# Relay Switching Help



## vadsy (Dec 2, 2010)

I have this idea where I'd like to use a home made foot switch on my pedal board to control the gain toggle switch on a pedal. I've come up with an idea where a voltage regulator and a small 5 volt relay hidden in the battery compartment controls the pedal with the normally open contacts wired in parallel with the pedal switch. I've drawn up a bit of a plan but my concern is the voltage after the relay going back to negative, it feels like something is missing... Can you guys look over this and tell me your thoughts? I'm sure more info might be needed so ask away.


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## dtsaudio (Apr 15, 2009)

It's drawn correctly. as long as the footswitch is a maintained switch it will work the way you specify. Only concern might be current draw if running on battery, and your capacitors might be too small. Using a wall wart power supply you may need to smooth it out a bit. 10ufd should be enough. Also keep the cap that is on the output side of the regulator as close as possible to the regulator.


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## vadsy (Dec 2, 2010)

The foostwitch is maintained, forgot to mention. The power is coming from a Voodoo Lab PP2+ so it should hold indefinitely. The manufacture spec says 0.1uF is recommended on the output side, would you change it up? The cap will be right on the regulator output so distance isn't going to be a factor. 

My concern was/is the 5 volts into 9 volts after the relay at the source, seems like a bad idea mixing things like this. I might be just not seeing the big obvious picture and making a big deal out of nothing.




dtsaudio said:


> It's drawn correctly. as long as the footswitch is a maintained switch it will work the way you specify. Only concern might be current draw if running on battery, and your capacitors might be too small. Using a wall wart power supply you may need to smooth it out a bit. 10ufd should be enough. Also keep the cap that is on the output side of the regulator as close as possible to the regulator.


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## dtsaudio (Apr 15, 2009)

The cap is there to prevent oscillation of the regulator. 0.1ufd is fine as long as it's a low ripple supply. Seems a bit small, but it should be fine.


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## nonreverb (Sep 19, 2006)

Should be fine. You may want to put a suppressor diode across the relay to drain the spike voltage when it shuts off


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## epis (Feb 25, 2012)

Why 5V relay ? I would go with 9V or even 12V relay without voltage regulator. No need to complicate it.

P.S.

You may put a small resistor in series with 5V relay coil to work with 9V supply. 
Measure first how much relay draws at 5V and use Ohm's law to calculate the value of resistor..


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## dtsaudio (Apr 15, 2009)

> You may want to put a suppressor diode across the relay to drain the spike voltage


That's a good point. However may not be necessary as a lot of relays come with the diode already installed. The relay data sheet will tell you.



> You may put a small resistor in series with 5V relay coil to work with 9V supply


Using a resistor will work, however when the relay kicks in and out the voltage change will in all likelihood cause a large spike and loud pop. The regulator will be quieter and isolate the power supply better.


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## epis (Feb 25, 2012)

Well, he's gonna use regulated PS anyway, diode across the relay coil should take care of voltage spikes, I would be more concerned with pops caused by switching gain on the fly with original toggle switch.
Vadsy, what pedal you're talking about ? Can you hear any pops when changing gain on the fly ?


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## jb welder (Sep 14, 2010)

vadsy said:


> My concern was/is the 5 volts into 9 volts after the relay at the source, seems like a bad idea mixing things like this. I might be just not seeing the big obvious picture and making a big deal out of nothing.


Not sure what you mean, the bottom line is ground. Relay is from 5V to ground. 9V goes nowhere other than input of 7805.


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## vadsy (Dec 2, 2010)

epis said:


> Why 5V relay ? I would go with 9V or even 12V relay without voltage regulator. No need to complicate it.


The 5 volt relay was readily available, small and cheap ($2.50), the voltage regulators were also available and 4 for 90 cents. I had a hard time getting anything for 9 volt and up that wasn't huge and rated for 33 amps or stuff like that. I didn't want to mess around with buying online and shipping for such a small item. Plus, this is a good learning opportunity for me with a chance to built something cool, I hope anyway. I guess I could try a bit harder to find a 9 volt one if this doesn't work out.



dtsaudio said:


> That's a good point. However may not be necessary as a lot of relays come with the diode already installed. The relay data sheet will tell you.
> Using a resistor will work, however when the relay kicks in and out the voltage change will in all likelihood cause a large spike and loud pop. The regulator will be quieter and isolate the power supply better.


