MM DIY Sustainer is a guitar sustainer circuit. If you hold it close to a metal guitar string (or any steel string), it will make the string vibrate without touching it, and it will go on vibrating indefinitely. This allows you to make really cool sounds when playing the guitar. It is also perfect for building wierd robotic musical instruments. MM DIY Sustainer is easy to embed in projects, it can be operated manually or controlled with an Arduino, and it is open-hardware so it is easy to modify and build upon.
Included
- MM DIY Sustainer Board
- 2 Inductor Coils
- 9V Battery Terminals
- 4-Pin Right-Angle Headers
This kit does not include a 9V battery due to shipping restrictions.
Inductors
There are 2 inducutors included in the kit. They have the following specs:
- Input Coil Approximately 1.9kΩ and 540 mH at 120 Hz; 7100 turns of 42 AWG.
- Output Coil Approximately 15Ω and 3.7 mH at 120 Hz; 600 turns of 32 AWG.
The inductors need to be soldered to the board. The polarity is important. Each inductor has a square tab and a rounded tab. On the board, the silkscreen for each inductor also depicts a square tab and a rounded-ish tab labelled +. The rounded tabs on the inductors need to match the + on the silkscreen.
The inductors are fragile because the pins are press-fit into the plastic. Forcing them out of the plastic will cause the wires to break, and this will be irreparable. This will not be an issue once they are soldered in place.
The inductors contain neodymium magnets. They should be installed in the same direction as one another, meaning the inductors should repel one-another if you put them face to face. Neodymium magnets are potentially dangerous. They should be kept away from pacemakers and
all safety advice should be followed.
Other magnet-core inductors can be substituted for the ones provided in the kit, but the output coil should have at least 4Ω of resistance at DC.
Handheld Operation
For handheld (battery) operation, the provided battery terminals should be soldered to the board. The smaller rounded one is the negative terminal, and the larger octagonal one is the positive terminal. On the board, the mounting positions are labelled + and -, and the silkscreen depicts the larger and smaller terminal to indicate the correct position.
After the terminals have been soldered in place, a regular 9V battery (not included) can be snapped on to them to power the board.
There is a three-position switch on the board, with the following function
- OFF In this position, the board is powered off.
- REG In this position, the board is in Regular Mode, meaning it is on and will operate normally.
- OVT In this position, the board is in Overtone Mode, meaning it is on and more likely to make the string play a higher pitch than its fundamental, usually an octave or 12th above. How well this works depends on a variety of factors.
By default, the Sustainer should be held with the input coil closer to to fixed-end of the string. However, interesting results can be obtained in the other orientation as well, it is fun to experiment with.
Battery Life and Current Consumption
When the switch is OFF, the board draws no current. When it is in REG or OVT mode, but not in use, it draws around 6-8 mA of current. When in use it draws around 70 mA of current. According to a
Duracell datasheet, a 9V battery would last around 50 to 100 hours when the Sustainer is on but not in use, and 6-8 hours when on and in continuous use. The Sustainer will not suddenly stop working when the battery drains, but will instead gradually become weaker and weaker with use. Remove the battery when not in use.
Computer Controlled Operation
The DIY Sustainer board can be controlled by an external microcontroller like Arduino or Raspberry Pi via the 4-pin header. To operate it in this mode, put the three-position switch in the OFF position. These are the pin functions:
- 5-16V Power input for the board. Recommended is 9V, but between 5V and 16V is within spec. This should be used instead of the positive 9V battery terminal for computer-controlled operation.
- GND Ground connection for the board. This should be used instead of the negative 9V battery terminal for computer-controlled operation.
- ENABLE If this pin is left open or connected to ground, the DIY Sustainer will be off. If it is pulled high (3.3V or 5V), the DIY Sustainer will be on, either in regular mode or overtone mode, depending on the state of the REGULAR pin. No current will flow into or out of this pin.
- REGULAR If this pin is left open or connected to ground, the DIY Sustainer will be in overtone mode, and if it is pulled high (3.3V or 5V) it will be in regular mode. No current will flow into or out of this pin.
This is the logic table to determine what state the Sustainer is in depending on the state of the ENABLE and REGULAR pins.
| ENABLE |
REGULAR |
STATE |
| LOW |
LOW |
OFF |
| LOW |
HIGH |
OFF |
| HIGH |
LOW |
OVT |
| HIGH |
HIGH |
REG |
Refer to the description of the three-position switch above for more information about REG and OVT.
Video
Watch on Youtube
Open Hardware
This product is compeletely open hardware.
MM DIY Sustainer by Metal Marshmallow LLC is licensed under Creative Commons Attribution-ShareAlike 4.0 International
