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2 Simple Induction Heater Circuits – Hot Plate Cookers

In this post we learn 2 easy to build induction heater circuits which work with high frequency magnetic induction principles for generating substantial magnitude of heat over a small specified radius.

The discussed induction cooker circuits are truly simple and uses just a few active and passive ordinary components for the required actions.


Update: You may also want to learn how to design your own customized induction heater cooktop:
Designing an Induction Heater Circuit - Tutorial


Induction Heater Working Principle

An induction heater simply is a device that uses a high frequency magnetic field to heat up a iron load or any ferromagnetic metal.



During this process electrons inside iron are unable to move as fast as the frequency, and this gives rise to a reverse current in the metal termed as eddy current. This development of high eddy current ultimately causes the iron to heat up.

The generated heat is proportional to (current)^2 x resistance of the metal. Since the load metal is supposed to be made up of iron, we consider the resistance R for the metal iron.

Heat = Ix R (Iron)

Resistivity of Iron is: 97 nΩ·m

The above heat is also directly proportional to the induced frequency and that's why ordinary iron stamped transformers are not used in high frequency switching applications, instead ferrite materials are used as cores.

However here the above drawback is exploited for acquiring heat from high frequency magnetic induction.

Referring to the proposed induction heater circuit below, we find the concept utilizing the ZVS or zero voltage switching technology for the required triggering of the mosfets.

The technology ensures minimum heating of the devices making the operation very efficient and effective.

Further to add, the circuit being self resonant by nature automatically gets sets at the resonant frequency of the attached coil and capacitor quite identical to a tank circuit.

Using Royer Oscillator

The circuit fundamentally makes use of a Royer oscillator which is marked by simplicity and self-resonant operating principle.

The functioning of the circuit could be understood with the following points:

  1. When power is switched ON, positive current begins flowing from the two halves of the work coil towards the drains of the mosfets.
  2. At the same the supply voltage also reaches the gates of the mosfets turning them ON.
  3. However due to the fact that no two mosfets or any electronic devices can have exactly similar conducting specifications, both mosfets do not turn on together, rather one of them turns ON first.
  4. Let's imagine T1 turns ON first. When this happens, due to heavy current flowing through T1, its drain voltage tends to drop to zero, which in turn sucks out the gate voltage of the other mosfet T2 via the attached schottky diode.
  5. Here, it may seem that T1 might continue to conduct and destroy itself.
  6. However, this is the moment when the L1C1 tank circuit comes into action and plays a crucial part. The sudden conduction of T1 causes a sine pulse to spike and collapse at the drain of T2. When the sine pulse collapses, it dries down the gate voltage of T1, and shuts it down. This results in a rise in voltage at the drain of T1, which allows a gate voltage to restore for T2. Now, its the turn of T2 to conduct, T2 now conducts, triggering a similar kind of repetition that occurred for T1.
  7. This cycle now continues rapidly causing the circuit to oscillate at the resonant frequency of the LC tank circuit. The resonance automatically adjusts optimally depending on how well the L1C1 values are optimized.

However the main downside of the design is that it employs a center tapped coil as the transformer, which makes the winding implementation a bit trickier. However the center tap allows an efficient push pull effect over the coil through just a couple of active devices such as mosfets.

As can be seen, there are fast recovery or high speed switching diodes connected across the gate/source of each mosfet.

These diodes perform the important function of discharging the gate capacitance of the respective mosfets during their non-conducting states thereby making the switching operation snappy and quick.

How ZVS Works

As we discussed earlier, this induction heater circuit works using the ZVS technology.

ZVS stands for zero voltage switching, meaning, the mosfets in the circuit switch ON when they have minimum or amount of current or zero current at their drains, we have already learned this from the above explanation.

This actually helps the mosfets to switch ON safely and thus this feature becomes very advantageous for the devices.

This feature could be compared with the zero crossing conduction for triacs in AC mains circuits.

Due to this property the mosfets in ZVS self resonant circuits such as this require much smaller heatsinks and can work even with massive loads upto 1 kva.

Being resonant by nature, the frequency of the circuit is directly dependent on the inductance of the work coil L1 and the capacitor C1.

The Frequency could be calculated using the following formula:

f = 1 / ( 2π * √[L * C] )

Where f  is the frequency, calculated in Hertz
L is the inductance of the Main Heating Coil L1, presented in Henries
and C is the capacitance of the capacitor C1 in Farads

The Mosfets

You can use IRF540 as the mosfets which are rated at good 110V, 33amps. Heatsinks could be used for them, although the heat generated is not to any worrying level, yet still it's better to reinforce them on heat absorbing metals.

The inductor L2 terminating from center of the main induction coil is a kind of choke for eliminating any possible entry of the high frequency content into the power supply and also for restricting the current to safe limits.

Relatively the value of L2 should be high enough, a 2mH will do the job well. However it must be built using high gauge wires for enabling high current usage through it safely.

