I need guidance and possible assistance with a Temperature monitoring and controll project that I am working on. I already have done one and working it uses a DHT11 sensor, arduino UNO, Ethernet shield and 1CH relay module.
Operation: The temperature data from the DHT is read and sent to ThingSpeak for monitoring and when temperature reaches and passes pre-defined temperature the relay is activated and fun turns on to ful speed, it turns off once it done.
Request: I want to now replace the relay with the Mosfet switch (already done) as in attached schematic and vary the speed of the fan in propotion to the temperature coming in via the arduino and maintain the temperature at set-point (Example 28 degrees Celsius). I want to keep using the DHT11 and also continue sending data to my ThingSpeak channel.
What model is the MOSFET? Often, unsuitable models are sold for use with Arduino by ignorant vendors.
It an IFR540N, It is working but with the code not changed, it still functioning as a relay. I used the mosfet because of that I am now going to change the speed of fan instead of just switching it to full speed.
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Unfortunately, that's one of the unsuitable MOSFETs I was talking about. It might be ok for small currents, but your fan is not going to get the maximum available voltage using that MOSFET. The suitable type is called a "logic-level MOSFET".
The usual approach to controlling the fan like you want us to use the "PID library". You can install it from the library manager and take a look at some of the example code you get with the library.
I have tried to use the PID library examples in my code as seen below, The problem is my project does the opposite of what I expect; When I set my setPoint to for example (30), the fan speed increases as temperature decreases below 30 and it stops when temperature reaches 30 and above
I am not sure whether it is my Tuning values or what?
// PIDController - Version: Latest
#include <PIDController.h>
#include <SPI.h>
#include <Ethernet.h>
#include "ThingSpeak.h"
#include "DHT.h"
#define DHTPIN 9
#define DHTTYPE DHT11
byte mac[] = { 0xXX, 0xXX, 0xXX, 0xXX, 0xXX, 0xXX}; //ETHERNET SHIELD MAC ADRESS
EthernetClient client;
PIDController pid; // Create an instance of the PID controller class, called "pid"
int outputPin = 3; // The pin the digital output PMW is connected to
DHT dht(DHTPIN, DHTTYPE);
unsigned long myChannelNumber = xxxxx; //ThingSpeak Channel ID
const char * myWriteAPIKey = "xxxxxxxxxx"; //PRIVATE WRITE KEY to ThingSpeak
void setup () {
Serial.begin(9600); // Some methods require the Serial.begin() method to be called first
pinMode(outputPin, OUTPUT);
digitalWrite(outputPin, HIGH);
dht.begin();
Ethernet.begin(mac);
ThingSpeak.begin(client);
pid.begin(); // initialize the PID instance
pid.setpoint(30); // The "goal" the PID controller tries to "reach"
pid.tune(3, 2, 1); // Tune the PID, arguments: kP, kI, kD
pid.limit(0, 255); // Limit the PID output between 0 and 255, this is important to get rid of integral windup!
}
void loop () {
float sensorValue = dht.readTemperature(); // Read the value from the sensor
int output = pid.compute(sensorValue); // Let the PID compute the value, returns the optimal output
analogWrite(outputPin, output); // Write the output to the output pin
delay(30); // Delay for 30 ms
Serial.println("======================================");
Serial.println("Temperature Monitoring");
Serial.print("Temperature= ");
Serial.print(sensorValue);
Serial.println(" C");
Serial.println();
ThingSpeak.writeField(myChannelNumber, 1, sensorValue, myWriteAPIKey);
delay(1000);
ThingSpeak.setField(1, sensorValue);
delay(2000);
}
int output = pid.compute(sensorValue); // Let the PID compute the value, returns the optimal output
if (sensorValue > 30) analogWrite(outputPin, output); else analogWrite(outputPin, 0); // Write the output to the output pin
it stops when temperature reaches 30 and above
How far above? Above 30, the fan should start to come on again, but slowly, and faster as temp increases.
It stopped exactly at 30 degrees. I adjusted the code, instead of sending the pid computed value to output pin, I replaced with the actual temperature "sensorvalue". It is now propotional but as you early suggested the Mosfet at 50 degrees draws upto 1.1V , I will have to get the Logic level mosfet
void loop () {
float sensorValue = dht.readTemperature(); // Read the value from the sensor
int output = pid.compute(sensorValue); // Let the PID compute the value, returns the optimal output
analogWrite(outputPin, sensorValue); // Write the output to the output pin
delay(30); // Delay for 30 ms
