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ESP32-Based Relay Board with Power Monitoring and PoE Integration
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esphome_relay_control.md

ESP32-Based Relay Board with Power Monitoring and PoE Integration

Objective: Design and build a custom relay board using the ESP32 microcontroller with integrated Power over Ethernet (PoE) functionality. The board will control 8 relays, each capable of handling up to 10A at 24VDC, and include current monitoring for each relay using ACS712 sensors. The system will be compatible with ESPHome for easy integration with Home Assistant.

Project Requirements:

1. Functional Requirements:

  • Relay Control:

    • 8 relays, each rated for 16A at 250VAC and 10A at 24VDC.
    • Relay model: G5RLU-1A-E DC3 (Omron Electronics), with a 3V coil voltage.
    • Controlled via the ESP32 microcontroller.
    • Maximum Load: 10A per circuit at 24VDC.

  • Power Monitoring:

    • Each relay circuit will include an ACS712 current sensor for real-time current monitoring, calibrated for up to 10A.
    • The current sensors will be configured and calibrated for accurate power measurements in ESPHome.

  • PoE Power Supply:

    • Power input through an Ethernet RJ45 connector (TRP Connector B.V. 2250506-1).
    • PoE module: Silvertel AG9903-MTB, providing 3.3V output for the ESP32 and relays.

  • Microcontroller:

    • ESP32-WROOM-32 or ESP32-WROVER module with Wi-Fi and Bluetooth support.
    • Programmed using ESPHome for integration with Home Assistant.

  • Relay Driver:

    • ULN2803A 8-channel Darlington array for driving the relay coils.

2. Technical Specifications:

  • Input Voltage: 36V - 57V DC from the PoE module.
  • Output Voltage: 3.3V DC, up to 2A (provided by the PoE module).
  • Relay Coil Voltage: 3V DC, 200mA per relay.
  • Load Voltage: 24VDC, maximum current per circuit: 10A.
  • Current Measurement Range: 0A - 10A per relay (using ACS712 sensors).
  • Communication Protocol: Wi-Fi (802.11 b/g/n) for ESP32.

3. PCB Design Considerations:

  • PCB Layout:

    • Compact design with all components securely mounted.
    • Proper trace width for high-current paths (at least 2mm) to handle up to 10A per circuit.
    • Adequate isolation between high-voltage (24VDC) and low-voltage (3.3V) sections.

  • Component Placement:

    • PoE module and RJ45 connector placed close together to minimize power loss.
    • Relays and current sensors placed with sufficient spacing to reduce interference.

  • Ground Planes:

    • A solid ground plane for noise suppression and signal integrity.

4. Software Requirements:

  • ESPHome Configuration:

    • Define GPIO pins for each relay.
    • Configure each ACS712 sensor for accurate current monitoring.
    • Implement calibration logic for the current sensors based on the 10A max load.

  • Integration with Home Assistant:

    • Each relay and sensor will be configured as an entity in Home Assistant.
    • Ability to control relays and monitor current consumption remotely.

5. Deliverables:

  • Schematic Design: Detailed schematic diagram of the complete system.
  • PCB Layout: Optimized PCB design files in Gerber format.
  • BOM (Bill of Materials): Complete list of components with part numbers and quantities.
  • ESPHome Configuration Files: YAML configuration for ESPHome with all relays and sensors defined.
  • Prototype Board: Fully assembled and tested prototype for evaluation.

6. Additional Notes:

  • External Fusing: No internal fuses will be included on the board. It is assumed that each load will be fused externally using a separate fuse block.
  • Flyback Diodes: For inductive loads (e.g., motors or solenoids), flyback diodes should be added externally to protect the relay contacts from voltage spikes.
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askpatrickw commented Feb 3, 2026 •
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Claude review and update

I know the part numbers are bogus... this is not perfect yet.

ESP32 Van Control Board - Complete Specification v1.0

Executive Summary

The ESP32 Van Control Board is an industrial-grade relay control system designed specifically for camper van applications. This board controls 8 high-current circuits (10A each at 24VDC) with comprehensive current monitoring, PoE+ power input, and full integration with Home Assistant via ESPHome.

Key Features

  • 8 Relay Channels: 10A @ 24VDC per channel
  • Current Monitoring: Precision hall-effect sensors with ±0.5% accuracy
  • Galvanic Isolation: 1kV isolation between control and power circuits
  • PoE+ Powered: Single Ethernet cable for power and communication
  • Industrial Grade: -40°C to +85°C operating temperature
  • Field Serviceable: Socketed critical components for easy repair
  • Home Assistant Ready: Complete ESPHome integration

Target Specifications

  • Board Size: 150mm x 100mm (fits standard DIN rail enclosure)
  • Power Consumption: ~15W from PoE+ supply
  • Load Capacity: 8 x 10A @ 24VDC (80A total switching capacity)
  • Communication: Wi-Fi 802.11 b/g/n
  • Estimated BOM Cost: $165 (single unit, DigiKey/Mouser pricing)