The Tank Circuit

C1 and L1 constitute the tank circuit here for the intended high resonant frequency latching. Again these too musts be rated to withstand high magnitudes of current and heat.

Here we can see the incorporation of a 330nF/400V metalized PP capacitors.

Circuit Diagram of the first Design

simple induction heater circuit using 2 mosfets

Now comes L1, which is the most crucial element of the whole circuit. It must be built using extremely thick copper wires so that it sustains the high temperatures during the induction operations.

The capacitor as discussed above must be ideally connected as close as possible to the L1 terminals. his is important for sustaining the resonant frequency at the specified 200kHz frequency.

Primary Work Coil Specifications

For the induction heater coil L1, many 1mm copper wire may be wound in parallel or in bifilar manner in order to dissipate current more effectively causing lower heat generation in the coil.

Even after this the coil could be subjected to extreme heats, and could get deformed due to it therefore an alternative method of winding it may be tried.

In this method we wind it in the form of two separate coils joined at the center for acquiring the required center tap.

In this method lesser turns may be tried for reducing the impedance of  the coil and in turn increase its current handling capability.

The capacitance for this arrangement may be in contrast increased in order to pull down the resonant frequency proportionately.

Tank Capacitors:

In all 330nF x 6 could be used for acquiring a net 2uF capacitance approximately.

how to assemble the main work coil for the simple induction heater

How to Attach Capacitor to the Induction Work Coil

The following image shows the precise method of attaching the capacitors in parallel with the end termianals of the copper coil, preferably through a well dimensioned PCB.

induction heater coil diameter and capacitor details

Parts list for the above induction heater circuit or induction hot plate circuit

R1, R2 = 330 ohms 1/2 watt

D1, D2 = FR107 or BA159

FR107 fast recovery diodes

T1, T2 = IRF540

C1 = 10,000uF/25V

C2 = 2uF/400V made by attaching the below shown  6nos 330nF/400V caps in parallel

0.33uF/400V capacitor MKT metallized polyester

D3----D6 = 25 amp diodes

IC1 = 7812

L1 = 2mm brass pipe wound as shown in the following pics, the diameter can be anywhere near 30mm (internal diameter of the coils)

L2 = 2mH choke made by winding 2mm magnet wire on any suitable ferrite rod

TR1 = 0-15V/20amps

POWER SUPPLY: Use regulated 15V 20 amp DC power supply.

simple induction heater set up details

Using BC547 transistors in place of high speed diodes

In the above induction heater circuit diagram we can see the mosfets gates consisting of fast recovery diodes, which might be difficult to obtain in some parts of the country.

A simple alternative to this may be in the form of  BC547 transistors connected instead of the diodes as shown in the following diagarm.

The transistors would perform the same function as the diodes since the BC547 can operate well around 1Mhz frequencies.

Another Simple DIY Design

The following schematic shows the second simple design which can be constructed quickly at home for implementing a desired induction heater coil.

second design of a DIY induction heater with minimum components

Parts List

R1, R4 = 1K 1/4 watt MFR 1%

R2, R3 = 10K 1/4 watt MFR 1%

D1, D2 = BA159 or FR107

Z1, Z2 = 12V, 1/2 watt zener diodes

Q1, Q2 = IRFZ44n mosfet on heatsink

C1 = 0.33uF/400V or 3 nos 0.1uF/400V in parallel

L1, L2, as shown in the following images:

L2 is salvaged from any old ATX computer power supply.

test results of a working induction heater simple set up
current limiter coil details for the simple induction heater
testing a bolt heating temperature inside a simple induction heater
red hot bolt test results

Modifying into a Hot Plate Cookware

The above sections helped us to learn a simple induction heater circuit using a spring like coil, however this coil cannot be used for cooking food, and needs some serious modifications.

The following section of the article explains, how the above idea can be modified and used like a simple small induction cookware heater circuit or an induction kadai circuit.

The design is a low tech, low power design, and may not be on par with the conventional units. The circuit was requested by Mr. Dipesh Gupta

Technical Specifications

Sir,

I have read ur article Simple Induction Heater Circuit - Hot Plate Cooker Circuit And was very happy to find that there are people ready to help youngsters like us to do something ....

Sir I am trying to understand the working and trying to develop an induction kadai for myself ... Sir please help me understanding the designing as I m nt so good in electronics

I want to develop an induction to heat up a kadai of dia 20 inch with 10khz frequency at a very low cost !!!

I saw your diagrams and article but was a bit confused about

1. Transformer used

2. How to make L2

3. And any other changes in the circuit for 10 to 20 kHz frequency with 25ams current

Please help me sir as soon as possible ..It will be help full if u could provide with the exact components detail needed .. PlzzAnd lastly u had mentioned to use POWER SUPPLY: Use regulated 15V 20 amp DC power supply. Where is it used ....

