Seven Segments and Current limit?

[SphinX]

Hi,

I have a project which i interface AT89C51 to 36 Seven Segments.
each 2 pins of the micro attach to three seven segments through 3 shift-registers.
The seven segments is the large one (about 7 x 4 cm or nearly)
I think AT89C51 can't drive these Segments directly.
What is the soultion ?

Thanx

 

[flatulent]

The usual trick is to use a BJT to increase the current capacity. If you logic line is high true use an emitter follower. If the logic line is low true, use a grounded emitter stage and do not forget to invert the logic level.

 

[Vonn]

I faced the same problem and was solved by using a HIGH-VOLTAGE HIGH-CURRENT DARLINGTON TRANSISTOR ARRAYS chip from texas
ULN2003A

 

[SphinX]

Hi,

Thanx.
I found also a chip to do that

ULN2803
https://www.webolution.de/Datasheet/uln2803.pdf

SphinX

 

[davorin]

Ever thought of using SPI LED driver chips from Maxim like the MAX6956?

Saves you some pins on your controller and LED current is set with simple resistor...and you don´t need resistor for each LED segment as with ULN drivers...

 

[sokrat]

DEAR SphinX


Yes you can use uln2003 if you will not use dot (decimal point)
For dot uln2803 "هتلاقيهم عند النخيلى" :lol:


S 8O KRAT