instructables

DIY Induction Heater

by tanner_tech

When you think of a way to heat up a metal object, paperclips in a matter of seconds. The video below
you think of fire -right? Fire is an inefficient, old gives a demonstration of this induction heater in
fashioned, and slow way to heat up metal objects. It action, along with another type of instruction on how
wastes lots of energy as heat and creates lots of dirty to build it.
smoke. Well, what if you could have a way to heat up
metal objects that solves all these issues -it would be Lets get started.
great, right? In this instructable, I am going to show
you how to build a ZVS induction heater. This is a
//www.youtube.com/embed/5WtUDRaOm-Y
device that heats most metals using a ZVS driver
circuit and electromagnetism. It is very efficient,
produces no smoke, and can heat up objects like

Step 1: How It Works

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Many of you who are reading this may be asking To understand how this power supply works, I will
"What is a ZVS driver"? Well, it is an extremely explain the different sections of it. The first section is
efficient oscillator circuit that is able to create an the 24 volt power supply. The power supply needs to
extremely powerful electromagnetic field that heats produce 24 volts at a current of 10 amps. For my
up the metal. It is the backbone of the induction power supply, I will be using two sealed lead acid
heater that this instructable is showing you how to batteries wired in series. The power is then fed into
make. the ZVS driver board. The ZVS oscillator pushes and
pulls current though a coil around the object that is

being heated. This constant changing of the current's inductive chokes into each side of the coil. The choke
direction creates a fluctuating magnetic field. This is to make sure the circuit does not draw to much
induces many small eddy currents in the metal(refer amperage on start up. The current also flows thought
to the diagram above). All of these currents are the two 470 ohm resistors into the gates of the two
relatively high, and because of the low resistance of Mosfets. Now, because no component is perfect, one
the target metal, heat is generated. According to Mosfet is going to turn on first. When this happens, it
ohms law, power converted to heat in a resistive hogs all the gate current from the other Mosfet. It will
circuit is P=I^2*R. also draw the drain of that Mosfet that is on to ground.
This will not only let current flow though the coil to
Now, the metal type of the object that is being heated ground, but it will also let current flow though one of
is very important. Ferrous metals have a higher the fast diodes form the other gate of the other
magnetic permeability, so they are able to harness Mosfet, locking it off. Because there is a capacitor in
more energy from the magnetic field. This allows parallel with the coil, it creates a resonant tank circuit
them to be heated quicker than other materials. that starts oscillating. Because of this resonant
Metals, like aluminum, have a lower magnetic action, the drain of the other Mosfet will swing back
permeability, so it takes longer for them to heat up. and forth in its voltage, eventually reaching 0 volts.
Things that have a high resistance and low magnetic Once this voltage is reached, the gate charge from
permeability, like a human finger, will not be heated at the Mosfet that is on will discharge though the fast
all by an induction heater. The resistance of the diode into the drain of the opposite Mosfet, effectivly
material is also very important. If you have a higher shutting it off. With this Mosfet off, the other Mosfet
resistance in the target metal, then less current will has the opportunity to turn on. After this, the cycle
flow, so the power converted to heat gets repeats thousands of times per second. The 10K
exponentially smaller. If you have a metal with a resistor is meant to deplete any excess gate charge
lower resistance, then the current will be higher, but on the Mosfet, because it is like a capacitor, and the
power loss will be lower due to ohms law. It is a little Zener diode is meant to keep the gates of the mosfets
bit complicated, but because of the relationship at 12 volts or under so they do not explode. This high
between resistance and power output, the highest frequency high power oscillator is what allows metal
power output is achieved when the resistance of the objects to be heated.
object approaches 0.
Now, its time to build this thing!
The ZVS oscillator is the most complex part of this
circuit, so I am going to explain how it works. First of
all, when the current is switched on, it flows though 2

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Step 2: Materials

To build this power supply, you will need a few parts, luckily, most can be salvaged for free. If you have ever seen
an old CRT TV laying on the side of the road, pick it up, because it has most of the parts needed for this project in
it. If you want higher quality components, you can buy them at the LCSC online store. Click the parts to bring up
the product links in LCSC.