Thanks

Dipesh gupta

The Design

The proposed induction kadai circuit design presented here is just for experimental purpose and may not serve like the conventional units. It may be used for making a cup of tea or cooking an omelet quickly and nothing more should be expected.

The referred circuit was originally designed for heating iron rod like objects such as a bolt head. a screwdriver metal etc, however with some modification the same circuit can be applied for heating metal pans or vessels with convex base like a "kadai".

For implementing the above, the original circuit wouldn't need any modification, except the main working coil which will need to be tweaked a bit to form a flat spiral instead of the spring like arrangement.

As an example, in order to convert the design into an induction cookware so that it supports vessels having a convex bottom such as a kadai, the coil must be fabricated into a spherical-helical shape as given in the figure below :

The schematic would be the same as explained in my above sevction, which is basically a Royer based design, as shown here:

Designing the Helical Work Coil

L1 is made by using 5 to 6 turns of 8mm copper tube into a spherical-helical shape as shown above in order to accommodate a small steel bowl in the middle.

The coil may be also compressed flat into a spiral form if a small steel pan is intended to be used as the cookware as shown below:

practical example of a simple pancake coil induction heater cooktop

Designing the Current Limiter Coil

L2 may be built by winding a 3mm thick super enameled copper wire over a thick ferrite rod, the number of turns must be experimented until a 2mH value is achieved across its terminals.

TR1 could be a 20V 30amp transformer or an SMPS power supply.

The actual induction heater circuit is quite basic with its design and does not need much of an explanation, the few things that needs to be taken care of are as follows:

The resonance capacitor must be relatively closer to the main working coil L1 and should be made by connecting around 10nos of 0.22uF/400V in parallel. The capacitors must be strictly non-polar and metalized polyester type.

Although the design may look quite straightforward, finding the center tap within the spirally wound design could pose some headache because a spiral coil would have an unsymmetrical layout making it difficult to locate the exact center tap for the circuit.

It could be done by some trial and error or by using an LC meter.

A wrongly located center tap could force the circuit to function abnormally or producing unequal heating of the mosfets, or the entire circuit may just fail to oscillate under a worst situation.

Reference: Wikipedia

SHARING IS CARING!


About the Author

I am an electronic engineer (dipIETE ), hobbyist, inventor, schematic/PCB designer, manufacturer. I am also the founder of the website: https://www.homemade-circuits.com/, where I love sharing my innovative circuit ideas and tutorials. If you have any circuit related query, you may interact through comments, I'll be most happy to help!



219 thoughts on “2 Simple Induction Heater Circuits – Hot Plate Cookers”


  1. Howdy, Friend! Interested to Learn Circuit Designing? Let's Start Discussing below!
  2. Dear master

    If I want to make a more powerful induction heater that can heat a voluminous iron rod in a high temperature what I must to do? Is it possible making such a heater? So what would be the circuit?

    • Hi Mans, for powerful heater you will have to upgrade the mosfets with higher rating, and use thicker tubes or wires for all the coils. Similarly the capacitors will also need to be rated with higher current values.

  3. Sir i made zvs circuit using 70t036h 60 amp mosfet and used 12v 20 ampere powersupply but my mosfets are getting really hot i don’t know why. but it does work and i dont think it will work for more than 5 secs as it will fry entire circuit.
    I used 560 ohm resistor instead of 330 ohm for gate driving and didn’t used lm7812 since i am using constant voltage

    • LM324,

      for the above circuits, mosfet will typically heat up due to the following reasons:

      high gate resistance or high gate voltage above 15V
      High collector current due to lack of resonance.
      L2 and L1 not correctly designed.

      I think you should try reducing the gate resistance to 100 ohms or even lower.

      Make sure the L2 inductance is adjusted to the specified. value.

      I hope you have used fast recovery diodes at the gates of the mosfets?

      make sure to use large heatsinks on the mosfets.

      Use a variable voltage power supply and try tweaking the voltage input and check which combinations produces the best resonance, using that as the reference keep adjusting the voltage and the L1/L2 turns until the optimal value is determined at the maximum voltage range.

  4. Sir i used 5 pairs on 13007 transistor instead of the mosfet you said in the diagram and for the inductor i made 10 wound of coil around ferrite transformer and the circuit worked when i connected it to variable power supply made using lm317t but when i connected to my 12v 5 amp battery it didn’t worked. Sir can you please help me to make this work

  5. Sir, Thanks for great design. I want to make 250 watt induction hot plate. what changes I would have to make in this circuit. What can be the design of heating coil?

  6. Dear sir… if i can get help from you having the Induction heater schematic that does not use Mosfets and also the Inverter 500watts+ it will help a lot… i have a lot of problems laying hands on mosfets in my location.

  7. i also came accross this project on your wall… please i will like to ask if this is a 500watts 220vac inverter that can be use for homes.
    here is the link below.

