i2c / MPR121 Capacitive Touch problem

[SyntaxError]

Hi, there is probably a simple wiring solution to this but I just can't see it.

I'm using an RPi version 2 and have been following the instructions for the beetbox from here: http://www.imthi.com/blog/electronics/c ... mrp121.php

Everything seems to be working in that I can touch the pin holes on the mrp121 board and get a drum sound but how do I get it to release?

Right now if I insert a wire into the hole it registers. Leaving go of the wire does nothing so I'm at a loss as to how I need to connect the wire so that me touching it registers a touch and leaving go registers a release. My assumption was that the wire into the mpr board needed to be touching the surrounding ring to make the connection but if I wasn't holding it then it wouldn't register.

If it makes any difference, I'm using a jumpered wire from the rpi to a bare wire into the mrp board, then another bare wire into the 0 hole on the other side of the mpr board.

(This probably isn't clear enough as it's late so if someone needs me to re-word this with a picture or two just let me know)

What am I missing?

SyntaxError

[BMS Doug]

have you tried connecting the wires while the power is off, then touch the wires once it is powered on?

I'm assuming that there is some kind of calibration process for the capacitive sensor and that it might auto-calibrate when it powers on.

the touch sensor just needs something to change about the input, the act of connecting a wire is as much of a capacitance increase as the touching of the root vegetable would be, more than enough to trigger the sensor.

these boards are sensitive enough* to detect the nearby presence of objects, they don't even need physical contact.
(*if you used all the inputs of one chip for the purpose).

[SyntaxError]

Thanks Doug, problem fixed!

It turns out that I had two problems.

One was indeed that I was connecting the wires after the Pi had booted.

The other issue was that I've so far been using wires just poked through the board holes and not fixed in. This seems to have lead to random results so I need to fix this somehow but not in a permanent fashion.

Cheers,
SyntaxError

[BMS Doug]

Thanks Doug, problem fixed!

It turns out that I had two problems.

One was indeed that I was connecting the wires after the Pi had booted.

The other issue was that I've so far been using wires just poked through the board holes and not fixed in. This seems to have lead to random results so I need to fix this somehow but not in a permanent fashion.

Cheers,
SyntaxError

yes, the capacitance sensor detects changes in the connections, so the loose nature of the breadboard connection will lead to issues.

have you tried using female to male jumper cables connected to the output pins?
that might be more stable while you are testing it but ultimately you will need soldered connections.

[SyntaxError]

I'm going to get a few from Maplins tonight.

[BMS Doug]

if they still move then try a bit of bluetack perhaps?