I am trying to make work 181 ALU. I do not claim to know anything. I am very amateur. I tried to connect everything correctly but I can not see leds working for a simple operation example -> 1+1=2. What am I doing wrong here ?

 

Hello,

You have the pins 7 and 8 floating.



Pin 8 is the M input and pin 7 is the CN input.

Bertus

 

74LS181 is a 5V device. B1 = 12V is too high.

All of your inputs are floating. With 7kΩ resistors in series your circuit is not going to work.
You need to guarantee valid LOW and HIGH logic levels on all inputs.

You should never connect LEDs directly to logic outputs. Use an LED driver circuit to power the LED.

 

That works now I think I got correct results with sum operation like: 3+3 = 6. That was not working before as ground and VCC pins are not given and I tried to use normal battery. Resistance is now 2k.

 

You don't want to use pulldown resistors with LSTTL. The inputs source current and will cause the voltage on those resistors to creep up toward the threshold

 

74LS181 is a 5V device. B1 = 12V is too high.

All of your inputs are floating. With 7kΩ resistors in series your circuit is not going to work.
You need to guarantee valid LOW and HIGH logic levels on all inputs.

You should never connect LEDs directly to logic outputs. Use an LED driver circuit to power the LED.

I corrected that now.