    3.bp.blogspot.com/-oyXtDjDRk84/VGB2oRtPPhI/AAAAAAAAIjE/irHRQ5SPagI/s1600/48%2BV%2Binverter%2Bcircuit.png

    i wait your reply and thanks for the great stuff's you have on your page.

  8. Dear sir.
    How many turns should L1 and L2 be? i wish to use this for my cloth dryer project.
    please i need your help on that.
    Thanks.

    • Dear Deogratia, please go through the article explanation, diagrams, and the comments, I have already explained L1/L2 details elaborately

  9. Dear sir,
    I need your help . I’m using preethi induction stove. My problem (2uF 275VAC Class X2 Box Type Capacitor) capacitor was Busted but my area only available in (2.2uF 275VAC Class X2 Box Type Capacitor) may I use 2.2uF this capacitor
    thank you

  10. Sir,
    . I have done first circuit by considering all the parameters you have told , it took 5 ferrite rod (each 20cm in length) by winding 1.5 mm copper wire to get 2mH by verifying on LCR meter , and even exat value 6 capacitor connected across parallel as mentioned in the article by giving 2uF , and finaly connected to a battery (12v/ 80ah) no sooner I cgave power supply one of the mosphet reches to a verry high temperature and blow off and other remain cool and this happens within 5-6 seconds

    I tried 4times the same circuit , evey time mospfet blow off , ialso used heatsinks

    • Adithya, why did you use 5 ferrite rods? The coil must be wound over a single ferrite rod…if you do anything randomly as per your wish, then you will keep blowing the devices.

      which diode did you use for the mosfet gates

      did you connect the LC tank as indicated in the 3rd diagram from top??

      the L2 must a be neatly wound inductor over a single ferrite rod, the shape does not matter.

      secondly your circuit must begin self resonating, and this will strictly depnd on the value of the LC tank circuit and the voltgae.

      you must begin with a low volatge may be around 6V and then gradually increase it until you have the best possible results.

      while doing this you must have an ammeter connected i series with the input supply, and you just have a iron rod inserted through the work coil. This iron could be any 2cm thick iron bolt, or a 2cm thick screwdriver spindle.

      the voltage should be tweaked in a such a way that it results in minimum current consumption and maximum heat on the rod…..a temperature meter could be installed with the iron rod fr monitoring the heat as the voltage is gradually increased….at some point you might find that the current is increasing, and heat going down this is point where you must stop, until this sweet point is not reached you must keep adjusting the voltage with some trial and error.

  11. Hi Asanthan, that may be possible, however for sealing plastic, ordinary heater coil would be much hassle-free and efficient.

  12. Hi sir. Can I use this system to make an induction sealer. Is this enough to seal aluminum foil lid with plastic cup.

  13. Hello good Morning.
    I am performing the assembly of an induction heating system,
    But the tank coil should have a 16-inch diameter and will be fixed in the heating core, but as the power supply intends to work with the voltage of 220V rectified, it will not cause risk because it will work totally isolated and away from the users.
    It would be possible to assist in the calculation of L1 and L2
    Noting that the high voltage of the power supply is due to the high power I need.
    10KW.
    Thank you for the attention
    I'm sorry, my English
    Any help will be appreciated

  14. Sir,
    . I used 2.5mF / 450v tank capacitor and I used ferrite rod and wound 100 rounds of 1mm copper wire and I connected L1 with insulated coper wire to the second circuit by using transitor and power supply with high guage copper wire to 12v80ah battery and as soon as I supply power , wire (from L1 to circuit )started melting and copper wire arround ferrite rod went to a verry high temperature ,
    Can u suggest a solution to my problem

    • Adithya, you must do EXACTLY as suggested in the above article.

      use 6 nos of 330nF/400V capacitors in parallel for making the 2uF capacitor, and connect them parallel with the work coil tube ends.

      the work coil must be built using copper tubes or very thick copper wires.

      don't use the last circuit, it's only a suggestion and needs to be experimented… use the first circuit with schotky diodes.

      for more info you can refer to youtube videos…there are plenty of videos which will show you how configure the above type of circuits.

  15. Dear swagatam,
    Do you know or can design a electronic circuit to mesure the real magnetic field strength. Generated in the coil. I amen how much mIliTesla i have ?, Thank you in advance

    • Hi Guillermo, I think the circuit can be configured using a Hall effect sensor and an opamp stage, if possible I'll try to publish a design soon.

  16. hey swagatam im having isues with designing a mini induction heater can i use a set of irfz44n transistors for building a small zvs driver and if possible can you give me a half bridge schematic!

