I'm making an electronic drum set with piezo sensors. Currently I have two issues. First, the piezo's are producing relatively small signals. When printing the digital values on the serial monitor, the highest values are in the 30s (on a scale to 1023 of course). The sensors are in parallel to a 1Mohm resistor (I copied this from a few other piezo projects I found online).

The other problem is that I'm getting multiple triggers from a single drum hit. I'm assuming this is because the arduino samples the piezo signal multiple times after a single drum hit because the fall time of the sensor is slow relative to the arduino loop time. Is this accurate?

Any ideas on fixing these issues?

Thanks!

Thank you both for your suggestions. I think I'm going to use two 4051's to allow for future expansion.

I'm building an electronic drum set and I need more than 8 analog inputs, so I can't use a single 4051 multiplexer. Since some of the consecutive hits on a single sensor (say the snare drum for a drum roll) will be fast, I'm looking for the fastest method of multiplexing, so that each hit is registered.

Also, if anyone has any other suggestions to ensure that each hit is registered, please fill me in.

Thanks!

I've got it! I was using Serial.print() and getting random sounds but when I changed to Serial.write() it worked! If I have any further questions, I'll be sure to post them.

Keith thanks for the suggestion but I'd rather not have to mess with the firmware.

dxwood I've tried that but I can't seem to get it to work. When I choose the MIDI baud rate (31250), it won't let me choose an output port, but I can select it for any other baud rate. And sometimes the Serial RX square at the bottom blinks red depending on which baud rate is selected. Also, how can I tell if garageband detects the device. Will it automatically start making noises when I open it?

Any help is greatly appreciated. Thanks!

So I want to make an electronic drum set and right now I'm trying to figure out how to get the arduino to interface with garageband. I have never used MIDI before and I don't really know much about it or how it works. I've done some research, but it seems like there are many ways to do this. Also, some of the resources I've found haven't been too detailed. Just trying to find out the best and easiest way to accomplish this task.

Thanks!!

I'm trying to make an electronic drum kit. I've found a ton of stuff online, but right now I'm just working on getting the Arduino to communicate with Garageband. I downloaded this Serial-to-MIDI converter http://spikenzielabs.com/SpikenzieLabs/Serial_MIDI.html
I'm also running a simple sketch that plays various notes. However, when I open Garageband, I don't hear anything.

Any ideas?!

I'm trying to write a function that will display text on an LCD and then expand it.

So, as an example, it will first display:

"hello world"

then...

"h e l l o  w o r l d"
"h  e  l  l  o    w  o  r  l  d"

..until it is completely off of the screen.

Ideas? Thanks!!

@AWOL I tried searching for the actual library code, but I was unsuccessful.

@majenko I understand that but how do you split the 8 bit character in the array into two 4 bit parts?

I'm trying to write a function that prints a string to the lcd screen but without using the lcd library, and I'm not sure how to do it. I thought about using a character array, but I'm not sure how to send the 8 bit characters over a 4 bit bus.

Any help is greatly appreciated it.
Thanks!

Okay so I just measured the current at both the microphone ground and the resistor to 5V and there is no change at all when the motor is ON. Could the motor current be affecting the op amps?

I'm sorry for my lack of intelligence on the subject, but I'm a bit confused. MarkT I don't quite get this:

Signal ground is _not_ power ground....

So, are the microphone ground and the motor ground connected or not?

The circuit is on a PCB, and I placed a ground plane on the top of the board and a power plane on the bottom of the board. So, everything that says 5V is connected to the bottom, and everything that has a ground symbol is connected to the top of the board.

dc42 I did this:

pcb trace between the positive side of C2 and the Vin pin of MDR as short as possible

But I didn't do this:

the wire from the negative side of C2 and motor negative side/D1 anode needs to be a short as possible

I simply connected both the negative side of C2 and the motor negative side to the top plane. What does making this path short actually do?

Also, can you explain this a little more:

No part of these wires or pcb traces should be in the supply or ground path to any of the sensors or the mcu

Sorry for all the questions! Thank you both!

MarkT I think you may have nailed it.

In order to determine the effects of the actual EM field, I placed a different motor (not connected to the circuit) near the circuit and turned it ON. I observed absolutely no interference. So, it has to be something within the circuit itself and MarkT you're suggestion makes sense because it doesn't seem possible for the motor to feedback through the motor driver, the microcontroller, the op amps, and still show up at the microphone.

So, when you say "on a separate wire" what exactly do you mean? Two different grounds?

Can you explain the shielding...I've heard the term, but I'm not really familiar with it.

Here is the full schematic: https://plus.google.com/u/0/photos/112970352885170654279/albums/5734988209816271265/5734988211154316818

The pots on the right side set certain regions, and when the microphone level is within one of the regions, the microcontroller turns the motor ON (here's the motor http://www.precisionmicrodrives.com/new-vibration-motors/310-101-10mm-coin-vibrator-motor

The microphone is placed in the ear and is connected to the op amps through a 3.5 mm jack as shown.

All of the circuitry is on a PCB and the motor is next to the PCB.

Is that enough info, or would more help? If so, what else would you like to know lighty?