An integrated IoT (Internet of Things) solution for controlling 4-Channel BTA16 TRIAC Board. This project is part of ProgrammableIoTEnvironmentChamber.
This section will guide you through the main progresses we have achieved.
The box can be compatible with fans range from 40mm to 70mm. It prevents electric shock caused by human contact and effectively dissipate the heat generated by the controller. For each of the base piece and the cover piece, a perfectly plain surface is designed to make the 3D printing process easier. The CAD files in both .SLDPRT and .STL can be found in the Dimmer Box CAD directory of this project.
This section will guide you through the software and tools required for building this project.
Visual Studio Code, also known as VSCode, is a popular and powerful text editor for developers. A good text editor is crucial for speeding up the coding process and debugging process.
We recommend to use the official website for downloading the packages. Please go to https://code.visualstudio.com/ and follow the instruction on the web page.
We recommend you to install the listed extensions for boosting your coding experience with VSCode
- Arduino
- C/C++
- Python
- vscode-icons
Arduino IDE is a open-source integrated development environment designated for all Arduino boards. We will use this software to compile our code and burn it to our Arduino. It also has a serial monitor which allows us to interact with Arduino through serial communication.
We also recommend to use the official website for downloading the packages if you are on a Windows or MacOS machine.
Simply go to https://www.arduino.cc/en/software and find out your version.
If you want to use a Raspberry Pi or a Linux machine to program the Arduino, you can simply update your software list by sudo apt-get update and install Arduino IDE by sudo apt-get install arduino in your console.
Python is a widely used program language and both python2 and python3 interpreters are pre installed into Raspberry Pi OS and MacOS.
Go to https://www.python.org/downloads/ and choose the version you prefer. Don't forget to add PATH for python interpreter.
pyserial can be installed through command line with pip. Type pip install pyserial to add pyserial library.
Node-Red is a visual programming tool based on Node.js. It allows you to edit working flows inside a web browser through a wide range of nodes and deploy your flow by simply click deploy button on the right top corner.
If you are using Raspberry Pi and you chose "Raspberry Pi OS with desktop and recommended software", Node-red is already installed into your Raspberry Pi. Simply click the start button on the top-left and go to programming tab. Then, you will able to find Node-Red.
If you are using a Windows machine, you first need to install Node.js and nmp. Go to https://nodejs.org/ and download for Windows. Run the MSI file as administrator. Accept the default settings while installing. When finishing the installation, type node --version; npm --version in Powershell or node --version && npm --version in cmd to make sure that your installation is completed.
You should see something similar to this:
v14.15.3
6.14.9
Then, install Node-Red through npm install -g --unsafe-perm node-red and add node-red to your system path.
If you are using Linux, you can install Node-Red with npm, docker, or snap. You can follow the Documentation on Node-Red official website.
To install the node-red-dashboard, click the Menu button on the top right and select Manage palette. Then search for node-red-dashboard and click install.
Or use npm i node-red-dashboard to install it in command line.
Use http://localhost:1880/ui to open the dashboard if it is on you local machine. Change the URL to your server if Node-Red is running on other devices.
Phase Angle Control is also known as "Phase-fired control (PFC)". Its principle is to modulate a thyristor or a TRIAC to control the amount of voltage, current or power flow into the controlled systems.
The Zero-Crossing Points are the exact time that the AC voltage reaches zero. We first need to use a full bridge rectifier to convert AC into DC. Then we will use a optocoupler to drop the voltage from 120V or 220V to around 5V, which allows us to use an Arduino to process the signal through digital input.
The kind of interrupt we are going to use is also known as external interrupts. However, not all of the pins on the Arduino support external interrupts. For Arduino UNO, only PIN2 and PIN3 and be used as external interrupt. You can check out attachInterrupt() - Arduino Reference for more information.
Syntax attachInterrupt(digitalPinToInterrupt(pin), ISR, mode)
| Mode | Description |
|---|---|
| LOW | to trigger the interrupt when the pin is low |
| CHANGE | to trigger the interrupt when the pin state flips |
| RISING | to trigger the interrupt when state goes from low to high |
| FALLING | to trigger the interrupt when state goes from high to low |
| HIGH | to trigger the interrupt when the pin is high (only support Due, Zero, and MKR1000) |
Code for this project:
// Define the pin number as a variable will make the developing process easier and less likely to make mistakes
int zeroCrossing = 2;
void setup() {
// Initialize external interrupt
attachInterrupt(digitalPinToInterrupt(zeroCrossing), sequenceStart, FALLING);
}We choose 115200 as the baud rate and 115200 is the highest rate that Arduino support. This will allow us to have a smaller lag when we assign new instructions. We will dive deeper into the serial connect in the next section.
