MIDI Solenoid Drum Kit

Large push-pull solenoid

Solenoids are basically electromagnets: they are made of a big coil of copper wire with an armature (a slug of metal) in the middle. When the coil is energized, the slug is pulled into...

$14.95

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Adafruit Perma-Proto Half-sized Breadboard PCB - Single

Top view of Adafruit Perma-Proto Half-sized Breadboard PCB.

Customers have asked us to carry basic perf-board, but we never liked the look of most basic perf: it's always crummy quality, with pads that flake off and no labeling. Then we...

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$4.50

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ULN2803: 8 Channel Darlington Driver (Solenoid/Unipolar Stepper)

Bring in some muscle to your output pins with 8 mighty Darlingtons! This DIP chip contains 8 drivers that can sink 500mA from a 50V supply and has kickback diodes included inside for...

$3.95

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1 x 10-Wire Cable

Silicone stranded-core 28AWG

5 x DC barrel jack

Panel Mount 2.1mm DC barrel jack

Add 5 to Cart

4 x 2.1mm DC Plug

DC Jack Adapter Cable

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1 x 12V 5A Power supply

12V 5A switching power supply

1 x Feather Header Kit

Header Kit for Feather - 12-pin and 16-pin Female Header Set

1 x USB Cable

Fully Reversible Pink/Purple USB A to micro B Cable - 1m long

1 x 10-wire silicone ribbon cable

10-wire silicone ribbon cable

6 x JST PH 2-Pin Cable

Female Connector 100mm

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6 x JST PH 2-Pin Cable

Male Header 200mm

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1 x Toggle Switch

Mini Panel Mount SPDT Toggle Switch

1 x 18 Pin DIP Socket

18 (2 x 9) Pos DIP, 0.3" (7.62mm) Row Spacing Socket Tin Through Hole

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1 x 2020 Extrusion

Slotted Aluminum Extrusion - 20mm x 20mm - 610mm long

Download CAD files from PrusaPrinters

1 x Slim T-Nuts

Aluminum Extrusion Slim T-Nut for 20x20 - M4 Thread - pack of 50

No Longer Stocked

1 x M4 Machine Screw

Button Hex - 8mm long - pack of 50

No Longer Stocked

1 x Remo Drum Pad

Gray Tunable Practice Pad with Ambassador Coated Drumhead

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1 x Small Cymbals

2pc First Note FN240 Firstnote Cymbals

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Hardware List

Screws, standoffs hex nuts and locknuts used to assemble and fasten parts.

Mallet Assembly (Single Set)

12x M3x6mm screws
4x M3x10mm standoffs
2x M3x16mm screws
3x M3 locknuts
1x M3x14mm screw

Kick Drum Assembly

1x 2020 Aluminum Extrusion – 305mm long
4x M4x8mm screws
4x M4 slim t-nuts
2x M3x10mm screws
2x M3 hex nuts
4x M3x6mm screws
4x M5x30mm screws
6x M5 hex nuts

Cymbal Assembly

1/4-20 D-ring tripod screw
3/8 to 1/4 screw adapter
2x M5x10mm screw
2x M5 hex nuts

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The diagram below provides a visual reference for wiring of the components. This diagram was created using the software package Fritzing.

Adafruit Library for Fritzing

Use Adafruit's Fritzing parts library to create circuit diagrams for your projects. Download the library or just grab individual parts. Get the library and parts from GitHub - Adafruit Fritzing Parts.

Wired Connections

Feather M4 Express

D5 from Feather to Pin #5 on ULN2803A
D6 from Feather to Pin #6 on ULN2803A
D9 from Feather to Pin #7 on ULN2803A
D10 from Feather to Pin #8 on ULN2803A
3V from Feather to VCC (upper) rails on Perma-Proto
GND from Feather to Ground (upper) rails on Perma-Proto

Switch

EN from Feather to Switch
GND from Feather to Switch

DC Jack

Ground to Ground (lower) rails on Perma-Proto
VCC to VCC (lower) rails on Perma-Proto

ULN2803A

Pin #10 (VCC) from ULN2803A to VCC (lower) on Perma-Proto
Pin #9 (GND) from ULN2803A to GND (lower) rails on Perma-Proto

Powering

The Adafruit board can be powered via USB or JST using a 3.7v lipo battery. In this project, a 400mAh lipo battery is used. The lipo battery is rechargeable via the USB port on the board. The switch is wired to the enable and ground pins on the board.

