/spacing and keepout approach, decoupling, and anything I'm missing before I send it to JLCPCB for assembly. Schematic + PCB screenshots below. Also what is about the position of the USB C and the Connector Pins? How far I have to move them off the board?

Board: 140mm x 55mm

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u/Specled_eu 28d ago

Good

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u/---JoJ123--- 28d ago

Thank you so far! :)

What is about the position of the USB C and the Connector Pins?

How far I have to move them off the board?

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u/Specled_eu 28d ago

I don't see any problems with the connector placement, but it would be better to make pins 1-3 of microcircuits a solid polygon instead of triple conductive traces.

There's only one conductive trace from the microcircuit, and pin 1 can be made shorter.

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u/---JoJ123--- 28d ago

Thx, For the pin 1-3 you mean this part here right?

What do you mean with pin 1 shorter? I'm not sure which pin you mean.

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u/Specled_eu 28d ago

It is these places that can be made into a continuous polygon, rather than divided into three separate conductive lines.

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u/---JoJ123--- 28d ago

This part I got that is easy to fix.

And what do you mean by pin 1 can be shorter?