How is it possible.. LEDs getting powered without cathode connected?

[{{909}}]

Tried in vain to get info from google on this but everything just leads me to guides on installed LED lighting, so you guys are my only hope.

been building a kit circuit thing called an LED cube, this model being an 8x8x8.



nothing in the construction is beyond my ability and so far I haven't had any problems, soldered the SM chips clean and initial testing has been problem free.

However this morning I came to work on it and although it worked perfectly fine last night, this morning its very strange.

In its current set up, I've soldered half the LEDs and stuck them into the base motherboard, only the anodes are connected and to test you need to run a wire from one of the 8 cathode connection points to the rows of connected LEDs. this was as it should be last night. This morning the LEDs are illuminated without connecting the cathode legs to anything, and the thing seems to be running through some sort of light pattern routine that it wasnt last night, albeit looking like its not working properly.

My question is, firstly how the fark can this be happening? I have no idea how to problem solve an issue that to my limited knowledge is impossible.

The LEDs are connceted like this:



Although I somehow ended up with my LEDs pointing in the other direction, the polarity is the same.

[pickie]

without seeing pictures of your setup we cant see whats going on, somewhere in the circuit its connected, you cant light a led with only 1 leg

[{{909}}]

Thanks for your reply Pickle.

without seeing pictures of your setup we cant see whats going on, somewhere in the circuit its connected, you cant light a led with only 1 leg

mine is almost identical to the final photo, all the anodes are in each column are connected to each other and slotted into a socket in the motherboard, all the cathodes in each row are connected together and will end up being connected to a single cathode point on the board.

heres a quick explanation:


This is pretty much how mine is, except the LEDs are facing north, in the photo the cube is being tested and the guy building it will add power and then use a wire to connect the white point on the board to one of the rows of connected rows cathode point. In my case some of the LEDs are illuminated and I havnt connected the cathode. None of the points coming from the board which are connected are cathode connection points and surely if there was some kind of short on the board meaning some were, wouldnt it just not work at all?

[Over Carl]

Can you get hold of a multimeter? In the UK, you can get cheap ones for around £5-10. Taking readings at various points would probably give you an idea of what is actually happening.

[pickie]

its possible that a few of the leds that are in the base are the wrong way around ??

[{{909}}]

its possible that a few of the leds that are in the base are the wrong way around ??

If that was the case then the circuit would still work, just the LED thats the wrong way round wouldn't illuminate. It makes no sense since none of the points connected at this stage are cathode points, I can only imagine that the motherboard is somehow misbehaving...but then it still wouldn't work because the whole thing would short.

[{{909}}]

Can you get hold of a multimeter? In the UK, you can get cheap ones for around £5-10. Taking readings at various points would probably give you an idea of what is actually happening.

I bought one with the kit and the damn thing doesnt have a proper beeping continuity test, just a zero ohm setting.

Looks like I better get one, I'm reluctant to continue soldering the remaining 206 LEDs if its never gonna work!

[Over Carl]

I was thinking use the Volts DC setting, put meter across each LED that is illuminated, then you may get an idea of which areas seem to be getting power, then you may be able to figure out where the power is coming from.

[beansontoast]

There was recently a few programmes on BBC called power to the people. At the beginning of one of the shows the presenter was walking amongst rows of fluorescent tubes with one end not connected and yet they were all illuminated. He was underneath cables between two pylons. You're not building this circuit underneath 11kV cables for some reason?

[{{909}}]

There was recently a few programmes on BBC called power to the people. At the beginning of one of the shows the presenter was walking amongst rows of fluorescent tubes with one end not connected and yet they were all illuminated. He was underneath cables between two pylons. You're not building this circuit underneath 11kV cables for some reason?

On the 26th floor, so no pylons overhead but this is China, they probably have 11kV cables running through the walls.

[{{909}}]

I removed a couple of 8x8 'slices' of LEDs today (4 were fitted out of 8) and it seems the 3rd has some issue, when I removed that the remaining lights started to perform properly. Still cant fathom out how this problem is happening but gonna crack out the meter later as overcarl suggested and see what exactly is coming out of the pins from the motherboard.

[pickie]

did you get this sorted ??