7 Segment LED 6's and 9's have no tails

[jack0987]

I am using a 4511 7 segment display driver but I noticed the 6's and the 9's have no tails.

By tails I mean, for a 6, segment "a" is not on, and, for a 9, segment "d" is not on.
Segments "a" and "d" would be the tails.

If I want tails, do I have to roll my own?

 

[birdman0_o]

Yea they draw them in a weird way, most likely simplified the logic. It would take a whole bunch of gates to add the tales, is that what you want?

 

[jack0987]

I could figure out the gates. Was hoping that they made a display driver that would do it.

 

[birdman0_o]

Many times easier to program a uC to display the numbers how you want them...just sayin

 

[jack0987]

Hmmm. Good idea. Did not think of that. I have a PIC programmer.

What way should I go about doing this?

 

[birdman0_o]

I have no information about what you are making

 

[MrAl]

I am using a 4511 7 segment display driver but I noticed the 6's and the 9's have no tails.

By tails I mean, for a 6, segment "a" is not on, and, for a 9, segment "d" is not on.
Segments "a" and "d" would be the tails.

If I want tails, do I have to roll my own?

Hello,

Check out the 74246, 74247, and 74248 or their LS (or other logic family) equivalents. They allow tails.

 

[Boncuk]

Hello,

Check out the 74246, 74247, and 74248 or their LS (or other logic family) equivalents. They allow tails.

... with the 74247 allowing a tail on the "6", none on the "9".

Boncuk

 

[MrAl]

... with the 74247 allowing a tail on the "6", none on the "9".

Boncuk

Hello there,


That's interesting, where did you get that information? The Texas Ins. data sheet says that they are all the same with tails on both.

There's also the MC14513B (cmos) which has tails on both the 6 and 9.

 

[jack0987]

The motorola data sheet I have for the 74LS247, 74LS248, & 74LS249 shows no tail for the 9 in their NUMERICAL DESIGNATIONS AND RESULTANT DISPLAYS graphic. However, their truth table contradicts this.

Let me ask this. Would one of them be pin for pin compatable with the 4511?

Going to my parts box now to see if I have any one of them.

Later edit: Bummer. I do not have any of them here.
Later, later edit: Double bummer. Unfortunately, I think the 74LS247-249 do not have a latch.

 

[MrAl]

Hi there,

There appears to be a discrepancy between data sheets then so you would have to get one of each and test yourself or maybe find a website where someone did this already. Some of them might be hard to find anyway. Did you check out the MC part number yet? So you need it to latch too? Well, good luck with it.

 

[jack0987]

Thanks so much all of you for your input.

At a glance the MC14513B may very well do. I'll get one and test it.
Not pin for pin compatable with the 4511, though. Darn.

 

[RODALCO]

tails at 6 and 9 's

I have succesfully used BC 547's and a AND gate to drive the a and d segment to get tails on a 7447.

You could probably do someting similar with your c-mos ic.
AND gate the BCD data and drive a PNP transistor in your case.

 

[jack0987]

Hi Rodalco:

In my case, I want a latch and the MC14513B would be the best choice, I think, so far I know of.

Just trying to think what your circuit would look like. For reference to others, if you have time, please post a quick schematic.

 

[Boncuk]

Hello there,


That's interesting, where did you get that information? The Texas Ins. data sheet says that they are all the same with tails on both.

There's also the MC14513B (cmos) which has tails on both the 6 and 9.

I used the ON-Semiconductor (Motorola) data sheet of the SN74LS247 which shows no tail on the "9".

Boncuk