I found the data sheet online here, if it does't have a diode or similar system I'll likely ask on what and where to install, since that's beyond my knowledge of basic electronics. I do want to minimize noise, if the potential exists, they are dry contacts so it should be ok, right? I also just realized my drawing in the first post is incorrect as I believe I need to switch a DPDT toggle, see the hyperlink for the pedal schematic below. It's the thread that started this journey, should be half way down or so. The relay is DPDT so that should still work.



epis said:


> Well, he's gonna use regulated PS anyway, diode across the relay coil should take care of voltage spikes, I would be more concerned with pops caused by switching gain on the fly with original toggle switch.
> Vadsy, what pedal you're talking about ? Can you hear any pops when changing gain on the fly ?


The pedal is a Wampler Black 65, I've been using it for 6 months and it's a keeper so I'd like to implement the switching system. I first thought about it here in this thread, and now its time to make it reality. I can't recall any noise from switching on the fly but I don't think so. I'd have to test it out and it's a bit late for that today.

Thanks for the help guys!

- - - Updated - - -



jb welder said:


> Not sure what you mean, the bottom line is ground. Relay is from 5V to ground. 9V goes nowhere other than input of 7805.


Yea, I'm over thinking it and making myself crazy.


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## gtrguy (Jul 6, 2006)

Why bother with the relay switching? Simply wire a 1/4" jack in parallel with the switch, plug in a footswitch and done... Or maybe I'm missing something?


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## vadsy (Dec 2, 2010)

gtrguy said:


> Why bother with the relay switching? Simply wire a 1/4" jack in parallel with the switch, plug in a footswitch and done... Or maybe I'm missing something?


You might be on to something way simpler and easier. A 2PDT footswitch could easily do, right? I could just hardwire with a multi conductor cable and actually disconnect the pedal toggle altogether. Will length of cable run play a factor on the circuit?


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## dtsaudio (Apr 15, 2009)

> A 2PDT footswitch could easily do, right? I could just hardwire with a multi conductor cable and actually disconnect the pedal toggle altogether. Will length of cable run play a factor on the circuit?


Should work. 
Downside, depending on the way the internal switch is wired, you may need 4 conductors. Try finding a 1/4" plug and jack for that. However it's possible you don't need four conductors.
Also if signal is going through the switch, like in a true bypass, you may pick up noise or adversely affect the sound. That will most likely depend on cable length.


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## vadsy (Dec 2, 2010)

dtsaudio said:


> Should work.
> Downside, depending on the way the internal switch is wired, you may need 4 conductors. Try finding a 1/4" plug and jack for that. However it's possible you don't need four conductors.
> Also if signal is going through the switch, like in a true bypass, you may pick up noise or adversely affect the sound. That will most likely depend on cable length.


I think if I go this way I'll just take a 4 conductor and hardwire it, pedal board is all screwed down anyway. I do believe the signal travels through the switch so it might be trouble but this is easy enough to try without too much trouble.


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## vadsy (Dec 2, 2010)

So I abandoned the relay switching system, can't really remember why I decided to go that way. I recall at first thinking about hard wiring a switch using a multi-conductor, even bought some parts, but someone at work suggested the relay which I jumped on without realizing all the trouble involved, especially without a 9 volt relay available on short notice. I think it was because the idea of leaving the stock switch in place and having the relay work in conjunction with it was appealing to me but it might not have operated properly since the switch is 2 poles and the relay wouldn't physically move the contacts of the switch. Anyways... it's $3.50 I won't get back but I did learn a few things along the way. One night over the holidays I decided to tackle this job using a 3PDT foot switch. I didn't have 6 conductor cable so I paired and twisted some wire and encased it with heat shrink. I used the third pole for an LED and powered it separately by splicing in with the loopers I have installed on the board. I'm happy to say everything works, no pops on switching or any extra noise with the addition of the wire into the circuit. Thanks for the help and suggestions, here are some finished pictures.


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## gtrguy (Jul 6, 2006)

Cool, sometimes a simple or 'brute force' approach is the way to go versus a more finessed solution.


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