How to Make a Soldering Iron?

Soldering irons are accessible, relatively affordable tools; however, sometimes you don’t have one handy or want to make your own just for fun.

In this article, I will give you some ideas to make cool homemade soldering irons. Let’s get started!

Essential Basics on How Soldering Irons Work

Before you start making a soldering iron at home, it is essential to know the basic working mechanism of the tool. Soldering irons’ working principle is straightforward, but let’s go over it one more time.

The heat at the tip of the soldering iron is generated by a component called the “heating element”, which consists of a resistor. Resistors are materials that have low electrical conductivity, causing them to restrict the flow of electric current.

When electricity tries to go through a resistor, the restricted energy is transformed into heat – fundamental physics at work.

It’s important to remember that if you connect the positive wire with the negative without zero or minimal electrical resistance, you will create a short circuit.

All this being said, it’s important to highlight that the core of your homemade soldering iron will be a resistor, and you should know the electrical properties of the materials you will be working with to be sure that you are using a proper resistance and won’t be creating a dangerous tool.

Approximate Wattage Calculation

So, making a homemade soldering iron is about considering what power source to use, for example, an old PC power supply, a USB charger, or a car’s battery.

Of course, you can also consider using grid current, but remember that this is the most dangerous power source. Be extremely careful and use it only if you have experience working with high-current.

Making an approximate calculation of your soldering iron’s wattage is as simple as applying this simple formula:

The wattage is the amount of electrical power that will be dissipated in the form of heat by your soldering iron. Watts or electric power is a rate of energy conversion, and it will determine how quickly the tool will heat up and its capability to melt solder.

Voltage expresses the voltage of your power supply; let’s say 12V, for example.

Current is the flow of electric charge that will be determined by the value R (Resistance) of your resistor expressed in Ohms according to the practical and great Ohm’s law:

So, imagine you are using a 10 Ohm resistor (10Ω), and your power supply delivers 12V.

The current that will flow through the resistor will be:
12 Volts divided by 10Ω = 1,2 Amps.

Now, going back to the other formula, let’s replace I with this result:
W (or P for Power) = 12V*1,2Amps, which equals 14,4 Watts.

So, if you use a resistance that generates a current of 1.2 amperes and use a 12V power supply, your soldering iron will have 14.4 Watts.

Now, imagine you want to make a 40W soldering iron to connect it to a 220 power outlet. You know the Wattage and the Voltage, but you need to determine the resistance and current.

It’s a simple equation system.

Let’s replace the variables that we know:
40W = 220V*I, so the current needed to generate 40W is 40W/220V = ~0.1818 Amps.

Now, we can calculate the resistor needed to generate that current:
I=V/R so R = V/I. Replacing with the values, we have = R = 220/0.1818 = ~1.210.12Ω.

If we check these values, W = V*I and 220V*0.1818 = 39.96 Watts, almost 40W.

The above data is provided to illustrate the calculation involved. When building your DIY soldering iron, do not use the 220V power due safety risks.

It’s essential to ensure that the material you choose to make your heating element (resistor) can handle the electrical and heat load. This will prevent overheating and ensure safe and efficient operation.

Homemade Soldering Iron Examples

Now that we have left the boring math behind, let me give you some ideas to make your own soldering iron!

1. DIY Soldering Iron Using a Screwdriver

An old screwdriver is a good base for making a cool homemade soldering iron.

Things You Need (Materials List):

• An old screwdriver
• Choose your power source. You can use an old 12V power supply or battery charger.
• Copper wire or any wire that you can use to connect it to the screwdriver’s rod.
• A pair of alligator clips for the positive and negative terminals when using 12Volts.
• Electrical tape or heat shrink tubing.
• A rag or a piece of plastic, wood, or anything you can use as a handle.

