Esphome Web 4C96D0 Modbus Register 40099: DC Voltage Scale

Technical Definition

The register DC Voltage Scale at address 40099 is used to monitor dc voltage scale on the Esphome Web 4C96D0.

• Protocol: Modbus RTU
• Data Type: S WORD
• Unit:
• Access: Read Only

How to Read (Python pymodbus)

Use this code snippet to read this specific value via RS485:

from pymodbus.client.sync import ModbusSerialClient

client = ModbusSerialClient(method='rtu', port='/dev/ttyUSB0', baudrate=9600)
client.connect()

# Read DC Voltage Scale (Address: 40099)
# Note: Check if your device uses 0-based or 1-based addressing
result = client.read_input_registers(address=40099, count=2, unit=1)

if not result.isError():
    print(f"Raw Value: {result.registers}")
else:
    print("Error reading register")

client.close()

Integration (Home Assistant)

Paste this into your configuration.yaml:

- platform: modbus_controller
  name: "DC Voltage Scale"
  address: 40099
  value_type: S_WORD
  unit_of_measurement: ""

Connection Diagram

Here is the standard RS485 wiring for this configuration:

graph TD
    PLC[Host Controller / Home Assistant]
    Device[Esphome Web 4C96D0]

    PLC -- "A+ (D+)" --> Device
    PLC -- "B- (D-)" --> Device
    PLC -- GND --> Device

💡 Engineer's Insight

Analysis: Multiplier for scaling the 'DC Voltage' value. Defines the unit and precision (e.g., 0.1 for Volts, 0.01 for dVolts).

Troubleshooting: An incorrect scale factor will result in inaccurate voltage readings. Ensure the scale matches the device's voltage range.