Trying to make a Pip-Boy like game with LED buttons on a breadboard

Question

I'm new to making electronics and I'm having a hard time of going about this. I have had a little help but I'm stuck.
The way I'm wanting to have the circuit work is there are 3 LEDs with 3 switches connected ( with the LEDs very close t its switch so it can behave like the real Pip-Boy). So each LED has its own momentary push button switch.
What I'm trying to accomplish is when I hit the momentary button it will light up its LED and stay on until I press button number 2 which will shut off the first LED without hitting its button and so on with the third, so no matter which button I press it will kill power to the previously pressed button's LED.
I'm not the best with translating circuit diagrams to the breadboard but I'm willing to try anything without an Arduino or Raspberry Pi, I wasn't wanting to code anything due to the Pip-Boy being a limited size. Thank you

Answer 1

You don’t need no stinkin’ Arduino.

What you need is a latch for each button A, B, C. When A is pressed you want to Set the A latch on. But if either B or C is pressed you want to Reset the A latch to off.

The set/reset latch is easily accomplished with two NOR gates. The OR function is easily accomplished with two more NOR gates.

You get 4 NOR gates in the cheapest 14-pin DIP package you can buy (CD4001, 74HC02, etc).

So the whole thing can be done with three quad NOR ICs and a few resistors and your switches and LEDs.

I chose to use the inverted Q output to drive the LEDs because some gates are better at sinking current than sourcing.

EDIT to show NAND version

With NAND gates the Set and Reset inputs become active low, so the inputs now idle high and are pulled low with the switch.

We still want an OR function but that’s ok because you can convert an AND to/from an OR by inverting all the inputs and outputs (DeMorgan’s theorem). This works to our advantage because the NAND converts to an OR with active low inputs, which is what we have. The 4th gate is just an inverter to create an active low signal: creates an active low Reset when either input goes low.

So the final circuit would be something like:

EDIT#2 to show 74LS00 pinout

Here is what one section should look like.

The other two sections are copies so work on getting a single section working first. Make sure pressing the A button turns the light on and that it stays on when you release the button. Verify the LED turns off when the B button is pressed. Turn it back on with A and verify it turns off again when C button is pressed.

There's no guarantee which state the set/reset flip flop will power up in. If you want to guarantee the A LED turns on (and B and C turns off) at power up you could add a capacitor (.01 to 1uF) across the A switch. This would have the effect of pressing the button briefly on power up to get it into a known state.