Ever tried those small relays PCB designed for Arduino/Raspberry Pi?

Discussion in 'Shock Brother's DIY Amps' started by Badside, Feb 19, 2020.

  1. Badside

    Badside Tele-Meister

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    Talking about this: https://www.amazon.ca/dp/B00E0NTPP4...4UTADuhCeMsG7dsSZTyRckYoCjSSsEQhp7NsAtaduvKLU

    They have many versions of them, from 1 relay to 16 on the same board.
    5VDC is easy to obtain from the 5VAC tap when you're not running a tube rectifier (I use a Delon voltage doubler to make sure I have enough voltage before the regulator, works like a charm).

    I've been putting relays on small perfboards in the past to keep the diode and cap close, and it works well. But this is so simple and quite cheap, even has optocoupling baked in. Only takes a few mA's to trigger it.

    Can't really think of a reason not to try it, worse case I'll be out a few bucks. But was wondering if anyone else has tried it.
     
  2. sds1

    sds1 Tele-Afflicted

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    Sure, not sure what all is on that board but I use similar 5V relays powered by a simple regulated DC power supply tapped off the 6.3VAC secondary. Basically what hoffmania sells on his site :

    https://el34world.com/projects/relay_switch.htm
     
  3. Badside

    Badside Tele-Meister

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    The extra components is for the optocoupling, basically the signal you send through your footswitch isn't directly turning the relays on and off, rather is just turns on a LED in the optocoupler (what looks like a small IC) which in turns energizes the relay coil. This is of course not entirely necessary for our application.

    Also, instead of a single DPDT relay you get to SPDT, which can be connected together of course, or used independently.

    I'm not a fan of running off the 6.3VAC line because I pretty much always DC elevate my filaments which means the footswitching circuitry must be kept isolated from ground at all points. Of course, my way requires an unused 5VAC winding on the transformer so not always an option.
     
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  4. sds1

    sds1 Tele-Afflicted

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    Yeah, elevated or not you must float the relay power supply if the filament winding has CT. This includes isolating the footswitch jack. Otherwise bad things will happen. Like this :

    [​IMG]
     
  5. Badside

    Badside Tele-Meister

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    The way is do this has the 5VAC filament only used for the relays (and these very rarely have a CT, which would only matter if you connected it somewhere anyway), therefore I refer it to ground and that means no need to isolate the footswitch jack, and these accidents basically can't happen.

    Requiring isolation bothers me because if someone uses a footswitch from a different amp that happens to have a metal case connected to ground, that means that metal case is now elevated and can wreak havoc if it touches another pedal.

    So, having the relay supply be on its own dedicated winding just saves me some trouble. Again, it requires a PT with a rectifier filament tap that is unused.
     
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  6. Whatizitman

    Whatizitman Friend of Leo's

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    Yes. I made a pi controller for a xmas light display. Never really used it, though. The process was more fun than the product, you might say.

    I have a couple of the 8 relay boards. I have never tried switching anything more than 120VAC, though. The xmas lights were about as crazy as I would get with that. They are cheap, though. I'd be far more worried about breaking something else with them!! :eek:
     
  7. sds1

    sds1 Tele-Afflicted

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    Interesting. How would this be different from a pedal powered by battery?
     
  8. Badside

    Badside Tele-Meister

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    Wouldn't be different really, the issue is more about shorting to the signal ground.
     
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