    Frank:

  17. Hi, thanks for the explanation. Really helpful stuff. I'm trying to make a heating circuit using Li-ion 3.7V battery. The end result is to heat a small piece of stainless steel. Don't know if I can use this technique as the battery power isn't that much. If I can please guide me how and if not , can you provide an alternative ? I'm looking at resistive heating

    • sorry that may not be possible.

      you will require at least may be 300 to 500 watts of power for melting a piece of steel which cannot be achieved from a 3.7v cell

    • I don't need to actually melt it. Just to heat it to a temp of around 200deg C. timing isnt crucial. But yes cell power is way too less I think for the application.

    • It my be possible if the mosfets are appropriately upgraded with higher current ratings and the supply is also proportionately increased with higher current capacity.

  18. Hello
    what is the maximum temperature which our metallic target reach inside the coil?
    and i wanna to know moreover current , what parameters effect on the final temperature (like frequency, voltage , coil diameter , etc) ?
    i assembled your designing circle , and the frequency has a tolerance between 70 to 120 kHz,can you give me an advise what's the matter?

    i really appreciate it in advance.

    • Hello, it will depend on the input current and the coil wire thickness, and also the voltage level, higher parameters will allow higher temperatures and vice versa…..

      it's a self-resonating type of circuit, and the frequency will adjust as per the inductor efficiency…..a better optimized coil will enable better resonance and proportionately more heat.

  19. No, the voltage at drain will be above zero only when the device is not conducting, and will be zero the moment it starts conducting.

    the work coil definitely needs to be mounted on a core otherwise the resonance will never happen and the devices could get damaged.

    the core here is the metal which is being heated, that is the iron bolt or rod whatever it may be.

    the capacitors, the coil and the iron core together forms a "tank" circuit which reaches the resonance level during the operations and causes the desired heating effect.

  20. Hi, since both the fets cannot switch ON together due to the slight difference in their switching characteristics, let's assume T2 initiates first on power switch ON,
    as soon as this happens its gate potential is instantly grounded by its own drain/source terminals via D2 and L1….dropping its gate potential to a a level where it's forced to shut off.

    This enables T1 to initiate the process and it eventually ends up shutting off in the same manner…the cycle keeps regenerating and continues rapidly giving rise to the required phenomenon…

  21. Hi Swagatam, i love your projects and my son regularly builds them at school in science lessons.
    i lastly got him the parts to build a simple Royer style induction heater working from 12v DC but i wonder could your simple inverter circuit using the IR 2153 from 12v DC be changed to build a more exciting and challenging induction circuit ? would it be as simple as adding capacitors to the secondary with working coil?
    i thank you in anticipation.

    regards Kevin

    • Yes Hi Swagatam, a very interesting self oscillating circuit i will build it one day.
      However my aim is to get Dan (my son ) to build something more controllable which is why i mentioned the IR 2153 controller, i would like him to achieve some shutdown / protection techniques either with current a transformer or other direct circuitry and from what i have seen of this IC it does most of this, so if there is any chance of further guidance in this direction i would very much appreciate it.
      It does not have to be very powerful but a nice little controllable safe circuit, as in over current and short circuit protection these are the techniques that i would like Dan to start learning.

      regards Kevin.

  22. Hi,
    for a school project i need to construct an AC induction cooktop and was wondering if you could help me put together a part list for a much weaker induction cooktop than yours, it only has to warm up a few ML's of water. is this something that is possible?

  23. Hi, I am glad you could succeed with the above project, but I am sorry I am not entirely sure about the mathematical details of this concept…

    If you wish you can send the working details of the project with pictures and get paid for the submission, I'll publish it in my website.

  24. Initially you should try with a lower voltage may be around 12V, if everything goes well then you can increase it to higher levels for acquiring higher heating ranges.

  25. Hi, yes 17V, 25 amp will do.

    L2 will need to be built by winding 22 SWG enameled copper wire until you reach a 2mH value. the current could be around 10 to 20 amps through L2
    there are some good videos in Youtube which you can see for a clearer view of the procedures.

  26. Hi, Have you ever done or thought to a circuit relevant an induction heater with a function generator as a controller?
    The sense of this request is that I wish to build an induction cooker circuit with the possibilities to verify the frequency value, through my function generator I’m able to achieve a few KHz to a few MHz; my problem is How can I feed the cooker coil without a sort of amplifier? The power after function generator isn't sufficient to feed the coil. In other terms I wish to implement this: Function Generator -> Electronic -> Cooker Coil. Have you got any idea?

