1. Project description    

        The main control is ESP32-PICO-D4, and the heating core is the A1321/A1322 heating core used in the 936 soldering station. The temperature is obtained through INA226 sampling of the thermocouple potential/thermal resistor voltage divider. The 0.91-inch OLED screen displays various information; 3 micro It is operated by moving the switch, and the EEPROM saves the user settings. The power supply should preferably support PD100W output (65W is also acceptable). The handle is designed by Jiali Chuang using solidwork. The TYPE-C interface can be used for program debugging, downloading and power supply.

        1. The temperature is adjustable from 0 to 500 ℃ (accuracy cannot be measured)

        2. The rated power can be set from 1 to 100W. If the rated power exceeds the rated power, the PWM duty cycle will no longer be increased (used to adapt to different power supplies)

        3. 0.91-inch OLED digital display, with multiple main interfaces and setting interfaces, which display various corresponding information respectively.

        4. The sleep time is adjustable from 1 to 100 minutes . If the sleep setting time is not used, the heating will be turned off. Shake the handle to exit the sleep mode and start heating to the set temperature.

        5. Plug in the power supply and turn it on. It will automatically read the settings and then automatically heat and sample the display.

        6. CH224K fast charging decoy supports up to PD100W and is backward compatible with 65W and other inputs. The maximum input voltage of other external power supplies is 24V and the current is 10A.

        7. SHT30 collects temperature and humidity, MPU6050 collects motion posture, INA226-1 collects voltage and current, INA226-2 collects temperature

2. Heating core

      The default PD100W input can provide 20V5A current

      Different heating cores need to download different programs and modify the two voltage dividing resistors on the hardware. For details, see the schematic notes.

      1. When using the A1321 ordinary thermal resistance heating core, the internal resistance of the heating wire is generally 3.5R, and the maximum heating power is 20*20/3.5=114W.

      2. When using the A1322 ordinary thermocouple heating core, the internal resistance of the heating wire is generally 10R, and the maximum heating power is 20*20/10=40W. Please note that the thermocouple has sequence requirements.

3. Program download

     The program is developed based on Arduino IDE. Add the ESP32 development board into the IDE and add the relevant libraries, then connect the soldering iron with the data cable. Select the EAP32 Pico Kit model and select the corresponding serial port to compile and upload.

    Relevant information is in the attachment 

4. Precautions

     1. The cost of using INA266 for thermocouple sampling is too high and the voltage sampled near room temperature is inaccurate. However, the advantage is that the accuracy is higher and it is not affected by the accuracy of the ESP32 ADC.

     2. When using INA266, be careful not to buy the one with the default address 0X44. It will not work. The default address that can be used for genuine products is 0X40.

     3. Functions such as program interaction and data analysis need to be further optimized.

     4. PCB proofing 4 layers 1.6 board thickness. Component parameters are subject to the schematic diagram.

     5. The soldering iron is mainly composed of a PCBA 3D printed shell (heating core, sleeve, and soldering iron tip removed from the 936 handle)