induction heater using PLL chip for resonance lock
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- Опубліковано 12 вер 2024
- Tutorial to learn how to use the PLL to tune your induction heater and get it ready for microprocessor control of the resonant frequency.
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![[NEW] Great idea You Haven't Seen It Before / You Don't Need a Coil for an Induction Heating](http://i.ytimg.com/vi/L5Cmmd_F7b4/mqdefault.jpg)
I really like your explanation of the PLL chip controller. This is the first time after listening that it dawned on me what is going on. Thanks
It works really well.
@@imsmoother Please tell me something. Could this type of circuit be used to heat a home ??? I know that I am going out on a limb with this open ended question but that has always stuck in my mind. Thanks
Hi, I built one of these from your tutorial, the previous version using just the 4046 to do the phase shift. It's great! Thanks putting all the information out there.
Glad I could help.
I hadn't seen anything in a while from you - nice to see you're back! have you done a pcb design of your induction heater? Hope you're staying well during COVID - it's getting bad here in Ontario.... take care, Doug
Excellent explanation, really good to follow concept with output of scope.
Nice!
You actually don't have to use a micro processor for that. Of course if you are used to designing circuits using micro processors, that may be the best choice - but for me and others who have not gotten into the world of micro processors yet, I found another way.
I did put a capacitor between the VCO control pin and ground (to make the frequency more stable), then a pull up resistor to VCC and a small signal NPN pull down transistor (BC547b in my case) to ground.
Then I put a simple RC filter (resistor and capacitor) on the PLL output pin to get a smooth DC voltage out, that depends on the duty cycle (just like you do for the simplest form of PLL). But instead of connect that back straight to the VCO control pin, I put a trim potentiometer on the output as a voltage divider (so that the exact voltage output at 50% duty cycle can be tuned) - then I connect the output of that voltage divider thru a zener diode (with a zener voltage roughly about half the VCC) to the base of the pull down transistor on the VCO control pin
Now at start up the frequency ramps up, as the VCO capacitor charges up and so does the duty cycle. Once it get high enough, current starts flowing thru the
zener diode and base of the pull down transistor, wich in turn opens and stop the VCO capacitor from charging any more. Now if the duty cycle get too high (when you for example put something in the work coil of the heater and resonance frequency goes down), the pull down transistor base opens more and discharge VCO capacitor slightly, lowering the frequency. If duty cycle gets too low (for example when the curie point is passed) it closes more allowing the VCO capacitor to charge up sligtly ramping up the frequency slightly.
The circuit can then be tuned to resonance by adjusting the voltage divider trim pot. This works over a very vide frequency range, so different coils can be used - and will not have the problem with the duty cycle "drifting" with the frequency (as you get if with the simplest PLL setup). I will put up schematic when I build mine later
I would love to see the schematics. However, a microprocessor does more than just control the frequency lock. You can use it to detune if the current exceeds a critical range (if the work piece gets removed the current can shoot up), or monitor the temperature of the mosfets and turn the unit off if needed.
@@imsmoother That's true. A micro processor is indeed nice. But needs some programming (wich can be a little tricky those of us, who haven't done it before).
Power regulation and current limiting can also be done by a buck converter pre regulator that adjusts the voltage going to the inverter bridge (wich I have done on my small prototype heater that I have built so far). But that on the other hand, makes the power circuitry more complex.
@@Speeder84XL that sounds like a really cool learning discrete component project! I'd love to replicate it if you're keen to share your schematic and any build notes for me to learn from. Pretty please?
@@vardfriki7274 I have started working on the power source right now - which will turn mains power (230 V, 50 Hz AC in my case) into current regulated DC. Which is probably more work than the heater it self (but that power source can then be used for a lot of other projects as well). I will be putting up videos of that quite soon with scematic. When that is done, I will build the heater.
This circuit will actually work the best by running off a constant current DC source. That's because input impedance/load relationship is inverted, compared to a typical resistive load. The more load there is on the coil, the higher the input impedance gets - and the opposit. So if the circuit is running off a typical constant voltage source (such as a variac and a simple rectifier with smoothing capacitor) with the coil empty and a big piece of metal is put into the coil, the input current will drop a lot and not much power is transferred to the work piece. If the voltage is increased quite a bit, the piece will start heat up quickly as a lot of power is transferred. Now if it's taken out again without lowering the voltage - the current will shoot up and may blow things up.
A constant current source will counteract that "problem" by increasing/deceasing the voltage to keep the input current constant. Now the input power will be low with no load on the coil (just a small amount of losses), then goes up with the load - as it should do.
You can run this circuit off a variac and simple rectifier - but then you have to be very careful adjusting the voltage to the present load on the coil. That's also why he wanted the micro controller - to get protection from blowing things up in case there is a sudden decrease in load on the coil (the micro controller can detune the circuit to prevent the current from shooting up dangerlusly much). But a constant current source is a better solution (espesially in ny case where that power source will be used for a lot of other projects as well)
@Speeder84XL what cc source are you using? Welder?
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How to lock resonant of smps power supply ? Can this way be applied to smps resonant mode
Can u send ardiuno code
Dear sir i set my cd4046 frequency 40khz but my drive transformer providing me 90khz is it right? Plz help
Hi I saw your liquid air generator from a few years back and I would like to build one myself, can you give me some build instructions and material lists if you still have them?
I never put together a parts list. Basically, a high pressure compressor, thin-walled stainless steel tubing, teflon tubing to cover the stainless, generant stainless needle valve, ceramic fiber insulation, stainless vacuum 500ml-750ml container, baffle to reduce speed of jet. These are the main components and you can see them if you freeze my video at homemadeliquidnitrogen.com
@@imsmoother I saw on the website that you were also selling these? Does the offer still stand?
zvs with gate driver IC
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