Simplified Wiring Diagram

The Key Insight: One Driver for Everything! 🎯

You only need ONE LM18200 H-Bridge driver - it handles both DC and DCC modes.

The ESP32 just sends different signals to the same pins depending on which mode you select:

         ESP32-2432S028R
         ┌─────────────┐
         │             │
GPIO 18 ─┤PWM / DCC_A  │───┐
GPIO 19 ─┤DIR / DCC_B  │───┤
GPIO 23 ─┤BRAKE        │───┤
GPIO 4  ─┤RELAY        │───┼──→ To Relay Module
GND     ─┤             │───┤
5V      ─┤             │───┤
         └─────────────┘   │
                           │
                           ↓
                   LM18200 H-Bridge
                   ┌──────────────┐
        GPIO 18 ───┤ PWM Input    │
        GPIO 19 ───┤ DIR Input    │
        GPIO 23 ───┤ BRAKE        │
        GND     ───┤ GND          │
        5V      ───┤ VCC (logic)  │
        12-18V  ───┤ VS (power)   │
                   │              │
                   │  OUT1  OUT2  │
                   └───┬──────┬───┘
                       │      │
                       ↓      ↓
                   Track Rail 1 & 2

How It Works

DC Analog Mode

When you select DC Analog mode in the UI:

GPIO 18 outputs 20kHz PWM (0-100% duty cycle for speed)
GPIO 19 outputs HIGH or LOW (sets direction: FWD or REV)
LM18200 amplifies this to create variable DC voltage on the track
Your DC locomotive responds to the voltage

DCC Digital Mode

When you select DCC mode in the UI:

GPIO 18 outputs DCC Signal A (square wave: 58μs or 100μs pulses)
GPIO 19 outputs DCC Signal B (inverted version of Signal A)
LM18200 amplifies these to create DCC waveform on the track
Your DCC decoder locomotive responds to the digital commands

Complete Connection List

LM18200 to ESP32

LM18200 Pin	ESP32 GPIO	Purpose
PWM Input	18	Speed (DC) / DCC Signal A (DCC)
Direction Input	19	Direction (DC) / DCC Signal B (DCC)
Brake Input	23	Emergency stop
GND	GND	Ground reference
VCC (logic)	5V	Control logic power

LM18200 Power & Outputs

LM18200 Pin	Connection	Purpose
VS (motor power)	12-18V supply +	High current power
GND (power)	12-18V supply -	Power ground
OUT1	Track Rail 1	Amplified output
OUT2	Track Rail 2	Amplified output

Relay Module (2-rail/3-rail switching)

Relay Pin	ESP32 GPIO	Purpose
Signal IN	4	Relay control
VCC	5V	Relay power
GND	GND	Ground

Power Supply Connections

12-18V Power Supply
    ├─→ LM18200 VS (motor power)
    ├─→ DC-DC Buck Converter → 5V → ESP32 + Relay + LM18200 VCC
    └─→ GND (common ground)

Why This Works

The LM18200 is just an amplifier. It doesn't care if you're feeding it:

PWM signals (for DC speed control)
DCC square waves (for digital commands)

It simply takes the 3.3V logic signals from the ESP32 and amplifies them to track voltage (12-18V).

In DC mode: The amplified PWM creates variable DC voltage In DCC mode: The amplified square waves create the DCC signal

Safety Notes

✅ Always power OFF before switching modes (automatic in the UI) ✅ Common ground - All GND connections must be tied together ✅ Heat sink - LM18200 can get hot, use appropriate heat sinking ✅ Fusing - Add fuse on track output for overcurrent protection

No Separate DCC Booster Needed!

You do NOT need:

❌ Separate DCC booster circuit
❌ Different outputs for DC vs DCC
❌ Mode selection switches in hardware

Everything is handled in software by the ESP32 touchscreen UI.

Bottom Line: Wire up ONE LM18200, and you're done. The ESP32 software handles the rest!

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