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Author Topic: Large 12v LED Xmas Display - Help to control please  (Read 466 times)
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North London
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Hi all,
Ive been reading through this forum for many months but this is my first post.
I’m struggling with an LED PONG game display I’m making for my mum for Christmas. Urgent help would be very much appreciated as the big day is almost here.

I have created a large 8x8 LED matrix using over 600 LED’s with resistors for each group of parallel connected LEDS. I have groups of 3 LED’s at each intersection so as to power them using a 12v power supply. When I supply the 12v to any column and row the LEDs light up nicely. I’m confident the matrix is working well and can be sent 12v current directly to make it all light up.
My problems have been with the Arduino. My first circuit consisted of direct outputs from the Arduino, 8 pins going to 50v NPNs transistors which had the 12v gnd and another 8 pins going to small NPN’s which in turn switched on 50v PNP’s fed from the 12v +. Naturally I had pull down and pull up resistors too. This worked except the LEDs were only getting 7-9v and were dim. If I supplied a 5v feed to the pins manually, I got the full 11.5v and the display lights up correctly.

I figured there was too much drain on the Arduino (outputs were only 0.5v when high) so I made circuit No.2. This time I used 74HC595 shift registers to control the NPNs & PNP’s. This didn’t work well at all and have now damaged my NPN/PNP setup.

I’m now looking at using two tpic6a596 shift registers to directly control the LED matrix which will be driven from the Arduino.
Before I spend any more cash, and more importantly, every day between now and Xmas, would anyone be able to advise me on my circuit to get a 12v feed to my LED Matrix, driven from my Arduino so that I can play pong?

I have a smaller prototype using just 64 LED’s (5v power supply) and this works fine.
NB, I’m using a 12v 1.5A DC power supply and have used a 78M05 to step down the voltage supply to the Arduino.
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North London
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NB, I had been trying to use the Arduino code from here : https://github.com/FredrikL/Pong
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