  27. Dear sir
    im using index sun pijeon rapido my problem is contin.. sart bip sound and disply no 3 back on wrong side so please solve my problem

  28. hi Swagatam, Thank you for The circuit. I have a question and a clue. I want to measure the magnetic field in the working coil. As the frequency is higth, i don't know how to measure. Could you help me ? How Many tesla or mili tesla. can produce. (B) it is possible to measure or calculated. Thank you in advance

  29. Dear Swagatam,

    can i make this for smaller diameter of induction coil as small as 5 mm to 1 cm wide to heating a small wire? i need it for an experiment for microbiological purpose…

    thank you

    • Dear Prasetyo, the above design is a self resonating kind of circuit so I am not sure whether a coil with a different dimension would automatically adjust with it…or what necessary modifications might be required.

      you can try though by changing the L2 specs also, through experimentation

  30. hii im onkar ,
    i have made circuit using irfz44n ,diodes=1n5819
    and used the power supply of 24v/10amp. with lm7812cv as vr,also i used 2x.47 uf capacitors
    but when i start the supply my rectifer and choke coil gets too hot.and circuit does not work at all..
    what would be the problem ??pls reply me sir…

    • Onkar, it will be difficult to troubleshoot because I do not know what mistake you might have made in it.

      L2 is around 2mH…did you verify this inductance value?

      initially use a 200 watt bulb in series with transformer primary, and check whether the coil produces heat or not….

      the work coil needs to be built exactly as shown in the above figure, and same is true for the capacitor bank

      you can check a few you tube videos on this subject and see how it's is implemented practically…

  31. Hello sir i make this circuits but not succed.
    I use mosfet irfp250
    Capasitor csd mer 165j400v
    470ohm 2w resistor
    12v 1w zea diod
    Diod 4100e
    10k 1/4w resistor
    Induction coill old pc power suply
    I use 24vdc 14amp power suply
    I make heting coill 9 trun copartube 7mm.coill diametar 1.5"
    So what is tha miss take.pless helf me

    • hello Saiful, where did you use the zener diode, if you used it for the 7812 it might have got burnt and shorted, make sure you use a 7812 IC as shown in the first diagram and not a zener diode….
      if you use a 12V/15amp transformer you can get rid of the 7812.

  32. helo sir! my name is biniyam i'm from east africa, ethiopia,i'm universiity student
    i sincerly ask u to help me om my semister project which is to replace "enjera"(which is staple food in ethiopia) making stove with induction cooking system

    • Hello Biniyam, You can try the above explained concept first, if you succeed then we can appropriately modify this into a cooker kind of heating system.

  33. I need your help to design a working induction heater model for my son studying in 8th standard

    would like to get some details on exact materials and design

    Please help

    ramakrishnan

    9821075029

    • bill of material is provided in the article

      if you follow everything exactly as suggested, you could make it work successfully without much effort.

      however this project can be quite difficult for a school student.. as it might involve many complex measurements, adjustments and other related procedures

  34. Hi

    I have put a similar induction coil in a range cooker, instead of a circular cast iron hotplate, I have a circular plate glass sitting in the old hotplate recess with the induction coil underneath, will the all the cast iron in the cooker top affect the induction unit.
    It worked for a while but now I am receiving an E0 error on the control panel, but I am going to switch to manual control, Potenimeter I think? would this help Thanks.

    Regards Denis.

    • Hi,

      sorry, I could not understand your question, do you mean you used a glass instead of cast iron and you are wondering if that would affect the results, then probably the answer is yes, if the cooker is a non-magnetic thing it won't react with the coil's magnetic induction and won't heat up.

      where do you intend to use the potentiometer?

  35. My requirement is heating water ,approx 170ml, upto 90○C. Would it be possible using above circuit?
    If not what changes are required? Also would it be possible to run the above circuit on battery power?

    • plz let me know that which circuit diagram is right . as i run both but not working a single and i used 12v,10A supply .

    • both the circuits are correct, but the first one is better recommended.

      there are many related youtube videos, you can refer any of those for a detailed help.

    • let me know about the l1 coil turns and i have to use same wire or other bcoz temporary i used different copper wire and let me know that can ckt run on 12v 10a

    • i want to ask you that either this circuit is run in PROTEOUS 7 simulator becoz i m not getting output in that as well as in real time circuit

    • I have updated the coil data in the parts list.

      I have no idea regarding the simulation details, however the circuit has been already tested practically successfully with no issues whatsoever

    • as you can see in the image, L1 consists of two separate coils made by curling two turns each of brass pipes and then then by joining the center together…..so total it becomes 4 turns, but you can try 3 turns each to make 6 turns.

      power supply should be 15V minimum and 15 amps

      please check the youtube videos you'll able to see these circuits in real and how these are configured and tested to produce heat.

    • hey swagatam i would like to thank you for updates but how many wound i have to take for
      l1 and directly can i use 12v 10a power supply last question is iff i use ditto component then i get output otherwise no t

  36. if 15amp is the breakdown limit of the choke then it will not do, if it's the optimal rating then it won't be a problem.

    I think the choke wire should be at least 2mm thick or made by using 2 strands of 1mm wire to be able to withstand 15amps

  37. Hi thanks, D3—D6 can be any rectifier diode capable of handling 25amp current, you can inquire about it with your local component dealer, he will know better and will guide you with the correct number.

