Hello!
I want to automate my Philips 3300 Series LatteGo coffee machine, and ideally without opening it up and voiding warranty.
The cheapest, simplest idea seemed to be remotely activating the capacitive touch buttons on the control panel of the machine.

It seems remote activation of capacitive controls is a niche problem, and the best design I could find was from Leo's Bag of Tricks here .
I created three of these modules, based on this circuit.

When I have a piece of copper tape over a button on the 3300 panel, I can touch the tape to activate the button, capacitive touch works through and across the tape.

The moment I stick on the module however, it more or less doesn’t react to my finger at all. Tapping the tape over the button, the tape bridging the gap, the tape on the module, nothing.

If I tap the tape WITH the module itself as I hold it, it will only activate if I hold across the copper of the module, bypassing the circuit, but if I hold on the in-out pins of the module, it more or less never activates from a tap.

I tried wiring the module up to GND and digital pin 5 on an Arduino UNO R4, which I plugged via usb-c to the wall. Running the code:

void loop() {
  pinMode(triggerPin, OUTPUT);
  digitalWrite(triggerPin, HIGH);
  delay(350);
  pinMode(triggerPin, INPUT);
  delay(3000);
}

The LED on the module blinks just fine, but it does absolutely nothing to trigger any manner of capacitive touch, and this has been tried with various lengths and widths of copper tape. With conductive adhesive, of course, 3M #1181.

Is the parasitic capacitance of the circuit/PCB as a whole too high, making the 3300 simply ignore the input, or not register it?

I would really love to automate the capacitive controls on this, and many other devices, but with very little similar projects to go off of, and a limited understanding of electronics, I'm at a standstill here.

 

Here are the modules themselves for additional reference.

 

What is the action of the module? What does it do actually when it triggers? It shorts the left pin with the right?

 

Do you even understand just what the input function of the touch button actually is?? Some touch inputs are a capacitive load that reduces the buttons potential, while other touch inputs sense the capacitance by charge reduction, and then some touch inputs sense the added electrostaic voltage you deliver by touching.
Those different schemes require different inputs. You need to know which.

 

Do you even understand just what the input function of the touch button actually is?? Some touch inputs are a capacitive load that reduces the buttons potential, while other touch inputs sense the capacitance by charge reduction, and then some touch inputs sense the added electrostaic voltage you deliver by touching.
Those different schemes require different inputs. You need to know which.

I see, I just assumed most capacitive touch on commercial machines works on the same principles... I couldnt find any concrete technical data on the 3300, but I suppose I've ought to dig a bit deeper and see if I can find the concrete technology it uses for the touch panel!

 

What is the action of the module? What does it do actually when it triggers? It shorts the left pin with the right?

The problem is I somewhat blindly followed the linked video, as I am all digital and programming by education, with no experience with analog and electronics. From what I understand, the circuit simply mimics the capacitance of a finger-touch when powered, remaining "floating" when unpowered.

 

Since one method does not appear to work, I suggest trying a different scheme. Solder a six inch long piece of thin insulated wire to your piece of copper tape, then put the tape on the touch button. Then touch the other bare end of the wire with your finger, and if that does nothing, then grasp the bare end between thumb and finger, to get a better connection. The two touch sensing schem that this can work with are the one where the induced charge from your finger triggers the switch, and the one where the touch from your finger draws a high frequency signal away from the touch button, reducing the signal to a sensing circuit.