ModbusBox device hardware design.
ModbusBox allows the integration of Modbus RTU networks to a WiFi connection. It is capable to read data registers from Modbus slaves (tested with 4 ) then send data periodically to cloud services using the very popular MQTT protocol. Data is serialized using Json format , the information can be processed and displayed in dashboards by many open source IOT platforms like Node-red, Influxdb & Grafana, Ubidots educational and its pay platform which is very powerfully and easy to use.
ModbusBox has been tested and optimized to be connected to Variable frequency drives that uses modbus RTU as base protocol , but it can be used with any other device that uses modbus rtu over RS485. protocol .
Processor : ESP32-WROOM-32
DC Input : 7~ 26v ( step down dc buck regulator).
Current consumption: <100ma when DC input =20 ~27v
Hardware interfaces.
- 1x RS485 port (RJ45), non insolated.
- 1x programing connection (tx0/rx0).
- 1x SPI port.
- 1xI2c port.
- 3x micro buttons for ESP programing mode and device setup.
Led indication.
- 1x power led.
- 1 x MQTT activity ( msg send/received).
- 1x Neopixel RGB led for device status indication.
- 1x Modbus TX led.
- 1x Modbus RX led.
Additional Features.
- Dc input voltage measurement (voltage divider connected to GPIO35).
- DC input capacitor act as short voltage backup , when combined with the voltage divider measurement can be used in the ESP32 program to send and alarm ( for example an MQTT message ) before the voltage stored in the capacitor reach 3.3 volts.
WiFi Specs.
IEEE 802.11 b/g/n
Freq Band: 2.4 ~ 2.462 GHZ.
Integrated Antenna.
Unassembled top layer PCB photo.
Unassembled bottom layer PCB photo
PCB Photos
The Modbus Box had been tested successfully with several AC drives models of the recognized brad Nidec Control techniques , some of the drive models tested are : M200/300/400 and C200. Modbus Box can be connected directly to the drive AI-485 adaptor which also have 24 volts , there is no requirement for additional power supply . An ethernet cable Cat5e can be used to make the connection between the Modbus box and the drive RS485 port.
In order to connect Modbus box to other Modbus slaves we recommend the following connecting accessories that can be found on eBay or Aliexpress.
- RJ45 Female To Screw Terminal 8 Pin Connector : ebay link, aliexpress link.
- Ethernet cable Cat6e 0.5m ...50m : aliexpress link.
- DC 24 or 12 volts 1 amp power supply : aliexpress link