  38. Hello,

    My application requires that the object being heated (will be very thin) can be inserted and removed through the side of the coil, as both ends of that object will be fixed and unable to be pulled through the center of the coil. Are you able to tell me if there is any way to construct this without a completely closed heating coil (i.e. with a C-like cross-section instead of an O-shaped cross-section) to allow for side entry of a thin (~2mm diameter) object?

  39. am working on this circuit from few weeks and am facing the same proble as soon as i turn on the supply the current increses upto 40-70 amps and the mosfets blows up . am using irfz44n and 17v 10 amps power supplt from a transformer( its basically a battery charger) am not using any choke please help me out, ? 🙁

    • the choke (L2) is specifically introduced to limit current and to optimize resonance frequency, if you remove it the circuit is bound to fry immediately.

  40. am working on this circuit from last few weeks but its not working as i expect it too. am using a coil of 12 gauge 9 turns center taped mosfet irfz44n ,22uf 4 caps in parallel adn the voltage suply is 15 v 12 amps its from a transformer ( battery charger) as i turn on the circuit the the mosfets blows up within seconds seeps like shor circuted help pe am not using any choke .

  41. Hey, great thread. I was wondering what changes would need to be made to the schematic and the induction coil to work using 3.7vdc max 30amp load. This would obviously be used in a micro induction coil to heat small objects such as a sewing needle. And suggestion on coil size, wrapping and component change on the schematic would be greatly appreciated.
    Thanks!
    Dan

    • thanks Dan, I think it may have to be done through some trial and error since I do not have a formula for calculating the coil.

      The only thing I know is that as the turns increase and the diameter decrease the operating frequency and the current consumption also decrease proportionately, so on this basis you could probably do some experimentation.

      L2 and the other components except the voltage may not require a change as per my knowledge

    • hi sir…we try the circuit using the power supply of the computer as the power supply to the circuit….in our first try….the metal that we put on the middle of the working coil gets hot….but the mosfets gets hot too…..so we decided to change the heatsink with bigger one……after changing we try it again…….and the metal dont get hot……why is it happen sir??thanks for the reply

    • Hi Christian, I guess this could be related to some frequency variations due to the introduction/removel of the metal plate.

      heating up of the msgfets might be hampering the generation of the resonance frequency which might be getting corrected with the addition of the larger hetasink and resulting in an automatic correction of the frequency.

      Not sure though, this could be the reason.

      by the way you are not supposed to put a metal inside the working coil, this might seriously affect the functioning of the circuit

    • but, is it ok that we use a power supply of a computer as the supply for this circuit?

      what could you suggest sir for us to make this induction warmer work.?

    • I'm sorry sir… the metal that we put inside the working is a screw driver just to test if it is working already,if the working coil produce induction heat
      .

    • oh… that was quite silly of me, I completely forgot that a metal (magnetic) needs to be inserted inside the work coil for implementing the design, make sure the heatsinks are perfectly aloof and are not touching anything in the circuit….

      any power supply will do as long as it's able to generate 15 to 20 amps for the circuit.

    • good day sir…..in the 2 small diagram above…..the c1 and c2 are in different position…which capacitor do we need to parallel in the l1?

    • we use a power supply of a computer….if we use the bridge driver type circuit…do we still needed to parallel a capacitor with the + and – of the power supply??

    • C1 value needs to be arranged by putting many MKT capacitors in parallel.

      If you are using a pure DC from an SMPS in that case C2 can be eliminated….

  42. Hi there,

    Its a very nice technology. Thanks for the circuit.
    What is the value of L1 and can i use pan cake coil of the same inductance?

    • The inductance value is not crucial, you can make it as per the given instructions in the diagram, yes with little modifications it can be converted for the pan type implementation.

    • Sir,
      Cant we heat the coil with Dc source using driver circuit??

      I did an oscillator circuit of a supply of 24Vdc and 0.3A and got an output of 46MHz and 19v as peak to peak voltage.
      Can we heat the coil with that frequency ?? what are the possible ways??

    • Jayalaxmi, the coil is not supposed to heat, the vessel is supposed to get hot.

      0.3A will not produce any result…it should be at least 10 to 15 ampere

  43. dear sir I have a old induction heater coil . i want to use that coil . how can i use that coil for heat the panel. please tell me with using simple words. thank you…,…

    • Dear Kamaljeet, without seeing the coil it would be difficult to suggest anything, anyway a commercial induction coil will require a sophisticated circuitry, much complex than the above published design…

  44. Dear Swagatam, thank you very much for the details of the construction of this circuit. I built the heater and works well. I have a question related to the possibility to change the frequency of the system. I need differents frequencies. And I am thinking of if possible to change Capacitor and L at the same time to get any frequency. This is possible? Like for example 200Khz , 300 Khz, 400 and soon.
    Also I would know how I can calculate the magnetic intensity of the system.
    Thank you very much.

