Novice Question (Latching vs Momentary Switching)

Discussion in 'General Electronics Chat' started by pimpdaddy, May 30, 2008.

  1. pimpdaddy

    Thread Starter New Member

    May 30, 2008
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    All,

    I am not an electronics expert but I have a technical mind being a network engineer. I am a guitar player and my question is related to some equipment I am trying to use. Guitar amps usually have more than one channel and these channels are selected or changed using foot switches that connect via 1/4" phono jack plugs and use a latching or momentary(pulse) type switch.

    I am looking for an off the shelf device or schematic for how to create a little converter box. I want this device to be able to "see" a latching on or off change on one side via a 1/4" phono cable and send a momentary pulse out the other side on a 1/4" phono cable. This "device" might require some intelligence inside it but I wouldn't think it would be too difficult for someone who had the know how to design. I would prefer a passive device but if it needs to be plugged in that's ok too.

    Schematics, a link to a device that could provide that sort of fucntionality, anything would be great.

    Thanks
     
  2. bertus

    Administrator

    Apr 5, 2008
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  3. SgtWookie

    Expert

    Jul 17, 2007
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    That'll do ;)
    OK, well - switches need to be "de-bounced" - it's a LOT easier and more reliable if the switches are of the double-throw type. But I digress...

    Either an on or off change? That could be possible using some edge-detecting circuitry and a timer circuit, such as a 555. It would need some power, like perhaps a 9v battery, or power from somewhere.

    Tell us more about the signal level of the "latching on or off change on one side"... - is this merely a circuit opening or closing, or are there voltage levels? Or are you using a particular "stomp box" that you have schematics of?

    [eta]It would really be helpful to describe what you want to drive this add-on switch box from, or better yet, give a more complete description of your current setup. What does it take to switch to the next channel? Are you driving another box to do the change, or is it internal to the amp itself? What are the voltage levels and pulsewidths required to ensure reliable operation?
     
    Last edited: May 30, 2008
  4. pimpdaddy

    Thread Starter New Member

    May 30, 2008
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    SgtWookie, thanks for the response. I took a look at that wiki page that bertus suggested which had some interesting information but not exactly what I was looking for.

    My application is changing the channels on a guitar amplifier. Guitar amp channel selection is done via a powerless mechanical foot switch. They employ no battery or external power supply. I can't be 100% sure, but I don't think the amp provides any power via the 1/4" phone jack either.

    Simple guitar amplifiers employ two switching methods. Either latching or momentary. With a latching channel changing system the closing and opening of the latching switch on the foot switch allows you to select one channel or the other. With a momentary channel changing system I believe some sort of temporary connection is made. I have heard this called "pulse" but I'm not sure how you send a pulse with no power. Perhaps the momentary switching is just a momentary closing (latching) of the circuit.

    This could be the case because I have heard some issues where a guitarist has been using the wrong foot switch but can get channels to change by stomping on the pedal 2 or 3 times.

    I'm trying to give you enough help to help me so to speak but I am a bit outside of my box.
     
  5. SgtWookie

    Expert

    Jul 17, 2007
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    Don't worry about being "outside your box". It's good to do that, as it can make life more interesting ;) As long as nobody gets hurt! :eek:

    OK, it sounds like what would best suit your needs is a non-powered switch, where there is a common, and either one or the other connection is made. I don't know why you suggested the momentary pulse - perhaps neither do you. ;) That's OK though.

    At the moment, it seems like a single-pole double-throw switch might work, if it were latching. You could use a non-latching type if you were willing to hold your foot on it the entire time you wanted the sound switched to the other amp input.

    It probably would be best if it were non-powered, as a battery going dead in mid-performance could be quite annoying/distracting - unless you wanted to swap the battery out for a new one prior to each performance.

    Anyway, let's hear what you want to do.
     
  6. pimpdaddy

    Thread Starter New Member

    May 30, 2008
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    The latching switch isn't something I can replace. It exists within the pedal unit that I want to take advantage of. Basically I want an inline converter that converts latching to momentary. That might not be the way to say it.

    I think these foot switches for amps are very basic. All this latching and momentary stuff might just be closing or opening a circuit permanently or temporarily. I think perhaps I have this backwards and all of the complexity is in the amp. To restate in a different way what I think I need. I need something that will sense when a circuit changes from open to closed and closed to open on one side. Upon sensing either of these circuit state changes on one side I need it to momentarily close a circuit on the other side.

    I have a forum request into the actual designer of my amp and hope that he can shed some light on how this thing momentary switches.
     
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