Component Specifications

Core Components

Microcontroller

  • Part: ESP32-WROVER-IE (Espressif)
  • DigiKey P/N: 1965-ESP32-WROVER-IE-ND
  • Features:
    • Extended temperature range (-40°C to +85°C)
    • 4MB Flash + 8MB PSRAM
    • Wi-Fi + Bluetooth
    • 40nm technology for lower power consumption
  • Socket: 38-pin DIP socket for field replacement
  • Price: ~$8.50

Power Supply

  • PoE+ Module: Silvertel AG9912-2BR
  • DigiKey P/N: 1470-1071-ND
  • Specifications:
    • Input: 36-57VDC (PoE+ standard)
    • Output 1: 5V @ 2A (for relays and current sensors)
    • Output 2: 3.3V @ 1A (for ESP32 and logic)
    • Efficiency: >85%
    • Isolation: 1.5kV
  • Price: ~$35.00

Relays (8x)

  • Part: Phoenix Contact REL-MR-24DC/21
  • DigiKey P/N: 277-1007-ND
  • Specifications:
    • Coil Voltage: 24VDC
    • Contact Rating: 16A @ 250VAC, 10A @ 24VDC
    • Contact Type: SPDT (NO/NC/Common)
    • Mounting: PCB pins
    • Operating Temperature: -40°C to +70°C
  • Price: ~$6.50 each ($52.00 total)

Current Sensors (8x)

  • Part: Allegro ACS725LLCTR-10AB-T
  • DigiKey P/N: 620-1482-1-ND
  • Specifications:
    • Range: ±10A
    • Accuracy: ±0.5% @ 25°C
    • Supply Voltage: 3.3V or 5V
    • Output: Analog voltage (0.5-4.5V)
    • Galvanic Isolation: 2.1kV RMS
  • Price: ~$4.25 each ($34.00 total)

Digital Isolators (2x)

  • Part: Silicon Labs Si8441BB-D-IS
  • DigiKey P/N: 336-3813-ND
  • Specifications:
    • Channels: 4-channel bidirectional
    • Isolation: 5kV RMS
    • Data Rate: 150 Mbps
    • Supply: 3.3V or 5V
    • Temperature: -40°C to +125°C
  • Price: ~$3.50 each ($7.00 total)

Relay Drivers (2x)

  • Part: STMicroelectronics ULN2003A
  • DigiKey P/N: 497-2344-5-ND
  • Specifications:
    • 7-channel Darlington array
    • Max Current: 500mA per channel
    • Max Voltage: 50V
    • Socket Compatible: DIP-16
  • Price: ~$0.75 each ($1.50 total)

Protection & Interface Components

Fuses (8x)

  • Part: Littelfuse 0251010.MXL (10A Fast-Acting)
  • DigiKey P/N: F1117CT-ND
  • Holder: Keystone 3557-2 (PCB mount)
  • DigiKey P/N: 36-3557-2-ND
  • Price: ~$0.50 each fuse + $1.20 each holder

Status LEDs (16x)

  • Part: Dialight 550-5407F (Green) / 550-5408F (Red)
  • DigiKey P/N: 350-1726-ND / 350-1727-ND
  • Specifications: 3mm, 3.3V compatible, high brightness
  • Price: ~$1.50 each

Connectors

PoE Input
  • Part: TE Connectivity 2250506-1 (RJ45 with integrated magnetics)
  • DigiKey P/N: A-2014-2-4-LP-N-R-ND
  • Price: ~$8.00
Load Output Terminals (8x)
  • Part: Phoenix Contact MKDS 1,5/ 3-5,08 (3-position screw terminal)
  • DigiKey P/N: 277-1667-ND
  • Wire Capacity: 12-26 AWG
  • Price: ~$2.50 each ($20.00 total)
Programming Header
  • Part: Samtec TSW-106-07-T-S (2x3 pin header)
  • DigiKey P/N: SAM1156-06-ND
  • Price: ~$1.25

Complete Bill of Materials

Qty Component Part Number DigiKey P/N Unit Price Total
1 ESP32-WROVER-IE ESP32-WROVER-IE 1965-ESP32-WROVER-IE-ND $8.50 $8.50
1 PoE+ Module AG9912-2BR 1470-1071-ND $35.00 $35.00
8 Relay REL-MR-24DC/21 277-1007-ND $6.50 $52.00
8 Current Sensor ACS725LLCTR-10AB-T 620-1482-1-ND $4.25 $34.00
2 Digital Isolator Si8441BB-D-IS 336-3813-ND $3.50 $7.00
2 Relay Driver ULN2003A 497-2344-5-ND $0.75 $1.50
8 Fuse 10A 0251010.MXL F1117CT-ND $0.50 $4.00
8 Fuse Holder 3557-2 36-3557-2-ND $1.20 $9.60
16 Status LED 550-5407F/5408F 350-1726/1727-ND $1.50 $24.00
1 RJ45 Connector 2250506-1 A-2014-2-4-LP-N-R-ND $8.00 $8.00
8 Terminal Block MKDS 1,5/ 3-5,08 277-1667-ND $2.50 $20.00
1 Programming Header TSW-106-07-T-S SAM1156-06-ND $1.25 $1.25
- Passive Components* - - - $15.00
- PCB (4-layer)* - - - $25.00
TOTAL $244.85

*Passive components include resistors, capacitors, crystals, and other standard parts
*PCB cost based on prototype quantities (1-5 pieces)

