Zhuque T12 soldering station (replica version)

Note: The project file has been updated to Rev1.3.3, which is initially available; the professional version does not currently support previewing the project file, please click "Open in Editor" in the upper right corner; welcome to leave a message for discussion,
 
let me praise it first: this is a machine that has both good looks and strength. The soldering station not only has a beautiful UI, but also has excellent temperature control performance. Author @createskyblue is named after the ancient god Suzaku.
 
About this project:
1. Based on the open source project Zhuque soldering station. Special thanks to the original author @createskyblue, this is the second time I have used his work for free; thank you to Jialichuang for letting me use PCB proofing for free.
2. Hardware changes:
(1) Core changes: The original differential amplification circuit amplifies the thermocouple signal. When I was searching for information, I found its upgraded version: a three-op amp instrument amplification circuit (see information). The information is quite complicated. To sum up, it has both high input impedance and low output impedance; the input stage is set to a higher amplification factor to amplify the useful differential mode signal, while the gain of the harmful common mode signal is 1, and the common mode rejection ratio is obtained Significantly improved, the output stage is generally set to a lower magnification (within 2 times, usually designed to be 1 times), thereby significantly reducing the impact of resistor accuracy; only need to adjust the resistance of one resistor RG to adjust the total magnification. Paired with Suzaku's excellent software, it's a perfect match. Thanks to the excellent architecture, ordinary operational amplifiers and ordinary precision resistors can be used without significantly reducing performance. It is simply a must-have tool for DIY. The instrumentation amplifier circuit can also be further replaced by a finished instrumentation amplifier chip, but the cost increases sharply.
        The Rev1.1 version (the custom hardware version number of this project) was found not to work in actual testing. Further investigation revealed that the input stage did not work and only the output stage worked; simulation analysis found the reason: input stage op amp (see A1 and A2 in Figure 1) A negative power supply is required, or the input signal requires a bias voltage above +1V. Rev1.3 adds a negative power supply chip, and it works normally according to actual tests.
        Figure 1 Instrumentation amplifier circuit composed of three operational amplifiers:
        Figure 2 Internal schematic diagram of TI instrumentation amplifier INA128/129:
(2) The price of USB-to-serial chip has also increased. Considering that the utilization rate of this part of the circuit is also low, it is switched to Make it into a burner and leave a burning interface on the control board. For details on the production and verification of the burner, see ESP32 automatic downloader.
(3) In order to reduce the difficulty of PCB layout and welding, the DC-DC step-down was changed to an original linear voltage regulator. As a handicapped person, the original operation is not advanced enough, but it is simple, direct and efficient. The actual measurement of Rev1.1 found that the 7812 generates too much heat, mainly due to the operating current of esp32-S reaching 80mA. Rev1.3 uses DC-DC+LDO.
(4) Based on the software, the rotation direction of the rotary encoder can be exchanged in the menu. In order to reduce one wiring crossover, pins A and B were exchanged.
(5) The thermocouple signal is separated and used for the JBC245 soldering iron tip that is compatible with three wires. Please refer to the schematic diagram for the wiring method. This also leads to the use of 6-pin aviation plugs. Rev 1.3.3 was changed to 5-core, because the differential amplifier circuit offsets the voltage drop of the sampling resistor, so it does not affect the signal amplification.
(6) The welding positions of two To-252-2 P-MOS and two current sampling resistors are reserved for future use as a DIY reflow soldering heating station to improve the large current passing capacity. Maybe one is enough, but using two will double your confidence and double your happiness.
(7) The PCB matches the aluminum alloy shell of 8838 specifications. Nothing new, but it’s easy to buy and comes with free shipping. The sizes produced by different manufacturers are not exactly the same. I only verified the ones I have on hand.
(8) The PCB matches OLEDs with two specifications of 0.96" and 1.3". I only verified 0.96".
3. See gitee for the software, as shown in the picture below; I used Visual Studio Code to compile; the software has not been changed, only I2C is enabled. I did not download the distribution version because the latest version v2.2.1-beta of the distribution version was updated in September 2021 and does not seem to include some recent modifications.
      Changing I2C requires modifying two files. The two modified files have been uploaded in the attachment. (The library file is too large and cannot be uploaded in full). For other files, please go to the original author's gitee project to download.
4. Based on the modular idea, this project has produced the following project packages:
(1) CH340 burner: see ESP32 automatic downloader.
(2) Handle: supports two sleep modes: vibration switch and reed switch, see reed switch + vibration switch T12 bracket.
(3) 8838 front panel made by PCB: 8838 front and rear panels. +GX12-F-5-core through-wall aviation plug
(4) OLED display module: 0.96 inches (compatible with 1.3 inches)
5. Verification:
Rev 1.3.3 2022.5.17
Video: https://www.bilibili.com/video/ BV1Za411j7fz/
has been verified by Rev1.3 board and the project file has been updated to 1.3.3. All changes are verified in Rev1.3 flying line. Please see the schematic diagram for the detailed change record and will not be repeated here
 
 
. Version 4, connected to 5-core wire:
 
 
 
Rev1.1 2022.4.1
First verification version Rev1.1, the verification situation is recorded in detail on the schematic diagram, the following are photos:
 
6. Precautions for modifying this project file:
          (1) PCB used A large amount of copper is laid. The green squares in the picture below must be placed in front and the priority order must be maintained. Usually the order will change after the copper placement is adjusted. The priority must be adjusted as shown below to ensure that the copper placement is correct; Be sure to check the DRC after modification to ensure that it is correct.
          (2) Some copper laying uses the custom pad connection rule "direct connection". Modifying the copper laying may restore the default divergence. If the copper laying connection is found to be abnormal, especially in small areas. You may find that the pad cannot be connected, please modify it as shown below:
7. For other information, please check the original project.
8. This project also refers to the following projects:
(1) ATmega-Soldering-Station: https://oshwhub.com/oshwlab. /ATmega328Pde-T12kuai-su-jia-re-han-tai#P4
(2) Bar T12-PD decoy: https://oshwhub.com/jie326513988/tiao-xingt12-pd-you-pian-ban
(3) OpenHeat: https://github.com/peng-zhihui/OpenHeat