Can ayone tell me how to add an LED to a footswitch?

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by SoCalSteve, Jan 27, 2008.


  1. SoCalSteve

    SoCalSteve Member

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    I'd like to add a light to the channel switching footswitch for my Budda. Is there a standard way of doing this? Would it help if I posted a picture of the inside of the pedal?

    Thanks.
     
  2. MisterAgreeable

    MisterAgreeable Member

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    We'd need to know if the amplifier is designed to drive an LED through the switch signal cable. Plug a cable in and measure for voltage with a meter. If none, there's no simple mod you can make to your footswitch to get it to light up.

    If it's not sending power, Boss makes a battery-operated switch that will light up when the circuit is closed.
     
  3. iaresee

    iaresee Supporting Member

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    +1 to what MisterAgreeable said: your amp needs to supply power when the circuit is closed. If it doesn't you can use a DPDT switch and wire up an LED + resistor on one of the poles, powered by a 9V battery, and the amp channel change connection on the other pole. The battery will last a long time. You could even wire in a Boss-style power adapter jack if you like.
     
  4. HipKitty

    HipKitty Silver Supporting Member

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    To further add, if you need to add the LED with a 9-volt battery, you're going to need to add a resistor, 1k, 1.5k or so, on the anode side of the LED...this is the side that will go to the + (red) side of the battery connector.
     
  5. AdmiralB

    AdmiralB Silver Supporting Member

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    Why would the location of the resistor matter?
     
  6. iaresee

    iaresee Supporting Member

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    It does not.
     
  7. AL30

    AL30 Member

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  8. AdmiralB

    AdmiralB Silver Supporting Member

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    Yes, the PRESENCE of the resistor matters. Contrary to an above post, the LOCATION of said resistor with respect to the diode does not.
     
  9. iaresee

    iaresee Supporting Member

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    +1. It can be +9V -> R -> LED -> Gnd or +9V -> LED -> R -> Gnd. Doesn't matter where you put that resistor, on the anode or the cathode of the LED.
     
  10. HipKitty

    HipKitty Silver Supporting Member

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    This is true for most LED's. We have actually come across some from our vendor (same stock number) that won't allow the voltage to run the + (attenuated) from the cathode to the anode.

    Now mind you, we are using the type of LED you won't get at your local Radio Shack.

    So, in order to ensure a working LED all the time in our builds, we have set our own standard of running the (attenuated) + voltage through Anode, out the Cathode to the negative supply (ground).

    Moral to the story, you may come across a situation where your LED isn't working...if this happens, place the resistor as I mentioned above.
     
  11. AdmiralB

    AdmiralB Silver Supporting Member

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    This makes absolutely no sense. Doesn't matter what kind of LED it is, the resistor placement makes no difference.
     
  12. iaresee

    iaresee Supporting Member

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    Let me make sure I understand what you're saying: you've got a batch of LEDs, all the same part number, all from the same vendor, and some of them only work when you put your resistor after the cathode in the circuit. But most of the work regardless of where the resistor is placed?

    I'm not saying your observations are false. I will question why you're still using those parts. I would discard them and return them. It sounds like your vendor has manufacturing issues because it shouldn't matter which side the resistor is on. It especially shouldn't be a non-deterministic property of the part you're using.
     
  13. HipKitty

    HipKitty Silver Supporting Member

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    We are NOT using them as we did return them. At that time (four years ago), it's all that we had to run with to complete orders, so we used them until replacements came in the next week.....therefore, I established a change to the build charts. Since they were changed, we've kept them that way and run it this way as our standard to this day.

    The manufacturer's explanation was interesting...but that's another story.

    The bottom line....is that if we only got 500 of those Red LED's that were part of a batch run of 10,000, somebody's got to have them....maybe Radio Shack? Who knows.
     
  14. SoCalSteve

    SoCalSteve Member

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    Thanks guys. Sounds like it's alot easier to just buy one!
     
  15. iaresee

    iaresee Supporting Member

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    Yea, but not nearly as much fun. :AOK
     
  16. iaresee

    iaresee Supporting Member

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    As an EE in semi-conductor design and manufacturing I'm dying to know the story. PM if you like. I've been trying all afternoon to think of a reason one resistor/LED configuration would work and not the other and I can't.

    Boo-urns to those LEDs even getting past quality control at the source.
     
  17. HipKitty

    HipKitty Silver Supporting Member

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    Trust me, at the time, I couldn't figure it out. When I called the rep, he had a quick explanation as to them being "reverse biased". Now, I generally like to keep things simple as to not complicate things to some. However, this wasn't one of those times so I went "technical" on him...I wasn't placing the + side of the 9 volt on the cathode, it was on the anode side as it should be. His reply was a deviation from his original answer..."the alloys were changed". Hmmmmm. With him on the phone, I ran a 1k pot in series, as a replacement of the 1k resistor...when placed in series with the -side of the 9 volt, I got it to light up at a very low setting, while on the + side, everything was as it was supposed to be. What light I did get was very faint when the pot was on the cathode side. I honestly didn't meter where the pot was at because I pretty much was ticked off by then and the rep was pushing for replacements and no further explanations.

    I guess it could've been the materials of the LED's...it was just the red ones, not our greens or yellows. I don't know and couldn't care at that point...they were defective in my mind and I was a week away from replacements that I had to qc upon arrival.
     

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