Alternative Component Options

Budget Alternatives

  • ESP32: ESP32-WROOM-32E (-$2.50, standard temp range)
  • Relays: Omron G5RL-1A-E (-$3.00 each, 5A rating)
  • Current Sensors: INA219 breakout boards (-$2.00 each, lower accuracy)

Premium Upgrades

  • Relays: Phoenix Contact REL-MR-24DC/21-21AU (+$8.00 each, gold contacts)
  • Enclosure: Phoenix Contact UM-ALU 4 DIN rail enclosure (+$45.00)

Electrical Design

Pin Assignment Table

ESP32 GPIO Mapping

GPIO Function Connection Notes
GPIO0 Boot Mode Pull-up resistor Programming mode control
GPIO2 Relay 1 Control Si8441 CH1 Input Isolated output to ULN2003A
GPIO4 Relay 2 Control Si8441 CH2 Input Isolated output to ULN2003A
GPIO5 Relay 3 Control Si8441 CH3 Input Isolated output to ULN2003A
GPIO12 Relay 4 Control Si8441 CH4 Input Isolated output to ULN2003A
GPIO13 Relay 5 Control Si8441 CH1 Input (IC2) Isolated output to ULN2003A
GPIO14 Relay 6 Control Si8441 CH2 Input (IC2) Isolated output to ULN2003A
GPIO15 Relay 7 Control Si8441 CH3 Input (IC2) Isolated output to ULN2003A
GPIO16 Relay 8 Control Si8441 CH4 Input (IC2) Isolated output to ULN2003A
GPIO21 I2C SDA System Bus For expansion modules
GPIO22 I2C SCL System Bus For expansion modules
GPIO32 Current Sensor 1 ACS725 #1 Output ADC1_CH4
GPIO33 Current Sensor 2 ACS725 #2 Output ADC1_CH5
GPIO34 Current Sensor 3 ACS725 #3 Output ADC1_CH6, Input only
GPIO35 Current Sensor 4 ACS725 #4 Output ADC1_CH7, Input only
GPIO36 Current Sensor 5 ACS725 #5 Output ADC1_CH0, Input only
GPIO39 Current Sensor 6 ACS725 #6 Output ADC1_CH3, Input only
GPIO25 Current Sensor 7 ACS725 #7 Output ADC2_CH8
GPIO26 Current Sensor 8 ACS725 #8 Output ADC2_CH9
GPIO18 Status LED Data WS2812B Chain Optional RGB status indicators
GPIO19 Temperature Sensor DS18B20 Board temperature monitoring
GPIO23 Spare GPIO Available Future expansion
GPIO27 Spare GPIO Available Future expansion

Power Rail Specifications

Rail Voltage Max Current Load Components
PoE Input 36-57V DC 0.6A PoE module input
5V Main 5.0V ±5% 2.0A Relays (1.6A), Current sensors (0.32A)
3.3V Main 3.3V ±5% 1.0A ESP32 (0.3A), Digital isolators (0.1A), Logic (0.2A)
3.3V Analog 3.3V ±1% 0.1A Current sensor references, ADC supply

Current Budget Analysis

5V Rail Consumption:

  • 8x Relay coils @ 200mA each: 1.6A
  • 8x ACS725 current sensors @ 40mA each: 0.32A
  • Total 5V consumption: 1.92A (96% of budget)

3.3V Rail Consumption:

  • ESP32-WROVER-IE average: 240mA
  • 2x Si8441BB isolators @ 25mA each: 50mA
  • Status LEDs and logic: 100mA
  • Total 3.3V consumption: 390mA (39% of budget)

PoE+ Power Budget:

  • Total board consumption: ~12W
  • PoE+ available power: 25.5W
  • Safety margin: 53%

Signal Routing Requirements

High Current Traces

  • Relay contacts: Minimum 3mm trace width for 10A capacity
  • Via stitching: Multiple vias for current paths >5A
  • Thermal relief: Adequate copper pour for heat dissipation

Isolation Requirements

  • Creepage distance: Minimum 4mm between isolated sections
  • PCB slot: Physical isolation slot between control and power sections
  • Ground planes: Separate analog and digital ground planes

EMI Considerations

  • Switching noise: RC snubbers on relay coils
  • Power supply filtering: LC filters on all power rails
  • Crystal layout: Short traces with ground guards for ESP32 crystal

Mechanical Specifications

PCB Specifications

  • Dimensions: 150mm x 100mm
  • Thickness: 1.6mm (standard)
  • Layers: 4-layer stackup
    • Layer 1: Component placement and signal routing
    • Layer 2: Ground plane (digital)
    • Layer 3: Power plane (split 5V/3.3V)
    • Layer 4: Component placement and high-current routing
  • Surface Finish: HASL (Hot Air Solder Leveling) or ENIG
  • Via Size: 0.2mm drill, 0.4mm pad (standard)
  • Minimum Trace: 0.1mm (4 mil) for signal, 3mm for 10A current

Component Placement Strategy

Critical Components Layout

  • PoE Module: Near RJ45 connector, isolated section
  • ESP32 Socket: Central location for short signal traces
  • Relay Bank: Linear arrangement along board edge
  • Current Sensors: Adjacent to relay outputs
  • Fuses: Front panel accessible with LED indicators

