How to connect a 7-Segment display?

[Lac]

Am I able to connect a BCD to 7-segment decoder with active-LOW outputs (7447) to a Common-Cathode 7-segment display? I assume I'm not able to do that, but is there a way to convert the BCD decoder chip's output, so I'm be able to run the Common-Cathode 7-segment display at that chip? I mean, are there a way to make the output signal of the 7447 to be HIGH instead of LOW`?

The reason for this is that i have bought the wrong chips for my 7-segment displays.

Cheers!
Lac.

 

[DigiTan]

I had the same problem once. You could try placing a string of NOT gates in between the inputs. Phillips builds a 74F756 octal inverter-buffer (with open-collectors) that should work well enough. Other octal inverters are available for other logic families too, of course. It might just be easier to order a 7448, or a common-anode display.

 

[Lac]

After a lot of searches, I found out that the 7448 is obslette! And i don't want to spend a lot of money buying new 7-segments! The solution with NOT chip uses awfully lot of space! I have got like 32 7-segments and each of them have got 7 inputs, that's 224 lines that I have to connect a NOT gate to, and each chip conatains 6 NOT gates. That means that I need 38 NOT chips!!! That will use up WAY to much space!

Any other solution? Aren't there any substitute for the 7448 since it obslette?

Cheers!
Lac.

 

[k7elp60]

Any other solution? Aren't there any substitute for the 7448 since it obslette?

You may want to try using CD4543, they are listed as BCD to liquid crystal display drivers, but the National data book I have says they will directly drive LED's. Pin 6 is Ph, when at Vss it drives common cathode LED's on the outputs pins thru a current limiting resistors, and when Ph is connected to Vdd it drives common anode LED's thru a current limiting resistors on the output pins. So the polarity of the level of the Ph pin determines wheter it is driving common anode or common cathode displays. Two US sources are
www.digikey.com and www.jameco.com.

 

[Lac]

Thanks!! I found those chips here in Norway too, and they were pretty cheap (half a dollar - 4,74 NOK)! Thanks again! Now I just hope these chips will work

BTW. what is Vss and Vdd? I assume Vss is +5V and Vdd is ground? Am I right?

Cheers!
Lac.

 

[jbeng]

BTW. what is Vss and Vdd? I assume Vss is +5V and Vdd is ground? Am I right?

You've got them backwards - Vss=ground, Vdd=+5v.
Sounds like those chips should work well for your application ...