digital-logic
I need to build the following cicruit: F = (A AND B) OR (A XOR B) and I came up with the circuit in the image above. The bulb is only turning on when both A and B are OFF. The expected behavior is for the bulb to turn on if (A OR B).
I tested all the gates and bulb seperately and they all work as expected but the switch inputs don't, so I'm thinking it has something to do with the switch.
Same deal as Keelan's answer, but using a single 74xx00 series NAND chip (4 gates):
simulate this circuit – Schematic created using CircuitLab
The concept looks sound.
The main thing I see is that your 5.6K resistor is way too high to guarantee a low level for a 'LS04. The 100 ohm resistors you used elsewhere are okay (but they'll get warm if the switch is held).
Suggest you use ~150 ohms for the pull down resistors and maybe 4.7K for the LED resistors.
It would be better to use a spare inverter for each of the LEDs (so the output is low for LED 'on') and connect the LED + resistor between Vcc and the output. That's because you're loading the outputs with the LED and TTL can't source current that well. Then you can use 470 ohms or even less for the LEDs and they'll be much brighter.
Best Answer
I took a quick look at your Tinkerc cct.
Inputs to the 7486 XOR gate are both at logic 0 always. They are connected to GND. Output of the XOR will therefore always be 0 too. You need to connect the inputs to the upper side of the slide switch.