Capacitive electrode and the wand


I’m currently dealing with the creation of a capacitive button. Since yesterday, I can talk with the capacitive sensor controller and thus, I can read the state of a specific sensor that I’ve configured as a button.

The problem is that as soon as I plug something on the sensor pin, I got the maximum value when I read the sensor output, in counts unit. I have tryed and tunned different configuration registers but I still got the same issue.

I was using a simple iron wire with a circular copper welded on one side, and the controller sensor pin on the other side. In general, the electrodes are directly over the PCB but in our case, we want the electrode to be remote from it. So, I think that the design of the electrode wasn’t good there is no ground close to it. I am presently reading the doc more carefully and I will try an other electrode design tomorrow, based of the information that I found on one of the datasheet.

Lastly, two wands have been printed but they have been a little deform, because of they’re position during the printing, implying difficulties to fit together the different parts. Mickael has adjusted some parts of the wand this evening to avoid this problem during the next printing of tomorrow.

You can see below 3 members of the Expelliarose team and the actual printed wand.


Good night !

3 comments to Capacitive electrode and the wand

  • Would a simple resistive sensor work for you?
    A bit like in the makey makey, you can add a ground wire near the sensor wire, it should work if the hand touch both.
    You would have a simple threshold to check, your MCU might even have a hardware comparators to wake it up and/or call an interruption routine.
    Find your driest hand neighbor to set the threshold and you’re good to go 😉

  • Alexis Polti

    Yep this is of course an option. But a proximity sensor such as the one chosen could recognize dark-magic hand moves around the wand. More magic power 🙂

  • chikhaoui

    Thank you Drix for your proposition 🙂
    Like Alexis said, we prefer to have a proximity sensor to get the hand presence around the wand handle.
    Have a nice week end.