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MIDI Relay Programmable Unit
The MIDI relay programmable unit utilizes:
- a 2.1mm power socket, on/off switch, and associated LED, and 9v
battery connector
- a 4-way DIP switch which selects the MIDI channel at power-on, shown
in table 1
- a MIDI 5-pin DIN input socket.
- each relay is programmable, via MIDI input, to any Note-on (0-127)
Programming the unit:
At power-on, if the programme switch is simultaneously held on, then the unit
will enter programme mode, and the first programme LED is lit, see circuit
diagram. Now the first
four Note-on's from a MIDI keyboard or sequencer are detected and stored in the
EEPROM associated with relays 1 to 4. As each Note-on is detected the programme
LEDs switch on in sequence. After the fourth Note-on is detected the unit goes
into normal operating mode. So any relay can be programmed to operate from any
Note-on.
Normal Mode:
At power-on the DIP switch positions are read and the unit will operate in a
MIDI channel as shown in Table 1.
Note that at power-on, if the programme switch is ignored then the unit
operates as previously programmed.
Operation:
The unit detects the incoming MIDI data and if the MIDI channel corresponds
to the DIP switch MIDI channel setting, when a corresponding Note-on is
detected, (to the pre-programmed note-on relay data), the relay is switched on
and stays on until the corresponding note-off is detected. This allows each
relay to operate independently. The corresponding RELAY STATUS LED lights while the relay is
closed.
Purpose:
The MIDI relay unit can be operated live 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 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 analog 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. 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 using the 4-way
Midi distribution unit so that a single MIDI input can be fed to multiple
MIDI relay units.
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DIP Switch Selections |
MIDI Channel |
| 4 |
3 |
2 |
1 |
| on |
on |
on |
on |
1 |
| on |
on |
on |
off |
2 |
| on |
on |
off |
on |
3 |
| on |
on |
off |
off |
4 |
| on |
off |
on |
on |
5 |
| on |
off |
on |
off |
6 |
| on |
off |
off |
on |
7 |
| on |
off |
off |
off |
8 |
| off |
on |
on |
on |
9 |
| off |
on |
on |
off |
10 |
| off |
on |
off |
on |
11 |
| off |
on |
off |
off |
12 |
| off |
off |
on |
on |
13 |
| off |
off |
on |
off |
14 |
| off |
off |
off |
on |
15 |
| off |
off |
off |
off |
16 |
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Table 1 MIDI Channel |
MIDI Relay Programmable Unit
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TOM SCARFF
1 Martello Court
Portmarnock
Dublin
Ireland.
Email: tscarff@eircom.net
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