12V Power

The 12V 5A power supply is plugged into the DC jack on the lower power and ground rails on the Perma-Proto.

The power and ground rails connected to the 12V 5A power supply must only be used to power the solenoids NOT the Feather!

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Parts List

STL files for 3D printing are oriented to print "as-is" on FDM style machines. Parts are designed to 3D print without any support material. Original design source may be downloaded using the links below.

File names & Quantity

1x snare-noid-mount.stl
2x snare-extrusion-mount.stl
2x snare-extrusion-bracket.stl
3x mallet-stick.stl
3x mallet-noid-plate.stl
3x mallet-noid-linkage.stl
3x mallet-noid-holder.stl
3x mallet-noid-bottom-base.stl
6x mallet-ball.stl
1x feather-case-top-cover.stl
1x feather-case-frame.stl
1x feather-case-bottom-cover.stl

Download CAD files from Thingiverse

Mallet Assembly

The solenoid is inserted into the holder. The solenoid holder is attached to the standoffs on the base with M3x6mm screws. The linkage connector is pinned to the solenoids plunger with an M3x16mm screw and locknut. The linkage mounting plate is secured to the solenoid holder with M3x6mm screws. The linkage is then secured to the mounting plate with an M3x16mm screw and locknut. M3x10mm long standoffs are secured to the base for evelation.

Kick Drum Assembly

The solenoid is secured to the mounting plate. Two mounting brackets are secured to the slotted holes on the mounting plate. The brackets slide onto the profile of the 2020 extrusion and secured with M4x8mm screws and slim t-nuts. The base mount is secured to the 2020 extrusion with an M4x8mm long screw and slim t-nut.

Motion Linkage

This selection analysis shows the linear motion of the plunger pushing the linkage bar and pivoting at the joint to make the mallet strike. This was created in Fusion 360 using joints and contact sets. Revolute joint type is used in the pivoting point in the linkage bar. Slider joint type is used in the plunger of the solenoid. Contact sets are created between the linkage bar and M3 screw secured to the plunger.

Slicing Parts

No supports are required. Slice with settings for PLA material.

The parts were sliced using CURA using the slice settings below.

PLA filament 220c extruder
0.2 layer height
10% gyroid infill
90mm/s print speed
60c heated bed

Design Source Files

The project assembly was designed in Fusion 360. This can be downloaded in different formats like STEP, STL and more. Electronic components like Adafruit's board, displays, connectors and more can be downloaded from the Adafruit CAD parts GitHub Repo.

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CircuitPython is a derivative of MicroPython designed to simplify experimentation and education on low-cost microcontrollers. It makes it easier than ever to get prototyping by requiring no upfront desktop software downloads. Simply copy and edit files on the CIRCUITPY drive to iterate.

The following instructions will show you how to install CircuitPython. If you've already installed CircuitPython but are looking to update it or reinstall it, the same steps work for that as well!

Set up CircuitPython Quick Start!

Follow this quick step-by-step for super-fast Python power :)

Download the latest version of CircuitPython for this board via CircuitPython.org

Click the link above and download the latest UF2 file.

Download and save it to your desktop (or wherever is handy).

Plug your Feather M4 into your computer using a known-good USB cable.

A lot of people end up using charge-only USB cables and it is very frustrating! So make sure you have a USB cable you know is good for data sync.

Double-click the Reset button next to the USB connector on your board, and you will see the NeoPixel RGB LED turn green. If it turns red, check the USB cable, try another USB port, etc. Note: The little red LED next to the USB connector will pulse red. That's ok!

