MIDI Panic Switch

If you have a MIDI module that sometimes has MIDI note-on commands producing 'stuck' notes which drone on and on, then this circuit design will produce a series of 'All Notes Off' commands or individual 'Note Off' commands if a switch or foot-switch is pressed, and switch all the notes off.

The MIDI Panic Switch unit utilizes:

• A Printed Circuit Board (PCB), 
• A pre-programmed 16F877 PIC,
• A PCB screw terminal power socket  and associated LED, and 9v battery connector
• A MIDI 5-pin DIN input socket,
• A MIDI 5-pin DIN output socket,
• A 1/4 inch Jack Socket for a foot-pedal switch,
• The circuit schematic is available in GIF format,
• The circuit layout is also available.

The MIDI  Panic Switch unit requires:

• A 9 Volt battery or equivalent 9 Volt DC power source
• An external push to make foot-pedal switch

Operation:

Because some MIDI machines do not respond to the 'All Notes Off' command there are 2 modes of operation:

Mode 1:

If  the foot-pedal switch and momentary action switch are connected to the PORT B7 pin 40 (RB7) then when either of them are operated the unit produces the 'All Notes Off' MIDI command on all 16 MIDI channels. These commands take approximately 16 mS to transmit.

If MIDI data from any MIDI channel is detected it is re-transmitted to the MIDI out socket. 

Mode 2:

If  the foot-pedal switch and momentary action switch are connected to the PORT B6 pin 39  (RB6) then when either of them are operated the unit produces the 'Notes Off' MIDI command on all notes (0-127) and on all 16 MIDI channels. These commands take approximately 2048 mS to transmit.

If MIDI data from any MIDI channel is detected it is re-transmitted to the MIDI out socket. 

TOM SCARFF
1 Martello Court
Portmarnock
Dublin
Ireland.

Email: tscarff@eircom.net