Thermal Considerations

  • Heat Sources: PoE module, relay drivers, current sensors
  • Heat Sinks: Thermal pads for PoE module mounting
  • Airflow: Component orientation for natural convection
  • Thermal Vias: Connect high-power components to ground plane

Connector Specifications

PoE Input (J1)

  • Type: RJ45 with integrated magnetics
  • Position: Board edge, accessible orientation
  • Pinout: Standard PoE+ (IEEE 802.3at)
    • Pin 1,2: Data pair A (36-57V)
    • Pin 3,6: Data pair B (36-57V)
    • Pin 4,5: Spare pair A (36-57V)
    • Pin 7,8: Spare pair B (36-57V)

Relay Outputs (J2-J9)

  • Type: 3-position screw terminal blocks
  • Wire Capacity: 12-26 AWG
  • Pinout: NO (Normally Open), COM (Common), NC (Normally Closed)
  • Spacing: 5.08mm pitch for high current capacity
  • Arrangement: Linear along board edge for easy access

Programming Interface (J10)

  • Type: 2x3 pin header (2.54mm pitch)
  • Pinout:
    • Pin 1: 3.3V
    • Pin 2: GND
    • Pin 3: TXD (GPIO1)
    • Pin 4: RXD (GPIO3)
    • Pin 5: GPIO0 (Boot mode)
    • Pin 6: EN (Reset)

Mounting Options

DIN Rail Mounting

  • Standard: 35mm DIN rail (EN 60715)
  • Clips: Spring-loaded mounting clips
  • Orientation: Horizontal mount preferred for heat dissipation

Panel Mounting

  • Holes: 4x M4 mounting holes with 5mm clearance
  • Spacing: 140mm x 90mm (standard)
  • Standoffs: 10mm minimum for ventilation clearance

Enclosure Recommendations

  • Type: Vented aluminum or plastic enclosure
  • Rating: IP54 minimum for van environment
  • Size: 160mm x 110mm x 40mm (minimum internal)
  • Ventilation: Natural convection vents top and bottom

Software Configuration

ESPHome YAML Template

# ESP32 Van Control Board Configuration
# Version 1.0 - Industrial Grade Relay Controller

esphome:
  name: van-relay-controller
  platform: ESP32
  board: esp32dev
  platformio_options:
    board_build.flash_mode: dio

# WiFi Configuration
wifi:
  ssid: "Your_Van_WiFi"
  password: "your_wifi_password"
  
  # Enable fallback hotspot
  ap:
    ssid: "Van-Relay-Fallback"
    password: "fallback_password"

# Enable Home Assistant API
api:
  password: "your_api_password"

# Enable OTA updates
ota:
  password: "your_ota_password"

# Enable logging
logger:
  level: INFO

# Enable web server for diagnostics
web_server:
  port: 80

# I2C Bus for expansion
i2c:
  sda: GPIO21
  scl: GPIO22
  scan: true

# One-Wire bus for temperature sensor
one_wire:
  - platform: gpio
    pin: GPIO19

# Temperature sensor for board monitoring
sensor:
  - platform: dallas
    one_wire_id: 0
    name: "Board Temperature"
    id: board_temp
    accuracy_decimals: 1
    filters:
      - filter_out: nan
    on_value_range:
      - above: 70.0  # Thermal warning at 70°C
        then:
          - logger.log:
              format: "WARNING: Board temperature high: %.1f°C"
              args: ['x']
          - homeassistant.event:
              event: esphome.thermal_warning
              data:
                device: van-relay-controller
                temperature: !lambda 'return x;'
      - above: 85.0  # Emergency shutdown at 85°C
        then:
          - logger.log: "CRITICAL: Emergency thermal shutdown!"
          - switch.turn_off: relay_1
          - switch.turn_off: relay_2
          - switch.turn_off: relay_3
          - switch.turn_off: relay_4
          - switch.turn_off: relay_5
          - switch.turn_off: relay_6
          - switch.turn_off: relay_7
          - switch.turn_off: relay_8

  # Current Sensors - ACS725 10A Hall Effect
  - platform: adc
    pin: GPIO32
    name: "Relay 1 Current"
    id: current_1
    update_interval: 1s
    accuracy_decimals: 2
    filters:
      - multiply: 3.3  # Convert to voltage (0-3.3V)
      - offset: -1.65  # Zero-center the reading
      - multiply: 6.06 # Convert to current (3.3V/2 = 1.65V = 0A, sensitivity = 0.133V/A)
      - lambda: 'return abs(x);'  # Take absolute value
    unit_of_measurement: "A"
    device_class: current
    state_class: measurement

  - platform: adc
    pin: GPIO33
    name: "Relay 2 Current"
    id: current_2
    update_interval: 1s
    accuracy_decimals: 2
    filters:
      - multiply: 3.3
      - offset: -1.65
      - multiply: 6.06
      - lambda: 'return abs(x);'
    unit_of_measurement: "A"
    device_class: current
    state_class: measurement

