Hello!
It's time to make a good diy interface for me and it's the first time I write a schematic. So i want to post it here hoping that someone will see it and write me if there's some horrible mistake.
Basically I want to:
Connect 16 pots to my arduino board through CD4067BE (by texas instruments).
Drive a 4x4 bicolor (red/green) ledmatrix through 74HC595N and 4 transistors 2N3904 (the transistors connect the columns to ground).
Use the same 4 transistor to drive the rows of a 4x4 switch matrix.
I've never build a led or switch matrix and I've never multiplexed before so I'm not sure that my schematic will work.
I have some questions:
a. It's the CD4067BE arduino compatible?
b. It's the 74HC595N wiring right?
c. It's the 2N3904 fast enough?
d. It's a good idea use the transistor for both matrixs?
e. Will it work?
You'll find the schematc's link in the next post because I can't post links in my first post.
Well done I have seen some very bad first attempts but this is fine. The only thing is that you have not put the 5V and ground for each chip on the schematic. Also you need some supply decoupling on each chip. That's a 0.1uF capacitor fitted across the supply of each chip as close to the chip as possible and 47uF or 100uF (or larger) capacitor across the supply close to the 595 chip. If you miss this out you could get erratic operation.
The switches pull down through a diode, that means you will get 0.7v as a logic low which should be just enough to grantee detection, although I would be inclined to make the 2K2 pull up resistors 4K7 just to drop the current through the diodes a bit.
