Solution Finder

7-Segment with BCD LED Driver Problem

Posted by: Aubreyhu on Thu, 09/23/2021

Hi, all

Hardware:
CL5631BW - 3 Digit 7 Segment Display
CD4511BE BCD LED Driver Decoder

Attachment:
The BCDA inputs are wired with 680 Ohm Resistor and the outputs are wired with 680 Ohm Resistors to the 7 Segment correctly.

Problem:
All Numbers shown on the Display are inverted (All segments that should be illuminated are dark and vice versa).

I think the decoder is for Common Cathodes. Is it possible to change the mode for the decoder to Common Anode? Thank you in advance.

Files

Attachment Size
CD4511BE BCD LED Driver Decoder 20.35 KB

Comments

Submitted by PI-Zek on Sat, 10/02/2021

Hi Aubreyhu,

The CD4511BE BCD decoder is used for common cathode applications. A common cathode driver such as CD4511 will switch the logic of the segments between +Vcc and open circuit to drive each individual anodes in a common cathode 7 segment LED display.

CL5631BW is a common anode 7 segment display with +Vcc supply as the common connection. Each cathode for each segment will be pulled low to ground by the transistors driven by a common anode driver.

So if you choose a common anode for a common cathode decoder, you need to invert the logic of its outputs by using an external circuit. You can also choose to use a common cathode 7 segment display for your CD4511BE BCD LED decoder to match its application without additional components or vice versa.