Effect of lengh of wires in matrix

Sounds like a good design. My money is on it working just fine. There is a built-in lag in reading via the shift registers.

Luhan

Luhan

But are those long wires to all those butttons (256) in a 100cm x 100cm wooden plate gonna interfere my circuit in any way?

Thankls

The shift register used for input should have 330 ohm pull-up resistors to prevent noise pickup. The output shift register should then drive one line low at a time.

You may also wish to 'debounce' the input by reading the input s/r several times in a row for each change of the output s/r.

If your environment has a lot of electrical noise, put a grounded layer of foil on the back of the wooden plate.

Good luck, Luhan

When I built my pipe organ, the keyboards were 8x8 keying across 36" (91cm) but only 3" wide. The scan rate was 3kHz. The matrix board was connected to the microcontroller board with 18" of ribbon cable. Pullup or pulldown (whatever is appropriate) resistors are needed. The stop knob matrix was across the width of the console (60") and also had no issues for the 13 years I had it. The exposed wiring did have a tendency to make some RFI as I didn't shield anything. It mainly messed up a nearby AM radio. The controllers were 5 8031s.

I was concerned about pulse rise/fall times and all that capacitance from the ribbon cables so the 'scanning' of the stop knobs was not raise 1 bit high and look for what comes back. Instead, the switches all came into tri-state buffers and the buffers were enabled in sequence. The software was identical but the long lines in the ribbons were not being pulsed.

GG