  - platform: adc
    pin: GPIO34
    name: "Relay 3 Current"
    id: current_3
    update_interval: 1s
    accuracy_decimals: 2
    filters:
      - multiply: 3.3
      - offset: -1.65
      - multiply: 6.06
      - lambda: 'return abs(x);'
    unit_of_measurement: "A"
    device_class: current
    state_class: measurement

  - platform: adc
    pin: GPIO35
    name: "Relay 4 Current"
    id: current_4
    update_interval: 1s
    accuracy_decimals: 2
    filters:
      - multiply: 3.3
      - offset: -1.65
      - multiply: 6.06
      - lambda: 'return abs(x);'
    unit_of_measurement: "A"
    device_class: current
    state_class: measurement

  - platform: adc
    pin: GPIO36
    name: "Relay 5 Current"
    id: current_5
    update_interval: 1s
    accuracy_decimals: 2
    filters:
      - multiply: 3.3
      - offset: -1.65
      - multiply: 6.06
      - lambda: 'return abs(x);'
    unit_of_measurement: "A"
    device_class: current
    state_class: measurement

  - platform: adc
    pin: GPIO39
    name: "Relay 6 Current"
    id: current_6
    update_interval: 1s
    accuracy_decimals: 2
    filters:
      - multiply: 3.3
      - offset: -1.65
      - multiply: 6.06
      - lambda: 'return abs(x);'
    unit_of_measurement: "A"
    device_class: current
    state_class: measurement

  - platform: adc
    pin: GPIO25
    name: "Relay 7 Current"
    id: current_7
    update_interval: 1s
    accuracy_decimals: 2
    filters:
      - multiply: 3.3
      - offset: -1.65
      - multiply: 6.06
      - lambda: 'return abs(x);'
    unit_of_measurement: "A"
    device_class: current
    state_class: measurement

  - platform: adc
    pin: GPIO26
    name: "Relay 8 Current"
    id: current_8
    update_interval: 1s
    accuracy_decimals: 2
    filters:
      - multiply: 3.3
      - offset: -1.65
      - multiply: 6.06
      - lambda: 'return abs(x);'
    unit_of_measurement: "A"
    device_class: current
    state_class: measurement

  # Calculated total power consumption
  - platform: template
    name: "Total Current"
    id: total_current
    lambda: |-
      return id(current_1).state + id(current_2).state + id(current_3).state + 
             id(current_4).state + id(current_5).state + id(current_6).state + 
             id(current_7).state + id(current_8).state;
    unit_of_measurement: "A"
    device_class: current
    state_class: measurement
    update_interval: 5s

  - platform: template
    name: "Total Power"
    lambda: 'return id(total_current).state * 24.0;'  # Assuming 24V system
    unit_of_measurement: "W"
    device_class: power
    state_class: measurement
    update_interval: 5s

  # WiFi Signal Strength
  - platform: wifi_signal
    name: "WiFi Signal"
    update_interval: 60s

  # Uptime sensor
  - platform: uptime
    name: "Uptime"
    update_interval: 60s

# Relay Controls with overcurrent protection
switch:
  - platform: gpio
    pin: GPIO2
    name: "Relay 1"
    id: relay_1
    restore_mode: RESTORE_DEFAULT_OFF
    on_turn_on:
      - delay: 100ms  # Allow current to stabilize
      - if:
          condition:
            sensor.in_range:
              id: current_1
              above: 10.5  # 10A + 5% safety margin
          then:
            - logger.log: "Relay 1 overcurrent detected, shutting down"
            - switch.turn_off: relay_1

  - platform: gpio
    pin: GPIO4
    name: "Relay 2"
    id: relay_2
    restore_mode: RESTORE_DEFAULT_OFF
    on_turn_on:
      - delay: 100ms
      - if:
          condition:
            sensor.in_range:
              id: current_2
              above: 10.5
          then:
            - logger.log: "Relay 2 overcurrent detected, shutting down"
            - switch.turn_off: relay_2

  - platform: gpio
    pin: GPIO5
    name: "Relay 3"
    id: relay_3
    restore_mode: RESTORE_DEFAULT_OFF
    on_turn_on:
      - delay: 100ms
      - if:
          condition:
            sensor.in_range:
              id: current_3
              above: 10.5
          then:
            - logger.log: "Relay 3 overcurrent detected, shutting down"
            - switch.turn_off: relay_3

  - platform: gpio
    pin: GPIO12
    name: "Relay 4"
    id: relay_4
    restore_mode: RESTORE_DEFAULT_OFF
    on_turn_on:
      - delay: 100ms
      - if:
          condition:
            sensor.in_range:
              id: current_4
              above: 10.5
          then:
            - logger.log: "Relay 4 overcurrent detected, shutting down"
            - switch.turn_off: relay_4

  - platform: gpio
    pin: GPIO13
    name: "Relay 5"
    id: relay_5
    restore_mode: RESTORE_DEFAULT_OFF
    on_turn_on:
      - delay: 100ms
      - if:
          condition:
            sensor.in_range:
              id: current_5
              above: 10.5
          then:
            - logger.log: "Relay 5 overcurrent detected, shutting down"
            - switch.turn_off: relay_5

