3 Relay / Footswitch in 124 question

[mauiboy81]

Hi there everyone. Thanks for all of the incredible information and insight into building the dream amp. I am very appreciative.

So I am starting a build based on #124 with a few tweaks here and there. I am feeling pretty confident with it except the whole relay/footswitch thing eludes me. I've been reading all the threads and feel like I'm getting a handle on things and then the curve ball comes flying by and I'm left scratching my head.

So this is where I am at....

I want to have 3 relays for OD, PAB, and Mid Boost. I do have a 12v radio shack transformer but I would really love to make use of the separate 6V 4A winding on my PT.

Is it possible to modify the #124 relay ps to accomodate the extra relay and led?

Or should I use the relay circuit from HRM BM schematic?

Or maybe a hybrid with the 6V winding -> voltage doubler -> regulator -> HRM BM relay and footswitch setup?

It would be cool to be as accurate as possible to the man with the large pants but I am ok with modifying it too. Whatever will be best.

I haven't ordered relays or anything yet so I am open to your suggestions if you want to help out.

I know there are some Wizards here who can shake their little finger and the perfect amp will appear before me........

Thank you all again

[heisthl]

Since you have the tap available use 5 volt relays - here is the simplest method I've come up with - extremely reliable and minimal parts (use a cheapo bridge rectifier and MIDI connector) as no regulation is necessary.

[wjdunham]

ampdoc who is active on this forum sells a nice 3-relay setup complete with a 5V regulator that runs off the extra PT tap, I installed it in my D'Lite, saved a lot of trouble.
Bill

[mauiboy81]

Thanks a lot Heist.

So in this setup the leds are on when the switches are engaged correct?

What are the ratings for the leds?

What kind of diodes do you use, are they all 1N4007?

And I know I'm a bit bone headed but what is the diagram in the bottom right showing me? Is it where the different relays connect to the din? Why does it show a switch on the mid-boost?

[mauiboy81]

Hey Bill,

Thanks for the heads up. I did contact ampdoc last week about the relays but I already have 3 universal boards that I would like to use.

Nick

[heisthl]

Thanks a lot Heist.

So in this setup the leds are on when the switches are engaged correct?

What are the ratings for the leds?

What kind of diodes do you use, are they all 1N4007?

And I know I'm a bit bone headed but what is the diagram in the bottom right showing me? Is it where the different relays connect to the din? Why does it show a switch on the mid-boost?

1. Yes LEDs on with relay.
2. Any common LED works because the resistor across it serves 2 purposes A. limits voltage across the LED and B. drops some voltage so you don't have to worry about over voltage on the relay with an unregulated supply. Bonus - the footswitch still works if the LED fails
3. Any diode works even a 1N914
4. Just showing that the relays need a Diode across the coil. You can connect the DIN pin out any way you feel is a standard for you.
5. I don't know why that switch is there - it shouldn't be.

[Structo]

Not to beat this to death but, I have my led's in series with the relay and switch.

The leds are very bright but I was concerned about losing too much voltage with a resistor and the relays not latching.

I only have two switches on my footswitch, OD and PAB.

I am using the PS and relay boards from Deric.

It has an 8v regulated supply with the 5v sensitive relays.

Not sure I can do what you are showing with a TRS type plug and jack.

I may need to go to the DIN type connector to wire it parallel.

[mauiboy81]

Thanks guys. Allow me to bust out my stick and take a few whacks.

I have a relay power supply board based on #124

I've drawn out a little something based on the #124 ps and HRMBM footswitch schematics I have come across. This would use 5/6V relays.(??)

Does this look like it would work?

The switches all go to ground on one side but on the other side the PAB is NC and the others connect back before the resistor, what's up with that?

Would it need the resistor and power LED after the regulator to drop the voltage a little more?

Drawing these thing out helps me get my mind around it so bear with me.

Thanks for your input.

Nick

[mauiboy81]

eh?

[mauiboy81]

Does anyone have any more insight into my relay predicament?

I may be forced to draw more pictures, take pictures of the pictures, and post them?

[heisthl]

Just my 2 cents but I've never been a believer in using a LED in line with a relay. Put the LEDs in parallel with the resistors, allow for a 2.5 volt drop. Most relays are pretty forgiving on the max and min voltages that allow them to work so read the relay spec sheet before choosing the rated voltages.

[mauiboy81]

Thanks Heist!

This sounds good to me. So you recommend an unregulated ps?

Of these which would you go with?

Omron- http://www.mouser.com/Search/ProductDet ... hwGQ%3d%3d

NTE- http://www.mouser.com/Search/ProductDet ... aoK5GlQ%3d

Nick

[mdroberts1243]

Thanks Heist!

This sounds good to me. So you recommend an unregulated ps?

Of these which would you go with?

Omron- http://www.mouser.com/Search/ProductDet ... hwGQ%3d%3d

NTE- http://www.mouser.com/Search/ProductDet ... aoK5GlQ%3d

Nick

I used the NTE 5/6 V relays... it is the widest range of operating voltage I've found... pickup on 70% of rated and allowable is 200% of rated... so you can range from 3.5V to 12V with that part.

If you use the series LED approach the range of the parts values/voltages are a bit more finicky than Heistl's method.

[heisthl]

what he said

[mauiboy81]

Thanks again you guys.

If I use 3v-4v blue LEDs will it drop the voltage too much or does the resistor prevent that?

With all 3 footswitch LEDs on will there be enough voltage to operate the relays?

Also, will adding a capcitor across the switch help with noise when switching or are they not necessary?