8 X 8 LED dot matrix display
Max7219 driver and board
This is a self assembly kit and requires soldering. The results however are worth it. It has 5 connections, 3 for SPI and +5v and Ground. These units can be daisy chained together to form complex displays.
work with Arduinos (see here) and have also been used with Raspberry Pi's (See here).
The kit includes:
- PCB, 5CM X 3.2CM
- 2 5 way angled headers to connect to the module and daisy chain from.
- 24 way IC socket.
- MAX7219 common cathode LED driver (Data sheet here)
- 10uF electrolytic capacitor
- 0.1uF ceramic capacitor
- 10K Ohm resistor.
- 2 X 8 way turned pin headers for the dot matrix display.
- 8X8 red common cathode LED display, 3.2X3.2 CM
When built the module has an input and output set of 5 way headers with pins as follows: - VCC (5V)
- GND (Ground)
- DIN (Data In)
- CS (Chip select, also referred to as "load" in some libraries)
- CLK (Clock)
To assemble: The board has silk screen printing which is clear on where things go, with the exception of the polarity of the electrolytic capacitor who's positive lead is, as you look at the top of the board, goes in the hole nearest C2.
We soldered in the in and out 5 way headers first, then the small components, the resistor, ceramic capacitor and electrolytic. Be careful with this, observing polarity of the electrolytic capacitor. Note also that we bent this over so it had no chance of fouling the LED display which plugs in directly above. We then soldered the IC socket. When we soldered the headers for the LED display we plugged them into the display then inserted them into the board. This ensures they are square.
Inserting the MAX7219 is tricky. We find that most IC's supplied in DIP packages have their pins a little wider than the sockets they are supposed to go in. Place edge on a flat surface, and gently push the rows of pins together so that it fits.
When we built our test ones we plugged in the dot matrix display the wrong way round. It displayed odd horizontal and vertical patterns. We the turned it around and all started working. Please be careful with polarity. There isn't supposed to be any polarity protection in the MAX7219 so be careful. We did get away with it but may have damaged our chip. **
There are various Arduino libraries around, for example see the link at the top of this listing. We used the LedControlMS.h which we found here, and it works well.
**Please don't try that at home...
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