7 Segment Display - Anode vs Cathode

I bought the following 7 segment display:

https://www.electro-tech-online.com/custompdfs/2011/03/LTC-4627JR.pdf

The common pin is common anode. As the display counts, the lit segments should be off and the off segments should be on. In other words, I see a "-" for the number "0". Should I have bought a common cathode display or a universal display? Short of changing the code for each number, is there a way to make this work?

I am using PIC16F690 with 100 ohm resistors from PORTC to the appropriate segment pin on the display. Each common anode digit pin is connected to a transistor (BC184L). The transistor has to be connected to the positive bar to work.

Any help would be greatly appreciated.

Yes. It appears your code was for a common cathode display.

The BC184L is an NPN transistor. You should use a PNP one instead for the common pins.


If you still have the source code and a means to change it, do so.

I would have literally taken you less time to make the changes in the code (flipping the bits in the digit look-up tables) than it what it likely took for you to compose that post.

DemonicSandwich said:

Yes. It appears your code was for a common cathode display.

The BC184L is an NPN transistor. You should use a PNP one instead for the common pins.


If you still have the source code and a means to change it, do so.

I would have literally taken you less time to make the changes in the code (flipping the bits in the digit look-up tables) than it what it likely took for you to compose that post.

Click to expand...

Thanks for confirming my suspicion. One more question. Should a PNP transistor be used for an anode common pin and an NPN transistor be used for a cathode common pin?

Yes, in an application were the transistor is being used as a switch, you should use an NPN for low-side switching (common cathode) or a PNP for high side switching (common anode).