That's a good tip with the glue! How much working time does it give you?
I'll have to give it a shot next time I need small text.
The capacitive part is surprisingly very simple. I'm not using any special chips just a 10M resistor and a copper sheet. Here's the circuit for the sensor.
![](https://i.imgur.com/wVY8Nyb.png)
(The 0J resistor is just a jumper)
The line going off screen connects to an IO on the AVR chip. The capacitive plate part is simply a header that goes to the larger copper area you see on the frame.
The AVR chip drives the line high. I use 1mS. Longer than needed just to make sure it's charged.
Then I switch the pin to high impedance mode and wait 150uS. At the end of 150uS I measure the value of the pin. If it reads high than some one has a hand near it.
They way it works if the plate acts as a capacitor similar to phone touch screen. It's discharges through a 10M resistor to ground. If you touch it or are near if you increase the capacitance of the plate.
Since humans act as earth referenced capacitors for some AC signals. The increased capacitance means that it's not discharged at the end of the 150uS time period and the chip will read a high.
I hope that clears it up. If any part of thats still fuzzy just ask.