This i a instructables about making a 16 x 16 LED matrix that takes money so i is somewhat like a piggy bank, but cooler and way more fun to make

Step 1: Parts List

What you need?

256 x LED's (i recommend high brights)
16 x NPN transistor
11 x 220 ohm resistor
2 x 74HC595 - 8 bit skifteregister
1 x ATMega328 with Arduino Uno bootloader
1 x Electronic coin selector (or somthing like it)
?? x wires
1 x rotary encoder
1 x 7805 Voltage regulator
2 x 10 uF capacitors
1 x 16 MHz clock crystal
2 x 22 pF capacitors
1 x momentary normally open button
solder and soldering iron

Arduino software

sandpaper
saw
power drill
iron
inkjet photo paper
laserjet printer
blank PCB
Natriumpersulfat

Step 2: How It Is Going to Worke

The arduino is going to control two shift registers that will control a multiplexed LED matrix

the shift registers control the Anods aka the x-axis

and the arduino will control the cathods aka the y-axis

but because of the limited amount of output pins on the arduino we are sending the signal through two lines of transistor arays and that way control 16 LEDs with 10 arduino pins.

Step 3: PCB

Now to making the PCB

- cut the PCB to size 66 X 75 millimeters
- sand down the edge
- remove any fat left by your fingers
- put your glossy photo paper in the laser jet printer and print out the circuit (print as many as you can on one paper if you fail to get a descent transfer)
- cut the paper to size and place it on the cobber side of the PCB
- now put greaseproof paper on top of ti all an use the iron to transfer the print (remember to move the iron about to get an even coverage)
- it will take about 3 minutes or until it is evenly golden brown
- now place it in some water until the paper is dissolving
- now rub of the paper with your thumb
- if you, like me failed the first time like me just sand it down and try again
- if there is only some small gaps in the print you can use some water resistant pen
- now flow the instructions for the solvent(acid) that you are going to use(it probably says something like heat to 50 degrees Celsius)
- put your print in the solvent and leave it til it is don and you can see the plastic underneath the cobber

- now is a good time for a cup of tee

- clean the PCB free from acid and check that all is well
- now put a 0.8 millimeter drill bit in your power drill (a fixed power drill is a rely big help) and drill out all the holes