You will need:

IRFP260 Mosfets
Fast Diodes
12 volt Zener Diodes
220 Ohm resistors
10K Resistors
10x /.047uF capacitors
2x 50uH inductors (Get from a computer power supply)
Copper wire
Wood
2x Sealed Lead Acid Batteries

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Step 3: Tools

For this project, you will need:

Soldering Iron
Wire strippers/cutters
Multimeter

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Step 4: Transistors and Cooling

In this circuit, because the transistors switch at 0 volts out your FETs. My heat sink was from a computer
(Hence the name, Zero Voltage Switching ZVS) they power supply, and already came with a piece of
do not get very hot, but they should still be mounted insulating silicone, so my transistors are isolated. To
on a heat sink if you are planning on running this make sure that your transistors are isolated, touch
circuit longer than 1 minute. I mounted both of the your multi-meter to the middle pin of both transistors,
transistors on one heat sink. When you do this, make the drain. If you get continuity, then your FETs are not
sure you isolate the metal backs of the FETs from the isolated.
heat sink. If they both touch, it will short out and blow

Step 5: The Capacitor Bank

In this circuit, the capacitors get very hot. This is due in the resonant circuit. What I did, is make a ring of
to them always having current flowing thought them. copper, and add 10 .047uF capacitors in parallel
Now, the capacitor value we need to make this circuit around it. This makes the combined capacitor bank
work properly is 0.47uF, so we will need the most have a capacitance of .47uF, with lots of surface area
amount of capacitors together to reach this same for air cooling. This capacitor bank will be in parallel
value, but have a larger surface area for heat with the work coil.
dissipation. You also need to get the voltage rating of
them above 400 volts due to inductive voltage spikes

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Step 6: The Work Coil

This part of the circuit is what generates the magnetic the coil the subject of the induction heating, which
field. It is formed using copper wire. It is very wasted the power and stopped it from heating the
important that you use copper. I started this project material inserted. I am not sure if this is the exact
using a steel work coil. It did not work very well. reason this wasn't working, but it is the most logical
When it was running with no load, it was drawing 14 argument based on the evidence provided.
amps!! When I switched it out with a copper coil, it
drew only 3 amps. I think that this is because the To make your coil, use stranded copper wire, and
ferrous material in the steel coil had eddy currents wrap it around a piece of PVC pipe about 9 times.
induced into it. Its high magnetic permeability made

Step 7: Building the Circuit Trial and Error

Building this circuit took a lot of trial and error. My the steel coil did not work. This high current draw due
number one issue was my original power supply and to the steel coil blew a few mosfets too. In total, I lost
coil. The power supply is an 55 amp 12 volt switching about 6 mosfets to explosion. This may be bad, but I
supply. I think that this power supply drove the ZVS learned from my mistakes.
circuit with too high of an initial current, this blew out
the mosfets. They exploded, like in the first picture. Over the course of this project, I built the circuit over
This probably could have been fixed by adding larger again many times, but I will just explain how I built the
inductors, but I decided to just use lead acid batteries. most successful version.

My second issue was the coil. In step 6, you saw that

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Step 8: Building the Circuit

To build this ZVS driver circuit, you will need to follow drain(pin 2). Then, attach the VCC wire -from your
the above circuit diagram. I first took the zener diode power supply- through 2 220 ohm resistors to the
and twisted it together with the 10k resistor. You can gate of each transistor. Ground both sources. Then,
then take this pair of components, and solder it solder the work coil and capacitor bank in parallel
between the gate and ground of the mosfet. Make with each other and solder each end to a different
sure that the black end of the zener diode faces the drain. Finally, run power to the drains of each mosfet
gate. Then, solder the mosfets to a piece to perf through 2 50uh inductors. These can be toroidial
board. Use the bottom side of the perf board to solder cores with 10 turns of wire. With that, your circuit
two fast diodes between the drain and the gates of should be ready to use.
each fet. Make sure that the white line faces the

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Step 9: The Base

The base of your induction heater is just to support all of the components. I used a piece of 2x4 wood scrap. The
circuit board, capacitor bank, and work coil were all hot glued to the wood. I think this setup makes it look cool.

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Step 10: Testing Your Induction Heater

To power up your induction heater, just connect it to in vacuum tubes. It is also human safe, so you will
the power supply you have. Then, insert the part you not get burned by putting your finger inside the coil. It
are trying to heat up into the coil. It should start will, however, burn you if you touch an object that has
heating. I was able to get a paperclip to red hot already been heated.
temperatures in 10 seconds. Other things, like a nail,
took about 30 seconds. With these objects inserted, This heater has many possibilities, tell me in the
the current draw rises by about 2 amps. This is a fun comments what you plan to use it for!
circuit to build an play around with. It can also be
used very practically. It can heat up objects without Thanks for reading!
any of the soot that comes from smoke. It can even
heat up isolated metal objects, like the getter material

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