What's better than a single LED? Lots of LEDs! A fun way to make a numeric display is to use a 4-digit 7-segment display. LED matrices like these are 'multiplexed' - so to control all the seven-segment LEDs you need 14 pins. That's a lot of pins, and there are driver chips like the MAX7219 that can control a matrix for you but there's a lot of wiring to set up and they take up a ton of space. Here at Adafruit we feel your pain! After all, wouldn't it be awesome if you could control a matrix without tons of wiring? That's where these adorable LED matrix backpacks come in. We have them for a variety of 8x8 and 7-segment displays. They work perfectly with the displays we stock in the Adafruit shop and make adding a bright display trivial.
The backpacks use a driver chip that does all the heavy lifting for you: They have a built in clock so they multiplex the display. They use constant-current drivers for ultra-bright, consistent color (the images above are photographed at the dimmest setting to avoid overloading our camera!), 1/16 step display dimming, all via a simple I2C interface. The backpacks come with address-selection jumpers so you can connect up to eight 7-segments (or a combination, such as four mini 8x8's and four 7-segments, etc) on a single I2C bus.
The product kit comes with:
- A fully tested and assembled LED backpack
- Ultra-bright 4-digit 1.2" tall yellow seven-segment display
- 5-pin header
A bit of soldering is required to attach the matrix onto the backpack but its very easy to do and only takes about 5 minutes.
Measurements after you mount the screen:
- 50mm/2" wide
- 120mm/4.7" long
- 13mm/0.5" high
- This board/chip uses I2C 7-bit addresses between 0x70-0x77, selectable with jumpers.
- EagleCAD PCB files, datasheets, and Fritzing available in the product tutorial