# Footswitch Instead of Toggle…



## Coda (Nov 13, 2021)

I have a project that includes two different sets of components that I switch between with an on/on toggle. As I transfer the project from breadboard to enclosure, I want to convert that toggle to a footswitch. It’s as simple as center row: in, top/bottom rows: out, correct. I know that is true, but I am troubleshooting the project and trying to eliminate all possible issues. 

Also, if I wanted to hook up a bi-color LED to said footswitch, would I just connect the two cathodes to the top and bottom rows?


----------



## fig (Nov 13, 2021)

Coda said:


> I have a project that includes two different sets of components that I switch between with an on/on toggle. As I transfer the project from breadboard to enclosure, I want to convert that toggle to a footswitch. It’s as simple as center row: in, top/bottom rows: out, correct. I know that is true, but I am troubleshooting the project and trying to eliminate all possible issues.
> 
> Also, if I wanted to hook up a bi-color LED to said footswitch, would I just connect the two cathodes to the top and bottom rows?


What type of footswitch are you envisioning? You'll want common cathode LED if using ON/ON as the anode leads would go to two of the ON poles.


----------



## Big Monk (Nov 13, 2021)

Coda said:


> I have a project that includes two different sets of components that I switch between with an on/on toggle. As I transfer the project from breadboard to enclosure, I want to convert that toggle to a footswitch. It’s as simple as center row: in, top/bottom rows: out, correct. I know that is true, but I am troubleshooting the project and trying to eliminate all possible issues.
> 
> Also, if I wanted to hook up a bi-color LED to said footswitch, would I just connect the two cathodes to the top and bottom rows?



You got it Man!


----------



## Coda (Nov 13, 2021)

fig said:


> What type of footswitch are you envisioning? You'll want common cathode LED if using ON/ON as the anode leads would go to two of the ON poles.


Common anode or common cathode?


----------



## fig (Nov 13, 2021)

Here's why I redacted my comment. You'll need enough current through that switch to power an LED, so I'm thinking it depends on the switch and pre/post switch circuits.


----------



## Coda (Nov 13, 2021)

I was going to run power from the 9v jack to a 4k7, and the to the LED. It’s not working though, I think I keep frying the LED.


----------



## Big Monk (Nov 13, 2021)

Coda said:


> I was going to run power from the 9v jack to a 4k7, and the to the LED. It’s not working though, I think I keep frying the LED.



Are you sure it’s a common anode?


----------



## Coda (Nov 13, 2021)

Yes.


----------



## fig (Nov 13, 2021)

do you have a coin battery?


----------



## fig (Nov 13, 2021)

That's common cathode alright 😁


----------



## Coda (Nov 13, 2021)

I figured out the led thing, I had it plugged into the wrong spot on my mod board. I was feeding it 9v…


----------



## fig (Nov 13, 2021)

Yeah, I have a half a working one because of that very thing 😑


----------



## Coda (Nov 13, 2021)

what voltage should I look for? I’m using a 4k7. Should I go up?


----------



## Big Monk (Nov 13, 2021)

Coda said:


> what voltage should I look for? I’m using a 4k7. Should I go up?



Set up a 5k pot as a variable resistor on the breadboard with input from power, wiper to power rail and output to ground. 

Insert the 4.7k fixes resistor in series with the wiper and then tweak until you get the brightness you like. 

You could even make the pot larger if you anticipate that it will be high brightness with a lower value resistor.


----------



## Coda (Nov 13, 2021)

Big Monk said:


> Set up a 5k pot as a variable resistor on the breadboard with input from power, wiper to power rail and output to ground.
> 
> Insert the 4.7k fixes resistor in series with the wiper and then tweak until you get the brightness you like.
> 
> You could even make the pot larger if you anticipate that it will be high brightness with a lower value resistor.


I’ll run some tests. For now, I seem to have an issue regardless, as I am measuring 9v after the 4k7. This idea is a complete mess.


