Electronics > Projects, Designs, and Technical Stuff
Qtouch - How to bridge a 3-5 mm gap between PCB and touch surface
ricko_uk:
Hi,
I have a PCB with a number of Qtouch pads but mechanically there is a gap between the PCB top surface (with the pads copper is) and the bottom of the 3mm-thick plexiglass front panel.
Such air gap is fixed once the design is finalised but at this stage can be anything from 3 to 5 mm.
Any suggestions on how I can electrically/capacitively "couple" the plexiglass touch area to the PCB copper pad? One solution would be to have a metal spring (which being conductive would transfer the charges). But cannot find any spring that is soft enough and which is only few mm long while being also 10-15mm in diameter.
Any other solutions?
Thank you :)
Gyro:
Pads of soft (Black) antistatic foam, cut to size / shape? You should be able to get resistance down to a few k.
ataradov:
They sell springs that widen into a bigger "pad" just for that purpose. I'm not sure if any of them are 3-5 mm though.
Here is one example https://www.aliexpress.com/item/32655220502.html . This is just a first link I found. They should be available from regular parts suppliers as well.
ricko_uk:
Thank you Gyro and Ataradov! :)
Gyro, have you tried it or do you know someone who has?
Many thanks
Gyro:
Not personally, but I doubt an extra few k on a capacitive touch switch would have a significant effect (as I say, use the soft black conductive stuff, not the pink dissipative one). It sounds as if it would be fairly quick to test (you must have an old IC box kicking around somewhere).
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