Hi all,
If anyone has face this problem to help me,
In my project I have 12V and 5V , 12 volt for driving 12 seven segments and UDN2981 and 5V to drvie PIC16f877a, max7219, LCD, barcode reader (PS/2 ), DS275 and serial eeprom . when I useing only 3 digits of seven segments my project work fine without any problems and the barcode reader working without any problems but when I add 9 digits of seven segments the project is working with all seven segments but I when I insert the id card in the barcode reader it's not working well it's powered on with 5 volt but no response when I insert the ID card , I think that the current is not sufficient to drive the barcode reader , anyone to help me ?

I get 5V from 12V with 7805 regulter