DIY

Digital soldering station for little money

Digital soldering station for little money  Digital soldering station for little money  Digital soldering station for little money The soldering station differs from a conventional soldering iron, at least in the presence of a control and management module that allows you to maintain a given temperature on the soldering iron.
In this article, a wizard will tell us how to make an affordable digital soldering station. The project requires only a few components and costs about $ 7 (excluding the power supply).
Device specifications:
Designed for Hakko 907 soldering iron
Compatible with similar soldering irons
Temperature range: 27 ° C-525 ° C
Warm-up time: 25-37 s (325 ° C)
Recommended power supply: 24 V, 3 A
Power: 50 W (average)
Tools and materials: -Hakko 907 handle; -Arduino Nano; -Down converter (MP2303); – 5-pin DIN socket ; -DC connector (2.1 mm); – Power supply 24 V, 3 A; -LCD display 16X2 I2C; -Circuit of the operational amplifier LM358; -IRFZ44N MOS transistor; -Electrolytic capacitor 470mF 25V; -Resistor 470 Ohm 1/4 W; -2.7 kOhm Resistor 1/4 W; -Resistor 3.3 kOhm 1/4 W; -Resistor 10 kOhm 1/4 W; -Potentiometer 10k;
-LED;
-Multimeter; -Soldering equipment; -3D-printer;
-Aerosol paint;
-Wires;
-Screwdriver;
-Screws;
Scheme, printed layout boards, code, and STL files can be downloaded here.
Digital soldering station for little money Digital soldering station for little money  Digital soldering station for little money Step one: about soldering irons
In this step, the wizard examines the pros and cons of various devices for mounting radio components.
An ordinary soldering iron.
Regular soldering irons are good, but they have a few drawbacks. These soldering irons take about 7-15 minutes to heat up. After heating, such soldering irons will continue to operate in the maximum temperature range. In some cases, they can damage electronic components with prolonged contact. According to the experience of the master, when working with perforated boards, copper pads sometimes come off due to strong heating.
Conventional soldering irons with temperature control.
There is a simple and common way to control the temperature of conventional soldering irons, is to regulate it with a dimer. But even such soldering irons have one significant drawback – the lack of temperature feedback.
When soldering, the temperature of the soldering iron tip drops. You can compensate for the drop using the regulator, but at the end of the soldering, the temperature will be higher than the required one and you will need to reduce the temperature again.
Digital soldering station.
The principle of operation of the station is similar to a soldering iron with a dimer, but it has feedback and, accordingly, maintains the set temperature on the tip of the soldering iron. Simply put, the automated electronic control system of the soldering station constantly adjusts this “dimer knob” for the user. When the controller detects that the temperature of the soldering iron tip is lower than the user-set temperature, it increases the power. When the temperature exceeds the set temperature, the power to the soldering iron is turned off and this leads to the cooling of the tip. The system makes this process very fast, constantly turning on and off the heating element of the soldering iron.
Digital soldering station for little money Digital soldering station for little money  Digital soldering station for little money Digital soldering station for little money Step two : design
Inside the handle of Hakko 907 there is a heating element and a temperature sensor located next to it. Both are encased in a ceramic shell. A heating element is simply a coil that generates heat when power is applied. On the other hand, the temperature sensor is a thermistor. A thermistor is a resistance thermometer or resistor whose resistance depends on temperature.
Unfortunately, Hakko does not provide enough data on the thermistor inside its heating elements. For many years this remained a mystery to the master. Back in 2017, he ran a small test to check the thermal performance of the mysterious thermistor inside. He installed a temperature sensor on the soleplate of the iron, connected an ohmmeter to the iron's thermistor contacts, and connected the heating element to a tabletop regulated power supply. Then I increased the temperature and recorded the corresponding resistances of the thermistor. Eventually he received a data graph. He found that he probably had a PTC thermistor with a PTC thermistor. This means that as the temperature around the thermistor increases, the resistance of the thermistor also increases.
Digital soldering station for little money Digital soldering station for little money To get a useful output signal from the thermistor temperature sensor, you need to connect a voltage divider to it. Again, there is no datasheet for the cryptic sensor, so the wizard installed an upper resistor on the voltage divider to limit the maximum power dissipated by the sensor (setting it to a maximum of 50mW). Now that there is an upper voltage divider resistor, it has calculated the maximum output voltage under maximum operating temperature conditions. The output of the voltage divider was about 1.6 V. Then he decided the ADC was compatible with the 10-bit ADC of the Arduino Nano and eventually found that it was impossible to connect the voltage divider sensor directly, as the values ​​were too small to accurately determine it.
To prevent the potential problem of gaps between temperature readings, an op-amp was used to amplify the low peak output voltage of the 1.6V voltage divider. After a series of calculations, the master came to the conclusion that the gain of 2.22 should give a sufficiently large margin so that the project could work with this soldering iron and with other models, if their voltage is higher than 1.6V.
