3 channel footswitch

[brianqq]

Hi,
I am in the process of designing a 3 channel tube amp, an actual 3 channel not just drive and more drive, that is separate.
I am trying to figure out how to build a footswitch to control either 3 SPST relays or 1 DPST and 1 SPST. What it needs to do is be able to not only select the relay that the button activates, but also turn off the previous selection. Can this be done mechanically, or does something closer to a microcontroller need to be used? I have seen footswitches online that might work but it is impossible to find a schematic to show how they work.

Can any one help?

[gmphadte]

A simple CMOS msi
CD4028

Gajanan Phadte

[gmphadte]

I just browsed for the cd4028 images and see what I found.
Electronique - Realisations - Commutateur audio 003

Enjoy
Gajanan Phadte

[chrispenycate]

I have done this in the past both with relay switching logic, using a C/O contact on the relay itself, and simplistic transistor logic (well, there were a few diodes in it, too).

I take it you don't want there to be any possibility that pushing two switches at the same time latches you into two inputs?

And I suppose I could translate the French of the previous link…

[brianqq]

This simular to a PIC circuit I just found.
I just need to figure out which one works the best.
This amp project just keeps getting more complicatd with each day.
I guess I have noe one to blame but myself

Thanks for the info.

You know if these big companies would stop gaurding their gear
like they were national secrets it would be a lot easier.
I would probably just buy one, but they won't even tell you how they work

Brian

[gmphadte]

PIC needs programming, this one is totally hardware based.

Gajanan Phadte

[brianqq]

I was just looking at this and it seems it still has the problems that all mechanical controllers have. You have to select and unselect each switch. With the PIC, any (momentary) switch selection can cancel any previous selected switch. This is what I am looking for. I think I did find it but have not had time to really get into it.

Brian

[Hi-Q]

Hi Brian, this is a part of the schematic I used to control 4 channels via an infra red remote controller. I had no means of programming a PIC so did it the old fashioned way using latches to control relays. I used CD40107 devices as they have a sinking capability of around 130mA so no relay drivers were required. In fact, by using sensitive relays I was able to insert 68 Ohm current limiters to keep the latches happy. The 5th input deselects the lot and at switch on, you can arrange for any one of the 4 channels to come on as a default using one of the DIL switches (SW1). The relay outputs either dumped the sources to ground via 47 ohms or were switched to the output sockets, obviously you would wire the relays as required for your application. A bit agricultural but no device programming required and it did the job, in fact a number of the original units have been built without any problems.
Les