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Build an affordable Homebrew Hakko 907 Digital Soldering Station! Enjoy the variable and constant temperatures that can reach up to 525C. The project only requires few components and roughly costs around $7 (excluding the repurposed power supply). Barely could I find detailed tutorials on one so I decided to make a video and Instructable about it.
Project Specifications:

Designed for Hakko 907 handles
Compatible with similar handles
Temperature Range: 27°C-525°C
Warmup Time: 25s - 37s (325°C)
Recommended Supply: 24V, 3A
Power: 50W (Average)

Regular Soldering Irons:

Just like any other hobbyist, I started with a regular soldering iron. They’re great but they do come with several cons. Any hobbyist who have tried one knows the struggle that these irons take around 7-15 minutes to warm up before being able to solder. Once warmed up, these irons will remain operating at their maximum temperature range. In some cases, these irons can potentially damage electronic components when contact is prolonged. From experience, the intense heat sometimes knocks off the dotted copper pads when dealing with perfboards. There are ways and techniques to overcome this but once you have tried a digital soldering station, you’ll never have the urge to go back.

Regular Soldering Irons With Variable Dimmers:

There’s a simple and common way to control the heat from regular irons, this is by connecting a dimmer circuit to limit the power going to the heating element. These are also present in some products, I once owned a Weller soldering station that had these. They’re really good! The only disadvantage is that there is no closed loop temperature feedback. In some instances, you won’t be getting the temps marked on the dimmer knob, as the temps would drop when you are soldering components that absorb heat. You can turn up the knob to compensate for the thermal temp drops but once you stop soldering the temps would increase again. You can ramp up the warm-up times by turning the dimmer knob all the way up then turning it down once it’s hot.

Digital Soldering Station:

This is my favorite among the three. It’s very similar to the variable dimmer irons but everything is automated with a PID system. In simple terms, the automated electronic control system of your soldering station, constantly adjusts that “dimmer knob” for you. When the system detects that your iron’s tip temperatures are lower than your set temperature, the system will ramp up the power required to generate heat on your iron’s tip. When the iron temperature is higher than your set temperature, power is cut from the iron causing a drop in temperature. The system does this process really fast, constantly turning the heating element of your iron On and Off to maintain a constant temperature at your tip. This is why warm-up times are significantly faster with digital soldering stations.

Prices would vary depending on where you get your components (Alixpress is the cheapest). I will be updating this step with links once I source out the cheapest online components. I bought my components locally at E-Gizmo Mechatronics Manila’s shop.

Materials Needed:

- Hakko 907 Handle ($3 Clone)
- Arduino Nano
- Buck Converter (MP2303)
- 5 Pin DIN Female Connector
- DC Jack (2.1mm)
- 24V 3A Power Supply
- 16X2 I2C LCD
- LM358 Op-Amp IC
- 470uF 25V Electrolytic Capacitor
- 470Ω 1/4W Resistor
- 2.7kΩ 1/4W Resistor
- 3.3kΩ 1/4W Resistor
- 10kΩ 1/4W Resistor
- 10k Potentiometer”

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