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Yeeeeha! Microprocessor controlled induction heater

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Mike

Mon Aug 09 2010, 06:11PM

Registered Member #58 Joined: Thu Feb 09 2006, 05:40AM
Location: Tri-Cities, Washington, US
Posts: 317

iamsmooth, is it correct that i see you are using +/-15V for the LM6172 . If so, how did you accomplish this, did you take something like 24VAC and rectify it such that the positive swing goes to a 7815 vreg and the negative swing goes ato a -15V reg?

IamSmooth

Mon Aug 09 2010, 09:42PM

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

Mike wrote ...

iamsmooth, is it correct that i see you are using +/-15V for the LM6172 . If so, how did you accomplish this, did you take something like 24VAC and rectify it such that the positive swing goes to a 7815 vreg and the negative swing goes ato a -15V reg?

yes.

Mike

Tue Aug 10 2010, 05:28PM

Registered Member #58 Joined: Thu Feb 09 2006, 05:40AM
Location: Tri-Cities, Washington, US
Posts: 317

Hi I had one more question.. for the alternate ground section(the LM6172 and one of the FOD3180's.... im correct in that these grounds should just all connect to eachother and nothing else? Also if so, is it correct that on the FOD3180 that pin 5 is not an alt ground ? (im assuming this is because it is powered off the +15v supply and needs to be grounded to it as well.

IamSmooth

Tue Aug 10 2010, 06:29PM

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

The 3180 is an optically isolated driver. Pins 8 and 5 are the output leads. Pins 2 and 3 are the input leads. Originally, in order to maintain complete isolation of the high frequency, high voltage tank capacitor from the driver, I was going to power the 3180 from a separate power supply; hence, the alternate ground/return and -15v supply. The 3180 uses an LED to couple the signal to the output. I was afraid of noise affecting the driver loop.

I found that the resistor on the line from the capacitor was enough to damp any noise, and complete isolation was not necessary. The alternate ground is connected to the primary ground. The primary ground is connected to the ground plane on the driver. I am not sure if it would have been a better practice to have made the grounding plane connected to earth ground. I did not want the driver's grounding plane to be connected to the grounded shielding on the high current/voltage.

The 3180s allow me to make a clean square wave from 0 to 15v. It also converts the Arduino's 5v pwm into a 15v waveform.

Mike

Tue Aug 10 2010, 07:43PM

Registered Member #58 Joined: Thu Feb 09 2006, 05:40AM
Location: Tri-Cities, Washington, US
Posts: 317

ah okay, although I assume you meant to say 7 and 6 are the output (8 and 5 are supply).

IamSmooth

Tue Aug 10 2010, 08:23PM

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

yes. 8 and 5 are supply for the output side, which is what I meant to say.

Are you going to build a heater this powerful?

Mike

Tue Aug 10 2010, 08:27PM

Registered Member #58 Joined: Thu Feb 09 2006, 05:40AM
Location: Tri-Cities, Washington, US
Posts: 317

Im considering it. I have had some free time without much to do so I did a board in Eagle. Unfortunately it is well, probably one of my first board designs so it is not the best. I still need to add a ground plane and some other things:

EDIT: Here is rev3 , my attempt at a groundplane

EDIT3: I should note that the left ground plane is the "alt ground" and the right ground plane is normal ground. Hopefully this will work alright.

Edit4: One more rev

Uploaded with ImageShack.us

I ran out of room (didnt organize things) and didnt have space for the pos/neg supply. I kinda did crappy job but I got it in, hopefully it will work.

Mike

Wed Aug 11 2010, 04:40PM

Registered Member #58 Joined: Thu Feb 09 2006, 05:40AM
Location: Tri-Cities, Washington, US
Posts: 317

double post but hopefully its alright after my 5th edit. Someone tell me if otherwise and i'll delete it.

Finished up the Controller board and the gate drive board.

I've attached the eagle board files for both but be warned they are untested and contain no part designations :) I'll try it soon though. Thoughts?
]inductionboardnew.zip[/file]

IamSmooth

Sun Aug 15 2010, 05:30AM

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

Here I am heating a brick of iron for forging.

I don't forge, but this is the test piece I was given in an attempt to get it to yellow to yellow/white heat.

Mike

Mon Aug 16 2010, 03:51AM

Registered Member #58 Joined: Thu Feb 09 2006, 05:40AM
Location: Tri-Cities, Washington, US
Posts: 317

Hi, great video, that some power you got there.

As for the circuit, I was looking at

and the circuit seems different as before as the microcontroller is not there.. I created a eagle board with the microcontroller but if you have removed it maybe I should modify it.

Thanks,
mike

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