Timeline for Question about capacitive sensor designs with direct touch to copper or aluminum
Current License: CC BY-SA 4.0
6 events
| when toggle format | what | by | license | comment | |
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| Aug 2, 2020 at 2:53 | answer | added | AJN | timeline score: 1 | |
| Aug 1, 2020 at 18:03 | comment | added | AJN | I think that the user can be modelled by a capacitor in parallel with a resistor. When the pin suddenly changes state, the user capacitance acts as a short and user resistance is irrelevant till the time it takes the capacitor to charge. | |
| Aug 1, 2020 at 17:59 | comment | added | AJN | Following a link in the link you posted, they say "a more useful range of values is obtained if the sensor is covered with paper, plastic, or another insulating material, so that users do not actually touch the metal foil.". So the system does work better when not corrupted by a conducting user. | |
| Aug 1, 2020 at 17:08 | comment | added | Nick Nagy | I don't have a great schematic in mind, the question was more of a conceptual one. I guess I had misinterpreted the role the user takes (I thought of a user as ground, but sounds like they can be considered a new dielectric) in a capacitive touch design. The example I had in mind was this Arduino design (mathworks.com/matlabcentral/mlc-downloads/downloads/submissions/…) which times how long it takes for two pin's states to match and gives a rough approximation of capacitance using the RC factor. | |
| Aug 1, 2020 at 16:52 | comment | added | AJN | Can you add a sample schematic you have found. Or a link ?. If the user is touching only one piece of conductor and they are insulated from chassis or ground, there is no (return) path for a continuous current flow. So resistance measurement will not be practical. However, the insulated user will still have some capacitance to chassis / ground. A sample circuit diagram will help clarify if the circuit is measuring capacitance or resistance. | |
| Aug 1, 2020 at 16:47 | history | asked | Nick Nagy | CC BY-SA 4.0 |