The Maxim MAX7219 IC is a serially interfaced 8 digit LED display driver. So it’s the ideal chip to drive an 8×8 led matrix. I got interested in these chips when I saw that lots of Chinese electronics shops were selling small MAX7219 led matrix modules. The weird thing is that the MAX7219 IC is not exactly cheap. Digikey wants +10$ for 1 IC in DIP format. The Chinese shops are selling 32mmx32mm led matrices + PCB with MAX7219 IC for less then 3$. I bought 8 of these modules from ICstation. While these modules work I don’t think the IC’s are really made by Maxim…
To drive the MAX7219 I used an Arduino with ATmega328. You only need 3 pins on the micro controller to drive the MAX7219. I found the fantastic Parola Arduino library on Codeplex which makes it really easy to make a scrolling text display. The following video shows one of the example sketches of the Parola display using 8 small led matrix modules:
I found some really cheap 60mmx60mm LED matrices @ Electrodragon (1.6$ a piece). So I needed PCB’s to plug the LED matrices in. On the Parola codeplex website you can find Eagle and gerber files to make such a PCB. This design uses wires to connect the different modules. I prefer to use jumpers. So redesigned the PCB in Eagle and used Dirty PCB’s in Shenzhen China to make them. The design is really simple, there is only the MAX7219 IC, 2 capacitors and 1 resistor to set the current for the LED’s (I used 33K resistors).
The jumpers make it really easy to connect them together:
I soldered up 10 PCB’s and tried them out:
Now I need to connect a bluetooth module to the Arduino and find an Android app to sent text to the Arduino 🙂