7 segment display limitations


I am trying to control a 4 digit 7 segment display (without a driver) directly from an arduino nano.

I have realised theres a limitation to the combination of LED’s I can have on/off. For example If I want the first digit to display the number “1” and the second digit to display the number “2”, thats not possible. I have attached the 7 segment display circuit diagram.

Have I missed something?


I just realised theres a thing called multiplexing

Screenshot 2019-09-06 at 11.15.52.png

I just realised there's a thing called multiplexing

Great discovery.

OK, now you can do some experimentation with multiplexing code. Note - you need a 1k resistor in each of the eight cathode lines which you connect to the Nano (which is far better than the UNO for this sort of experimentation, generally with a "solderless breadboard").

It is good fun but do not consider using that in a design when you want to use it for a serious project. 7-segment display modules using MAX7219s or (not so useful) TM1637s are inexpensive and perform all the multiplexing for you and provide much higher brightness - I specified 1k resistors for a reason, nothing lower in value.

Also, practice downloading the graphics themselves from websites to pass on rather than screenshots. Do you see what funny thing happened to the diagram?

Thank you for the response! Yes I do see - some of the lines have disappeared.