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Capacitive sensing seems to replace often mechanical switches. Is there a way to convert them back to mechanical switches?

Problem at hand is a cooking device with interfaces with the user via the dreaded capacitive touch buttons. If I had mechanical buttons or even better switches I could simply interface this cooking device with my arduino and let my program emulate the button pressed.A set of relays would do this nicely. Now I have those "capacitive touch" button points and have no idea how to use arduino GPIO to fake button pressed.Any ideas on how to interface?

To trigger a button pressed at those dreaded capacitive touch buttons, what I would need to do is to increase capacity (as that is what happens when a finger approaches, right?)

Autistic
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humanityANDpeace
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  • Well, the capacitive controller can not read capacities, AFAIK, but can just read voltages. Maybe you can fake the behavior with a GPIO or a transistor. First you should measure the signal attaching an oscilloscope probe before and after the finger pression, compare the two signals and try to emulate it.. – frarugi87 Jan 21 '16 at 15:22
  • Have a look at related questions: http://electronics.stackexchange.com/questions/23036/how-can-a-capacitive-touch-screen-be-triggered-without-human-contact?rq=1 and http://electronics.stackexchange.com/questions/60385/how-to-use-a-capacitive-touch-screen-without-a-human-hand?rq=1 – pjc50 Jan 21 '16 at 15:27

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The capacitive sense controller is measuring capacitance. However, it may not be so obvious to what it is measuring capacitance to.

There are at least two broad systems, capacitance to ambient, and mutual capacitance. In the first, your finger makes a larger capacitive connection back to the circuit's own ground. This is connected to real ground in the vicinity, and it is assumed your body is well coupled capacitively to this ground. This kind of sensor could be activated by a metal pad that is either switched to be connected to ground or not.

In the second case, your finger makes a capacitive connection between two conductors. The system essentially detects the presence of a conductor, not a connection to elsewhere. In fact, the connection to elsewhere is something that is cancelled out somewhat. In this case, you have to find the location of the two pads it is detecting capacitance between. Each gets its own metal pad with a switch between them connecting them or not. This will be more tricky to fake out.

Olin Lathrop
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  • Thank you. It seems that the first step would be to find out which of the two capacitive couplings are used to dedect the input. Indeed my device provides 6 capacitive touch buttons. All have 1 unique connection to the IC and one common to what I expend to be the ground of the circuit as it also enters the IC on one pin. Would this layout indicate either of the two options? – humanityANDpeace Jan 21 '16 at 16:13
  • @hum: It sounds like it might be the second case if there's a common line to all the sensors, but this line goes back into the chip. – Olin Lathrop Jan 21 '16 at 16:39