[SOLVED] common cathode 7-segment display driver resistors on anodes or cathodes?

[neazoi]

Hi, I have a common cathode 7-segment display and I am trying to decide where to put the resistors, on the anode (one for each segment) or at the cathode (only one resistor required)?

Obviously just one resistor on the cathode ismore economical but how about the display brightness, will it be affected depended on the number of segments lit?

 

[esp1]

Obviously just one resistor on the cathode ismore economical but how about the display brightness, will it be affected depended on the number of segments lit?

Yes it will, more segments On, less LED light intensity.
E

 

[FvM]

Obviously just one resistor on the cathode ismore economical

Just a bad idea.

 

[condorxan]

You definitely should use resistor for each LED segment on the anode side, this way you'll have constant brightness. You may also want to have a look at constant current LED driver circuits. MAX7219 would be really good choice for your application.
Good luck.

 

[neazoi]

Thank you all for your replies!