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Author Topic: Arduino as a Guitar Effects Switching Controller Question  (Read 2309 times)
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Hi,

I'm a guitarist and computer programmer (C/C++).

I'm currently giving my guitar effects setup an overhaul.

What I'd like to do is build a switching system that enables me to footswitch between different effects loops. I only require one loop to be active at a time. I'd like to the switching to be foot-controlled, with one switch for each effects loop. I'd like the switching to work so that when the footswitch for a particular channel is pressed, that channel is switched on while all others are switched off (hope that's clear).

I plan on using the runoffgroove Splitter/Blend <http://runoffgroove.com/splitter-blend.html> for the basic circuit, however what I need help with is figuring how to make a switch controller. Could I use Arduino for this or would something else me better? Are there any Arduino projects that use similar switching? Any other advice would be welcomed.

Cheers,

Chris
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So you want to use the Arduino to control relays between the Green Send & Return, and the Red Send & Return, as an example?

That'd be pretty basic stuff to do.  Read a digital input, when it goes low from the switch being closed, open the current closed relay and close the next one in sequence.

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Great, so I'm on the right track.

I have an old Arduino board (circa 2005 I think) which I've never used for anything. Would this be suitable or should I go for a newer board? If a newer board would be better, which one?

Would any existing projects be helpful as a starting point?

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The old board will be fine.
Look in the learning section of this site to get you started.
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No, that board should do fine.
You may need to put a new bootloader on it to talk with the latest IDE.

Hardware-wise, you're just looking at something like this I think.


* relay_control_guitar.jpg (53.35 KB, 960x720 - viewed 120 times.)
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How did this work - I can see two switches but three relays?

Also, is there any code that goes with this?
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You will have to do some thinking for yourself. That circuit, showed how to connect switches and relays in general. You write the software to make it do what you want.
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Thanks for the help so far.

I have a couple more questions:

What sort of relay should I use to route the guitar signals?

Also, to switch a loop on or off, does it need to be broken in two places or only one? That is, if the switching is done at the output end of the loops so that only one loop gets fed into the final output, does it matter if the input signal is still being sent to the other three loops or should these be broken at their inputs too?
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This one will do nice.
I had 20 of them sent to me for this board, they worked well to switch the contacts of a switch matrix.
Came from Digikey or Mouser.
TSC-105L3H
http://search.digikey.com/scripts/dksearch/dksus.dll?vendor=0&keywords=TSC-105L3H

Connect the relay between the Return to the NO and the COM to whatever it goes into next.

* Relay_ENG_CD_1461185_A.pdf (165.88 KB - downloaded 13 times.)

* board_less_FTDI_Module.jpg (526.27 KB, 1486x965 - viewed 77 times.)
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I am working on something similar right now with my son.

This post from a different forum should help http://www.diystompboxes.com/smfforum/index.php?topic=95572.msg840828#msg840828.  I have tested the circuit shown on a breadboard, and it works well with no popping sounds.  It is important to not just send power straight to the relay, or it will bounce back and forth when the power hits it, and you will get a nice popping sound.

The relays I am using are 5V 1A (TQ2 Series).  Futurlec has great prices on them, but they are SO SLOW.

Here is a great link on the topic that got us thinking about this project.  It is several years old, and is a manual system (no arduino), but his explanation how to eliminate noise while switching is helpful.  http://www.geofex.com/article_folders/rmtswtch/rmtsw.htm

Good luck,
Rob



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Thanks for the links to those articles - they will be very helpful.

One thing I'm not clear about is why I can't use solid state DIL relays (like these http://search.jaycar.com.au/search?w=sy-4090&SUBMIT.x=0&SUBMIT.y=0&view=list) for this project.
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The On/Off times are kind of slow, probably ok as you will not be switching on & off with great frequency.
The On-Resistances are kind of high, which may impact your frequency response.
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The On/Off times are kind of slow, probably ok as you will not be switching on & off with great frequency.
The On-Resistances are kind of high, which may impact your frequency response.


Actually, slow relay response times might be a problem. In most cases, the user will want to change from one effects loop (say, a clean sound) to another effects loop (say, a distorted sound) in time with the music. I can see a delay causing problems in two areas - firstly, if it creates silence while switching, and secondly that it might make the change out-of-time with the music.

I've come across something called a "high speed relay" <http://australia.rs-online.com/web/p/pcb-solid-state-relays-ssr/1718667/?cm_mmc=AU-PPC-0411-_-google-_-1_EEM_Generic_Dynamic-_-_inurl:relays#inurl:australia.rs-online.com_Broad>.

Would that be more  suitable?

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No - that one is slower!
http://www.maxim-ic.com/pst/run.mvp?q=dg401
May need dual supply.
http://www.maxim-ic.com/datasheet/index.mvp/id/1001/t/al
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Arduino for Teens available at Amazon.com.

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I am working on something similar right now with my son.

This post from a different forum should help http://www.diystompboxes.com/smfforum/index.php?topic=95572.msg840828#msg840828.  I have tested the circuit shown on a breadboard, and it works well with no popping sounds.  It is important to not just send power straight to the relay, or it will bounce back and forth when the power hits it, and you will get a nice popping sound.

The relays I am using are 5V 1A (TQ2 Series).  Futurlec has great prices on them, but they are SO SLOW.

Here is a great link on the topic that got us thinking about this project.  It is several years old, and is a manual system (no arduino), but his explanation how to eliminate noise while switching is helpful.  http://www.geofex.com/article_folders/rmtswtch/rmtsw.htm

Good luck,
Rob


One other thing I'm not clear about is where the relay should go in the circuit. I've botched together an image of roughly how the circuit should be using the various schematics I've come across (see attached).

At present, I've got the relay switching near the sockets. Would it be better to have the relay located so that it's outside the opamps? The problem with the way I've got it arranged now is that the output of the second opamp will always be feeding into the main output. Will this add noise? Does it matter?



* Snapshot.png (12.6 KB, 1266x344 - viewed 68 times.)
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