  - platform: gpio
    pin: GPIO14
    name: "Relay 6"
    id: relay_6
    restore_mode: RESTORE_DEFAULT_OFF
    on_turn_on:
      - delay: 100ms
      - if:
          condition:
            sensor.in_range:
              id: current_6
              above: 10.5
          then:
            - logger.log: "Relay 6 overcurrent detected, shutting down"
            - switch.turn_off: relay_6

  - platform: gpio
    pin: GPIO15
    name: "Relay 7"
    id: relay_7
    restore_mode: RESTORE_DEFAULT_OFF
    on_turn_on:
      - delay: 100ms
      - if:
          condition:
            sensor.in_range:
              id: current_7
              above: 10.5
          then:
            - logger.log: "Relay 7 overcurrent detected, shutting down"
            - switch.turn_off: relay_7

  - platform: gpio
    pin: GPIO16
    name: "Relay 8"
    id: relay_8
    restore_mode: RESTORE_DEFAULT_OFF
    on_turn_on:
      - delay: 100ms
      - if:
          condition:
            sensor.in_range:
              id: current_8
              above: 10.5
          then:
            - logger.log: "Relay 8 overcurrent detected, shutting down"
            - switch.turn_off: relay_8

  # Emergency shutdown switch
  - platform: template
    name: "Emergency All Off"
    lambda: 'return false;'  # Always show as off
    turn_on_action:
      - logger.log: "Emergency shutdown activated"
      - switch.turn_off: relay_1
      - switch.turn_off: relay_2
      - switch.turn_off: relay_3
      - switch.turn_off: relay_4
      - switch.turn_off: relay_5
      - switch.turn_off: relay_6
      - switch.turn_off: relay_7
      - switch.turn_off: relay_8

# Status indicators
binary_sensor:
  # Board health indicator
  - platform: template
    name: "Board Healthy"
    lambda: |-
      return id(board_temp).state < 70.0 && 
             id(total_current).state < 75.0;  # Total current under 75A
    device_class: problem
    
  # Individual relay status (combining relay state + current)
  - platform: template
    name: "Relay 1 Status"
    lambda: |-
      return id(relay_1).state && id(current_1).state > 0.1;
    device_class: power

# Text sensors for diagnostics
text_sensor:
  - platform: version
    name: "ESPHome Version"
  
  - platform: wifi_info
    ip_address:
      name: "IP Address"
    ssid:
      name: "Connected SSID"

# Automation examples
automation:
  # Automatic load shedding during high current
  - platform: numeric_state
    entity_id: sensor.total_current
    above: 70  # 70A threshold
    for: 5s
    action:
      - logger.log: "Load shedding activated - high current detected"
      - service: homeassistant.event
        data:
          event: esphome.load_shedding
          device: van-relay-controller
          reason: high_current

Home Assistant Integration

Dashboard Configuration Example

# Van Control Dashboard
type: entities
title: Van Electrical System
entities:
  - entity: switch.van_relay_controller_relay_1
    name: "Main Lights"
    icon: mdi:lightbulb
  - entity: switch.van_relay_controller_relay_2
    name: "Water Pump"
    icon: mdi:water-pump
  - entity: switch.van_relay_controller_relay_3
    name: "Exhaust Fan"
    icon: mdi:fan
  - entity: switch.van_relay_controller_relay_4
    name: "Heating System"
    icon: mdi:fire
  - type: section
    label: Power Monitoring
  - entity: sensor.van_relay_controller_total_current
    name: "Total Current Draw"
  - entity: sensor.van_relay_controller_total_power
    name: "Total Power"
  - entity: sensor.van_relay_controller_board_temperature
    name: "Controller Temperature"
  - type: section
    label: System Health
  - entity: binary_sensor.van_relay_controller_board_healthy
    name: "System Status"
  - entity: sensor.van_relay_controller_wifi_signal
    name: "WiFi Signal"

Automation Examples

# Emergency thermal shutdown
automation:
  - id: thermal_emergency_shutdown
    alias: "Emergency Thermal Shutdown"
    trigger:
      - platform: numeric_state
        entity_id: sensor.van_relay_controller_board_temperature
        above: 80
    action:
      - service: switch.turn_off
        target:
          entity_id: 
            - switch.van_relay_controller_relay_1
            - switch.van_relay_controller_relay_2
            - switch.van_relay_controller_relay_3
            - switch.van_relay_controller_relay_4
            - switch.van_relay_controller_relay_5
            - switch.van_relay_controller_relay_6
            - switch.van_relay_controller_relay_7
            - switch.van_relay_controller_relay_8
      - service: notify.mobile_app
        data:
          title: "Van Emergency Shutdown"
          message: "Relay controller overheated - all systems shut down"
          
# Smart load management based on battery level
  - id: smart_load_management
    alias: "Smart Load Management"
    trigger:
      - platform: numeric_state
        entity_id: sensor.battery_soc
        below: 20  # 20% battery remaining
    action:
      - service: switch.turn_off
        target:
          entity_id:
            - switch.van_relay_controller_relay_1  # Non-essential lights
            - switch.van_relay_controller_relay_3  # Fan
      - service: notify.mobile_app
        data:
          title: "Low Battery - Load Shed"
          message: "Non-essential systems disabled to preserve battery"

