Multiple loop switching

[Unlikekurt]

Hello all.

The goal of my project is to make a pedal that controls some loops.
The pedal needs to have three momentary switches and the function should be
Switch A: Engages Bypass - - Disengages Loop A - - Disengages Loop B
Switch B: Engages Loop A - - Disengages Loop B - - Disengages Bypass
Switch C: Engages Loop B - - Disengages Loop A - - Disengages Bypass

I have been looking into some CMOS circuits and analog switch IC's and have read some of the information found on RG's site.  But I have yet to come to a concrete enough understanding to determine which way I need to go for this.
If anyone can offer some advice or point me in a useful direction that would be greatly appreciated.

Thank you very much.

James

[Groovenut]

You could try something like this for the switching logic


Using the mosfets to drive your choice of relay for each loop and bypass

or

You could also dive into uControllers. Less parts but more programming 

[Unlikekurt]

Dang! Thanks!   That's pretty much exactly what I was looking for.
Now I wonder if it would make sense to use this circuit to drive analog switch IC such as a CD4053 or small signal relays?

James

[Unlikekurt]

Or, rather, as this ic produces a steady state output, is there something similar that'd drive dual latching relays with a pulse ?

[Groovenut]

Or, rather, as this ic produces a steady state output, is there something similar that'd drive dual latching relays with a pulse ?

maybe something like this

[J0K3RX]

Look here > https://soundwavedesign.wordpress.com/moebius/   

It's all in Italian but it translates pretty well..

The eagle files are at the very top of the page.

It's designed to have remote switching but that's an easy work around.. or you could have the option for both.

[Unlikekurt]

Thanks groovenut, the flip flop would be great for a latching relay, but i'd still need the individual momentary switches to disengage the OFF loops.
Im hoping to find something like the aiken circuit you originally posted that would provide a pulse output to trigger latching relays instead of a steady state output to hold a non latching relay.

[R.G.]

The circuit groovenut showed is good. There is a sneaky, one-IC way to do the same thing. It was on geofex - until geofex got hacked early this year. I thought I had restored it all, but I see that this article doesn't respond the way I thought. I'll see if I can get this one back up.

The circuit is a "one of N" selector, also sometimes called a "radio button" circuit, after the way that old car radios used to have six or eight mechanical buttons. Press a button and that one button's action (i.e. station selection ) happens, and earlier actions are released.

The trick is to use a CMOS transparently latch, and some diodes to form an "OR" gate to reset. The latch circuit is the same as the latches in groovenut's post, but the diodes take the place of the other gates. It can also need some Rs and Cs to get the timing right.

[Unlikekurt]

RG,

Are you referring to the programmable fx switcher with the 74C373 chip?

James

[R.G.]

Yes. Using the 74C373 chip is the heart of a one-of-N, and the outputs can be used for any logical (  ) purpose.

The 74C373 is special in that the setup and hold times on the data and latch pins can let you use simple diodes for the 8-way OR gate. But you can fake this with other chips by using an R-C hold network on each input.

The 74C chips are expensive and hard to find, but if you want only one or two switchers, they might well be worth the work.

These days I'd use a microchips PIC. I have set up the programming environment so that programming a one-off is simple. Of course, you can get a clone of an Arduino Uno for about $5, so that kind of sets an upper limit on what parts should be. Well, the Arduino is a bit power-hoggish, too. It wants 100ma of +5. The PIC will live on 100uA exclusive of the output currents.

[Unlikekurt]

Thanks RG

Do you think that switch debouncing and momentary muting the output to hide the relay click would be necessary with the Aiken circuit?  If so, it seems as though going with a microprocessor (or processors if adding LED indication and momentary muting) might be the more direct manner - aside from the programming necessity. ?

[R.G.]

Do you think that switch debouncing and momentary muting the output to hide the relay click would be necessary with the Aiken circuit?  If so, it seems as though going with a microprocessor (or processors if adding LED indication and momentary muting) might be the more direct manner - aside from the programming necessity. ?

I'm interpreting this question as "is there a difference between using "hard" logic chips and a microprocessor in whether switch bounce and/or relay click will be a factor in the analog performance".

To a very large extent, the issues are identical. No matter how you generate the on/off signal to turn on a relay, the relay's analog performance is the same. If a relay is going to induce a click in the analog channel by switching, it doesn't matter what made it change state.

I think that the two approaches - hard logic chip implementation versus microprocessor - are exactly equal in terms of what happens at the relays. They differ in
(1) how much time, effort, and parts/pcb/wiring cost does each take?
(2) how much time, effort, etc. does it take to expand or modify?

I have personally built loop switchers both ways. One used the 74C373, because it was cheap and available at the time (1990s). It worked. One used a single PIC controller for all of the electronics except the relay-driver transistors. It worked. I have not built a relay looper from multiple hard logic chips because it's a huge amount of work to wire all that mess up (IMHO). CMOS hard logic prices are relatively higher now than when I started with it. An 8-wide transparent latch will cost you $2-$3. A mid-range PIC costs $3-$4. The PIC needs essentially nothing in the way of support chips. A set of CMOS hard logic chips to do the same job will cost ~$10 I suspect.

And the dollars are trivial compared to the cost of the relays, switches, housing and mechanical work.

The big issue is NOT the electronics. It's really your skill set. If you want a DIY looper and can program uCs, in my opinion it is silly to do it any other way. If you can't program uCs, you're stuck with hard logic unless you can convince someone who can program them to do it for you. In either case, the mechanical setup - switches, lights, relays, jacks, boards and wiring - is still going to be a massive job.