Trigger a 3 V line with 12 V

Question

I would like to trigger a 3 V line (a push dimmer circuit) with a touch button (which is powered by 12 V).

Closing the 3 V will turn off (short press)/turn on (short press)/dim (long press) the LED strip.

Here is my complete circuit:

How can I connect the outgoing 12 V line from the touch button to close the 3 V line (the red question mark)?

Can this be realized by a transistor, optocoupler, etc.?

Hardware used:
LED controller: GLEDOPTO GL-C-013P (zigbee (3 wire/2 wire 2in1)) LED Conttroller
Touch button: Touch Button

Answer 1

If the gnds of 3V and 12V are or can be connected together (not isolated), you can use a NPN transistor like 3904 with 47k in base. Otherwise you have to use an optocoupler.

Answer 2

Reduce the voltage with a Zener diode. Put a 10 kΩ resistor in series with the Zener diode to limit the current to the Zener. The capacitor and the second resistor will debounce the signal, avoiding erratic signals from the switch when pressing and releasing.

^{simulate this circuit – Schematic created using CircuitLab}

If you are using a power supply with screw terminals (not plug in like on the Ali Express website), you can do the following: Use the ground of the power supply and leave the V- not connected. Both schematics show a touch sensor switch (with the additional ground line).

ATTENTION: Do not use the "C" connections as ground.

^{simulate this circuit}