Bi-Color (Red/Green) 24-Bar Bargraph w/I2C Backpack Kit
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What's better than a single LED? Lots of LEDs! A fun way to make a small linear display is to use two 12-bar Bi-color bar-graphs. However, this LED bargraph is 'multiplexed' - so to control all the 48 LEDs you need a lot of pins. There are driver chips like the MAX7219 that can help control a bar-graph/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 colorful bargraph without tons of wiring? That's where this adorable LED bar-graph backpack comes in. Much like our 8x8 and 7-segment backpacks, this backpack pairs perfectly with our bar-graphs and manages all the LED control and multiplexing.
The backpack uses a driver chip that does all the heavy lifting for you: It has a built in clock so it can multiplex the display. It uses constant-current drivers for ultra-bright, consistent color, 1/16 step display dimming, all via a simple I2C interface. The backpack comes with address-selection jumpers so you can connect up to eight of these bar-graphs on a single I2C bus. You can also mix-and-match the bar-graph breakout with our other types of I2C LED backpacks.
The product kit comes with:
- A fully tested and assembled LED backpack stick
- Two 12-bar bi-color bar graphs
- 4-pin headers
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.
Of course, in classic Adafruit fashion, we also have a detailed tutorial showing you how to solder, wire and control the display . We even wrote a very nice library for the backpacks so you can get running in under half an hour, displaying images on the matrix or numbers on the 7-segment . If you've been eyeing matrix displays but hesitated because of the complexity, his is the solution you've been looking for! 
Bi-Color (Red/Green) 24-Bar Bargraph w/I2C Backpack Kit ( 4:37 )