Simple remote Loop Switch

[Minty]

...for a simple mind.

Hello all, I'm hoping you can help me.

I need a very simple FX loop switch that is controlled via signal from a cable (the source of which will be "Amp Control" output from a Boss GT8). Powered by a 9V source, preferably with a ground loop isolator if you think it's needed.

The basic idea is below, although I don't know what I need to make it work.

if anyone knows of a unit like this on the market then please let me know - I as yet can not find one, hence my presence here.

Thanks!  

[Minty]

Hello all, I've found the exact wiring diagram, except I want to run this at 9v, will this change the component values?

[Seljer]

The values are fine, the only thing you need to watch out for is the relay.

9V relays are kind of uncommon.

A 12V relay might still work at 9V, depends on what it says in the datasheet. A more consistent option would  be to use a 5V relay and wire in a series resistor, the drop the voltage from 9V down to 5V so you don't burn up the coil (use a multimeter to measure the relay coil's resistance and work out how much you need to add).


I'm not sure how the Boss GT8 runs it's amp control output but I'm guessing it's not a voltage signal, but rather it shorts out the input to ground (either with a relay or with a transistor). To make this circuit work with that you'd need to add a pull up resistor (about 10kiloohms should do) from left side of R1/D1 up to positive supply.

[Minty]

Hello Seljer. Thank you so much for taking the time to help me here. I am talking with CG who might be making one for me (with a ground loop isolator), but in case that falls through for any reason I'll continue with this conversation;

The values are fine, the only thing you need to watch out for is the relay. 9V relays are kind of uncommon.

Will THIS Work?

I'm not sure how the Boss GT8 runs it's amp control output but I'm guessing it's not a voltage signal, but rather it shorts out the input to ground (either with a relay or with a transistor).

Yes, I've checked with the Boss manual and it just closes the circuit between the Tip and the Sleeve of the jack plug.

To make this circuit work with that you'd need to add a pull up resistor (about 10kiloohms should do) from left side of R1/D1 up to positive supply.

Like this?

[Seljer]

Yes on that relay and yes on how you wired it

[Minty]

That's excellent!

Thanks for your help Seljer. If I end up making this myself for any reason, I'll post some results.

[Minty]

Hello again.

I'm ready to order the components and I have a couple of questions on Capacitors:

1. is it important what type (if so, what type should it be)
2. is the voltage important? I'm struggling to find a 0.1uF at 10v

Thanks!

[duck_arse]

C1 will be an (aluminium) electro, being a value over 1uF. usually, but not always. when using electros, you need to watch the voltage ratings, as they are usually very much lower than non polarised types. for your 12V supply circuit, you'd want 16V or 25V types, but 35V and 50V and 63V are all just as good. in fact, smaller values, like less than 10uF, will mostly be 100V rated. also fine.

you can also use a tantalum there, again 16V or more. as for the 0.1uF, 100nF cap, these will be "box", "green", "poly", "ceramic" caps, there are others. ceramics might be as low as 25V, polys etc will generally start at 50V, 100V is v. common. they will all be fine. you will be hard pressed to find a 100nF cap that won't go in that circuit.

[Minty]

Excellent, thank you for the quick reply.

This is actually going to be a 9V supply.

I was worried (not properly understanding caps) that a higher rating (such as 35v) would require a supply of 'at least' 35v in order to function properly.

This is brilliant, thanks for the help.

[PRR]

> worried (not properly understanding caps) that a higher rating (such as 35v) would require a supply of 'at least' 35v in order to function properly.

In capacitors, "35V" is a BLOW-UP number.

Actually I've put 36V on "35V" caps and they didn't blow-up in hundreds of hours; also 490V on "450V" caps for a few seconds. OTOH if it did blow-up at 35.001V the maker could say "We told you so!" and laugh.

Say I need engineering plans for a porch for my 9 dogs to lay on. Maybe Molly gets fat, or my lumber is crappy, so I should allow a little extra. A 16-dog porch is plenty strong for my 9 dogs. And also when 7 dogs are chasing cars and there's only a 2-dog strain. If it turns out that the smallest (cheapest) lumber will support 50 dogs, that's the way I'd go. (And no, it's only 2 dogs here, that was just example.)

There are old stories about using 450V electrolytics in 15V circuits, that they "decay" fast. This was true for some caps made 1950-1970. Cap technology has changed, and it does not seem to be true today. However simple price difference will encourage you to use 16V-100V caps instead of 450V electrolytic caps. (Price and size goes UP with voltage rating.)

[Minty]

Thanks again.

I'm sorry, I've more questions, based on the below diagram now including all jack socket connections:

QUESTION 1
Which of the jack connections should the signal carrier be connected to (I'm guessing the 'tip' - i.e. bottom terminal)?

QUESTION 2
"From FX Output" - should the relay be connected to the "Tip" of the jack (this appears to be connected to the sleeve (ground)?

