This is a complete kit containing a PCB and all the neccessary components to build a MIDI triggered, 8 port power switch.
Each port is switched on when the device receives a corresponding MIDI "trigger note" message from a sequencer / controller / DAW etc.
MIDI Switcher is highly configurable. For each of its 8 switching ports you can set:
The MIDI note that triggers the port
The MIDI channel for the trigger note
How long the output is switched on each time a trigger note is received for the port. Trigger duration is set as a fixed number of milliseconds, or for as long as the MIDI note is held.
The "duty cycle" of the output when switched on. This effectively allows power to be set as a % of full power, by having the output switch on and off very quickly during the trigger pulse.
Both the output pulse duration and duty can be modulated in real time using MIDI note velocity, a MIDI continuous controller or pitch bend. This can be set separately for each port and allows (for example) velocity sensitive solenoid strikes or dimming of lamps by MIDI controller.
The output can be inverted (so it is ON when the MIDI note is not triggered and goes off when triggered)
All of the settings can be configured for a given port independent of other ports. They are configured by MIDI NRPN messages and can be saved to EEPROM so they are remembered when the power is off and recalled next time power is on.
A simple Java application can be downloaded to help configure the board over MIDI and makes it easy to save (as text commands) a specific configuration set so you can send it back to the board at a later time.
There is a standard 5-pin DIN socket for receiving MIDI data. This is optically isolated in accordance with the MIDI specifications, ensuring your computer / sequencer / controller keyboard is electrically isolated from the board when controlling it.
You'll need a DC power supply that provides enough current for the loads you are driving. The board shares a power supply with the load and can be powered from approx 7-24 Volts DC, and receives power via screw terminals. An on board voltage regulator supplies the logic chips with 5V, including the PIC16F1825 microcontroller that is the brains of the operation.
Each of the 8 output ports has a 2 way terminal block. Switching occurs on the "low side" of the load (i.e. between the load and a GND which is common to all eight loads) and is implemented using TIP120 medium power Darlington transistors, which have integral flyback protection diodes for inductive loads like solenoids and motors.
The transistors can handle 5 amps each, but it is suggested that the total continuous current through the board does not exceed 5 amps. For transient loads like striking solenoids (which are triggered for a short period only) this should not be a concern, but for continuous loads (such as lamps and motors) care needs to be taken not to overload the board or damage could result to PCB tracks.
Be warned that some components (the transistors and the voltage regulator) can become hot during use. Take care when handling the board after it has been operating. Excessive heating may indicate the board is being overloaded.
You may be able to feel the "flyback" pulse from solenoids as a small electric shock if you touch their wiring or the transistors while the solenoids are being triggered. This shock is harmless but can make you jump if you are not expecting it.
NEVER NEVER NEVER even think about attaching this device directly to a mains electricity supply
Approx size 68mm x 70mm x 34mm H (sockets and feet attached). The approximate weight is 70g
See my Relay-Switcher product for a similar product that uses relays instead of transistors.
(Please note the video clip shows the earlier version of the board which had different switching transistors)
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I am an electronics hobbyist from Brighton UK. I love playing with microcontrollers and doing interesting things with MIDI and analog noiseboxes. Lots of new ideas in the pipeline so watch this space...
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