I'm thinking about making a project, I want to use some 7-segment displays, but I have no idea how I can use multiple 3-digit 7-segment displays. For my project I should need 4 of them. Can one of you guys help me and tell me which chip I should use or how I can do it. Maybe one of you has a circuit diagram that can help me?
If you use i2c 7 segment displays, you can add multiple sets of digits fairly easily, otherwise, you may need a Mega to have enough pins.
Adafruit, and others have i2c 7 segment displays, but usually in sets of 4 not 3 as you need. You can use the Adafruit matrix driver backpack to wire 3 sets of digits, and control them with i2c: Adafruit 16x8 LED Matrix Driver Backpack - HT16K33 Breakout : ID 1427 : $7.95 : Adafruit Industries, Unique & fun DIY electronics and kits
That’s what I was looking for, thanks!
For seven segment LED displays, you should use a MAX7219 as driver - very easy to drive using only three pins for (almost) as many as you need.
Each MAX7219 will drive up to eight digits, so two can drive four, three digit displays, two displays or six digits each driver. With only three such displays, you would want to program the MAX7219s the same, multiplexing as six digits even though one display is "missing", in order to get the brightness equal (though there is another way of doing that).