The next step on our tour is the controller board. The controller board is mounted in the top of the device, and connected to the power stage board by the ribbon cable we unplugged a little while ago. By removing a couple short screws, we can release the controller board from it’s flex-button prison and take a look.
Umm, buttons, 7-segments, discrete logic – not too exciting. That 20-DIP with the sticker on top is a micro that runs the show. It’s a Samsung S3F9454BZZ and from what we can tell, it’s notoriously hard to hack. So no firmware mods this time folks, this is strictly a strip show. Micro takes timing data (we speculate) from the current transformer and delivers pulses to drive the gates of the IGBTs. Get your timing right and you drive the tank into resonance with tasty results. Get your timing wrong and you try to switch 500V with 20A running in your IGBT and the 10kW transition loss blows your switch with very un-tasty results. So the controller is important, just not that interesting from a hacker sense.
Fig 9 – The Controller Board
Back to the mainboard. Back to the back of the mainboard, to be precise. In order to take a peek at those power components, we’re going to have to get the heatsink off. We can guess at their function, and we can see the IBGT markings straight away, but to be sure we’ll have to get the heatsink off. The only problem is: one of the components was screwed into the heatsink and THEN the components were soldered in! Now the screw is trapped!
Fig 10 – Back of the Power Stage PCB
If you search long enough you may find the missing hole that allows you to unscrew the heatsink without desoldering. In our board we just had to drill down into the PCB a bit and presto! The missing hole appeared.
Fig 11 – The Missing Hole
A bunch of the images on page 4 and 5 seem to be broken, please fix.
Otherwise excellent article, thanks
Thx for the heads up!
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hello,
i am just interested in doing some PEMF tests on myself, the induction cooking device is a ready made PEMF device that usually retails for thousands of dollars and is much the same as far as i can tell.
but how would one safely make this device work without the metal on top to trigger the coil to work at maximum all the time?
thank you,
gene
Try our article about Manual Control of the 1.8kW Induction Cooktop. That’s exactly what we’re doing there
i read your beautiful article.
but although i am technically minded i am not familiar with electronics; if the coil is tricked to be “ON” when there is no metal on it would it heat up to a self damaging degree?
thank you,
gene
You will want to run at a low power if there is no load. If there is no load, then the voltage ringing will be higher than if there is a load present because there is no place for the energy to go. If it gets too high, it will pop the power switches. The coil is at no risk of overheating – frankly, if any wiring were to burn out it’d be the PCB but that’s still no risk.
If you are going to do loaded/unloaded operation, please consider a foot pedal to increase the power setting once you have the object to be heated at the coil.
Great stuff lads, very interesting (and entertaining!)
I came across this article whilst trying to figure out if an induction cooker with enough oomph can be modified into a small heater for silver/gold melting. The idea I had is to swap out the L~C circuit for something a bit more industrial that I can drop a small crucible into. Temps required would be around 600 to 1500 degrees C, variable as required.
The unit I have in mind is the Buffalo CE208 (3kW) which sounds like it has enough juice, but I need to figure out (with my limited understanding of electronics) if a water-cooled, tuned tubular coil/cap setup can be used as the output stage. Typical coil inductance is a few uH in normal heaters if I’m not mistaken? Not sure about frequency though (65kHz??)
Do you think this is possible without nuking the IGBTs? Or myself? =:O lol
Your input greatly appreciated!
Hmm – maybe. Metals such as silver and gold are very conductive, meaning that you have to put a TON of power into them in order for them to heat up. Also, the lower frequencies of these stoves may not be great for heating the metal directly. BUT…
If you get yourself a graphite crucible then the graphite can be easily heated by even these stoves, and you probably won’t need 3kW to melt a modest (1oz-ish) amount of silver if the crucible is sucking up the power so easily.
As for the coil design – this coil is about 50 uH whereas a few spirals of copper tubing is barely 1uH. So they are pretty much incompatible. You could use many spirals of copper tubing or find some way to insulate/cool the litz wire coil from this beast. Rewound into a cylinder shape, of course.
The best idea may be to leave the coil as a pancake, use a flat graphite crucible/ingot mold, and place said mold on top of a thin ceramic tile that is NOT touching the work coil. Then direct a fan upwards to try to keep the tile’s heat from melting the coil’s insulation. Or something like that.
Thanks for the reply, that’s given me some great ideas & potentially made the job a whole lot cheaper!
I’ve heard of indirect heating but hadn’t really given it much thought until now & that definitely sounds like the way to go. Do you think the work coil could be re-wound as a cylinder with a heat shield between it & the crucible or will this radically change the inductive characteristics of the coil?
I would like eventually to get a small system up & running with a remotely operated ‘hatch’ at the base of the crucible, & the whole lot enclosed in a mini vacuum chamber. Moulding & general metal quality (esp with silver) is a lot better this way as it’s prone to porosity & nasty oxidation bubbles.
Thanks for opening up some very cool possibilities!!
Glad to help! You can certainly re-wind the work coil as a cylinder. In fact, ripping apart the pancake and winding a coil on PVC was one of our earliest experiments on the Burton stove. Wear gloves, the damn lacquer used to hold the original coil in place is as sharp as a razor blade when you break it up by unwinding the pancake.
