I know there are 3rd party programs out there that assist you in capturing data from the Arduino to put into a spreadsheet for analysis,  And I know that you can add an SD card reader to your project.  But I wanted an easy way to get my data into a spreadsheet without the hassle of downloading  some 3rd party program that might or might not come with some spam or spyware.  I didn't want to go to the trouble or expense of adding in the SD card reader for what might be a one time need to look at the data in graphical format, etc..
  So here is my solution:
/>
Pete Stanaitis
---------------

Several folks have been asking me the best way to temperature control the work coil of the induction heaters that I have been messing with. 
At this point, I think the best way is to use a PID controller and use the "Bang-Bang" approach of turning the DC power on and off as needed to maintain a set temperature.
  Mechanical relays can work, but they have limited life in that application and/or are pretty costly.  (We could argue that opinion somewhere else).
Anyway, I have had a hard time finding DC to DC SSR's, particularly cheap ones.
  But I did, just recently buy 2 40 amp 60 volt SSR's and 2 100 amp 60 volt SSR's .
I decided to try the 100 amp model first, just to give me some headroom, since my plan was to simply test the thing with a load going as high as about 40 amps.
  Well, I hooked it up, using a simple spst swtich to feed it a 12 volt signal and turned it on.  It worked properly with the 6 amp idle current that is normal for my 2500 watt ZVS induction heater. ---That is, when I turned the SSR "on"  the heater did oscillate normally.
Next, I added 40 amp load my putting a graphite crucible into the work coil.  Fine.  I threw the SSR's signal switch on and I got my 40 amps.  But--- when I turned the switch off, the current continued to flow.  I tried it a few times with the same result.  I powered down completely, then back up and the same result.
  I'm sure we have all heard about "fake" SSR's etc..  Right?
Well I tore this one down, thinking I simple replace its Mosfet with an IRFP260N.
No luck.
I finally did get the potting compound off of the "device", but it's labelled "JT1    A1009"  By the way, the thing is dead shorted.
The only A1009 I could find reference to is a BJT that is good for 2 amps!
Well, if that is correct. then there's no point in simply trying to replace it with a Mosfet, because I am pretty sure the gate/base driver won't work.

Moving on:
  I then installed one of the 40 amp SSR's and it has worked just fine, up to 30 amps.

My reason for posting this trial is just to see if others have more info about DC to DC SSR's.   I now have a list of about a half dozen of them in the 40 to 100 amp range, that are not horribley expensive.  So if any of you have a proven recomendation, I'd like to hear it.
(I will be putting up a video showing the ZVS heater being cycled in this way (manually) in a few days.)
There's a PID controller on the way.  I hope I picked the right one.

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

I am hitchhiking on Mads's recent post about server psu hacks.
That thread took a turn toward the subject of this post, so I thought I'd get more focused here.

Cheap!! is the focus!!!
The Goal: make a step adjustable 12 volt to 48 volt power supply to feed the power hungry ZVS induction heaters that are offered all over the world right now.
THE answer:
Four 1000 watt or larger 120 VAC MOT's. 
Primaries in series parallel so the thing could be connected across a 240 volt line.
Secondaries wound with large size enameled ("Magnet" or "Formvar") wire to provide 12 volts AC each.  They are connected in series, with taps at the output of each secondary.  This produces steps of 12, 24, 36 and 48 volts.
A homemade rotary switch to handle that high currents.  The reason for a rotary switch is to keep from short circuiting things that might occur if using individual SPST switches.   You can see many examples of such a switch in old books:  I tried to attach an example, but still can't figure out how this works- sorry.
-The steps could be made smaller by center tapping each secondary.
The output would, of course, be sent to a full wave bridge and  some sort of LC filter, as needed.
  I saw one guy who was even using 230 volt MOT's in various primary combinations to add more variability.

Major cost would be magnet wire (if you can't scrounge it) and capacitors for filtering. 50 amp bridge rectifiers aren't all that expensive.  I think effective  heat sinks could be made from the cylinder heads of junked lawn mower engines.

Anyway, I am saving up transformers.  Maybe I will get to it one of these days.

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

Lately some Russian hobby size induction heating videos have been coming up on my Youtube recommended list.  I don't understand the language, but I can get a pretty good idea of what is going on from almost all of them.
  Anyway, here's one where the guy simply couples the output from an induction HOB (British for "Hotplate Or Burner) to some copper coils and then parallels the output part of the coil structure to some capacitors.  So, as far as I can tell, without modifying the HOB in any way, he has a high frequency driver.  Maybe not great at power transfer, but I thought it was an interesting Hack:
/>
Pete Stanaitis
---------------

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
---------------

Hello Mads.
    I just saw your latest article on hacking the Induction Stove.
The amount of information displayed on the scope screen is pretty impressive.
Would you consider reviewing your Rigol DS 1504 'scope for us (me).
  My ancient Tektronix 422 is starting to fail and I guess I'm going to have to replace it one of these days.

I have spent a fair amount of time looking at specs for scopes within my price range (under $500 USD) and it is hard to tell if one scope or one set of features is better than others. 
Mind you, I bought about 50 of those Tek 422's in the late 60's, and they were a great field service tool for our needs back then.  But these days, I see all the digital scopes for sale, with lots of storage, etc..  I just can't separate all those features!!!

I won't need frequency response much over 50 MegaHz.
Two channels will probably do most of what I need, but the 4 channel idea sounds good, too.
One of the things that is really interesting is the idea of storing traces and being able to scroll through them after the fact.
I did buy a "knock-off" logic analyzer a couple of years ago (USD$8.00) and it does a surprisingly good job of the data storage, but it is only a 5 volt, digital signal only device. Works well with my many arduino projects, but not at all for this higher voltage analog stuff.
  A year ago I even bought one of those USD$50.00 DSO112 pocket sized 'scopes.  It works okay, but has only one channel and poor battery life.   And, since you have to switch screens all the time to access menus, it is a bit of a pain to use.  Triggering isn't the greatest.  Maybe it's just me.

Back to your  Rigol DS 1504:
Anyway, how do you like it?
Would you buy it again?
What issues does it have, if any?

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