I'm doing a counter project at the moment. The IC's are 4026's and the 7 segment displays are common cathode.

In designing the PCB for the 7 segment displays, I have joined up all the earth/Gnd pins. Is this OK or can any members see a potential problem? Any advice on this will be gratefully appreciated.

I have attached an image of the pcb I have designed for the displays.

Thanks a lot.........JDR04

 

You may find it easier to use a different ICs, namely the MC14553B (CMOS 4553) with a MC14543 per 3 digits. This way, you would use FOUR ICs for six digits.
The segments are connected together in a parallel bus, and the individual digits are selected by applying the supply to the common anode connections. This will save you a big headache with the wiring. This requires common anode displays instead of common cathode displays.

Datasheet:
http://www.onsemi.com/pub_link/Collateral/MC14553B-D.PDF
See page 6.

If you need down-counting as well as up-counting, then you will either need to go to the 4026, or more preferably go the microcontroller route; that'll really reduce your parts count.

 

Hello,

I have been using the 74C925 in the past.
http://datasheetcatalog.com/datasheets_pdf/7/4/C/9/74C925.shtml
I do not know about the availability now.

Bertus

 

Hello SgtWookie, thanks for the advice. Will investigate the route you suggested.

 

Thanks bertus, will check it out.

 

Hi Bertus, I hadn't seen those 74C925 IC's before, and unfortunately I probably won't see them in the future! Findchips.com doesn't find any at reputable suppliers, and those ICs are going for $10 each on auction sites!

At those kind of prices, it's just not worth it.

The 4543/4553 suggestion I posted before isn't really that wonderful either nowadays; so many ICs and discrete components are required.

Microcontrollers are so cheap, plentiful, flexible and powerful that trying to build something using discrete 74 or 4000 series is just painful and expensive. There ARE a few 74 and 4000 series ICs that go well with uC's though - so they are not completely out of the picture. Yet...