Switching Help Please

Discussion in 'The Projects Forum' started by Steelroller45236, May 10, 2008.

  1. Steelroller45236

    Thread Starter New Member

    May 8, 2008
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    Hello All,

    A newbie here.... really need some help in solving a problem.
    I am trying to build a remote switching footswitch for some of my rack effects for my guitar rig. Several of the units use a momentary contact switching requirement, which I've completed ....works fine, however I have no visual indicator of whether a unit is on or off. I have to keep turning around and walking back to the rack to see it's status. Not good for stage presence.
    Is there a way to make a LED light and stay on (or off) with a momentary switch setup?
    I have 4 devices that require this momentary setup.
    Any help would be greatly appreciated. And please keep it simple enough a caveman with a soldering gun could understand it.... Thanks,

    Wayne
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    There is a lot of information we would need in order to be helpful. What does the switch do, for instance? If it operates a device, can the LED indicator be botched onto the circuit, or must something halfway elaborate be added for that function? Do you have schematics for the several devices?
     
  3. Steelroller45236

    Thread Starter New Member

    May 8, 2008
    6
    0
    Since my post, I've discovered some things. It seems in both cases for each device, a push on/push off will work if you switch it twice. But on stage this is not really practical since there will be musical timing issues.

    I believe that there is a switching circuit in both devices not an actual relay. The switching in both cases either engages the device in the circuit or bypasses it. It does not turn the unit on or off, since audio passes through it. I am unable to find schematics on either of the devices as one company is out of business and the other only sells service manuals to qualified repair stations. And truly, it is more of a question of function vs. actual design or mods.

    Do you know of a circuit that allows a momentary switch to have a latching visual indicator LED that could be built inexpensively? It seems to be possible as I've seen other devices on the market accomplish this....but it is at the PCB level.

    I really do like this site, in just reading other problems/solutions for others, I've gained a bit more insight to circuits....thanks.

    Wayne
     
  4. beenthere

    Retired Moderator

    Apr 20, 2004
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    Such a device is almost certainly possible. It would probably be best as a stand-alone device that latched the momentary switch to control a status lamp and passed the switch contact on to the effects controller involved.

    Be very helpful to know more about the footswitch. Things like does it pull a line low (a line with some voltage present gets shorted to ground) or just complete a circuit. These are crucial details.
     
  5. Steelroller45236

    Thread Starter New Member

    May 8, 2008
    6
    0
    Ok, took me awhile to get that information but the answer is yes for one device and no on the other device. I could not locate a schematic of either device. I've tried and tried but no luck.
    More to the dilema....

    I have 9vdc 800 ma running to the pedalboard. It will be used to power a distortion pedal. I've got that working. I have 2- 4pdt (x-wing) switches that I want to control the amplifier channnel (switching between clean (chan. 1) and dirty (Chan. 2) and the reverb on/off. I want status LED's. I wired them up and the switches do exactly like they are supposed to however, adding the LED's (powered by the same 9vdc power supply that runs the distortion pedal, but blows the LED's out after a few seconds. So I tried a different wall wart One of those adjustable (from 3v to 12 vdc. 200 ma. and it works however that is not enough to power the distortion pedal and also the LED's seem a little dimmer as well. So I'm guessing that it is because they blew out because of too much amperage. Is that correct?

    My new $ 64K question is: how can I use the same 9vdc 800 ma. supply, "steal" from it and get the lights and pedal working simultaneously?

    I haven't given up on the previous issue yet with the momentary switches but it is becoming beyond frustrating.

    Any help is appreciated as always..... thanks,
    Wayne
     
  6. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    Your LED's probably burned out because you did not include current limiting resistors. See this reference for why they are necessary and how to figure them - http://www.allaboutcircuits.com/vol_3/chpt_3/12.html.

    I'm going to guess red LED's, so a limiting resistor to keep current down to 10 ma would be 750 ohms. If your LED's are blue, they have a larger drop, and you could use 680 ohms. This should let you work with the 9 volt 800 ma supply.
     
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