// opens serial port, sets data rate to 115200 bps
Serial.begin(115200);
// Initialize input pin
pinMode(zeroCrossing, INPUT);
// Initialize output pin
pinMode(ch1, OUTPUT);
pinMode(ch2, OUTPUT);
pinMode(ch3, OUTPUT);
pinMode(ch4, OUTPUT);
digitalWrite(ch1, LOW);
digitalWrite(ch2, LOW);
digitalWrite(ch3, LOW);
digitalWrite(ch4, LOW);
// Initialize hardware interrupt, start sequence
attachInterrupt(digitalPinToInterrupt(zeroCrossing), timerReset, FALLING);
}loop: For firing the pulse (BTA16 needs around 500ns of pulse to switch it on)
void loop() {
// ch1
if (micros() - previousMicros > timings[0] && micros() - previousMicros < timings[0] + 500)
{
digitalWrite(ch1, HIGH);
} else {
digitalWrite(ch1, LOW);
}
// ch2
if (micros() - previousMicros > timings[1] && micros() - previousMicros < timings[1] + 500)
{
digitalWrite(ch2, HIGH);
} else {
digitalWrite(ch2, LOW);
}
// ch3
if (micros() - previousMicros > timings[2] && micros() - previousMicros < timings[2] + 500)
{
digitalWrite(ch3, HIGH);
} else {
digitalWrite(ch3, LOW);
}
// ch4
if (micros() - previousMicros > timings[3] && micros() - previousMicros < timings[3] + 500)
{
digitalWrite(ch4, HIGH);
} else {
digitalWrite(ch4, LOW);
}
}We cannot use delay function inside the loop because we are controlling four different channels at the same time. The delay function will tied up the CPU so that other instruction cannot be executed. Additionally, there is no operating system inside the Arduino and Arduino also does not support threading and multiprocessing. As a result, we need to store the states and make a schedule the Arduino. After that, the Arduino will become a state machine.
Serial communication allow us to send our settings to the Arduino and also let the Raspberry Pi to monitoring the working status of the Arduino.
We need to set the exact same baud rate on both the Arduino and Raspberry Pi to make it functional.
On Raspberry Pi:
import serial
# The first argument specify the serial port of the device
# Usually 'COMx' for windows, 'dev/ttyUSBx' for Raspberry Pi
arduinoData = serial.Serial('COM1', 115200)On Arduino:
void setup() {
// opens serial port, sets data rate to 115200 bps
Serial.begin(115200);
}From Raspberry Pi to Arduino
arduinoData.write(str(power_set).encode())From Arduino to Raspberry Pi
void sendPower() {
Serial.print("[");
for (int i = 0; i < 4; i++) {
Serial.print(power[i]);
if (i < 3) {
Serial.print(",");
}
}
Serial.println("]");
}We only need to exchange the power levels for four channels so that we can arrange the power level into a Python list or an array. In python, we can use str() function to convert a list to a string. In arduino, we can define a small function to do the same job.
On Raspberry Pi:
dataFromArduino = arduinoData.readline().decode('ASCII')[:-2]
power_read = eval(dataFromArduino)Since we already arrange the data in the format of a Python list, we can use eval function to evaluate the string into a Python list. There will be a \n at the end of the data from Arduino. So, we can skip the last two letters.
On Arduino:
void receivePower() {
for (int i = 0; i < 4; i++) {
power[i] = Serial.parseInt();
timings[i] = map(power[i], 0, powerMax, 8100, 600);
}
bufferFlush();
sendPower();
}On Arduino we can use parseInt() function to get the settings from data sent by Raspberry Pi. parseInt() will skip the brackets and Brackets in between automatically. A serial buffer is designed to Arduino, we don't need to worry that the Arduino will miss the information sent by Raspberry Pi. We can also map the power level into the time "delay" to each zero-crossing time. We will never use a delay when multiple channels are working in the same time.
In the normal version, we added a function to the Arduino, which allows error checking by sending stored settings from Arduino back to Raspberry Pi. However, the serial communication and sending back process takes time, which will causing missing firing to the dimmer and LEDs will also blinking even frequently. Therefore, we did a simplified version which does not have the error checking function for faster response and performance.
Node-Red also integrated a serial module to its programming workspace. It is also possible to use control the Arduino without the Python script. We have already tested connecting Raspberry Pi to Arduino without Python script and the whole system work just fine. So, if you are not familiar with Python, we recommend you to do it directly.