If double-clicking doesn't work the first time, try again. Sometimes it can take a few tries to get the rhythm right!

You will see a new disk drive appear called FEATHERBOOT.

Drag the adafruit_circuitpython_etc.uf2 file to FEATHERBOOT.

The LED will flash. Then, the FEATHERBOOT drive will disappear and a new disk drive called CIRCUITPY will appear.

That's it, you're done! :)

Further Information

For more detailed info on installing CircuitPython, check out Installing CircuitPython.

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To use with CircuitPython, you need to first install a few libraries, into the lib folder on your CIRCUITPY drive. Then you need to update code.py with the example script.

Thankfully, we can do this in one go. In the example below, click the Download Project Bundle button below to download the necessary libraries and the code.py file in a zip file. Extract the contents of the zip file, open the directory MIDI_Solenoid_Drum_Kit/ and then click on the directory that matches the version of CircuitPython you're using and copy the contents of that directory to your CIRCUITPY drive.

Your CIRCUITPY drive should now look similar to the following image:

Download Project Bundle

# SPDX-FileCopyrightText: 2020 Liz Clark for Adafruit Industries
#
# SPDX-License-Identifier: MIT

import time
import board
import digitalio
import usb_midi
import adafruit_midi
from adafruit_midi.note_on import NoteOn

#  pins for the solenoid output signals
noid_pins = [board.D5, board.D6, board.D9, board.D10]

#  array for the solenoids
noids = []

#  setup for the solenoid pins to be outputs
for pin in noid_pins:
    noid = digitalio.DigitalInOut(pin)
    noid.direction = digitalio.Direction.OUTPUT
    noids.append(noid)

#  MIDI note array
notes = [60, 61, 62, 63]

#  MIDI in setup
midi = adafruit_midi.MIDI(midi_in=usb_midi.ports[0], in_channel=0)

#  delay for solenoids
speed = 0.03
retract = 0

while True:

    #  msg holds MIDI messages
    msg = midi.receive()

    for i in range(4):
        #  states for solenoid on/off
        noid_output = noids[i]

        #  states for MIDI note recieved
        notes_played = notes[i]

        #  if NoteOn msg comes in and the MIDI note # matches with predefined notes:
        if isinstance(msg, NoteOn) and msg.note is notes_played:
            print(time.monotonic(), msg.note)

            #  solenoid is triggered
            noid_output.value = True
            #  quick delay
            retract = time.monotonic()

        #  retracts solenoid using time.monotonic() to avoid delays between notes activating
        if (retract + speed) < time.monotonic():
            noid_output.value = False

# SPDX-FileCopyrightText: 2020 Liz Clark for Adafruit Industries
#
# SPDX-License-Identifier: MIT

import time
import board
import digitalio
import usb_midi
import adafruit_midi
from adafruit_midi.note_on import NoteOn

#  pins for the solenoid output signals
noid_pins = [board.D5, board.D6, board.D9, board.D10]

#  array for the solenoids
noids = []

#  setup for the solenoid pins to be outputs
for pin in noid_pins:
    noid = digitalio.DigitalInOut(pin)
    noid.direction = digitalio.Direction.OUTPUT
    noids.append(noid)

#  MIDI note array
notes = [60, 61, 62, 63]

#  MIDI in setup
midi = adafruit_midi.MIDI(midi_in=usb_midi.ports[0], in_channel=0)

#  delay for solenoids
speed = 0.03
retract = 0

while True:

    #  msg holds MIDI messages
    msg = midi.receive()

    for i in range(4):
        #  states for solenoid on/off
        noid_output = noids[i]

        #  states for MIDI note recieved
        notes_played = notes[i]

        #  if NoteOn msg comes in and the MIDI note # matches with predefined notes:
        if isinstance(msg, NoteOn) and msg.note is notes_played:
            print(time.monotonic(), msg.note)

            #  solenoid is triggered
            noid_output.value = True
            #  quick delay
            retract = time.monotonic()

        #  retracts solenoid using time.monotonic() to avoid delays between notes activating
        if (retract + speed) < time.monotonic():
            noid_output.value = False

Your Feather M4 Express CIRCUITPY drive should look like this after you've copied everything over:

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Importing the Libraries

The code begins by importing the CircuitPython libraries.

import time
import board
import digitalio
import usb_midi
import adafruit_midi
from adafruit_midi.note_on import NoteOn

import time
import board
import digitalio
import usb_midi
import adafruit_midi
from adafruit_midi.note_on import NoteOn

Digital Output Pins

Next, the Feather's digital pins are setup to be outputs to send on and off signals to the ULN2803, which will activate the solenoids.

