MIDI PROGRAM CHANGE
Uses MIDI Program Change Commands to operate the 8-way
changeover relay units
allows lights, guitar effects units etc. to be switched on and off and the sequence to be
stored in real-time to a MIDI sequencer. Each Program Change
value, from 0 to 127, can control up to 8 relays. There is
also a MIDI out socket so the MIDI data can be looped through a
number of units, allowing control of more than 8 relays.
An advantage of using
Program Change data, instead of Note on/off commands, is that you
can interface with a lot of MIDI controlled effects units.
The MIDI 8-way Program Change utilizes:
- A Printed Circuit Board (PCB),
- A pre-programmed 16F877 PIC,
- A PCB screw terminal power socket and associated LED, and 9v
battery connector
- The 4-way DIP switch which selects the MIDI receive channel via DIP switches 1-4
(See Table 1)
- A MIDI 5-pin DIN input socket,
- A MIDI 5-pin DIN output socket,
- A record on/off toggle switch and associated LED
- The circuit schematic is available
in GIF format,
- The circuit layout is also available.
The MIDI 8-way Program Change unit requires:
- A 9 Volt battery or equivalent 9 Volt DC power source
- 8 toggle switches
Operation:
The MIDI 8-way Program Change unit can operate in two modes Normal
and Record mode. In Normal mode the toggle switches are not
required as the MIDI information is read from a
hardware/software MIDI sequencer, when this controller command
information is fed to the MIDI IN socket on the unit.
1) Normal Mode
In normal mode the MIDI 8-way Program Change unit receives input
MIDI data and when it detects a Program Change Command, on the right MIDI channel, it switches the associated
relays ON or OFF, as appropriate. The MIDI data can be generated by
a MIDI sequencer or by the 8 toggle switches in record mode.
2) Record Mode
In record mode the 8 toggle switches are set ON or OFF as
required and when the correct values are set the MIDI input is scanned and when
a MIDI Program Change is detected the switch values are
stored in the EEPROM and the record LED is turned ON. So for any
Program Change number (0 to 127) the associated relay ON/OFF
values are stored.
Also the corresponding MIDI Program Change Command is transmitted
to the MIDI out socket, where it can be sent to be recorded on a
MIDI sequencer in real-time. The units can be linked serially
together ( MIDI OUT to MIDI IN) if more than 8 outputs are
required.
Guitar Effects Operation
The relays can be wired so that a guitar effects unit can be switched in or
out of a effects loop chain. Wiring of the relays is shown at Guitar
Effects (FX) Unit Relay Switching. Any ON/OFF relay combination can be pre-programmed
to a particular Program Change.
|
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 |
|
Table 1 MIDI Channel |
TOM SCARFF
1 Martello Court
Portmarnock
Dublin
Ireland.
Email: tscarff@eircom.net
|
