# LED polarity



## PedalPCB

*The LED symbol printed onto PedalPCB circuit boards is being updated, please read!


Proper installation of LEDs in PedalPCB circuit boards*

Traditionally the *Cathode* of a diode is installed into the *Square* pad of a PCB.     

*Symbol #1* and *Symbol #2* conform to this standard.   *Symbol #3* is technically incorrect by this standard and will be phased out of all future PedalPCB circuit boards.   This transition will be progressive as new stock is ordered, so care must be taken to ensure that the correct pinout is identified during this period.

Whenever possible identifiers (A for Anode, K for Cathode) will be printed beside the LED symbol on the PCB for clarification.


----------



## Willybomb

Just want to say thanks for updating this.  I was as confused as hell.


----------



## damonp

Im building the duo-phase right now and Im a little concerned as there are 2 different identifiers on the board, the implication of this article is I should wire them opposite of each other...


----------



## Robert

That's correct.


----------



## damonp

Robert said:


> That's correct.


So, top is Anode square, bottom is cathode square?


----------



## Robert

damonp said:


> So, top is Anode square, bottom is cathode square?



Yep.


----------



## evitative

Just to make sure I understand: for polarized caps the square pad indicates the anode and the circular pad indicates the cathode, but for LEDs it's the opposite?


----------



## Robert

I've never really referred to the positive side of an electrolytic as the anode, although that _is proper _terminology...

But yes, the positive lead of polarized caps go into the square pad.    The silkscreen is marked with a + so there shouldn't be any confusion there.


----------



## Diatrive

Are clipping diodes different?
I am building the Parentheses Fuzz and what looks to be the status LED's are like symbol 1 but there is one that has the square pad under the A.
What do I do with those? 

Thanks!


----------



## Robert

Haha, well that's confusing, ain't it?

This same thing applies to clipping diodes, but the silkscreen is backwards on that one.....    

Install the anode into the Round pad.


Thanks for pointing that out, I'll get it corrected ASAP.


----------



## JetFixxxer

Robert said:


> Haha, well that's confusing, ain't it?
> 
> This same thing applies to clipping diodes, but the silkscreen is backwards on that one.....
> 
> Install the anode into the Round pad.
> 
> 
> Thanks for pointing that out, I'll get it corrected ASAP.



So is that my issue with my Parentheses Fuzz?


----------



## K Pedals

damonp said:


> Im building the duo-phase right now and Im a little concerned as there are 2 different identifiers on the board, the implication of this article is I should wire them opposite of each other...
> View attachment 665


I wish I would have seen this post before I built mine because I assumed if the square pad was the positive on the led it was the positive for the ldr led... and I had to desolder both ldr leds


----------



## Robert

JetFixxxer said:


> So is that my issue with my Parentheses Fuzz?



It might be why you don't hear a difference between the two switch positions, but I doubt it has anything to do with the octave / blend issues.

If it's easier for you, you can reverse the polarity of D4 and D5 (two diodes left of the DPDT) rather than having to fool with the LED.


----------



## ody

Hello,

on the Parentheses Fuzz I do not understand the use of the switche, what is it supposed to do? D4 and D5 is the same pair as D7 and D8. Someone to tell me the role of the three positions?

the switche has been replaced by an SPST, for reasons of rationality or is there a major change? Was there a bug with the previous DPDT?


----------



## Robert

D4 has D6 (3mm LED) in series, so it's asymmetrical clipping on that side.

Center position has no clipping.

The other position is D7 / D8 (symmetrical clipping).


The DPDT was overcomplicated, the same job could be done with an ON/OFF/ON SPDT (which are much easier to find) so the board was updated.


----------



## the_grumpy_gnome

Fyi: If you're still unsure, LEDs are a pretty easy thing to test and flip if necessary.


----------



## Mourguitars

Thermionic Distortion the LEDS on the circuit its self is long leg round hole correct?


----------



## Robert

Mourguitars said:


> Thermionic Distortion the LEDS on the circuit its self is long leg round hole correct?



It depends on which revision of the board you have, refer to the symbols in the first post.


----------



## Mourguitars

Trying to up load a photo but files to large....I put long leg in ( A )


----------



## Kelmark1

Robert said:


> D4 has D6 (3mm LED) in series, so it's asymmetrical clipping on that side.
> 
> Center position has no clipping.
> 
> The other position is D7 / D8 (symmetrical clipping).
> 
> 
> The DPDT was overcomplicated, the same job could be done with an ON/OFF/ON SPDT (which are much easier to find) so the board was updated.




