Strange LED behavior

I have a series of LEDs and switches wired to pins 11 and 12.
Works perfectly I throw the individual switch and the appropriate LED lights.
I added another switch and LED wired to pin 8.
When I throw the switch the LED lights bright and the LED on pin 11 lights, not full strength.
Having voltage on pin 11 when the switch on pin 8 is thrown is going to cause problems.


Hello Ralphpdq
Post your sketch, well formated, with comments and in so called code tags "</>" and schematic to see how we can help.
Have a nice day and enjoy coding in C++.

1 Like

Thanks for the reply!
Nothing to do with a sketch.
I have the Blink sketch from examples running if you want a sketch.

If I disconnect the UNO (no wiring to pins) the
second LED does not light. Only if the UNO is
connected does the second LED barely light when the other LED is lit.
It is as if GRN is bleeding through the UNO.

blink.ino from examples with switchs ??????

Please post your code and a copy of your circuit as well.
How have you got your switches wired,?

Have you got all the output pins you use declared as outputs in your code.

The fact that the 'Blink" sketch works, does not prove that your code has problems.

Tom.... :grinning: :+1: :coffee: :australia:

I just threw Blink to satisfy the request for a sketch.

As I said before the sketch has nothing to do with the problem, it could be any sketch, this is a hardware problem.

I did have a sketch with the pins as outputs. I will put together a new one and simplify the wiring.

Thanks everyone for your replies.

It will take a couple of days, but I will post a sketch and a schematic and some pictures and a video to
illustrate the problem.

Since I am using a UNO clone I will ask on the manufacturers (Adafruit) site also.


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