 Digital soldering station for little money Digital soldering station for little money Step three : scheme
The project uses a simple N-channel logic level MOSFET as a switching device for PWM control. It serves as a digital switch to supply power to the heating element. An operational amplifier (LM358) is used to amplify or scale the small voltages produced by the voltage divider thermistor. The 10k potentiometer is used as a variable temperature control knob and the LED is simply an indicator that the master has connected and programmed to indicate if the heating element is active. For this particular project, the wizard uses a 16X2 I2C LCD display as it is more convenient for beginners in electronics.
Digital soldering station for little money Step four : printed circuit board
The master has developed the layout of the printed circuit board in the Proteus program. For the convenience of making the board, he made a one-sided version on his own. The PDF file for printing can be downloaded from the link below.
It is also possible to order the board directly from PCBway.com without having to enter the Gerber files manually (Buy My PCB link).
PCB files (Proteus, Gerber and printed forms ) can be downloaded here.
Digital soldering station for little money  Digital soldering station for little money Digital soldering station for little money  Digital soldering station for little money Step Five: Buck Converter Calibration and Board Wiring Since most Arduino Nano clones can be powered with a maximum of 15V without overloading the AMS1117 5V regulator, and the heating element requires 24V for optimal operation, the wizard uses a buck converter. The AMS1117 5V regulator, which is found in most Arduino Nano clones, has a voltage drop of 1.5V, which means that the input voltage from the VIN pin of the Arduino Nano must be 6.5V (5V + 1.5V).
To adjust, follow these steps:
Set the power supply to 24V
Connect the power supply to the input of the buck converter.
Install the multimeter probes to the output pins of the buck converter
Adjust the output voltage with the trimmer to 6.5-7V.
Digital soldering station for little money Digital soldering station for little money  Digital soldering station for little money Digital soldering station for little money After adjusting the voltage, you can mount the board according to the diagram.
Digital soldering station for little money Digital soldering station for little money Digital soldering station for little money Step six : case
Any suitable plastic box can be used for the case. The master has 3D printed the body. It also includes a Solidworks file in case of need for editing and STL files to send to print.
Print options are as follows:
Printed on Creality CR-10
0.3mm layer height
Nozzle 0.5 mm
30% filling
No support required
Files for 3D printing can be downloaded here.
 Digital soldering station for little money Digital soldering station for little money After printing the master sanded and painted the body black.
 Digital soldering station for little money Digital soldering station for little money Step seven : assembly
Next, we start assembling the device.
Screw the LCD display, the 10 kΩ potentiometer, the DC connector and the driver board into their designated places on the case. Then glue the DIN connector and LED to the case.
Digital soldering station for little money Digital soldering station for little money Digital soldering station for little money Digital soldering station for little money If the user does not have a 5-pin connector, you can replace it with a 4-pin one. This is exactly what the master did.
Digital soldering station for little money  Digital soldering station for little money Digital soldering station for little money  Digital soldering station for little money Connects everything and installs in the case.
Digital soldering station for little money  Digital soldering station for little money Digital soldering station for little money Step Eight: Programming
Arduino needs to be programmed before final assembly.
Connect Arduino to your computer
Download a sketch of the program
Make sure that the Wire.h and LiquidCrystal_I2C.h libraries are installed.
Go
Tools & gt; Boards & gt; Select Arduino Nano
Tools & gt; Port & gt; Select the port the Arduino is connected to
Upload a sketch
Digital soldering station for little money Digital soldering station for little money Step nine : final assembly
Adjusts the contrast of the LCD with a trimmer. Sets the potentiometer knob.
 Digital soldering station for little money Digital soldering station for little money  Digital soldering station for little money Assembles the corpus.
Digital soldering station for little money Digital soldering station for little money Step ten : power supply
Any power supply can be used for power supply according to the table below. For maximum performance, you need to use a 24V, 3A power supply.
Digital soldering station for little money Step eleventh: bonus
For better thermal conductivity, you can add thermal paste to the Hakko 907 soldering iron tip. According to the master, this method works and significantly improves heat transfer. For the first 30 minutes of work, do not forget to release gases, as the grease will begin to boil and release vapors. After 30 minutes, the grease turns into a chalk-like substance.
The master warns that over time the paste will boil and when changing the sting it will be difficult to unscrew it by hand. To unscrew, you just need to knock on the tip with a metal object in the place of the thread.
< img class = "aligncenter" alt = "Digital soldering station for little money" src = "https://usamodelkina.ru/uploads/posts/2021-03/1614611481_1-50.jpg"/> Digital soldering station for little money Everything is ready.
 Digital soldering station for little money Watch the video for the complete assembly process.

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