Help with relays

[Buffalo Tom]

Im planning to build a rack mount 3 way input selector for guitar with tuner out function. So I'm starting with a input buffer on each input then I'm using maintained DPDT push button switches to send the signal either to a resistor summed output or to the "tuner section" of the switcher. Its with the tuner function I need some help. My idea here is to use three more push buttons that selects which signal is sent to tuner out jack. Im thinking this can be done with relays and momentary switches. But I only want one relay at the time to be "active" and send signal to tuner out. EXAMPLE: Let's say tuner button one is activated, lit up and sending signal to tuner out jack, by pressing tuner button two I want tuner button one to be muted and lit off. Hope someone here can point me in the right direction how to wire up 3 relays that communicates with each other like this. Thanks

[PRR]

How many hands do you have? Can you be playing one axe and tuning another at the same time?

I'd consider feeding the tuner the sum of all three inputs. It should lock to the largest signal. Which is basically the only signal, not counting the background hum of the idle guitars, which the tuner "should not" count. You have buffers so the summing is three resistors.

[Buffalo Tom]

How many hands do you have? Can you be playing one axe and tuning another at the same time?

I'd consider feeding the tuner the sum of all three inputs. It should lock to the largest signal. Which is basically the only signal, not counting the background hum of the idle guitars, which the tuner "should not" count. You have buffers so the summing is three resistors.

The rack is being used by a tech so there is a need for muting unused guitars to the tuner. The tuner should only see one guitar at the time. I found this amazing article "Preamp Input Switching Using Relays" and it explains a lot!  http://sound.whsites.net/project163.htm

[R.G.]

You're describing a "radio button" selector, the term coming from the old rack of half a dozen or so buttons on the front of a car radio, each of which selected one station.

There is a setup with relays that does the radio-button selection, one and only one choice being active, with a new selection muting the others. It is tricky and needs tuning for the relays used, and generally an extra pole on each one. It works on the principle that relays need a larger pull-in current than holding current, and a fixed minimal holding current. The whole array is fed a current sufficient to hold in one relay, but not two. The extra contact connects each relay's coil to the holding current, so the "on" relay connects itself and holds itself in. The pushbuttons connect each relay coil to an un-restricted source for the coils. When a button is pushed on a new relay, that coil gets full pull-in current, and turns on. Its hold-in contact now connects its coil to the limited holding current, where both it and the previously-on relay are contending for current. If they're identical, there's not enough for them both, and so the previously-on relay drops out, leaving full holding current for the one with its pushbutton on. The new "on" relay stays after its pushbutton is released. I only saw this implemented once, back in the mid 70s., As I remember, it's a true pain to set up and keep running and needs a clot of diodes and resistors to get the currents correct and in the right places.

The CMOS radio button setup that Rod shows in the link you provided is simpler and cheaper. It's a variation of a common setup. There's another version of this in my "Programmable Switcher" article at geofex.com from about 2000. Today, I'd just program a PIC to do the work. Much simpler and more flexible if you can program.

[Buffalo Tom]

You're describing a "radio button" selector, the term coming from the old rack of half a dozen or so buttons on the front of a car radio, each of which selected one station.

There is a setup with relays that does the radio-button selection, one and only one choice being active, with a new selection muting the others. It is tricky and needs tuning for the relays used, and generally an extra pole on each one. It works on the principle that relays need a larger pull-in current than holding current, and a fixed minimal holding current. The whole array is fed a current sufficient to hold in one relay, but not two. The extra contact connects each relay's coil to the holding current, so the "on" relay connects itself and holds itself in. The pushbuttons connect each relay coil to an un-restricted source for the coils. When a button is pushed on a new relay, that coil gets full pull-in current, and turns on. Its hold-in contact now connects its coil to the limited holding current, where both it and the previously-on relay are contending for current. If they're identical, there's not enough for them both, and so the previously-on relay drops out, leaving full holding current for the one with its pushbutton on. The new "on" relay stays after its pushbutton is released. I only saw this implemented once, back in the mid 70s., As I remember, it's a true pain to set up and keep running and needs a clot of diodes and resistors to get the currents correct and in the right places.

The CMOS radio button setup that Rod shows in the link you provided is simpler and cheaper. It's a variation of a common setup. There's another version of this in my "Programmable Switcher" article at geofex.com from about 2000. Today, I'd just program a PIC to do the work. Much simpler and more flexible if you can program.

Thanks for your help R.G. It is much appreciated!