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Old 1st September 2011, 04:33 AM   #1
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Default Slectable momentary or latching action

I've googled every combination on the words momentary, latching, toggle, selectable, switch I can think of, but haven't found exactly what I'm looking for.

In quite a few desktop microphones there is a multi-position switch that selects the desired behavior of the mic. Push to talk, push on - push off, push to mute. I'd like to duplicate this functionality.

Maybe I'm missing a keyword that will improve my searches. I've only found information on flip flip logic diagrams.. sr, jk, d, t flip flops.

What I'm looking to do is more than just use a momentary button in a latching circuit.

Objective is to have one multi-position switch determine whether the main button acts as a momentary on, momentary off, or latching switch.

Thanks for your time.
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Old 1st September 2011, 01:44 PM   #2
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It is not clear to me if you are looking for a circuit to do what you want to do or a mechanical switch. There are many toggle and rocker switches that do On-Off-Momemtary (spring return). E
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Old 1st September 2011, 02:34 PM   #3
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I'm looking to build this type of circuit into a project.
If a simple switch could do it I'd be fine with that, but to get the necessary functions, I'm pretty sure it will involve a chip of some sort. I can get any one behavior using discrete components, but to allow touching the main switch to result in momentary on, momentary off, or latching behaviors, I believe I need a microchip, or a schematic to follow.

It's such a common element in mics, I would think it must be available somewhere, but I can't find it online.

thanks for the reply
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Old 1st September 2011, 04:05 PM   #4
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What you want is an "intelligent" switch function. You are the intelligence to define that function.
My intelligence thinks: use 2 switches (or go to post #2). E
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Old 1st September 2011, 07:17 PM   #5
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I'm not sure I understand how to use the information you've provided. Googleing "intelligent switch" brings up networking components like routers.

This will be used in a foot switch, so toggle and rocker switches aren't viable... I'd need something that can be stomped on. The idea was to put a big ole' button on the floor, and then decide how each "stomp" is treated for the session (PTT-PTM-POnPOff) by the position of a selector switch on the back.

Here is one example of a desktop mic that has the feature I'm looking for...MTS 67 - Paging Microphones - Installed Sound Microphones - Product Line - Conference Technology - Conference Technology

Quote:
Depending on the application, it is possible to choose between three operating modes: ON/OFF, Push-To-Talk (PTT) or Push-To-Mute (PTM). The different functions are controlled by a micro-controller.
I've put in several hours looking for this sort of thing, I figure I must be missing something. This has been done by dozens of products.

Thanks for you help.
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Old 2nd September 2011, 12:09 AM   #6
Enzo is offline Enzo  United States
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I think you are looking for some ready made industry part that is configurable in the manner you desire. I have to say "good luck."

I wouldn;t assume a desk top mic gets all these options from the switch itself. Cleary they are not all the same, but from my experience a "paging" mic probably has a simple switch. For example, one I can recall, has a press bar near the front of the base. Push to talk. If you want to latch it on, you press down the bar, and slide it forwards. it mechanically latches the bar. So the bar is holding down the switch underneath, the switch itself is not latching. You want push to mute? Then you go inside and move a wire on the switch. A SPDT switch will have a normally open side and a normally closed side. SO it is simple to wire that switch for either "direction" of function.

Read the description of the example mic you linked. It tells you the functions are handled by a "microcontroller. In other words, a plain old momentary switch is fed to a CPU, which in turn does whatever it is programmed to. The switch itself is merely a push button. If one did not want to make a microcontroller - like a PIC - to do this, you could still put together a relay based or even solid state control circuit.

So you want a stomp switch for your microphone. How about two buttons? A momentary for push-to-xxx function, and a small toggle or slide switch somewher on ther to select which. Then a second push on/push off switch next to the momentary one. This would be wired as an on/off switch. Now with the mic connected through this box, yo can stomp on the momentary to briefly enable or kill the mic, your choice, or stomp on the other switch for it to stay on.

And for that matter, if this is a gig to gig decision, just make two boxes. One a momentary, the other a latch on. Then just use whichever box suits.

That solution is totally passive, with no support circuitry involved.
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Old 2nd September 2011, 02:19 AM   #7
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Thanks Enzo, you are right. I rarely do this sort of thing and I thought an industry standard part probably existed. If it doesn't, I can work on another solution.
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Old 2nd September 2011, 03:48 AM   #8
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How's this look as a starting point?
Click the image to open in full size.

The main switch is a momentary spdt spring loaded stomp button. the ptt/ptm switch is located on the back of the unit. The latching part I'm not sure how best to make.
It will need to take a momentary pulse, to toggle the output to the opposite of it' current state. I'm not sure if debouncing it i a concern, it could be I suppose.

Could anyone point me to information I'm missing? My best guess at this point is a T flip flop...but most flip flops require a clock signal, which my project doesn't have.

Thanks again.
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Old 3rd September 2011, 12:02 AM   #9
Enzo is offline Enzo  United States
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The clocking signal is the closure of the pushbutton.
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Old 3rd September 2011, 02:10 AM   #10
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Ah, so the momentary switch would be wired to both the data pin and the clock pin?
So each press would set the data pin state and also set the clock? This would set the clock line high (telling the flipflop that now is the time to check the data line and take on it's state) and also set the data line high (telling the flipflop that it should toggle to the opposite of the current state).

Did I get that right?
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