how to display E for error in single seven segment display with lowest number of chips when i have an input for an error then i want it to display E

 

You can do this with 1 resistor.

Remember the 7seg is JUST 7 LEDS.

So wire the 5 segments that make the 'E' to light when a pin goes high or low.

The 1 pin through a resistor to split to the 5 segments that make the 'E' then the common pin to high or ground..depending if the 7seg you are using is common cathode or common anode.

Are you doing anything else with the 7seg or just showing an error when it happens?

 

no i'm doing add/sub BCD so i got the seven segment with another display +/-1 for the rest of the number cuz it will not exceed 18, and the problem is when each input exceed 9 i will have a light and want the segment display E for error ^_^ and i might get red off the light if the E worked.

 

The 'E' would be nice, but for ease of use, how about just lighting the Decimal point to show an error?

 

i didn't think of it that is good idea. but i want my project to look neat so i don't want it to display the number in the display cuz when an input exceed 9 it will still work but in this case it would be binary add/sub

 

If you have the BCD driver constantly hooked up on the 7-seg, you can't just drive the segments separately to create the "E" display.

A way to overcome this is to put 2-input OR or NAND gates (depending on wheather the driver has active LOW or HIGH outputs) between the BCD driver and the 7-segment. That way, when you disable the driver (have it raise no segment to light) you will be able to input a different signal (in this case the "E" configuration) directly into the segments.

Is that clear?