I have one of the boards that has a DPDT to be put on it, the new boards have a SPDT switch there , what switch should I put on it?, one of those odd DPTP switches from bitches love my switches?


----------



## Robert

Yep, that's the one. 

Part numbers are listed in the v1 build docs.:
https://docs.pedalpcb.com/project/Parentheses.v1.pdf


----------



## Kelmark1

thanks


----------



## farwest1

Thank you! I just messed this up in a circuit, so this clarifies.

What does the K stand for? A is Anode I assume. If K is Cathode, why did the industry not make it C?


----------



## Robert

Cathode was derived from the Greek word "_kathodos":  https://en.wikipedia.org/wiki/Cathode#Etymology_


----------



## farwest1

Robert said:


> Cathode was derived from the Greek word "_kathodos":  https://en.wikipedia.org/wiki/Cathode#Etymology_


Exactly the kind of content I come to these forums for!  Thank you.


----------



## Nostradoomus

PedalPCB

Come for the fuzz, stay for the etymology.


----------



## zgrav

Step right up!  Come to the forums for some fuzzy etymology


----------



## irvmuller

I saw this and wanted to ask about replacing diodes with LEDs. I've been reading about it and wanted to make sure, if you do this, the shorter end goes on the side where the strip would go in the diode, correct?


----------



## Nostradoomus

That’s right. The stripe on the diode pad indicates the negative (cathode) end. If the legs on your LED are clipped you can tell the negative side still by the flat portion right where the legs attach to the epoxy. Generally you’ll want to experiment with the clipping diode sections of the circuit...don’t replace the 1n5817 with an LED


----------



## irvmuller

Nostradoomus said:


> That’s right. The stripe on the diode pad indicates the negative (cathode) end. If the legs on your LED are clipped you can tell the negative side still by the flat portion right where the legs attach to the epoxy. Generally you’ll want to experiment with the clipping diode sections of the circuit...don’t replace the 1n5817 with an LED



Thanks for the quick reply. Yeah, changing the 1n5817 can definitely lead to some trouble. I'm planning do experiment with the muffin fuzz. Gonna try using symmetrical and asymmetrical set ups and using yellow and red diodes to check out the differences. I'll be running it on bass so I'll see wha the effect is. Doing this with the Stomp 75/Ram's Head and the Green Russian.


----------



## Nostradoomus

I like orange the best!


----------



## Barry

I like Blue Blue Di-oode


----------



## Matmos

damn... that's why my led is not turning on


----------



## fig

You put the long leg in,
You take the long leg out,
You put the short leg in,
( okay done typing now  😁 )


----------



## Kyle-Vick

I just put a Little Debbie together and it sounds really good and everything works properly, but it seems noisy. I think it’s normal with the BE-OD because they have so much gain, but now I am wondering if it could be because I switched the LED polarity. Could that be a thing? The status LED functions properly, but I am pretty sure I switched the polarity on that and all of the clipping LEDs. My previous pedal I did before this was one from BYOC and the build docs said to put the long leg of the LED in the square pad, so that’s what I did here.

TL-DR: if I switch the LED polarity, will it make it quieter, or is it just the nature of the beast?


----------



## Robert

The indicator LED wouldn't light up if you installed it backwards.

As for the clipping diodes, as long as you reversed them _all _then they're still working properly.


----------



## Kyle-Vick

Thank you!


----------



## Kyle-Vick

I wasn’t paying attention and was using a AC adapter with that pedal, that is why the LED was still working. With a DC pedal, it appears to function properly, just no indicator. Would there be any benefit in swapping the 4 LEDs inside around when I swap the indicator? Should not sound any different?


----------



## Urshurak776

Just bought the Cobalt and noticed they are still like example 3. I guess it will change to example
1 or 2 with the next batch of boards?


----------



## Robert

Yes, some of the boards still haven't been reordered since the change.


----------



## jhaneyzz

I've screwed this up several times assuming that the square pad is "always" ground... (hint,,, It's not)


----------



## jhaneyzz

AH! I get it,  "Cathode" is "K" because "Cathode" starts with a letter that --sounds like-- "K"


----------

