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Messages - petespaco

Pages: [1] 2 3
1
It's working fine now:
/>
Pete Stanaitis
---------------

2
Mads-  Sorry to hear about your shipping issues.  I did get one or two of the 1000 watt units where one lead of  the 470 5 watt resistor had broken off the board.   The buck converter terminal on your board is different from any I have seen.  That makes me wonder how many actual manufacturers are in this game, and how much actual thought goes into each one's design variations.

the_anomaly-  I assume you will need to have some flexible way to get power and water cooling to your work coil if you plan to heat stuck bolts.  Please keep us/me informed on how you do that. 

3
Well, it is finally up and running properly.
 Drawing about 4 amps idle current (still using 48 volt power supply), then goes to about 35 amps with crucible fully inserted.  Now need to mount a fan on the radiator and do a few other things.  Hate to say it, but I am not certain what caused the difficulties.  Later in my troubleshooting, I discovered that two adjacent turns of the work coil were touching, but separating them didn't help.  I took the fans off to get at the coil so I could insulate it with high temperature fiberglass sleeving.  When I put it back together, it works fine.
Maybe a cracked foil on the board?  Don't know for sure.

Next steps if it continues to work properly:
  Shoot for max current of about 40 to 45 amps.
Place fire brick below coil
  Try some steel  (to max out current) and to see how quickly it heats things to 1200° C.
1" Sq.
3/4" pipe  (pipe heats real fast since its a one turn "coil"
Melt some copper.
   Make a crucible cover. 
   Find/make tongs for pouring.
   Make a simple open face mold?


4
Yesterday I added a short lead to each gate of the Mosfets so I could scope them.  I didn't change anything else, but when I fired it up, the idle current is only  about 14 amps instead of the 26 amps that I had previously!  Then, when inserting the crucible, the current went up to  36 amps instead of the previous 40 amps.
 The gate signals are all pretty good looking square waves and they are all the same.
Why the change???---  I don't know, but all I did was to solder those gate leads in place.  Bad joints???

The aliexpress vendor didn't seem to pay any attention to my problem description.  They emailed me back to say:
"friend , can you tell us in aliexpress message ?"
Aliexpress customer service, by the way, seemed very concerned when I chatted with them about the issue earlier.  But all they did was to pass my concerns on to the vendor.

I did make a short video of the the above and may put it up on youtube as a troubleshooting aid.
If anybody who is viewing this message has one of these 1800 watt or 2500 watt ZVS heaters running, please tell me what YOUR idle current is.

Thank you,
Pete Stanaitis
---------------

5
Today I examined the heater by eye and with an ohmmeter.  Can't yet see any reason why the idle current should be so high.
   Circuit components are identical to the 1000 watt board, Just twice as many.  Except that there are 9 of the 0.33 ufd capacitors and a 10 turn 60+ mm ID work coil.
Stumped.
   I did see one video where the guy was testing an 1800 watt board with an ammeter in the ckt.  That's where I got MY "expected" 6 amps idle current from.  That and the fact that my 1000 watt heaters do about the same.
  I may try a smaller diameter work coil just to see what happens.
But I am still hoping for some sort of feedback from the vendor.  Chinese new year for 2019 (year of the pig) apparently does not start for a few weeks yet:
Jan 28 to Feb 19.
  I now see that I can get the gate signals from the bottom of the board, so I can look at them once I get my courage up.

6
i just checked the current by adding a direct reading ammeter in series with the shunt meter.  The readings are the same, within a couple of amps, since the scale on the new meter is fairly coarse.
  Haven't yet dismantled the board to look at circuitry, or to scope the gates.  The way this thing is made, you can't see inside much because the 4 heat sinks cover the sides and the fans cover the top.  when I do dismantle it, I probably should bring out a couple of test points.
I was hoping that I wouldn't have to dig into the thing at all.
No feedback from the Chinese vendor yet.  Is it Chinese new year right now?

7
Thanks for your question, flyrod.
  Yes, the chip IS the "LM2596HVS" version.
That makes the Chinglish warning about not using the converter when the input is over 36 volts even more confusing..
When I looked up the datasheet a couple of days ago, i googled "LM2596" and got this:
http://www.ti.com/lit/ds/symlink/lm2596.pdf
I didn't look beyond the first few pages when I found the max input voltage to be 45.
I even found another datasheet when it was spec'd at 40:
https://www.onsemi.com/pub/Collateral/LM2596-D.PDF

It didn't occur to me that to investigate the "HV".  Sorry, I hope I didn't cause too much confusion.  I guess I was biased by the warning that I mentioned earlier.
http://hmsemi.com/downfile/LM2596HV.PDF

  By the way, my buck converter doesn't have the pot.  There's a fixed resistor in its place.

