# transistor-driven LEDs circuit in a 5*5*5 LED cube

Hello,

I've just finished my long-term project which consists of making a 5*5*5 LED cube controlled by Arduino Mega. Unfortunately, there must be a mistake in my circuitry bcs I dont seem to be able to light even one LED out of the whole CUBE. I tried several LEDs randomly but couldnt turn on any. I am certain about my code and I multi-checked my wiring for electrical shorts, soldering, etc.

http://imageshack.us/photo/my-images/823/wiringfinal.jpg/

So it seems only two things might have gone wrong.

1) there is a mistake in the wiring logic (I am quite new to transistor sourcing and sinking, might be a mistake in my Maths also)

2) Multimeter doesnt indicate connection across the resistors (but I have no idea why, bcs it is mechanically connected for sure and the resistance is not so high not to indicate connection)

To sum up, I would greatly appreaciate if someone could check my circuitry and do the Maths (which is really simple). I honestly tried hard to find the problem, might be shame really that I couldnt figure out what was wrong but I have no more ideas.

Thanks a lot to all of you, Mike

Mike What chip are the cathodes connected to ULN2803A? what is the forward voltage and current rating of your Leds?

In your pic you show "ARD GND" and 12V battery "-". Are they connected together or not?

@ Frisky: yes, it is ULN 2803, sorry, I omitted that. LEDs are rated 1.8 V, 20 mA.

@ Runaway Pancake: yes they are interconnected

Mike

Have you tried a test without any arduino I/O? With the +12V up/applied and 5V available: 1) clip +5 to one 2803 input - to enable one column 2) touch +5 to each UDN2981 input, one at a time, to see that each LED in that column lights.

Mike here is a nice video I found using that chip to source http://www.youtube.com/watch?v=wXvs0CrRPIw&feature=colike I would try what pancake said. Drive one pin on the source hi and the uln2803 the hi and see if you could manually turn them on. I really done see a issue with how you built the circuit. I don't have any source drivers to built it. I've used the uln2803 for all sorts of things. Let us know what you find. I'm thinking about making a cube they are amazing to watch! Good Luck Don