* Practical case: Lighting control from two points

* --- Power Supply ---
* V1: 5V DC Supply connected to VCC and GND (0)
V1 VCC 0 DC 5

* --- Input A ---
* S1: Momentary Push Button (NO)
* Modeled as a voltage-controlled switch (S1) driven by a pulse source (V_ACT_A)
* to simulate the physical user action of pressing the button.
V_ACT_A ACT_A 0 PULSE(0 5 50u 1u 1u 100u 200u)
S1 VCC NODE_A ACT_A 0 SW_BTN

* R1: 10k Pull-down resistor for Input A
R1 NODE_A 0 10k

* --- Input B ---
* S2: Momentary Push Button (NO)
* Modeled as a voltage-controlled switch (S2) driven by a pulse source (V_ACT_B)
V_ACT_B ACT_B 0 PULSE(0 5 50u 1u 1u 200u 400u)
S2 VCC NODE_B ACT_B 0 SW_BTN

* R2: 10k Pull-down resistor for Input B
R2 NODE_B 0 10k

* --- Logic IC U1: 74HC32 (Quad 2-Input OR Gate) ---
* Wiring Guide: Pin 1 to NODE_A, Pin 2 to NODE_B, Pin 3 to NODE_Y
* Pin 7 to GND (0), Pin 14 to VCC
XU1 NODE_A NODE_B NODE_Y 0 VCC 74HC32

* --- Output Stage ---
* R3: 330 Ohm LED current limiting resistor
R3 NODE_Y NODE_LED 330

* D1: Red LED Logic output indicator
D1 NODE_LED 0 LED_RED

* --- Models and Subcircuits ---

* Switch Model (Normally Open)
* Vt=2.5V: Threshold voltage for switching
* Ron=0.1: Low resistance when closed
* Roff=10Meg: High resistance when open
.model SW_BTN SW(Vt=2.5 Ron=0.1 Roff=10Meg)

* LED Model (Generic Red LED)
.model LED_RED D(IS=1e-22 N=1.5 RS=5 BV=5 IBV=10u CJO=10p)

* 74HC32 Behavioral Subcircuit
* Implements robust continuous logic to avoid convergence issues
.subckt 74HC32 1 2 3 7 14
* Pin Definitions: 1=InputA, 2=InputB, 3=OutputY, 7=GND, 14=VCC
* Logic: Y = A OR B
* Implemented using Sigmoid function S(x) = 1 / (1 + exp(-k*(x-threshold)))
* OR(A,B) is equivalent to 1 - (NOT_A * NOT_B)
* V(14) scales the output to the supply rail
B_OR 3 7 V = V(14) * (1 - ( (1/(1+exp(-20*(V(1)-2.5)))) * (1/(1+exp(-20*(V(2)-2.5)))) ))
.ends

* --- Simulation Directives ---
* Transient analysis for 600us to capture all logic states of the pulses
.tran 1u 600u

* Print required voltages for analysis
.print tran V(NODE_A) V(NODE_B) V(NODE_Y) V(NODE_LED)

* Calculate DC operating point
.op

.end

* Practical case: Dual Sensor Alarm System
* Corrected SPICE Netlist based on BOM and Wiring Guide

* ==============================================================================
* POWER SUPPLY
* ==============================================================================
* V1: 5V DC Supply
* Wiring: Positive to VCC, Negative to 0 (GND)
V1 VCC 0 DC 5

* ==============================================================================
* INPUT SENSORS
* ==============================================================================
* Sensor A: Front Door (S1, R1)
* Wiring: S1 connects VCC to IN_A. R1 connects IN_A to 0 (Pull-down).
* Simulation: S1 is modeled as a voltage-controlled switch driven by a control pulse
* to simulate a button press sequence.
V_CTRL_A CTRL_A 0 PULSE(0 5 10u 1u 1u 100u 200u)
S1 VCC IN_A CTRL_A 0 SW_GEN
R1 IN_A 0 10k

* Sensor B: Back Door (S2, R2)
* Wiring: S2 connects VCC to IN_B. R2 connects IN_B to 0 (Pull-down).
* Simulation: S2 control pulse is offset to test all truth table combinations.
V_CTRL_B CTRL_B 0 PULSE(0 5 10u 1u 1u 200u 400u)
S2 VCC IN_B CTRL_B 0 SW_GEN
R2 IN_B 0 10k

* ==============================================================================
* LOGIC IC: U1 (74HC32)
* ==============================================================================
* Wiring: Pin 1=IN_A, Pin 2=IN_B, Pin 3=SIG_OUT, Pin 7=0, Pin 14=VCC
* Uses a subcircuit to model the OR gate logic
XU1 IN_A IN_B SIG_OUT 0 VCC 74HC32

* ==============================================================================
* OUTPUT STAGE
* ==============================================================================
* Wiring: SIG_OUT -> R3 -> LED_ANODE -> D1 -> 0
R3 SIG_OUT LED_ANODE 330
D1 LED_ANODE 0 LED_RED

* ==============================================================================
* MODELS & SUBCIRCUITS
* ==============================================================================

* Model for Switch (Idealized Push-Button)
.model SW_GEN SW(Vt=2.5 Ron=0.1 Roff=10Meg)

* Model for Red LED
.model LED_RED D(IS=1u N=3 RS=5)

* Subcircuit for 74HC32 (Quad 2-Input OR Gate)
* Implements OR logic: Y = A OR B
* Mathematical implementation using De Morgan's Law for continuous signals:
* Y = 1 - ( (1-A) * (1-B) )  (normalized 0-1 logic)
.subckt 74HC32 A B Y GND_PIN VCC_PIN
    * Sigmoid function to normalize inputs: 1/(1+exp(-20*(V(in)-2.5)))
    * Logic formula: V(Y) = V(VCC) * (1 - ( (1-Sig(A)) * (1-Sig(B)) ))
    B_OR Y GND_PIN V = V(VCC_PIN) * (1 - ( (1 - 1/(1+exp(-20*(V(A)-2.5)))) * (1 - 1/(1+exp(-20*(V(B)-2.5)))) ))
.ends

* ==============================================================================
* ANALYSIS
* ==============================================================================
* Transient analysis to verify truth table (00, 10, 01, 11)
.tran 1u 500u

* Monitor Input and Output Voltages
.print tran V(IN_A) V(IN_B) V(SIG_OUT) V(LED_ANODE)

* Compute DC Operating Point
.op

.end