I did fire the system up yesterday and it worked, BUT the idle current (current flow with nothing in the work coil) is at 26 amps.  I think it should only be about 6 amps.  It IS oscillating. When I put a graphite crucible into the work coil the current does increase to 40 amps.  Frequency is about 77Khz, by the way.
I have attempted to contact the vendor through aliexpress.  We will see how that goes.

For that initial test, I did add a radiator and  unplugged the buck converter and powered  the fans and pump from a separate supply, just in case.

Sorry for jumping to conclusions,
Pete Stanaitis
---------------


8
Hello, Mads.
I hope I am not getting ahead of myself here, but I see a new issue with both the 1800 watt and the 2500 watt versions of these ZVS heaters.
  It has to do with the little buck converter that runs the fans, and in the case of the one the I bought, the pump.
Here's what I have to say:
---------------------------------------------------------------------------------------------------------------------------------------------------------------------
Important note if you intend to run your heater on 48 Volts:
You can NOT use the little power supply (buck converter) for the fans! You will have to provide a separate 12 volt supply at a couple of amps.
That is because the maximum rating of the regulator chip on the buck converter board is 40 volts. Don't ask me why they did that, but, hidden in the Chinglish, is a warning that operation at voltages higher than 36 will "burn" the fans and/or pump.
---------------------------------------------------------------------------------------------------------------------------------------------------------------------
I'm getting closer to powering the thing up.  I checked the no load current draw of the pump and its only about 300ma, but I will need to connect it to the actual system and fill it with water to see how much current it will draw,  Then, same for the fans.  Then find or make a simple power supply for them.

Have you noticed this situation, and what is your feeling about using that buck converter?

Pete Stanaitis
---------------

9
Good eye, Mads.
   Yes, I now see the extra heat sinks and additional pair of gate resistors.  So now it looks like 3 Mosfets in parallel on each side.
And I also now see that the 1800 watt model  has 90mm fans, versus the 120mm fans for the 2500 watt model..
I can only say that I did some  sloppy investigation!
I'll already updated  my pages to reflect this difference.

I will look forward to your comments when you get your board.
By the way, we have all heard the warnings about NOT connecting these zvs heaters directly to a switched mode power supply and then plugging the power supply in.  They say that the slow start characteristics of the SMPS cause it to start slowly and cause the mosfets to lock up.
And I am sure that is generally true.  But the server power supply that I got with my Aliexpress heater (Emerson 48-2900U Switched mode Power Supply)
doesn't even turn on until about 7 seconds after power us applied.  I will probably set my system up to power the supply first anyway, just to be safe.

(a bit red-faced),
Pete Stanaitis
   

10
I have been experimenting the the popular "12-48 Volt 1000 Watt ZVS Induction heaters" for a year or two and have many videos and web pages describing that work, as many of you may know.
   More recently, an improved version has become available and is being sold by well over a dozen vendors.  Instead of one pair of IRFP260N's driving the coil, they doubled up on them and added 2 fans on top.  The also added 50% more capacitance to the  tank circuit and increased the number of turns of the output coil from 7 to 10.  These tank changes should lower the oscillation frequency which is good for many things that people would want to heat.

  Just recently, I ordered one of them, a complete kit, called "Combo 2" by seller Aliexpress.
I had to wait quite a while for an analog ammeter and it’s here now.  I still haven’t connected it all up yet, but I have spent a lot of time unraveling the various  descriptions and pseudo instructions that I see on the vendor offerings.  These units are seldom soldi n as complete a kit form as the one the I got from Aliexpress.
Some vendors call them 1800 watt, some even call them 2500 watt, but I’m pretty sure they are all the same.
  Yesterday I put up a new web page to help new buyers understand what they just bought and how to set it up with a minimum of disappointment.
I tell you all this, because I’d like to get this link to others, since I am already getting inquiries anyway.
There are two web pages referenced here on this cover page:
 https://spaco.org/Blacksmithing/ZVSInductionHeater/ZVS1800Watt/1800-2500WattZVSInductionHeaterNotes.htm

Both pages are pretty messy, but, due to the apparent popularity of these devices, I wanted to get something out there.
Time will tell.

I will add to that page and to my youtube channel once I get my system up and running.

Pete Stanaitis
---------------

11
Getting a car battery:
  Many car batteries are replaced before they are totally shot.
Assuming that you do have a battery charger of some sort:
So, go to a car repair shop and ask if you can pick through their used batteries.  They get $5 or $10 in trade, right?  Prepare to pay that much.  If you tell them what you are doing with them, they may even sell them for less.
   Find one or two that still have some life left.  I know this is a rough "rule of thumb", but if the terminal voltage is above 12.2, it will probably take a charge, at least long enough for experimental purposes.