The vacuum chamber is a great idea, as you can heat right through the sidewalls and you don’t have to worry about vacuum sealing a bunch of hot power terminals. Are you thinking about melting and casting all in the vacuum? Just trying to imagine how to flip that hot tube upside down to get the melt into the mold. Not our area of expertise, of course.
Keep us posted on your project – we’d be happy to post your writeup here if you end up with a system you’d like to share with others.
Once again, thanks for the info & reply! I was wondering about the resin holding the coil together, thought that might be an issue & will try a hair drier to soften it up first. As for the vacuum chamber, I’m planning on incorporating the coil, crucible, trapdoor actuator for pouring/vacuum release timing electronics yada yada inside the chamber. I’m currently looking for a suitable weldable steel box section over 300mm round or square to house it all. It’s a pretty mammoth job, but the results will be well worth the effort.
Hey, how cool is this?…. I managed to get the entire guts of the 3kW Buffalo cooker without the casing etc for £56 here:
http://www.nisbets.co.uk/products/productdetail.asp?productCode=CE208 (under the Spares & Accessories tab) seems to be only available within the UK though?
One issue that I’m perplexed by is how to incorporate a thermistor in direct contact with the outside surface of the coil while avoiding a)vaporizing it by inductive heating! b)shielding it from magnetic interference & getting a false voltage from it. Any ideas? I just wanted a way to monitor the coil for overheats, but if this is as challenging as I think in this kind of environment, I may just run it & pray. At some point I want accurate control of the heat for things like annealing & tempering, so will be incorporating a laser thermometer directed into the crucible area since a pyrometer inside the coil will definitely vanish in short order! lol.
Delivery of the parts Monday, next step is the crucible & insulation. That will probably be a graphite tube with two spaced layers of ceramic tubing to support & insulate it plus fiberglass cloth shielding for the coil turns. etc etc. Will take some pics of the setup as I go.
As far as the resin – it was just broken up by forcefully unwinding the coil while wearing gloves. Heat may soften it, but maybe not as it’s intended to endure heat all the time. Watch out that the outer steel box you plan to hold this project is not too close – even with a cylindrical coil it may pick up some field and steal power away from your melt (while heating itself, of course).
That deal on the 3kW heater really is great! Keep in mind that the Buffalo device may be very different from the Burton we opened up here, but it should be no problem to mod that one for similar manual control. Looking forward to seeing pics!
The Burton heater has a thermistor stuck right in the small central hole in the pancake coil to check overheating of the hob surface. That probably picks up as much stray field as your external thermistor would, meaning that your idea will probably work fine without shielding or anything. The saving grace might be that the turns ratio between the coil and your thermistor is low (thermistor = 1 turn) as well as the fact that the thermistor being outside the coil is not well coupled so the actual current induced in the thermistor is probably nil. If your coil wiring is horizontal, then run the thermistor wiring vertically in order to cut down on the coupling.
Hey you guys, it’s me again.
Eventually got all the parts & find that the 3kW model is almost identical to the 1.8kW version, with a few components shuffled around on the mainboard. The only real difference is the control board, which has a completely different user interface system – no logic buttons on this model, according to pictures of the complete unit it’s operated with a single rotary control knob (& nothing else) which I don’t have & a 4 pin socket on the control board to attach *something*. Tracing the pinouts on the socket, to the best of my ability probably incorrectly, I arrive at what’s shown in the pic (see link at end)
As simple as that sounds, it leaves me completely stumped over how to fire up the mainboard correctly. What do you reckon that would be? A simple rotary pot, or say a 10 position selector with resistors/something else? As you can probably tell, I’m at the edge of my understanding of electronics here lol, & with hindsight I think I should have just bought a complete machine! Tried contacting Better Co for info but no response.
Lastly, the 3 pin socket on the mainboard (red circle next to the ribbon connector) – that’s for the thermistor right? Do you have a value for that component?
Thanks for your help! (and this noob apologises for pestering)
mainboard: http://i571.photobucket.com/albums/ss155/sirius_gem/MainBoard.jpg
control: http://i571.photobucket.com/albums/ss155/sirius_gem/Control.jpg
Wow, you lucked the f*ck out in that it is so similar – almost identical, just like you said! Great pics, and you’re definitely not pestering by the way – spawing new misuse of electronic gadgets is why this site is here!
The best suggestion would be to control the device manually using a potentiometer as described in our article on modding the 1.8kW cooktop, but since this mod may take a little more discussion than what we can fit here it might be a good time for us to introduce The Forum!
Why don’t you go over to the forum and start a topic about this 3kW mod. You can either place it in the Site Projects area under a topic like “1.8kW mod for 3kW hob”, or under the Your Projects area with whatever name you choose. We’ll keep an eye out for your post (or you can msg us here) and then we’ll get into the gory details of how to control this beast. Looking forward to it!
AHA! Manual control… AWESOME! I bookmarked that at the beginning & for some reason never revisited. So far it sounds remarkably simple, heading over to the forum after I’ve read through again. >:D
Any clue as to where to snip to disable the beeper?
Ok, found it, next to the ribbon cable that connects from the controls to the main board. It’s a black round cylindrical thing with a little hole in the top. There is nothing to clip, so I stuff some glue into the hole and it’s almost silent now. Now if I can find a quieter fan…