Published January 27, 2024 © GPL3+

ESP32 PLC for home and small industries appliances

The ESP-32 PLC is a home and small industry automation solution designed to simplify control and monitoring tasks.

IntermediateWork in progress20 hours2,647

ESP32 PLC for home and small industries appliances

Things used in this project

Hardware components

Espressif ESP32

Software apps and online services

Flux.ai

PCBWay

Hand tools and fabrication machines

Soldering iron (generic)

Solder Wire, Lead Free

Solder Flux, Soldering

Story

Introduction to the Custom PCB Design

The ESP-32 PLC is a home and small industry automation solution designed to simplify control and monitoring tasks. With the incorporation of an ESP-32 microcontroller, this PCB offers excellent processing power and IoT capabilities, making it suitable for a wide range of applications such as automation, smart home applications, cloud-based IoT applications, and more.

The inspiration for this project came from the need for a versatile PLC system that can handle both home and small industry applications. To fulfill this need, I decided to design a custom PCB that integrates all the necessary components for efficient control and monitoring.

Check out the full project on Flux (Schematic + PCB layout): https://www.flux.ai/rafalozano/esp32-s3-plc-for-home-and-small-industry

Design and Features

The PCB design of the ESP-32 PLC incorporates essential components to provide a reliable and efficient control and monitoring system. The key features of the PCB design include:

ESP-32 microcontroller: The heart of the system, the ESP-32 offers powerful processing capabilities and extensive IoT support.
8 Solid State Relays: These SSRs enable control of various electrical devices or systems.
8 I/O: This provides additional flexibility for connecting external devices or sensors.
1 ADC: The analog-to-digital converter allows for precise measurement and monitoring of analog signals.
USB-C: The inclusion of USB-C allows for easy and convenient connectivity options.

Role of ESP-32 Microcontroller in the PCB

The ESP-32 microcontroller serves as the central processor for the entire system. It is responsible for managing all the input and output functions, as well as communication with other devices. Due to its versatility and affordability, the ESP-32 microcontroller was chosen as the ideal processing unit for this project.

Here are some key features of the ESP32-S3-WROOM-1:

Dual-core Xtensa LX7 microprocessor with a clock speed of up to 240 MHz.
384 KB of ROM and 512 KB of SRAM.
Up to 16 MB of PSRAM 1.
802.11 b/g/n Wi-Fi and Bluetooth 5 (LE) connectivity.
Up to 36 GPIOs and a rich set of peripherals.
Built-in PCB antenna.

Key Features: USB-C, SSRs, I/O, ADC and Voltage

The PCB incorporates several key features to enhance its functionality. These features include a USB-C port for easy connectivity and compatibility, eight Solid State Relays for controlling various devices, eight I/O ports for additional input and output capabilities, and an ADC for accurate analog measurements.

Challenges in the USB-Serial Converter and Voltage Regulator

However, despite the meticulous design process and the incorporation of quality components, the initial version of the ESP-32 PLC faced some unexpected challenges. One of the main challenges encountered was with the USB-Serial converter (CH340E). The CH340E USB-Serial converter posed complications, causing issues with the communication between the PCB and external devices. Additionally, an error was discovered in the voltage regulator responsible for converting the 24V DC input to a stable 12V output. These complications resulted in the project not working as expected.

USB-Serial Converter

The WCH CH340E was chosen because it is the latest version of the previous CH340 chips. I followed the recommended design to enable a one-key download:

Source: Patrick Yang (X) https://twitter.com/patrick_riscv/status/1509353599100284928

CH340E in Flux

Voltage regulator

A major mistake I made was using too many decoupling capacitors, which interfered with the voltage regulators' operation. Additionally, some capacitors were polarized and I installed them with the wrong polarity.

Recomended design for the Voltage regulator

Uses of the 74HC14D

The 74HC14D is, in fact, a high-speed, low-power integrated circuit designed to provide robust signal conditioning functionality in digital environments. Essentially, it comprises six Schmitt-trigger inverters capable of converting standard digital signals into clean and stable ones, which is crucial for the proper operation of control systems. Additionally, its compatibility with a wide range of supply voltages makes it a versatile choice for various applications.

In the context of a PLC based on the ESP32 S3, the 74HC14D plays a vital role in the interface between external sensors and actuators and the main processor. It acts as a reliable intermediary ensuring that input and output signals are correctly interpreted and processed by the microcontroller, thus guaranteeing precise control and a rapid system response.

Functional diagram of the 74HC14D

The SN74HC541PWR IC

SN74HC541PWR in the project

The SN74HC541PWR IC can be used to transfer data between different parts of a circuit or system, such as LEDs and more. The IC has two output enable inputs (OE1 and OE2) that control the state of the outputs. If either OE1 or OE2 is high, all eight outputs are in the high-impedance state, which means they are disabled. If both OE1 and OE2 are low, the outputs are enabled and provide true data from the inputs.

The SN74HC541PWR IC operates with a wide voltage range of 2 V to 6 V, has low power consumption, high output current, and fast switching speed. The IC also has a data flow-through pinout, which means that the inputs and outputs are on opposite sides of the package, making it easier to design printed circuit boards.

Understanding the Power Requirements: Working with 24V DC

The ESP-32 PLC is designed to work with a 24V DC power supply. This voltage requirement was chosen to ensure compatibility with common industrial power systems and provide sufficient power for the connected devices.

Partnership with PCBWay: Sponsorship and Support

I would like to express my gratitude to PCBWay for their sponsorship and support in bringing this project to life. Their expertise in PCB manufacturing and assembly has been invaluable throughout the development process.

