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  • Need help with Line6 mod

    Hi folks. I'm fairly new to the message board here, but I wanted to see if I could get some assistance.

    I have a Line6 DL4, and I'm modding it with an expression switch in the form of a 3PDT switch fit with a 10K resistor and wired to a plug in the expression pedal jack. This is a very common mod that I'm sure most of you have seen before. Basically just like an expression pedal except it takes you from the minimum to maximum ends of the expression range instantly.

    The mod istelf is simple enough, except I'm doing an add-on, or attempting to at least. My original thought was to mount a second 3PDT switch, jump the leads from the tip and sleeve of the jack over from the first 3PDT, and connect an indicator LED and a photocell. The goal in this would be so that I would be able to kick on the second 3PDT, activate the photocell, and use that with my hand or foot to sweep up and down the expression range. I drew up and attached a wiring diagram of this set up so you can see where I'm at.

    Click image for larger version

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    This is where it gets complicated. In looking into it deeper, I decided that It may be more in my interest to use an IR proximity sensor instead of the photocell, both for the extended range of the IR sensor and due to the fact that most of the bars and clubs I play at are not extremely well lit, and I'd rather not have to rely on ambient light.

    I was advised by Colin over at Experimentalists Anonymous to check out this IR sensor:
    https://www.sparkfun.com/products/242

    After doing some research, I believe I could make an LED/LDR combo by directly attaching 1 or 2 LEDs "face-to-face" onto a photocell, sealing it with heat shrink and mounting it inside the unit, connecting the LEDs to the IR sensor, and thereby convert the voltage into resistance (voltage fluctuations from the IR sensor = light fluctuations from the LEDs = resistance fluctuations from the photocell = sweeps in the expression range). My concerns are:

    1. How exactly would I wire up that IR sensor? Although I'm fairly familiar with pedal circuitry, photocells and IR sensors are out of my range of experience.

    2. The DL4 operates at 12V, and that IR sensor has a supply voltage of 4.5V to 5.5V. If I wire the sensor to the power pads on the PCB, will there be an issue?

    3. The maximum output voltage of the IR sensor is 3.1 volts. Provided that I'm using waterclear, superbright LEDs with fairly low value resistors, will this much voltage be sufficient to light them brightly enough to activate the photocell?

    If I'm totally off base or crazy for thinking this would work, don't be afraid to tell me. Photocells and IR sensors are totally new territory for me so I'm just trying to figure it out.

    Any help would be greatly appreciated. Thanks!

  • #2
    Alright, I had a friend come over and help me figure through this, and this is what we came up with.

    Click image for larger version

Name:	Revised DL4 Schem.png
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    A few notes:

    The maximum voltage possible from the IR is 3.1V, and the LED feeding from it has a forward voltage of 3.4V, which is why there's no resistor attached.

    The 330 Ohm resistor between the 3PDT and the IR is needed to drop the DL4's 12V power feed down to the 5.5V supply rating on the IR.

    The LED I'm using is a Super Bright White, rated at 10,000 mcd maximum brightness (hard to look straight at). I'm guessing that I'll be running less than that because at best I'll be pushing it at 3.1V, .3V under it's forward voltage rating.

    The LED and Photocell will be attached via a dab of clear silicone and sealed together with heat shrink tubing.

    Anybody see anything I may have missed? I'm waiting on the parts to come in, within the next few days I'll know for sure whether the circuit works like it should.

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    • #3
      You must be kidding, huh?
      Juan Manuel Fahey

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      • #4
        No, just learning and putting myself out there to make some mistakes. If theres something I did that obviously won't work, an explanation would be nice instead of critical jokes, thanks

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        • #5
          I just had it brought to my attention that the DL4 is 9V, not 12 as I originally thought, so I'll have to change the resistor between the IR and the 3PDT switch down to 100 Ohm to drop the voltage.

          If anyone sees something I'm doing wrong and wants to point it out, I'd welcome the criticism. Not going to get my feelings hurt. I think I've covered all the bases on this but I'm no professional.

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