How to Make a Soldering Iron with a Screwdriver?
Step-by-Step Instructions:

1. Choose the screwdriver you will use for your project. Try to choose one with a flat and broad head, with the least possible rust.
2. Remove the handle or any non-metallic material surrounding the stud to prevent it from melting or burning by the heat.
3. Grab enough copper wire and strip off the insulation from both ends.
4. Wind the copper wire around the screwdriver’s tip.
5. Connect the top end of the copper wire to the positive terminal.
6. Connect the bottom end of the copper wire to the negative terminal (the part of the wire closest to the tip).
7. Insulate the copper wire you wrapped around the screwdriver using heat shrink tubing or electrical tape to prevent short circuits and protect it from burns.
8. Cover the rest of the screwdriver with the material you chose to make the handle to protect your hand from the heat generated while soldering.

Here’s a video that shows the process.

Testing Your Soldering Iron:

Connect both ends of the wire (if you use alligator clips, you can make a safer and better connection) to the positive and negative ends of the power source. It doesn’t really matter what’s the positive or the negative since resistors don’t have polarity.

Wait for the copper wire on the screwdriver to heat up.

After letting it heat up, touch the solder with the screwdriver’s tip. If it gets melted, voila, your soldering iron is working!

Some Considerations:

The screwdriver’s rod will work as a resistor and heating element.

The length of the rod and its composition will determine the resistance and the tool’s wattage.

2. Soldering Iron Using a Pencil

Graphite is a poor electrical conductor, which makes it an excellent resistor. Knowing this, you can create a nice soldering iron using a pencil.

Materials List:

• A pencil (preferably an HD).
• A pencil sharpener.
• A Utility Knife or a Razor Blade Box Cutter.
• Copper Wire (3 or 3.5mm will do)
• Electric Insulator Tape
• A piece of heat shrink tubing

Step-by-Step Instructions:

1. Use the razor blade to carefully split the pencil in two.
2. Sharpen one end of the pencil using the pencil sharpener. This will be the tip of the soldering iron.
3. Use the razor blade to leave the lead exposed. (About 1 ½ inches or 4cm would do)
4. You will use two wires, peel their ends, and on one end, you can use alligator clips to make the connection with the power supply easier.
   Twist the free end of the wires.
5. Use the razor edge to create a slot on the part of the lead next to the sharpened section, and make another in the part nearest to the pencil barrel.
6. Connect one wire by twisting it over the first slot and do the same with the other.
7. Apply electrical tape to insulate the connections.
8. Cover the pencil with the heat shrink tubing and heat it to insulate the whole pencil and the connections.
9. As an additional step, consider attaching a small metal tubing to the tip, because the lead tends to fade with heat.

Some Considerations:

The section of pencil lead between the wires will work as the resistor and heating element. The resistance will vary depending on the distance between the slots. You can play and experiment with this factor to regulate the tool’s power and watch the results. You can cut a portion of a pencil and measure the resistance between both ends using a multimeter or ohm meter to make the maths and determine what power source and lead length you will need, depending on your desired power output or wattage.

Safety Precautions

Besides the safety precautions you should take when using a soldering iron (you can find the safety guidelines here), there are some safety warnings you should use when making and using your homemade soldering iron.

• Use a safe and appropriate power source for the tool you are creating. If unsure, start small; for example, if you want to work with 12V and are in doubt, try using a 5V power supply first. The good thing about old PC power supplies is that they deliver 5 and 12 Volts, so if you have one of those unused, it’s a great tool to make experiments.
• Never leave naked wires, always use proper insulation, and ensure no wire is exposed.
• Use qualities thick enough to handle the current and heat generated by the soldering iron. Don’t use damaged or unreliable wires to prevent electrical hazards.
• Wear safety gear, such as safety glasses and gloves.

Conclusion

There are plenty of elements you can use to make your homemade soldering iron. Work carefully and safely, and don’t underestimate voltage, even with 5 or 12V DC. These projects are great for experimenting, learning, and having lots of fun. You can even add a knob control with a variable resistor to play with the heating element’s resistance and use it as a temperature regulator. The only limit is your imagination!