Big 7 seg LED display

[sayzer]

A concept as below could work, I think.

It is just a concept though. Can be modified for anode / cathode path.
You will need 8-transistors + 4 for the common ones.
ULN type of drivers could be handy here, but you need to make use of them with respect to anode/cathode issue.



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[mat janssen]

This will not work.
The transistor will work as a emittorfolower and the voltage on the emittor will not come over 4,3 volt.

[sayzer]

While I was editing the concept, mat posted.

How is it now?

[mister_e]

Nope ! or i have some doubt...

[mat janssen]

The schena above is still not ok.
Her an example how it should work.

From Darrel:
Mat, the file caused an error in vBulletin due the the filename "div. voltages.GIF". Can you try again?

[shahidali55]

Thanks for your replies everyone..
Is there any logic level convertion IC that can do this???

Sayzer, your idea for the a,b,c,etc segments is using NPN transistors is what i had in mind.
If i feed the output of the pic to a 4011 (AND gate with its both inputs made 1 common),
and then give it to a PNP transistor, will it work???
I think the AND gate will do the level conversion, i'm not sure ? ! ?

[mat janssen]

Here another try for the diagram.

[keithdoxey]

Thanks for your replies everyone..
Is there any logic level convertion IC that can do this???

If i feed the output of the pic to a 4011 (AND gate with its both inputs made 1 common),
and then give it to a PNP transistor, will it work???
I think the AND gate will do the level conversion, i'm not sure ? ! ?

No. The 4011 will still be connected to the 5v supply so the PNP will always be driven as its base will not be allowed to go to 9.6v to turn off.

You could use a chip with open collector or open drain outputs. Another ULN2803 would do the trick but would occupy about the same space as the three resistors and NPN transistors it replaced.