Project tutorial
DIY Soldering Iron Control for 862D+

DIY Soldering Iron Control for 862D+ © LGPL

Did your somewhat expensive ($50) soldering iron just die? Well then fix it with another one!

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  • 4 comments
  • 16 respects

Components and supplies

Ard nano
Arduino Nano R3
×1
in5404 diode
×1
irf540n n-channel mosfet
×1
5v linear regulator
×1
08377 02 l
Resistor 330 ohm
×1
pin headers(male)
×1

Necessary tools and machines

09507 01
Soldering iron (generic)
8mm drill bit /w drill

About this project

My 862D+ soldering iron broke, so instead of buying a new one I took a second iron and fixed it. The hardest part is that there was no solution elsewhere online. The PCB was broken because after replacing the iron it still said S-E or sensor error.

So I decided to create my own controller circuit, and stuff it inside. It required a second transformer but being cheap, there was plenty of room inside.

It may not look good, but it works like a charm. As a bonus, I removed the soldering iron power button, and added it between 5v and the arduino.

Above the large blue resistor combines with the thermistor in the iron to make a voltage divider. This voltage can then tell the arduino the temperature of the iron. For those who want to modify the code, settemp is what the iron holds temperature to. It's range is from 0 to 1023 with 1023 being the coolest. 0 would destroy the iron. ;) 300 degrees celcius or the melting point of solder is about 630 in settemp.

This picture show the back of the control circuit. As you can tell a second soldering iron is definitely needed. I borrowed one for a day after making the schematic.

Code

Control CodeC/C++
Paste this into the arduino and upload. This only works with the circuit provided
int output = 0;
int temp = 0;
int settemp = 630;
String inputString = "";         // a string to hold incoming data
boolean rap = false;
boolean stringComplete = false;  // whether the string is complete
int t = 0;

void setup() {
  Serial.begin(9600);
  inputString.reserve(200);
  pinMode(6, OUTPUT);
  digitalWrite(6, LOW);
}

void loop() {
  serialEvent();
  if (stringComplete) {
    Serial.println(inputString);
    t = inputString.toInt();
    //settemp = t //sets the set temp to the serial input
    inputString = "";
    stringComplete = false;
  }
  rapid();
  pid();
}

void rapid() { //Controls the soldering iron by rapidly heating it up in the beginning.
  if (rap == false) {
    digitalWrite(6, HIGH);
    do {
      temp = analogRead(0);
      Serial.print("rapid");
      Serial.println(temp);
    } while (temp - settemp > 10);
    digitalWrite(6, LOW);
    rap = true;
  }
}

void pid() { //Controls the soldering with slow active power heating.
  temp = analogRead(0);
  output = temp - settemp;
  if (output < 0) {
    output = 0;
  }
  if (output > 255) {
    output = 255;
  }
  Serial.print("pid");
  Serial.print(temp);
  Serial.print(", ");
  Serial.println(output);
  analogWrite(6, output);
}

void serialEvent() {  //Serial communication that can be used to update settemp
  while (Serial.available()) {
    char inChar = (char)Serial.read();
    inputString += inChar;
    if (inChar == '\n') {
      stringComplete = true;
    }
  }
}

Schematics

Control Circut
Use this schematic to create a circuit for the iron
Solderingiron schem sgt7f7aldl

Comments

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