Switch logic circuit

Question

I am trying to create a circuit but I don't know exactly which switch design or logic chip I would use to accomplish my goal.

Here's the scenario: I have 6 pins, let's call them A, B and C and 1, 2 and 3. Each of them are carrying a low voltage (<5V), low current (<20mA), analog signal which pertains to an analog synthesizer patch. I want to use a pushbutton switch to move through 3 different ways of connecting these pins.

Position 1: Pin A is connected to Pin 1, Pin B is connected to Pin 2, Pin C is connected to Pin 3 Position 2: Pin A is connected to Pin 2, Pin B is connected to Pin 3, Pin C is connected to Pin 1 Position 2: Pin A is connected to Pin 3, Pin B is connected to Pin 1, Pin C is connected to Pin 2

What is the simplest way of accomplishing this circuit using a pushbutton as the control interface?

Attached is a diagram in case that helps.

Thanks so much for any feedback!

Answer 1

Functionally, you need three 3PST switches and a stepper. Electrically, the stepper can be a CD4013 wired as a switch debouncer plus 2-bit counter. With 1x4 analog muxes, this gives four states in continuous rotation: all off, position 1, position 2, position 3, repeat.

1 - CD4013 dual D flipflop

2 - CD4052 analog muxes (three switches plus an unused spare)

1 - SPST switch

1 - resistor, debouncing

1 - capacitor, debouncing

3 - capacitors, decoupling

Answer 2

You're probably looking for an analog demultiplexer. Based on digital select inputs, it connects a wire with an analog signal to one of many output channels. The output channels are in high-Z when not selected.

For your situation, with 3 signals to multiplex, you may need 3 of these demultiplexers. The select lines come from your Position 1,2,3 signals. Each demultiplexer is responsible for switching one signal (A,B,C) between of one three of its outputs. Those demultiplexer outputs are connected together as your 1,2,3 outputs. When a demultiplexer's output is not selected, that's OK because it'll be high-Z.

Answer 3

There are ICs with a single-channel, single-pole, triple-throw analog switch out there, like the NX3L4357 and the TS5A3359.

Three of those could do it, but you would also have to have a two-bit counter "clocked" by the push button for the select inputs.

Problem is, of course, that these switches and the counter don't "store" a state; power off and the state is gone. The state of the select inputs would somehow have to be saved or mechanically switched.

Multi-channel stepping switches as used in old telephone exchanges come to mind, great fun, but probably not very practical for what you want.

Answer 4

Here's a way, using 3 magnetic latch relays K1, K2, K3 and 3 push button switches S1, S2, S3.

Actuating a push button would set a corresponding relay and reset the other two.

Gold-plated contacts are a must for the relays switching low-level analog signals.

Freewheeling diodes, across the relay coils, and LED indicators are not shown.