Show Posts
Pages: [1]
1  Forum 2005-2010 (read only) / Development / Re: CapSense Library on: February 10, 2010, 03:44:51 pm
Does anyone have experience using an IC for cap sens switches?

I have an Arduino Mega, and my project requires many (over 35) capacitive sensing switches.

I found a Freescale chip that allows for 12 inputs, but it occurs to me that I'll need code to interpret the output of this chip correctly.

http://www.freescale.com/files/sensors/doc/data_sheet/MPR121.pdf

Please advise.

CD
2  Forum 2005-2010 (read only) / Interfacing / Connecting Mega to two-way breath sensor on: January 16, 2010, 07:06:35 pm
Ok, it's actually a pressure sensor that has two ports.

http://www.freescale.com/files/sensors/doc/data_sheet/MPX12.pdf

It is the same one used in the bellows of a MIDI accordion.

I however need to use it as a breath sensor.  I figured that since this sensor is definitely the one that they use in the accordions, (I checked), that just blowing into it ought to put out at least something.

There is a very slight change when I use the sensor without and fancy resistors or op amps.  

I believe I need to amplify the signal and so I purchased a few LM324 op amps to play around with, but I'm not getting any change in the value at the data pin.

Of course, I may have the op amp hooked up wrong, but basically, I supplied it with 5+V and ground, and the other three pins are v1 in, v2 in, and v3 out.

Out must be the amplified signal, so that's going to my data pin.

V1 in is getting 5 Volts, and V2 In is getting the v out pin from the breath sensor.

Nothing seems to be happening.

CD
3  Forum 2005-2010 (read only) / Interfacing / Re: Help with interfacing to a pressure sensor on: January 15, 2010, 02:35:55 pm
Here is the data sheet on the sensor I'm using.

http://www.freescale.com/files/sensors/doc/data_sheet/MPX12.pdf

Which op amp should I use/try?   I'm using an Arduino Mega.

CD
4  Forum 2005-2010 (read only) / Interfacing / Re: Help with interfacing to a pressure sensor on: January 14, 2010, 03:13:10 pm
The pressure sensor that I'm using is much more robust than anything that would be used to measure barometric pressure and it is designed to measure the bellows pressure of the bellows of an accordion.

I'm making a musical instrument that is designed to be blown into.

The sensor puts out miniscule changes in voltage and I may have to use the 'map' function.

CD
5  Forum 2005-2010 (read only) / Interfacing / Re: Help with interfacing to a pressure sensor on: January 14, 2010, 01:39:50 am
Any luck with interfacing with this pressure sensor?  
I'm trying to do connect an Arduino Mega to a MPX12DP.

It's similar to the sensor you are using.

It seems to put out a tiny range, and also, with room pressure, it's putting out about 3 volts.   Changing the pressure by blowing into the end makes the needle of my volt meter barely move.  But move it does, so I'm thinking there must be a way to hook this up.

Thanks.

CD
6  Forum 2005-2010 (read only) / Exhibition / Re: Arduino as Capacitive Sensor on: December 14, 2009, 06:57:32 pm
I would like to try this, but a bit about my application.

I'm trying to create a midi bend up and midi bend down plate on either side of the right thumb for an "Electronic Wind Instrument" application.

What I need is for each of those sensors to return a value of 0 - 128) smoothly, as a function of how much skin is touching a piece of copper about a 1/2" square.
 
No skin contact needs to equal 0, and then as the thumb is rolled slowly onto the capacitance sensor, I need a smooth rise up to 128.

Is this even possible?  Because I will not investigate this further if it is not even possible.

CD

Thanks.

Pages: [1]