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Planned Improvements: Upcoming Version and Corrections

Despite the challenges faced in the initial version, I am excited to announce that a new version of the ESP-32 PLC is already in the works. The upcoming version will address the issues with the USB-Serial converter and voltage regulator to ensure seamless communication and stable power supply.

Adding Functionality: CAN Bus and Integrated Sensors

In addition to the necessary corrections, the new version of the ESP-32 PLC will also include additional features to enhance its usability and speed.

One of the planned improvements is the integration of a CAN Bus, which will enable communication and data exchange between multiple devices within a network.

This will allow for better coordination and control of various devices in home and small industry applications. Furthermore, I plan to incorporate an integrated sensor into the PLC. This sensor will provide valuable data for monitoring and automation purposes, further expanding the capabilities of the PLC.

Future Directions for Small Industry Applications

In the future, I envision the ESP-32 PLC being utilized in a wide range of small industry applications. Its versatility and ability to communicate with various devices make it a powerful tool for automation and control.

Conclusion: Evaluating Success and Lessons Learned

In conclusion, while the initial version of the ESP-32 PLC faced complications with the USB-Serial converter and voltage regulator, the project has provided valuable insights and learnings. Through the challenges encountered with the USB-Serial converter and voltage regulator, I gained a deeper understanding of the importance of thorough testing and validation in the PCB design process. These obstacles have led to valuable lessons in component selection, compatibility testing, and the critical nature of power regulation in electronic systems.

Moving forward, the upcoming version of the ESP-32 PLC not only aims to rectify the issues experienced but also to incorporate additional features that will further elevate its capabilities. The integration of a CAN Bus and an integrated sensor signifies an important step towards creating a more comprehensive and adaptable solution for automation and control.

With the continual improvement and expansion of features, the ESP-32 PLC is poised to become a reliable and flexible system for various small industry applications.

Also I want to say thanks to the Flux.ai team and user community, which has become an essential platform for my learning and an accessible tool to enhance my capabilities with modern electronic development. I believe that these types of design tools are instrumental in democratizing electronic design and fabrication, making it more inclusive and open to a wider audience.

Finally, I want to thank PCBWay for being an essential part of electronic development. PCB manufacturing is one of the most difficult and costly parts of the process, but thanks to PCBWay, it has become much easier and accessible to a large audience. Additionally, their support for the community of creators and entrepreneurs is truly admirable. Thank you PCBWay for making it possible for our projects to come to life! 🙌

Arduino code to read the temperature and turn ON/OFF a relay

#define ADC_VREF_mV 3300.0 // in millivolt
#define ADC_RESOLUTION 4096.0
#define PIN_LM35 12 // ESP32 pin GPIO12 (ADC0) connected to LM35
#define PIN_RELAY 38 // ESP32 pin GPIO38 connected to relay

void setup() {
  Serial.begin(9600);
  pinMode(PIN_RELAY, OUTPUT);
}

void loop() {
  // read the ADC value from the temperature sensor
  int adcVal = analogRead(PIN_LM35);
  // convert the ADC value to voltage in millivolt
  float milliVolt = adcVal * (ADC_VREF_mV / ADC_RESOLUTION);
  // convert the voltage to the temperature in °C
  float tempC = milliVolt / 10;
  // convert the °C to °F
  float tempF = tempC * 9 / 5 + 32;
  // print the temperature in the Serial Monitor:
  Serial.print("Temperature: ");
  Serial.print(tempC); // print the temperature in °C
  Serial.print("°C ~ "); // separator between °C and °F
  Serial.print(tempF); // print the temperature in °F
  Serial.println("°F");
  delay(500);

  // turn on/off the relay based on the temperature
  if (tempC > 25) { // if the temperature is above 25°C
    digitalWrite(PIN_RELAY, HIGH); // turn on the relay
  } else { // if the temperature is below or equal to 25°C
    digitalWrite(PIN_RELAY, LOW); // turn off the relay
  }
}

ESP32 PLC for home and small industries appliances

Things used in this project

Hardware components

Software apps and online services

Hand tools and fabrication machines

Story

Introduction to the Custom PCB Design

Design and Features

Role of ESP-32 Microcontroller in the PCB

Key Features: USB-C, SSRs, I/O, ADC and Voltage

Challenges in the USB-Serial Converter and Voltage Regulator

Uses of the 74HC14D

The SN74HC541PWR IC

Understanding the Power Requirements: Working with 24V DC

Partnership with PCBWay: Sponsorship and Support

Planned Improvements: Upcoming Version and Corrections

Adding Functionality: CAN Bus and Integrated Sensors

Future Directions for Small Industry Applications

Conclusion: Evaluating Success and Lessons Learned

Code

Arduino code to read the temperature and turn ON/OFF a relay

Credits

Rafael Lozano

Comments

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ESP32 PLC for home and small industries appliances

ESP32 PLC for home and small industries appliances

Things used in this project

Hardware components

Software apps and online services

Hand tools and fabrication machines

Story

Introduction to the Custom PCB Design

Design and Features

Role of ESP-32 Microcontroller in the PCB

Key Features: USB-C, SSRs, I/O, ADC and Voltage

Challenges in the USB-Serial Converter and Voltage Regulator

Uses of the 74HC14D

The SN74HC541PWR IC

Understanding the Power Requirements: Working with 24V DC

Partnership with PCBWay: Sponsorship and Support

Planned Improvements: Upcoming Version and Corrections

Adding Functionality: CAN Bus and Integrated Sensors

Future Directions for Small Industry Applications

Conclusion: Evaluating Success and Lessons Learned

Code

Arduino code to read the temperature and turn ON/OFF a relay

Credits

Rafael Lozano

Comments

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