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Yeeeeha! Microprocessor controlled induction heater

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IamSmooth

Mon Mar 15 2010, 10:47PM

Registered Member #190 Joined: Fri Feb 17 2006, 12:00AM
Location:
Posts: 1567

Well, I solved the uP reprogram issue. I was trying a new power supply, and for some reason the 15v output is unstable. It starts to jump all over the place. I may need a different step-down transformer for the 7815.

My question to those on the board is this now:

I noticed during my power-up on the IH I was getting a lot of noise at high currents. What is the best way to isolate the inverter section? I was thinking of using optocouplers (FOD3180). I was thinking of using one on the pwm output from the uP. I was thinking of using a pair to drive my gate-drive transformer instead of the TC4421 and TC4422.

Also, as of my last attempt, the inverter section was on the same board as my driver circuitry. I plan to put this on a separate board. THis board will contain the gate drive transformer, igbts and snubber capacitors. The connection from the gdt to the driver will be through shielded wire going to the optocouplers.

Does this sound reasonable? Any other suggestions?

Avi

Tue Mar 16 2010, 04:27PM

Registered Member #580 Joined: Mon Mar 12 2007, 03:17PM
Location: Melbourne, Australia
Posts: 410

That was pretty neat using it for the tuning. i have only used it to PWM the power and change the duty so it very slowly cools liquid wax down over a long period of time.

IamSmooth

Thu Apr 01 2010, 11:06PM

Registered Member #190 Joined: Fri Feb 17 2006, 12:00AM
Location:
Posts: 1567

I just wanted to update this thread that I have tested my new board, powering the inverter with >1.5kw going through it. The uP controlled resonance lock worked great. The tracing was clean, and did not wobble.

I need to upgrade my power supply to handle a larger more current.

Can I power the induction heater without a rectifier/smoothing capacitor? Can I run it straight off of the mains?

Killa-X

Fri Apr 02 2010, 12:55AM

Registered Member #1643 Joined: Mon Aug 18 2008, 06:10PM
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Posts: 1039

Looks like it runs very well, nicely done! I have the ATMEGA32 and ATMEGA644P models, So if you post your code along with the schematics over time, maybe I could try one :D

IamSmooth

Fri Apr 02 2010, 01:55AM

Registered Member #190 Joined: Fri Feb 17 2006, 12:00AM
Location:
Posts: 1567

No problem. I want to make sure it survives the 8-10kw test. I already got it to work off of my 240vac line, but only at 1/4 power. I will definitely post the schematics and code. It has taken some time, and help from some here, to come up with the proper filtering.

The trick was to find the balance between clean filtering, without delaying the feedback to the uP.

The next trick to eliminate the noise and cross-talk that was oscillating the operating frequency.

Right now I need to fix my power source.

wylie

Thu Apr 08 2010, 11:44AM

Registered Member #882 Joined: Sat Jul 07 2007, 04:32AM
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Posts: 103

Can I power the induction heater without a rectifier/smoothing capacitor? Can I run it straight off of the mains?

Wouldn't the switches explode when the AC passes through the 1st negative half of a cycle? Or would they function like a poorly-synchronized synchronous rectifier?

Steve Conner

Thu Apr 08 2010, 01:07PM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

wylie wrote ...

Wouldn't the switches explode when the AC passes through the 1st negative half of a cycle?

Yes, they would.

You can run without smoothing capacitors, but you need the rectifier and a RF bypass capacitor.

IamSmooth

Thu Apr 08 2010, 06:06PM

Registered Member #190 Joined: Fri Feb 17 2006, 12:00AM
Location:
Posts: 1567

Is the RF bypass capacitor connected to the AC input to the variac or HV power supply? What do I need?

Steve Conner

Fri Apr 09 2010, 09:43AM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

Oh come on, try to figure it out yourself for a change!

IamSmooth

Tue Apr 27 2010, 03:59PM

Registered Member #190 Joined: Fri Feb 17 2006, 12:00AM
Location:
Posts: 1567

I have just passed another milestone: I was able to levitate and boil a SOLID piece of copper. I have to check the power requirements, but I figure it was close to 4-5kw. Those of you may recall that I was able to levitate aluminum and hollow pieces of copper. The copper density was too much for the magnetic field to levitate it with my 1.5-2kw unit, and the PLL resonant lock would not stay completely on-tune, requiring adjustments that I could not make with a boiling piece of metal next to me.

The uP-PLL controlled unit found the frequency and stayed on it all by itself, and even kept the system stable when the copper boiled off.

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