Ghost LEDs? Weird phenomenon happening to my white leds :O

I was soldering an led array yesterday. It's made up of 5 rows of white leds connected in parallel via a single 5 ohm resistor to ground. Each row consist of 4 leds connected in series. I got an AC soldering iron. 30 watt, 240 volts, 50 hertz. As soon as i touched the leads of the leds with my bare hands while in the array and touched the soldering iron tip on the other side of the array, some of the leds would very dimly light up.

Do you guys have a clue why this is happening?

Thank you in advance

Additional:


The leds light up even brighter when one side of the array is connected to earth via a 3 pin UK socket without the need of me touching the connections with my bare hands

The tip of your soldering iron is connected to something. Most likely the ground of your mains plug.

PS: Soldering components that are connected to a power supply (eg. Arduino+USB) using an earthed soldering iron is a good way to destroy those components.

Your soldering iron is not well isolated? Measure it :slight_smile:

mjkzz:
Your soldering iron is not well isolated? Measure it :slight_smile:

Some are deliberately grounded.

fungus:

mjkzz:
Your soldering iron is not well isolated? Measure it :slight_smile:

Some are deliberately grounded.

You are absolutely right, I did not see your reply and could not find the right terms :slight_smile: But measuring it (careful, could be high voltage) can find out :slight_smile:

mjkzz:
You are absolutely right, I did not see your reply and could not find the right terms :slight_smile: But measuring it (careful, could be high voltage) can find out :slight_smile:

Just unplug it and measure the resistance between the tip and the prongs on the plug.

My soldering iron is not earthed. It's got a three prong british plug but the top prong (earth) is not connected to anything. Only the live and neutral wires leave the plug to go to the soldering iron.