Question on PCB notation

Discussion in 'Burnt Fingers DIY Effects' started by Meteorman, Jan 8, 2020.

  1. Meteorman

    Meteorman Tele-Holic

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    Kind of a pedal noob here. Did some BYOC units, basically paint by the numbers.
    Now I'm looking to build one of the overdrive units off the Effects Layout site, and the instructions are a little more sketchy (i.e. they assume I actually know pedal circuits).
    I'm stumped already by the notation on the PCB that the Effects Layout site sells.
    The I/O jack connection pads are laid out, left to right "IN" "GND" "L-" "OUT".
    My question is: what is the "L-" ? What gets connected there ?
    The schematic is here: http://effectslayouts.com/wp-content/uploads/2018/11/Exemplar-Drive-build-doc.pdf

    thanks for any help!
    this may not be my last question before this is done ....
    /mike PCB.jpg
     
  2. pj1440

    pj1440 TDPRI Member

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    I don't know much about pedals, but I can read the diagram.
    It looks like it will cause the LED to be lit when L- is shorted to GND.
    My guess is that it needs to go to a 3PDT bypass footswitch so it can be shorted to ground on one of the poles (the other two poles to do the bypass) when not in bypass and so indicate the bypass is not active.
     
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  3. matmosphere

    matmosphere Tele-Holic

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    PJ1440 is correct.

    There is a CLR and a LED directly under the gain switch that show when the pedal is on. The L- is to activate the LED when the pedal is turned on. The ground from the switch that activates the LED should be connected there.

    Every company that sells PCB's does things a little differently with this stuff. If you need I could draw up a diagram but if you follow the off board wiring diagram here (or a similar one) all you need to do is connect lug 4 (the one connected to the LED) from the 3pdt in the diagram to L-. There are several ways to wire a 3pdt switch, so if you use a different one just connect whatever lug connects to the LED to L- and it will all work well.

    http://effectslayouts.blogspot.com/p/general-layout-notes.html
     
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  4. Meteorman

    Meteorman Tele-Holic

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    Excellent - thank you gents !
    Makes sense now that “L-“ stands for the LED ground.
    Cheers
     
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  5. Meteorman

    Meteorman Tele-Holic

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    The PCB from Layout Effects arrived and it came with a bonus daughter board for ease of wiring the 3PDT footswitch.
    It includes wiring nodes for the sleeves of the In and Out jacks.
    I assume these are grounded thru the "GND" node on that daughter board - wired to the GND node on bottom of mother board.
    I don't see what, if anything, goes to the "GND" node on the top left of mother board (pic above), between the treble and presence pots.
    Is there such a thing as a ground loop in pedals, similar to amps ?
     

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  6. Feral Feline

    Feral Feline TDPRI Member Silver Supporter

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    DIY-PCB suppliers often include extra pads (your "nodes") in their layouts to enable the DIYer to customise a build. GuitarPCB, for example, often has several extra ground and power pads as well as pads for wiring up an optional extra switch, or to alter a control or add additional clipping options, etc.

    For example, you could use that extra ground-pad at the top of the Exemplar circuit-board to ground another circuit if you want to build a combo pedal.

    Otherwise, ignore the extra ground pad and focus on deciding whether you want the 3PDT-board or the main-circuit board to handle LED-indication duties — for example if you choose the 3PDT-board then you can leave the LED and CLR pads unpopulated on the main board.

    You'll feed the 3PDT-board's "LED" with power from the battery/DC-jack, or from the Exemplar's "PWR+" (which is in turn connected to the DC source) or use the "CLR" pad off the main board to power the 3PDT daughterboard's LED — use a multi-meter to determine which CLR pad on the main board goes to "PWR+", that's the one you'd wire to the daughterboard.

    I'm sure if I've got something wrong above, someone with more experience will correct me.


    I've got a few PCBs from Storyboardist to build up, but alas the Exemplar isn't one of them.

    Cheers,
    FF
     
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