Update: I have listed the LED Matrix Link on Tindie as a fundraiser to get this started. You can support it here: https://www.tindie.com/shops/FriedCircuits/led-matrix-link/
This prototype stems from another projectproduct to be that I haven’t posted about except for this sneak peak: Project Sneak Peak. I noticed that most LED Matrix drivers on the market use shift registers to give a microcontroller the ability to control more LEDs than would be possible. Last year I came across the MAX7219 from Maxim Integrated. This cool little IC does all the work for you to drive a LED Matrix or LED Segment display. It uses a variation of the SPI protocol and can be daisy chained. The other cool feature is you only need 1 resistor to set the max current and therefore the brightness. The best part is there is an Arduino library already.
Since I have been playing with this IC and getting to know it I decided to make a carrier board that fits on the back of a 3mm (each LED size) LED Matrix. As seen below, the left is the input side and the right is the output side. The Arduino library lets you daisy chain 8 of these together. If you want more, then you just use a separate set of pins and another instance of the library. I think there is a way to get more than 8 in a row but you might need a buffer or something.
I have a few things to tweak in the design, but I plan on listing these on Tindie if anyone would like to buy them. Depending on the price I can get on the MAX7219 will determine if I need to do a fundraiser or not. They are rather a pricey IC but I would like to get them as cheap as possible as most people will need more than 1.
With the EXT_DIN right angle header (included) you can use this on a breadboard if needed. Otherwise I am working on a microcontroller link. It is the same size and has a Atmega328p. All you have to do is attach it to the EXT_DIN connector. This is great for permanent installation and you don’t have to tie up your UNO or other microcontroller. It makes a nice fit for ease of use with the pre-programmed sample sketch.
One of my uses for this is I want to setup 8 of them to display messages during the reception for my upcoming May wedding. Maybe give the ability for guests to send messages to it!
