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Help with slide potentiometers and momentary switches?

Discussion in 'General Electronics Discussion' started by AGLite, Feb 19, 2012.

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  1. AGLite

    AGLite

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    Feb 19, 2012
    Hi guys!!
    I'm slightly new to electronics and need some help.

    I am a lighting designer and need some help modifying my lighting control board. The board has Slide potentiometers that set the values of the light fixtures, I'm looking to put in a momentary switch so when I press the switch it makes the value for that potentiometer go to 100%, without messing up the actual potentiometer. so I want the potentiometer and switch to work, so I can either hit the button for 100% or use the potentiometer to set the level i want. Please help!!! Thank you.

    -Austin
     
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,477
    2,820
    Jan 21, 2010
    Well, if you have a SPDT momentary push button, the NC contact goes to the wiper, and the common connection to whatever the wiper was connected to. The NO contact goes to the "top" end of the pot. So whenever you push the button (and hold it), it's just like you moved the slider right to the top.
     
  3. AGLite

    AGLite

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    Feb 19, 2012
    Thank you so much that was exactly what I was looking for!! But I just learned about pots today so I have no idea where the wiper is...heres a picture of the pots front and back.
     

    Attached Files:

  4. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,477
    2,820
    Jan 21, 2010
    You'll need to measure. There will be a pair of connectors where the resistance is unaffected by the slider's position. These are the two ends of the pot. There will be a third connector which will change resistance to either of the two previously located connections as the slider is moved (this is the wiper).

    Beware that the pots could be stereo, in which case there will be two sets of these. Given the use of the pot, it is likely that if the pot is stereo, only one half is used.
     
  5. AGLite

    AGLite

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    Feb 19, 2012
    Well theres four pins in all, two on each side. Three seem to be hooked up, one on the bottom and two on the top.
     
  6. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,477
    2,820
    Jan 21, 2010
    Most likely you'll find that either 2 are connected together, or one is not connected at all.
     
    Last edited: Feb 21, 2012
  7. AGLite

    AGLite

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    Feb 19, 2012
    so is the one on the bottom most likely the wiper? or one of the top?
     
  8. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,477
    2,820
    Jan 21, 2010
    You have to tell me that. (The instructions are above)
     
  9. AGLite

    AGLite

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    Feb 19, 2012
    okay so I found out the top right make the pair, then if you connect either of them to the top left they change with the pot. so is the top left the wiper? also where would the common go because there is three places the pot goes to.
     
  10. AGLite

    AGLite

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    Feb 19, 2012
    nvm I figured it out, thank you so much for your help. Is there anyway to get rid of the delay?
     
  11. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,477
    2,820
    Jan 21, 2010
    What delay?

    It is possible that the circuit smooths the output of the pot so that a "noisy" pot doesn't make the lights flicker as you move the slider.

    It's also probably better for your lamps that they not go from cold to max brightness. The drivers for the lamps may do this to prevent excessive current.
     
  12. AGLite

    AGLite

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    Feb 19, 2012
    well they are led lights and every other big lighting console has momentary push buttons for flashing the lights. but when I press the button there is a half second to a second of lag from when I press the button and the light flashes, this does not happen with the pot. is there anyway to reduce the lag?
     
  13. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,477
    2,820
    Jan 21, 2010
    no idea.

    Perhaps you can show us some pictures of your mods, including the tracks you've cut to make this work?
     
  14. AGLite

    AGLite

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    0
    Feb 19, 2012
    The button is drilled through the circuit board NOT interfering with any tracks. It is a NO single pull single throw momentary switch. It's soldered to the pot on the back side of the board. (wiper and top of the pot like you said) Its has lag, I do not know why. There is three tracks coming off the pot and I didnt know where to attach the common if I had an SPDT momentary button. So I choose a NO momentary. It works good it just has lag.

    Trying to get rid of the lag, maybe a capacitor or something?
     

    Attached Files:

  15. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,477
    2,820
    Jan 21, 2010
    The correct way to do it is as follows:

    Doing it your way can effectively short the ends of the pot together and that may be a very bad thing to do.
     
  16. AGLite

    AGLite

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    0
    Feb 19, 2012
    Ahh I see, I will change that. Okay so the NC contact gets soldered to the wiper, NO goes to the contact right next to the wiper (in my case). Then do I follow the wiper track all the way to the PIC or cut the track (for the common)?
     
  17. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,477
    2,820
    Jan 21, 2010
    use a craft knife to cut the track going to the wiper. Do it in a place where you can easily solder a wire across the gap if you want to remove this modification.

    I generally make 2 cuts about a mm apart and use the knife to remove the copper between the cuts.

    Connect the wire at the most obvious place. This may mean following the cut track back to the nearest solder joint, but if soldering a wire on there is difficult, you can remove some of the solder mask on the cut track somewhere and solder the wire to that.

    Edit: I can't guarantee the button will flash the lights instantly, but it may help.
     
  18. AGLite

    AGLite

    35
    0
    Feb 19, 2012
    Okay so I cut the track and leave the gap in the track? will this affect the pot? and then solder the common to the pot side of the cut track or the other side.
     
  19. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,477
    2,820
    Jan 21, 2010
    The other side. The switch in the NC position (i.e. unpressed) will connect across the break.
     
  20. AGLite

    AGLite

    35
    0
    Feb 19, 2012
    So this will not affect the pot right????? So the NC goes to the pot side of the cut track then the common goes on the other side??
     
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