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4 Change-over Relay Unit Schematic

    

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4 Change-over Relay Unit Layout

 

 

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8 Change-over Relay Unit Schematic

 

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8 Change-over Relay Unit Layout

 

 

MIDI Change-Over Relay Units

 The 4-way and 8-way MIDI change-over Relay units can be used in conjunction with the MIDI Program Change, the MIDI 8-Way Controller or the MIDI to 24 Outputs units. 

The MIDI relay units consists of:

  • Screw terminal connections for inputs and outputs, 
  • a Light Emitting Diode (LED) associated with each input, 
  • 2-way Power Supply screw terminals  and associated power-on LED,
  • Open Collector Transistor drivers for each relay and associated back E.M.F. diodes in parallel with each relay.

The MIDI relay units require:

  • a Power Supply voltage,
  • Connecting to one of the MIDI  units, mentioned above.

 

Operation:

The inputs of the relay units are fed directly from the MIDI unit outputs. Each relay is switched ON when a positive voltage (+5 Volt) is applied to the input. There is also a Light Emitting Diode (LED) associated with each input and each board has a power-on LED. The corresponding RELAY STATUS LED lights while the relay is closed. 

Purpose:

The MIDI relay units can be operated live, in conjunction with the MIDI units  in real time from a MIDI keyboard or from a hardware/software sequencer with pre-programmed MIDI Note on/off data. The relays can be used to switch guitar effects (FX) units, electrical devices, such as lights, motors, pumps etc., in time with the music. Use the relays to control  tape decks, or energize and synchronize auxiliary circuitry. This provides a direct interface to the world of analogue electronics. 

Specification: 

The relays are rated for: 

  • Switching capacity: 10A @ 125Vac, 6A @ 277Vac, 10A @ 16Vdc 
  • Operate/Release time: 10mS/10mS 
  • Coil Impedance: 69.4 ohms
  • Coil Consumption: 360mW
  • Contact Material: Silver alloy

 

MIDI Specification: 

Relays are switched ON via MIDI 'Note-On' commands and OFF by MIDI 'Note-off' commands, or by Controller Commands or Program Change commands depending with which MIDI unit they are used. These MIDI commands are all channel (1-16) dependent. Also, all relays will switch off if the 'All Notes-Off' command is received. This MIDI command is  channel independent.

 

Expansion:

The MIDI relay units can be combined and expanded so that a single MIDI input can be fed to multiple MIDI relay units.

 

 

 

 

TOM SCARFF
1 Martello Court
Portmarnock
Dublin
Ireland.


Email: tscarff@eircom.net