# 2-color LED not working (Muzzle)



## raydomz (May 2, 2019)

(First my mini review)
I was excited to get my Muzzle build completed last night. I ran it with a jumper across the key input (still need the right jack) and ran it through the front end of my Thrasher 50. It's excellent! Identical to the Zuul I've tried in quickly chopping the signal for a very tight attack. The thrasher is already a quiet amp but with the Muzzle through the front end I only get a small amount of power amp noise. I am excited to get the the key input sorted out so it can be placed in the loop where it should be. 

(Now my tech issue)
My 2-color LED is not changing color at all. I have it wired (I believe) to be red when gated and yellow when open, but it remains red at all times. It does turn on and off with operation of the foot switch. Like I said in the review, it's a very responsive gate and I don't think it has any effect on the function of the pedal (and to be honest I am ok with it always being red) but I did want to learn more about what might be causing this issue. I am new to pedal building and have never dealt with a 2-color LED so I'm not sure where to start. Any help is much appreciated! 

Thanks!


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## Robert (May 2, 2019)

Is your LED a Common Cathode 2-color LED?    If it's Common Anode it won't work properly.


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## raydomz (May 2, 2019)

I can't say for sure. I am using this - http://www.pedalpartsplus.com/product-p/5513.htm it's not marked as cathode/anode common.
I am going to stop by our local store tomorrow and get one that is marked and try it out. 

If it is indeed a common cathode, what could be causing it to stay a single color?


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## chongmagic (May 3, 2019)

raydomz said:


> I can't say for sure. I am using this - http://www.pedalpartsplus.com/product-p/5513.htm it's not marked as cathode/anode common.
> I am going to stop by our local store tomorrow and get one that is marked and try it out.
> 
> If it is indeed a common cathode, what could be causing it to stay a single color?



That looks a lot like the 2 color LED that GuitarPCB sells, those are common anode.


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## raydomz (May 3, 2019)

chongmagic said:


> That looks a lot like the 2 color LED that GuitarPCB sells, those are common anode.


I'm going to check them with my multimeter tonight. I guess the only way to know for sure is to check the continuity of the center pin. 

I went to buy a new 2-color LED today and was surprised to find that this kind of distinction is not labeled clearly on any of the brands available (4 different brands at the electronics store.) We even looked through the parts book data sheets and none of bi-color LED's were labeled. 

At any rate...I'll check out what I've got tonight and report back.


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## raydomz (May 4, 2019)

Got this one solved last night!
It turns out the LED I originally used was a common anode, not the required common cathode.
The quick & easy test of this was to check the continuity of the center pin. Connecting the negative side of your multimeter to the center pin and the positive side to either of the outside pins will produce a lit LED if it's common cathode (will be one of the two colors depending on the side). This procedure is flipped for common anode LEDs. 

Thanks for the input guys!


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