QUESTION 3
This is the Jack socket that takes the signal to the GT8 "amp control" (i.e. the switch) - again, should this be the connected at the 'tip' - and should the return path be the sleeve? (I suppose it has to be).

Thanks for your patience!

[duck_arse]

remember when you're wiring up all those dogs, the collars have to point to the most positive end of the porch.

A1 - signal always to the tip connection, unless you have a very good reason for wiring otherwise. ground to sleeve, always.

A2 - see A1

A3 - see A2. the volts needed to turn on the base is more "signal" than the ground, so it goes to the tip.

always the signal to the tip. and if you have a socket with 2 dingers, the longer dinger will contact the plug-tip ding. the shorter dinger can be used for stereo signal, or for short-to-ground battery connection switch.

now you've spotted those errors, you'll need to redraw the corrections.

[Minty]

Awesome! Thanks. I do have more questions (regarding rounding of the signal and the return of the 9v) I'll redraw first.

Cheers!

[Minty]

Updated drawing below. My next questions are:

Signal grounding
G1 - G2 - G3 - G4 are all signal based, can these all be grounded together?

9v Grounding
G5 - G6 Guessing it's a bad idea to ground 9V and the signal together, so this needs to be isolated (The project box I have is aluminium) where do I send this?

GT8 Amp control 9v return
Since the sleeve of the this Jack socket will be carrying a 9v return when the circuit is closed, am I correct in saying I somehow need to isolate this?

Thanks again!

[duck_arse]

you will need to isolate something from something else. all the signal grounds on the G1-G4 need to be connected, yes. they can connect to the box if you isolate the switching grounds from the box. otherwise, the other way around, isolate all the (still connected) audio grounds from the box, ground switching to the box.

erm, the "+9V" needs to be referenced to the ground of the switching circuit. the switching signal also needs to be referenced to the same ground/0V. what is the "-9V" you have marked, where does it originate frumm? is it a real -9, or a mislabelled 0V?

[Minty]

you will need to isolate something from something else. all the signal grounds on the G1-G4 need to be connected, yes. they can connect to the box if you isolate the switching grounds from the box. otherwise, the other way around, isolate all the (still connected) audio grounds from the box, ground switching to the box.

So, G1 - G4 can all be connected together?

erm, the "+9V" needs to be referenced to the ground of the switching circuit. the switching signal also needs to be referenced to the same ground/0V. what is the "-9V" you have marked, where does it originate frumm? is it a real -9, or a mislabelled 0V?

In honestly, I'm not actually following this one. especially this bit

the "+9V" needs to be referenced to the ground of the switching circuit. the switching signal also needs to be referenced to the same ground/0V

+9V is from the positive terminal of the power supply
-9v is the negative terminal (should this be "ground")?

As I understand it, the GT8 doesn't ground the current itself, it just acts as a switch. Or am I wrong about that? (I'll get the multimeter on it this weekend).

I've since learned that the project box is actually plastic, with an aluminium 'lid' so that makes it easier.

[duck_arse]

G1 to G4 connected together, yes.

to measure your +9, you need somewhere to put your black meter lead. we therefore say the +9 is referenced to ... (whatever your black lead is on). if you have a 9V battery, and you put black on the (-) terminal, red to the (+) you will read +9V, because you referenced to the -, or 0V.

so, for your signals to talk from one end to the other, they all need to reference to signal ground. your switching section needs a source of power, something above zero volts. it needs to still be referenced to zero so it knows how high it is (9 volts, positive). anything (signal-wise) that is to switch it will also need to know how high it is, referenced to the power ground. so the signal to switch the power, and the power the signal is switching need a common ground or reference point. we call it 0V, and the voltages are positive.

hopefully prr will come by soon and explain this clearly.

[Minty]

Ah, I think I got it - where you said "referenced to" previously - I'd never heard that terminology before.

Man, you've been so helpful.

Just to finalise, the finished diagram is below, and if I understand this properly, the two ground symbols at the bottom (off C1 and Q1) will be connected to "0v"?

..also, if I want to put two LED's in there instead of 1, would this affect the rest of the circuit? Series/parallel?

Thanks again!

[duck_arse]

C1, Q1, 0V, yes, all connected.

two leds. well, you KNOW how to calculate the series resistor for a led, yes? well, instead of "1 led forward voltage", you will have, in series, 2 led forward voltage(s). if you used 1V6 for your one led calc, you would use 2*1V6 = 3V2 for two leds in series.

and if you put 2 leds parallel, it will be easier, because they both need their own series resistor. so, whatever value you had for one led (R3=4k7) goes in series with the second led (of the same colour: R3A=4k7), and that R3//LED1 string goes parallel the other R3A//LED1A string.

[Minty]

you KNOW how to calculate the series resistor for a led,

Actually I'm afraid not. Sorry, I've not done any of this since school.

and if you put 2 leds parallel, it will be easier, because they both need their own series resistor. so, whatever value you had for one led (R3=4k7) goes in series with the second led (of the same colour: R3A=4k7), and that R3//LED1 string goes parallel the other R3A//LED1A string.

So: