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Induction Cooker Tesla Coil

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RogerInOhio

Sat Nov 11 2017, 04:46PM

Registered Member #1034 Joined: Sat Sept 29 2007, 12:50PM
Location: Chillicothe, Ohio
Posts: 154

A while back I ordered this cool 2500 watt induction heater kit off of E bay. It comes as a circuit board and a flat spiral coil designed for heating steal pots on a stove. All you have to do is hook up the coil to the circuit board and hook up 220 volts to the circuit board and you are ready to cook. A green LED indicates you have power and the yellow LED flashes every two seconds when the unit checks to see if there is a load on the cooking coil . When it dose sense a load the yellow LED stays on and the power power ramps up.

Of course you can make your own coil as long as its inductance lets the cooker resonate in its range of 20 to 25 KHZ . If the resonant frequency is out of range the cooker just won't load up. So far I have found no way damage it.
So eventually I decided to I would try and make a Tesla coil out of this thing although I did have doubts about weather or not it would work. To make a secondary coil that would resonate around 25 KHZ I wound an 8.5 inch cardboard coil form with 34 gauge magnet wire to a length of 32 inches. It took some trial and error to get to that point because when you use such fine wire as #34 on a large coil form the windings tend to over lap each other some. This makes it hard to calculate the parameters in advance but fortunately it means you need fewer turns to achieve your goal.

The primary coil is 12 turns of 10 gauge wire space wound on a 12.5 inch coil form taped at 8 turns. The performance of the system is not that great. With 1500 watts input I get about a 12 inch discharge and the secondary coil gets warm from resistance losses. The cooker oscillator has an erratic wave form that makes for a noisy discharge unlike a vacuum tube Tesla coil. The induction cooker kit I used can be found on E bay or Banggood for around 60 to 70 dollars.

Sulaiman

Sat Nov 11 2017, 08:06PM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140

Excellent !

I bought a generic induction hob with similar internals, like this one

(but I paid GBP29.99 at Lidl some time ago)
and I was considering a similar project, even though the hob is for other purposes.
The main obstacle I guessed to be the relatively low operating frequency
requiring a very large topload and a lossy secondary winding, as you discovered.
Mine uses a rectified but not 'smoothed' supply, so would be very noisy.
Seeing that it can be done is great.
Seeing that it is not spectacular - thank you
- for relieving a little of my perpetual guilt of not doing stuff due to laziness.

Lovely project, thanks for sharing

paulj

Sat Nov 11 2017, 08:44PM

Registered Member #59353 Joined: Sun Apr 17 2016, 02:08PM
Location: France
Posts: 84

Hello,

it's very interesting, I would be curious to see the waveform goes out of the ossilator when the coil Tesla is connected.

PaulJ

RogerInOhio

Sun Nov 12 2017, 02:37PM

Registered Member #1034 Joined: Sat Sept 29 2007, 12:50PM
Location: Chillicothe, Ohio
Posts: 154

Hi Paul, unfortunately I don't have an oscilloscope that will freeze an image of the wave form. The one I have is an older type but maybe I will try hooking it up sometime just to see what I get. Given the erratic nature of this thing I don't think I would be able to see much. I did find a good you tube video that describes the quasi resonant wave form under normal conditions

Hi, Sulaiman thanks for the kind words and I hope you have fun with your cooker.

Mads Barnkob

Sun Nov 12 2017, 07:44PM

Registered Member #1403 Joined: Tue Mar 18 2008, 06:05PM
Location: Denmark, Odense C
Posts: 1968

Nice job Roger, you finished what I have not yet had time to, I am glad you could use my video :)

The small couple of kW units are simply too small to power such big resonators and the bigger ones are too expensive, there isnt really something really good and cheap here.

My project with the cheap Ikea hob is here:

paulj

Tue Nov 14 2017, 07:57AM

Registered Member #59353 Joined: Sun Apr 17 2016, 02:08PM
Location: France
Posts: 84

Hello

I guess a microcontroller on the board, this circuit has simple air, it must surely manage all the bridge, the power management system, the metal detection.

it can surely be modified to pull more frequency, but it's a blow to break everything

A linear power supply for the microcontroller on an induction hob: simple, and efficient

I'll be curious to see transistors, if they are IGBTs, or MOSFETs.

You measured the power consumed?

PS:" I love to criticize, but it's a secret :)"

Without describing the Tesla coil, just the Chinese kit.

-no security system present on the map:
-No ground, no RF filter at the input of the controller, and I doubt that the system is designed to cut in case of overcurrent.

Nothing but that, this assembly will not pass the quality control at home.

RogerInOhio

Thu Nov 16 2017, 02:31PM

Registered Member #1034 Joined: Sat Sept 29 2007, 12:50PM
Location: Chillicothe, Ohio
Posts: 154

I can only tell so much by looking at it but the circuit appears to be about the same as the one below. According to the specifications of the kit that I bought it has an adjustable power level of between 2500 watts and 2100 watts. They must be referring to peek power because when I run it it draws 6 to 6.5 amps at 230v which works out to 1500 watts. I haven't made any attempt to adjust the power yet. There is one pot on the board and I am assuming that is the power adjustment.. One of these days I might get up the nerve to turn it all the way up.

I see that at least it has a fuse on the board that might keep it from catching fire if something goes terribly wrong. I don't know where we would be without all this wonderful stuff from China. Can we keep running a trade deficit with them forever? I guess time will tell.

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