    • ty sir.
      can i fed the circuit with directly 20 amp or i have to increase it gradually because the insulation of my wire which are use for connection are burning along with mosfet.
      what is the reason for the same

    • increase it gradually, but if the mosfets are also burning it means the circuit is malfunctioning and there could be a fault in the circuit

    • sir plz help me out.
      when i increase the voltage with the variac my bridge rectifier burned out at 7 volt and if i fed the circuit directly my mosfet burned out.
      what should i do..

    • Pratik, it means the circuit is drawing huge currents without load, something is incorrect in your circuit.

      try a bridge driver type of circuit instead of the above self resonanat design for reliable results

  45. Thanks Swagatam
    I made my induction heater successfully now i want to increase its power..
    Can i increase power of this induction heater using more mosfets in parallel?
    Please scheme a circuit for parallel combination.
    Thanks

    • Thanks Waqar, to increase power you may try increasing the input current and also the voltage, and upgrade the mosfet with other higher rated ones, parallel combination may not be recommended.

      You can select an appropriate mosfet pair from the following article

      easydatasheets.blogspot.in/p/mosfets.html

    • you can use a 1000 watt halogen lamp in series with the mains input to the transformer, this will ensure that the initial amp intake does not exceed to dangerous levels.

  46. i have built one successfully but my capacitors tanks become very hot….
    i am using parallel cap at single point and where the all cap meet(at single point) they get very hot.
    should i mount capacitors on pipes at some distance?

  47. thank you very much.
    the number of turns can prove, but the electronic elements can recommend me what changes should be do.

    • The configuration will remain as is. The resistors could be increased to 1K 10 watt (wirewound) each, everything will need to be done through trial and error, though.

      For the mosfets you can use IRF840, however since mains voltage is involved, the risks of an untoward could be on the cards, I am not recommending use of 220V for this project.

  48. Hello Swatam
    what changes I should make in the circuit to operate at 220V , two phases, each 110 V and a power of 6kW.
    and I'm thinking to cool L1 and L2 with water that circulates inside
    this is possible.

    • Hello Paul,

      Sorry, I think that may not be recommended and could require more number of turns for L1/L2…I do not have the data for calculating those.

  49. is it safe that my transformer that is rated 6A only is giving me up to 10A of current. Because i connected it to a bridge rectifier and a 4700uF caps to make a dc power supply, then i successfully make the circuit work but when I measured the current flowing to the transformer using a clamp meter, it gives me up to 10A depending on the metal to be heated. is it still safe for the transformer producing greater current than its rating?

    • if it's showing more than the specified amps of the transformer means the voltage is being dropped proportionately in the course….so ultimately the total power is never being exceeded.

      as far as the above circuit is concerned, the coil would handle current depending upon its thickness, if it's correctly dimensioned it would be safe.

  50. Is there any alternative power supply? Cause its too expensive to buy a 20 A transformer then make it DC supply. By the way, could I use a power supply with adjuster in order to control the temparature of the induction coil?

    • sorry there's no direct alternative for high current. You can reduce it proportionately by increasing the voltage, but that would also require modifications in the work coil, the turns will need to be increased while the gauge will need to reduced accordingly.

    • thanks for the quick reply, I really want to learn more about induction heating. Where I can find a choke coil required L2 because I can't find one of it in some electronics store here in my place, is it okay not to put L2? I want to share my idea to you, I have a circuit design that I found in the internet to control temperature, how can I share it to you?

  51. Hello Swagatam,
    I have built my one successfully with DC power source of 18V connected to L2 while the other side keep 12V to drive MOSFET. I am also connecting ammerter in series to L2 to monitor the current. With some bolts and nuts or steel rod. They can turn red hot without problem. Current goes up from original L1 coil without anything inside to some level according to the object inside the coil. Somehow, I try this with 1/2" diameter steel pipe with 0.5mm thickness. Current goes up and increasing. After a while when pipe is in red hot, current suddenly increase very rapidly and FET burn-out. At this point, everything stop. I have to change FET as it was shorted Drain-Source. I used IRFP250N and diode BYV26E, pretty high rated voltage and current but still failed. Do you have any idea what I did wrong? Is this due to FET or Diode? Thanks.

  52. hello swagatam.
    Plz suggest a circuit to run cooling fan externally. i bought a amplifier unit the heat sense fan stops automatically after 1 minute. need a solid state cheap circuit to run fan directly from mains. (fan rated 12vdc 0.25amp 2.5w)

    • Hello Max,

      The only solution is to a use a readymade 12V ac/dc smps adapter rated at 500mA or 1amp current, because you won't get below this rating.

  53. Not worked swgtm. the material not even heat up & both mosfets burnt out. it specified 200kHz frequency. So can i use Astable multivibrator to set frequency 200Khz to drive the coils.

    • You can use BC547 transistor in place of the diodes. Connect base and collector together with the gate of the mosfet, and emitter to the drain of the other mosfet. Remember this is only a suggestion…

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