Hi Florian - thanks for your reply. I had to google dielectric.
The black plastic brackets are the grips on my PCB vice. I shot a short video of how the switch itself is assembled : https://cdn.hackaday.io/files/1871948008908096/20220907_200044.mp4
The white pad does press up against the back of the 'glass'.
My thinking is - If it turns out that I'm not smart enough to reuse the capacitive switch on this PCB , I may end up building my own circuit. To build my own, I will need something to interface the circuit to the back of the glass - and will need more of this foam, or something else suitable.
So I guess I can open my question up to - what is this foam, or what other materials could I use in its place?
My guess is this is just foam to prevent the PBC rubbing against the glass.
If you want to do your own capacitive switch have a look at the design documents/application notes from Atmel (now Microchip IIRC). They have both special purpose chips but also documents on how to use a normal micro controller.
Thanks. The lightswitch board has a clone of a holtek BS83A04A-3 - which would be ideal if I could have figured out how it had been programmed. I bet it's been programmed to read all three keys, even when two of them are unpopulated.
Instead I'm just using a pi pico to charge/read the capacitance of the pads:
As the switch has a glass front - which is probably very well insulating - the switch is most likely capacitive. It looks like the board has three capacitive pads side by side. So it can probably configured by software to act as a simple switch or up/down arrows or as up/stop/down.
I'd guess the pad is just there to glue the PCB to the glass front or at least to keep a defined distance. In theory it could be a dielectric to limit the effect of the pretty big gap between the PCB and the front of the glass.
I am wondering how this looks assembled as it looks like the pad is lower than the black plastic brackets at the side. So the pad may not touch the glass at all. Which would not go well with my explanation above.
Anyway unless you run into issues I would not bother about that pad.
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Hi Florian - thanks for your reply. I had to google dielectric.
The black plastic brackets are the grips on my PCB vice.
I shot a short video of how the switch itself is assembled : https://cdn.hackaday.io/files/1871948008908096/20220907_200044.mp4
The white pad does press up against the back of the 'glass'.
My thinking is - If it turns out that I'm not smart enough to reuse the capacitive switch on this PCB , I may end up building my own circuit. To build my own, I will need something to interface the circuit to the back of the glass - and will need more of this foam, or something else suitable.
So I guess I can open my question up to - what is this foam, or what other materials could I use in its place?
Are you sure? yes | no
My guess is this is just foam to prevent the PBC rubbing against the glass.
If you want to do your own capacitive switch have a look at the design documents/application notes from Atmel (now Microchip IIRC). They have both special purpose chips but also documents on how to use a normal micro controller.
Are you sure? yes | no
http://ww1.microchip.com/downloads/en/Appnotes/Capacitive-Touch-Sensor-Design-Guide-DS00002934-B.pdf
https://ww1.microchip.com/downloads/en/Appnotes/Atmel-42208-Low-Cost-Capacitive-Touch-TV-Control-Keypad_AP-Note_AT01486.pdf
There are more. Some are linked/mentioned in the documents above.
Are you sure? yes | no
Thanks. The lightswitch board has a clone of a holtek BS83A04A-3 - which would be ideal if I could have figured out how it had been programmed. I bet it's been programmed to read all three keys, even when two of them are unpopulated.
Instead I'm just using a pi pico to charge/read the capacitance of the pads:
https://cdn.hackaday.io/files/1871948008908096/20220908_190522.mp4
With the current setup, only the middle pad with existing foam will be usable, as the side pads will be air-gapped from the glass front panel.
Ideally I would get some more of this magic foam and adhesive, then I could use the side pads too.
Are you sure? yes | no
As the switch has a glass front - which is probably very well insulating - the switch is most likely capacitive. It looks like the board has three capacitive pads side by side. So it can probably configured by software to act as a simple switch or up/down arrows or as up/stop/down.
I'd guess the pad is just there to glue the PCB to the glass front or at least to keep a defined distance. In theory it could be a dielectric to limit the effect of the pretty big gap between the PCB and the front of the glass.
I am wondering how this looks assembled as it looks like the pad is lower than the black plastic brackets at the side. So the pad may not touch the glass at all. Which would not go well with my explanation above.
Anyway unless you run into issues I would not bother about that pad.
Are you sure? yes | no