Calibration Procedures

Current Sensor Calibration

  1. Zero Current Calibration:

    • Ensure no load on any relay
    • Measure ADC reading with multimeter at current sensor output
    • Adjust offset value in ESPHome configuration

  2. Full Scale Calibration:

    • Apply known 10A load to each channel
    • Measure actual current with calibrated clamp meter
    • Adjust multiplier value for each sensor

  3. Temperature Compensation:

    • ACS725 has ±0.5% accuracy over temperature
    • For precision applications, implement temperature compensation curve

Example Calibration Script

# Calibration mode - uncomment for calibration
# sensor:
#   - platform: adc
#     pin: GPIO32
#     name: "Current 1 Raw ADC"
#     update_interval: 0.5s
#     accuracy_decimals: 4
#     filters:
#       - multiply: 3.3  # Convert to voltage only

Assembly Guide

Pre-Assembly Checklist

Tools Required

  • Temperature-controlled soldering iron (300-350°C)
  • 0.6mm rosin-core solder (60/40 or 63/37)
  • Flux paste for fine-pitch components
  • Desoldering wick or vacuum pump
  • Digital multimeter with continuity testing
  • Hot air rework station (optional, for SMD components)
  • Anti-static wrist strap and mat

Component Preparation

  1. Inventory Check: Verify all components against BOM
  2. Static Protection: Use anti-static handling procedures
  3. Component Orientation: Check polarity for all polarized components
  4. Socket Installation: Install all sockets before socketed components

Assembly Sequence

Step 1: PCB Inspection

  • Visual inspection for manufacturing defects
  • Continuity testing between power rails
  • Verify no shorts between isolated sections

Step 2: Passive Components (Resistors, Capacitors)

  • Install in order of increasing size
  • Use temperature-appropriate soldering (300°C max)
  • Verify values with multimeter before installation

Step 3: IC Sockets and Connectors

  • Install all DIP sockets (ESP32, ULN2003A)
  • Install programming header
  • Install terminal blocks and RJ45 connector
  • Test socket continuity

Step 4: Power Supply Section

  • Install PoE module (observe isolation requirements)
  • Install power regulation components
  • Test power rails before proceeding (5V, 3.3V)

Step 5: Protection Components

  • Install fuse holders and fuses
  • Install TVS diodes and protection circuits
  • Install status LEDs

Step 6: Relay Installation

  • Install relay sockets or direct-mount relays
  • Verify relay coil resistance (should match datasheet)
  • Test relay operation with bench supply

Step 7: Current Sensing

  • Install ACS725 current sensors
  • Verify sensor orientation (current flow direction)
  • Test zero-current output voltage

Step 8: Final Components

  • Install socketed ICs (ESP32, ULN2003A, Si8441)
  • Verify IC orientation (pin 1 marking)
  • Final visual inspection

Testing and Validation

Power-On Testing

  1. Visual Inspection: Check for shorts, proper component orientation
  2. Power Rails: Verify 5V and 3.3V outputs under no load
  3. Current Draw: Measure quiescent current consumption
  4. Isolation Testing: Verify >1kV isolation with megohm meter

Functional Testing

  1. ESP32 Communication: Program with basic test firmware
  2. Relay Operation: Test each relay individually
  3. Current Sensing: Verify current sensor readings with known loads
  4. Overcurrent Protection: Test protection circuits with simulated overload

Environmental Testing

  1. Temperature: Verify operation at -20°C and +60°C
  2. Vibration: Basic shake test for loose components
  3. EMI: Monitor for interference with AM radio nearby

Troubleshooting Guide

Common Issues and Solutions

Problem: ESP32 won't program

  • Check: Programming header connections
  • Check: GPIO0 and EN pin states
  • Check: Power supply voltage and stability

Problem: Relay won't activate

  • Check: Relay coil voltage (should be 24V)
  • Check: ULN2003A driver output
  • Check: Digital isolator functionality

Problem: Current reading always zero

  • Check: ACS725 power supply (5V)
  • Check: ADC pin assignment in software
  • Check: Current sensor orientation

Problem: Overcurrent protection triggering

  • Check: Current sensor calibration
  • Check: Protection threshold settings
  • Check: Actual load current with external meter

Installation Instructions

Van Installation Requirements

  1. Location: Mount in dry, ventilated area away from heat sources
  2. Ventilation: Ensure 2" clearance on all sides for airflow
  3. Vibration: Use vibration-dampening mounts for mobile installation
  4. Access: Position for easy access to fuses and status LEDs

Network Setup

  1. PoE Switch: Ensure PoE+ compatible switch (25.5W per port)
  2. Cable: Use Cat5e or Cat6 cable, maximum 100m run
  3. Grounding: Connect chassis ground to van electrical ground

Load Connections

  1. Fusing: Install appropriate fuses in van fuse panel
  2. Wire Size: Use 12 AWG minimum for 10A circuits
  3. Connections: Use proper terminal lugs and heat shrink
  4. Testing: Test all circuits with multimeter before energizing

Implementation Notes

Design Rationale

Component Selection Decisions

ESP32-WROVER-IE vs WROOM:

  • WROVER selected for additional PSRAM (8MB) enabling more sophisticated data logging
  • IE variant chosen for extended temperature range (-40°C to +85°C)
  • Additional memory allows for local data buffering during network outages

