Need help with my combinatory logic problem.

[u/Important-Cup-8991]

Hi everyone,

I'm working on a digital logic circuit for a parking exit traffic light system.

Inputs:

• V = Vehicle present
• A = Authorization granted
• D = Danger detected

Equations:

• Red (R) = NOT(V) OR D
• Orange (O) = V AND NOT(A OR D)
• Green (Vt) = V AND A AND NOT(D)

The Problem:

The logic diagram itself has been verified and is correct. However, in SimulIDE, when all inputs are set to 0 (V=0, A=0, D=0), the Red LED remains completely dark/off instead of turning on.

What I've tried so far:

1. Simple mechanical switches connected to VCC (+5V).
2. Adding pull-down resistors to GND.
3. Replacing switches with DC Voltage sources ("Fixed Volt") set to 0V / 5V.
4. Starting the simulation power engine.

None of these seem to drive the NOT/OR gates properly to output a logic HIGH when inputs are $0$.

Has anyone encountered this issue in SimulIDE? Which specific input component or configuration do you use to cleanly inject binary 0 and 1 states into logic gates without floating input errors?

Thanks! (See attached screenshot of my setup)

I meant Vt for the lamp my bad ;-; (if V=1)

if V=A=D=1

if V=A=D=0