This project is a castration optimized board for the ESP32 936 Soldering Iron 5.0 project (link: https://oshwhub.com/FJ956391150/936-lao-tie-5-0 ). It uses the same shell structure while retaining most of the functions. Greatly reduces hardware cost and manufacturing difficulty

1. Project description    

        The main control is an ESP8266 or 8285 chip, and the heating core is an A1321 (50R thermal resistor/3.3R heating load) soldering iron core used in 936 soldering stations. The temperature is obtained through ADC sampling of the thermal resistor voltage divider, and the 0.91-inch OLED screen displays various information; 3 micro switches to operate, EEPROM saves user settings, TYPE-C interface power input CH224K PD decoy, the handle shell is designed using solidwork and made in Jiali Chuang, TYPE-C interface can be used for program debugging and power supply.

        1. Set the temperature 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 (adaptive to different power supplies)

        3.  0.91-inch OLED display, you can switch to different interface settings or display various parameters through buttons

        4. The sleep time is adjustable from 1 to 60 minutes . If the sleep setting time is not used, the heating will be turned off. Shake the handle or press the bottom button 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 the sample to display various information.

        6. CH224K fast charge decoy supports up to PD100W and is backward compatible with 65W and other inputs. Ordinary 5V USB can also be used, but the heating is a bit slow. The maximum input voltage of other external power supplies is 24V and the current is 10A.

        7. LIS3DHTR acceleration sensor is responsible for collecting motion postures, responsible for touching sleep wake-up, and providing chip temperature. ADC1 collects the voltage in a limited range (12~21V) without using INA219.

        8. When using ESP8266 as the main control, you need to weld an external Flash chip. When using the ESP8285 chip, the internal Flash is integrated. No additional welding of the Flash chip is required. The WIFI function is not used and only the antenna interface is reserved.

        9.CH340C can be used for program debugging and downloading through the TYPE-C interface

      10. When the maximum PD input is 100W, the ordinary PD power supply can provide 20V5A current. The internal resistance of the A1321 heating wire is generally 3.5R, and the maximum heating power is 20*20/3.5=114W. The output of the PD power supply is limited, so manual adjustment is required to limit the maximum power.

2. Program download

     The program is developed based on Arduino IDE. Add the ESP8266 development board into the IDE and add the relevant libraries. Then use the data cable to connect the soldering iron. Select the ESP8266/8285 model and select the corresponding serial port to compile and upload.

     The Arduino program with INA219 chip can accurately display the voltage, current and power and set the rated power.

     The Arduino program that does not use the INA219 chip can only display a limited range of power supply voltage (12~21V). The default display for voltages less than 11.45V is 11.45V. The remaining two positions are displayed to set the PWM duty cycle of the power and the resistance value of the soldering iron thermal resistor.

      A1321 ordinary thermal resistor heating core generally uses a standard thermal resistor of about 50R at 0 degrees Celsius, generally between 45 and 55R. The program temperature sampling is calculated according to the PT50 graduation table lookup table. There are no other temperature calibration functions that require manually filling in the calibration value in the program.

     Relevant programs and dependent libraries are in the attachment 

3. Precautions

     1. PCB proofing 2 layers 1.6 board thickness. Component parameters are subject to the schematic diagram.

     2. The soldering iron is mainly composed of a PCBA 3D printed shell (heating core, socket, and soldering iron tip removed from the 936 handle). The 3D printing file is in the attachment.

     3. There may be some heat where the handle is connected to the soldering iron core. Try to use high temperature resistant materials to print the shell.