12
Quote
finding a 24V psu that can drive this thing is not easy or cheap.

Just add another 12 volt lead acid car battery.

13
I wonder what the quote means by "shelf life".
  Where I worked, "shelf life" meant the time that a product could sit on a shelf before being used and then still work as intended when it finally got sold.

Are they really talking about the "in-service lifetime" of the product?

Pete Stanaitis
---------------

14
Electronic circuits / Re: Royer Refinements
« on: February 01, 2018, 02:11:00 PM »
Quote
How high of a frequency can your scope see? 

It is rated for 15 megahertz, but it has plenty of response left at 30.

Pete Stanaitis

15
Electronic circuits / Re: Current transformers and burden resistors
« on: January 19, 2018, 12:52:55 AM »
I don't see any reason to concern yourself with phase shifting if you want to produce a DC signal for an Aruduino's analog input.

Note:  The CR3110 is good for 75 amps and their CR3111 is good for 100 amps.


I just repeated and recorded some testing of rectified outputs with a few electrical devices:


I saw less than 50 millivolts ripple at the output.

I hope this helps,
Pete Stanaitis
---------------




16
Electronic circuits / Re: Current transformers and burden resistors
« on: January 18, 2018, 12:26:48 AM »
Quote
But wouldn't that result in 4.7V (the zener voltage) pretty much all the time regardless of the current flowing?

No.  unless I am missing something, any voltages below about 4.7 would pretty much just pass through to the Arduino.
The zener is there only to clamp to CT's rectified output below the 5 volts max, that the Arduino' analog input  can tolerate.

Read this:
https://www.evilmadscientist.com/2012/basics-introduction-to-zener-diodes/
and let me know if it makes sense.

I tested the circuit that I sent in my last post with 120 volt AC loads varying from about 150 watts to about 1000 watts.
I guess my attachment didn't work.

Oh, I guess I didn't see that you have to click "(insert Attachment 1)".
Hope it works this time.


Caution: NEVER leave the output of a CT open.  High voltages can occur.

Pete Stanaitis
---------------

17
Electronic circuits / Re: Current transformers and burden resistors
« on: January 17, 2018, 04:46:32 PM »
Maybe you could simply skip the "burden" resistor and clamp the DC output to a bit below 5 volts.
Also, since you won't be drawing much current, maybe use a single rectifier diode and a simple filter capacitor.
  I recently used a cheap CT in a circuit to sense whether a woodworking power tool was on or off using this idea and it worked.
I think I attached a hand drawn schematic of  what I am suggesting.

Here is the CT that I used:
10-Pack New CR Magnetics 3110-3000 Split-Core Current Transformers CTs
Not sure if the 10 pack is still available.  All ten only cost $30USD  in May of 2017.

Pete Stanaitis
---------------

18
I don't understand what the 3 recent pictures are intended to portray.
Are they components that have failed?

What does "then took auto relay" mean?

Pete Stanaiits

19
Electronic circuits / induction heating/Blacksmithing
« on: December 11, 2017, 04:30:06 PM »
Mads mentioned using an induction heater for blacksmithing; making knives.
  I do a fair amount of blacksmithing myself but am not a knife maker:
https://spaco.org/bk.htm

Anyway, I am very tempted to get one of the 7KW (sold as 15KW)  induction heaters from China.
Here's a guy in the USA who does a great job of explaining how they work and how to get one:
/>If you are at all interested in what he has to say, be sure to watch all of his videos on the subject.

Pete Stanaitis
---------------


20
Electronic circuits / Re: What kind of oscilloscope to buy?
« on: December 09, 2017, 05:08:54 AM »
Thank you guys for your input.
  Yes, I did recently watch the eevblog guy's review of it.
Now I am reminded that I didn't quite understand all the things he said about loading software and getting additional "apps" or whatever they are called.
Do either of you have comments about that stuff?  Does it work out of the box, or do you have to go find and load some sort of operating system?

I might add that the pressure to get a new scope is off a bit because I just fixed my old 422.  It had a bad intensity pot.  It was a special type of pot that is heavily insulated from the chassis because it is directly in the cathode/grid circuit.  No longer available.  I did find and buy a similar (but too large physically) pot that I thought I could parallel with a fixed resistor and remount in some horrible looking fashion.  But instead I took the pot apart and found the the grease they had put on in there had hardened up and actually created a BUMP that caused the wiper to loose all contact with the resistive element.  cleaned it off, carefully reassembled, and ready to go for another 50 years?

But I am still getting serious about a digiital scope.  I do make some youtube videos and it would be nice to be able to show the professional looking traces that you get, Mads.   This Rigol DS1504 still looks good to me.


Pete Stanaitis
---------------

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