----------



## Mcknib (Nov 13, 2021)

Your fwd voltages on both colours are pretty close so a 4K7 to the anode should be fine and would illuminate both sides about the same, with both cathodes wired to their 3PDT lugs as you say

It should definitely work as long as you've got ground going to the middle  common lug on the LED pole of the switch

Most LEDs are around 20 to 30mA fwd current so you'd need 300 to 450 ohms resistance to stop it burning up

So 4K7 is plenty it might even be too much if it's not a standard type LED

I had that before with blue ones where I whacked a 4K7 CLR on and it barely lit up turned out it was some fancy type that needed more current to illuminate

Just check your fwd current to make sure it's not a weird one and you can work it all out with ohms law if it is an oddity


----------



## Coda (Nov 13, 2021)

Mcknib said:


> Your fwd voltages on both colours are pretty close so a 4K7 to the anode should be fine and would illuminate both sides about the same, with both cathodes wired to their 3PDT lugs as you say
> 
> It should definitely work as long as you've got ground going to the middle  common lug on the LED pole of the switch
> 
> ...


Thanks for the input. Right now I am having trouble getting the voltage down. I can’t understand why I’m reading the same voltage before and after the 4k7.


----------



## fig (Nov 13, 2021)

What is "after" the 4k7? Just the LED?


----------



## Coda (Nov 13, 2021)

Here’s the schematic. It worked on the breadboard (didn’t use LED’s, or footswitches) so I am sure it’s a construction error.


----------



## Coda (Nov 13, 2021)

fig said:


> What is "after" the 4k7? Just the LED?


Yes.


----------



## fig (Nov 13, 2021)

Forget that....I see the schematic now.


----------



## fig (Nov 13, 2021)

what opamp is that please?


----------



## Mcknib (Nov 13, 2021)

Sounds like it may be a poor connection check your LED ground connections

The voltage drop across the resistor would be supply voltage less LED fwd voltage

So for yours one side would be 9v less 1.99v or 7.01v dropped and obviously 9v less 1.91v  or 7.09v dropped because  with a bi colour only one side lights at a time, on the LED side of the resistor you would get a voltage reading of whatever the voltage drop of the side being used is

If the circuits incomplete ie not grounded you'd get full voltage because it's got no where to go so maybe a bad connection somewhere breaking the circuit


----------



## fig (Nov 13, 2021)

Mcknib said:


> because it's got no where to go


I know _that_ feeling.


----------



## Coda (Nov 13, 2021)

fig said:


> what opamp is that please?


741.


Mcknib said:


> Sounds like it may be a poor connection check your LED ground connections
> 
> The voltage drop across the resistor would be supply voltage less LED fwd voltage
> 
> ...


Right now I have a 4k7 hooked up to the 9v. DMM from opposite 4K7 side to the power jack negative lug reads 9v.


----------



## fig (Nov 13, 2021)

Okay, that must be a "3" on the IN pin...looked like a 1?


----------



## Coda (Nov 13, 2021)

fig said:


> Okay, that must be a "3" on the IN pin...looked like a 1?


Yes. I apologize for the sloppy schematic. If I tried to use the DigiKey schematic software, I would still be working on it...


----------



## fig (Nov 13, 2021)

No apology necessary sir.


Coda said:


> Right now I have a 4k7 hooked up to the 9v. DMM from opposite 4K7 side to the power jack negative lug reads 9v.


Yes, as it should because there is no load correct?. Add the LED in series and check again. At the node where the resistor and LED meet, you should see a voltage drop.


----------



## Bricksnbeatles (Nov 13, 2021)

Coda said:


> Right now I have a 4k7 hooked up to the 9v. DMM from opposite 4K7 side to the power jack negative lug reads 9v.


If there’s just a single resistor and nothing else then then you should have no voltage drop across the resistor, and a current draw of ~1.9mA

Remember Ohm’s law— V=IR




*disclaimer: I just woke up from a nap, so I’m very possibly completely mistaken


----------



## Coda (Nov 13, 2021)

Bricksnbeatles said:


> If there’s just a single resistor and nothing else then then you should have no voltage drop across the resistor, and a current draw of ~1.9mA
> 
> Remember Ohm’s law— V=IR
> View attachment 18538
> ...


That makes sense…so I guess this Ohm guy is ok. I just have to find out why I keep blowing LEDs next.


----------



## Bricksnbeatles (Nov 13, 2021)

Coda said:


> That makes sense…so I guess this Ohm guy is ok. I just have to find out why I keep blowing LEDs next.


Have you tested the LEDs outside of the circuit? I’ve gotten bad bi-color LEDs a lot more than I’ve gotten bad regular LEDs.


----------



## Mcknib (Nov 14, 2021)

The way you've got the LEDs connected in the schematic would work I don't see any reason why it shouldn't as long as the CLRs are 4K7 it'll only allow the current needed to illuminate them


----------