#  pins for the solenoid output signals
noid_pins = [board.D5, board.D6, board.D9, board.D10]

#  array for the solenoids
noids = []

#  setup for the solenoid pins to be outputs
for pin in noid_pins:
    noid = digitalio.DigitalInOut(pin)
    noid.direction = digitalio.Direction.OUTPUT
    noids.append(noid)

#  pins for the solenoid output signals
noid_pins = [board.D5, board.D6, board.D9, board.D10]

#  array for the solenoids
noids = []

#  setup for the solenoid pins to be outputs
for pin in noid_pins:
    noid = digitalio.DigitalInOut(pin)
    noid.direction = digitalio.Direction.OUTPUT
    noids.append(noid)

MIDI Setup

The MIDI notes are setup next. If you need to change the MIDI notes that will activate the solenoids, you can edit this array with the note numbers that you need.

The MIDI object is setup after the notes. The Feather is setup to be a MIDI-in device, meaning that it is receiving MIDI data.

#  MIDI note array
notes = [60, 61, 62, 63]

#  MIDI in setup
midi = adafruit_midi.MIDI(midi_in=usb_midi.ports[0], in_channel=0)

#  MIDI note array
notes = [60, 61, 62, 63]

#  MIDI in setup
midi = adafruit_midi.MIDI(midi_in=usb_midi.ports[0], in_channel=0)

Time Keeping

Finally, two variables are setup. speed will act as a delay for how long the solenoids will remain activated before retracting. retract will be a time.monotonic() device.

#  delay for solenoids
speed = 0.03
retract = 0

#  delay for solenoids
speed = 0.03
retract = 0

The Loop

The loop begins by setting up msg to receive any incoming MIDI data.

while True:

    #  msg holds MIDI messages
    msg = midi.receive()

while True:

    #  msg holds MIDI messages
    msg = midi.receive()

Solenoid and MIDI Note Array Indexes

Next, the solenoids' array index position is setup the be held in noid_output. The same is done for the MIDI note numbers with notes_played.

for i in range(4):
        #  states for solenoid on/off
        noid_output = noids[i]

        #  states for MIDI note recieved
        notes_played = notes[i]

for i in range(4):
        #  states for solenoid on/off
        noid_output = noids[i]

        #  states for MIDI note recieved
        notes_played = notes[i]

Play the Drum!

Then the real action of the code takes place. If a NoteOn MIDI message is received that matches one of the MIDI note numbers listed in notes_played, then the matching solenoids are activated. retract is also updated to hold the current value of time.monotonic().

#  if NoteOn msg comes in and the MIDI note # matches with predefined notes:
if isinstance(msg, NoteOn) and msg.note is notes_played:
  print(time.monotonic(), msg.note)

  #  solenoid is triggered
  noid_output.value = True
  #  quick delay
  retract = time.monotonic()

#  if NoteOn msg comes in and the MIDI note # matches with predefined notes:
if isinstance(msg, NoteOn) and msg.note is notes_played:
  print(time.monotonic(), msg.note)

  #  solenoid is triggered
  noid_output.value = True
  #  quick delay
  retract = time.monotonic()

Finally, the solenoids retract when the sum of retract and speed (0.03) is less than the current time.monotonic() value.

By doing this, you can activate your solenoids at the same time to stay on beat. If you used the more traditional time.sleep(value) to delay the solenoids' retractions, you would run into delays in getting the solenoids to hit the drums.