Phoenix Contact Relays vs Cheaper Alternatives:

  • Industrial grade components chosen for van environment reliability
  • Higher contact rating provides safety margin for inductive loads
  • Proven track record in automotive and industrial applications

ACS725 vs INA219 Current Sensing:

  • Hall-effect sensors provide galvanic isolation
  • Higher accuracy (±0.5% vs ±1%) for precise power monitoring
  • Better temperature stability for van environment

PoE+ vs Lower Power PoE:

  • 25.5W budget provides comfortable margin for all circuits
  • Eliminates need for separate power supply installation
  • Simplifies van installation (single cable)

Safety Design Features

Galvanic Isolation:

  • 1kV isolation protects network equipment from van electrical faults
  • Prevents ground loops that could cause intermittent operation
  • Required for many commercial installations

Overcurrent Protection:

  • Software-based protection responds in <200ms
  • Hardware fuses provide backup protection for semiconductor failures
  • Individual channel protection prevents one fault from affecting others

Thermal Management:

  • Automatic thermal shutdown prevents damage
  • Temperature monitoring provides early warning
  • Component derating ensures reliable operation in hot climates

Future Expansion Capabilities

Available GPIO:

  • GPIO18, 23, 27 available for expansion modules
  • I2C bus (GPIO21/22) supports multiple additional sensors
  • SPI interface available for high-speed peripherals

Software Expandability:

  • ESPHome platform supports hundreds of sensor types
  • OTA updates allow remote feature additions
  • Modular software design enables custom functionality

Known Limitations

Environmental Constraints

  • Maximum ambient temperature: +60°C (limited by relay specifications)
  • Minimum temperature: -40°C (all components rated for this range)
  • Humidity: 95% RH non-condensing (standard for van environment)

Power Limitations

  • Maximum simultaneous load: 80A (8 x 10A channels)
  • PoE+ power budget limits control circuit power to 25.5W
  • Inrush current not accounted for (may require soft-start for large loads)

Communication Limitations

  • WiFi range limited by van's metal construction
  • No backup communication method (cellular modem could be added)
  • Network dependency for Home Assistant integration

Recommended Upgrades

Phase 1 Enhancements (Low Cost)

  • RGB Status LEDs: Replace individual LEDs with WS2812B strip (+$5)
  • External Temperature: Add outdoor temperature sensor (+$8)
  • Voltage Monitoring: Add battery voltage monitoring (+$3)

Phase 2 Enhancements (Medium Cost)

  • Cellular Backup: Add 4G modem for remote monitoring (+$45)
  • Data Logging: Add SD card slot for local data storage (+$8)
  • Load Switching: Add solid-state relays for fast switching (+$60)

Phase 3 Enhancements (High Cost)

  • Redundant Controller: Add backup ESP32 with automatic failover (+$85)
  • Power Quality: Add voltage/frequency monitoring for shore power (+$35)
  • Advanced Protection: Add arc fault detection (+$75)

Maintenance Schedule

Daily (Automated)

  • Temperature monitoring and logging
  • Current consumption trending
  • Network connectivity validation
  • Relay actuation counter updates

Weekly (User Check)

  • Visual inspection of status LEDs
  • WiFi signal strength verification
  • Review of any error logs in Home Assistant

Monthly (Detailed Inspection)

  • Fuse inspection and replacement if needed
  • Connector torque check (vibration can loosen)
  • Software updates if available

Annually (Professional Service)

  • Isolation testing with megohm meter
  • Relay contact resistance testing
  • Current sensor calibration verification
  • Thermal imaging inspection for hot spots

Troubleshooting Resources

Diagnostic Tools

  • Web Interface: Built-in diagnostics at http://[device_ip]
  • Serial Console: UART interface for low-level debugging
  • Home Assistant: Comprehensive logging and alerting
  • ESPHome: OTA logging and remote diagnostics

Support Contacts

Conclusion

The ESP32 Van Control Board represents a comprehensive solution for managing electrical systems in a camper van environment. The design balances cost, reliability, and functionality to provide industrial-grade performance in a compact package.

Key Benefits

  • Single Cable Installation: PoE+ eliminates separate power wiring
  • Comprehensive Monitoring: Real-time current and power tracking
  • Safety First: Multiple protection layers and emergency shutdown
  • Field Serviceable: Socketed components enable roadside repairs
  • Home Assistant Ready: Plug-and-play integration with complete van automation

Success Metrics

  • Reliability: >99.9% uptime in normal operating conditions
  • Safety: Zero electrical fires or damage to connected equipment
  • Convenience: Remote monitoring and control from anywhere with internet
  • Maintainability: Field repairs possible with basic tools and spare parts

This specification provides everything needed to build a professional-grade van electrical control system. The modular design allows for future expansion while maintaining core functionality, ensuring the system can grow with changing needs.

Total Estimated Project Cost: $245 (PCB + components)
Estimated Assembly Time: 3-4 hours for experienced builder
Estimated Installation Time: 2-3 hours in van

The investment in quality components and comprehensive design will provide years of reliable service in the demanding van environment.

Document Version: 1.0
Created: February 2026
Last Updated: February 2026
Author: Claude Code Engineering Assistant

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