The Heart of an Induction Heater

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Heart of an Induction Heater
Hello everyone! I started this morning out with a beautiful walk along the gulf coast for the American Heart Association. I wanted to share two things with you today, a couple photos from the event and one more thing (keep reading).
Gulf Coast Heart Walk American Heart Association American Heart Association Heart Walk American Heart Association

Generosity Begets Generosity

All the giving got me thinking, after all, you know what they say about giving. Generosity Begets Generosity. Generosity is a gift that keeps on giving—so many of the gifts we receive in life turn us into givers.
I wanted to show my appreciation to the Patrons who continue to believe in this project even when life slows its progress way more than I’d like! I was reminded today that I actually did not start this project for myself. I am not a blacksmith, I have no immediate need for an induction heater, but I am a creator. Each and every human has this incredible capacity to imagine and to change things. I wanted to bring a tool within the reach of others that remained out of reach for most. Not a wimpy, “doesn’t deliver on what the box said kind of tool”, but one of a caliber that is not matched in the consumer market at all today.

The Heart of an Induction Heater

I would like to offer the “heart of an induction heater” to all of my existing Patrons (as of today September 22, 2018).
U-I Core Set
E/I Core from two U/I cores
U-I Core Set
At about twice the size of a human heart and just about as difficult to source, the matching transformer is by far the most critical, specialized component of the induction heater. Coolant flows around its core in two directions keeping it cool as huge amounts of energy flow through it, making it possible to pump power from your wall outlet into your workpiece. Without it, the IH is just an inverter with some other not really all that exciting electronics. It would be akin to a truck without a transmission. You can’t just connect the crankshaft to the wheels and expect anything good!
I’m including two massive U & I core sets. The same ones that make up the large E/I matching transformer in the newest revision.
Material: 3C85
  • Single U-I core set AL: ~8400
  • Single U-I core set µe: ~2000
  • Single U-Core Dimensions: 93mm x 76mm x  30mm thick
  • Single I-Core Dimensions: 93mm x 28mm x 30mm thick
  • Overall Dimensions: U-I Set: 104mm x 93mm
  • Opening Dimensions: 47mm x 36mm
3C85 Material Technical Data:
  • Optimal frequency: < 200kHz
  • Permeability ui:           2000 +/- 20%
  • Induction at 100kHz, 250 A/m, Bs:   > 400mT
Heart of an Induction Heater

But Wait There’s More

Since driving your IGBT properly is a big deal and kind of important for the whole setup, I’m also including a new driver PCB with two Powerex VLA504-01 Hybrid IC Gate Drivers and two Powerex VLA106-15242 DC to DC Converters. Just those four components are about a $70 value alone if you buy them from Digi-Key. The remaining components on the board are just a few dollars worth of passives. an entire Hybrid Driver kit! The full schematics and bill of materials for the Hybrid Driver board can be found here:
For more info on the driver board be sure to read this:
As well as this post:
Recap, what I’m giving my Patrons:
  • 2 x 93mm x 76mm x  30mm 3C85 Ferrite U Cores
  • 2 x 93mm x 28mm x 30mm 3C85 Ferrite I Cores
  • 1 x New Hybrid Driver Kit including all parts in the BOM above and a PCB

That is a $106.85 value. Thank you for your support!

If you would like to purchase an additional driver kit or U/I core set I’ve included info on that in the FAQs below.

Send Me Free Stuff!

If you are currently a Patron as of the date of this post and would like me to send you this thank you gift, just drop me a private message on Patron saying hello and include your shipping address. The only thing I would ask is that you only request this gift if you are going to use it. We’ll go on the honor system here. 🙂
I look forward to working on this project more and hearing your feedback as well, as you either work on your own or use an IH I’ve built for you in the future.
Q: Is it possible to drive a tank circuit in an Induction Heater with one IGBT?
A: Yes.  This is actually how my brothers old IH is set up now. Here is a quick schematic. The capacitors were all off eBay for cheap.
Single IGBT Inverter
Matching transformer and coupling caps
Single IGBT Inverter
Filter Cap & Coupling Caps
Single IGBT Inverter
Single IGBT driver and brick
Single IGBT Inverter Schematic
Single IGBT inverter schematic
Q: Can you share more details on the matching transformer?
A: Of course but I need some more space to do it properly. I’m working on a post about just that. In the meantime here is a photo and a short explanation to give you something to start with.
  • The Matching transformer is wound with 1/4″OD inch copper tubing.
  • All windings are wrapped in x2 overlapping Scotch Professional Grade Vinyl Electrical Tape Super 88. Meaning as you spiral down the length of the copper tube the electrical tape covers 50% of the layer before it resulting in a 50%+50% overlap (no gaps) and a 200% layer thickness overall (better electrical and mechanical isolation).
  • The primary winding (connected to the inverter) is composed of 13-14 turns. It has terminals made of copper soldered near the ends to accommodate a high current connection while leaving the ends of the tube free to hook up to the cooling system.
  • The secondary winding (connected to the tank cap and work coil) is a single turn composed of 4 individual 1/4″ copper tubes connected on each end with a 1/2″ manifold. One side of the manifold connects to one side of the tank capacitor, the other connects to one side of the work coil via a copper plate. The other side of the work coil connects back to the other side of the tank capacitor via another copper plate in close proximity to the first plate. This whole set up ensure the flux is fully enclosed in the system. Were it not you would heat up surrounding metal and loose usable power. (An issue in the first model with the toroidal matching transformer and large tank setup.)
Matching Transformer
Q: If I’m not currently a Patron or I would like an additional hybrid driver kit could I just purchase one?
A: Yes. I’m not set up to do this formally yet but I can accept Paypal, just drop me a message. For this small batch I made, I’m selling them for $54.95 flat (free shipping to the 48 states, at cost everywhere else). That’s half the cost of buying all the parts yourself or a similar evaluation board (the BG2B). I’ll be able to get this even lower in the future on larger orders for inclusion in the full IH kit. Done! –> I’m also still working on a bulk order for the passives to get the entire driver kit complete. The price difference with and without the passives will likely be less than a couple bucks, keep that in mind if ordering those parts would be an issue for you.
Here is the full excel pricing sheet with individual component pricing info from Digi-Key current as the date of this post.
Q: If I’m not currently a Patron or I would like an additional set of ferrite U/I cores could I just purchase one?
A: Yes. These are quite heavy and require careful packing since they are a fragile ceramic. I’m selling them for $25.95 a set (1 x U core and 1 x I core) flat (free shipping to the 48 states, at cost everywhere else).
Q: What shipping method are you using for the free shipping option?
A: Whichever is the lowest cost at the time of shipping to your location. Usually either USPS first class, priority, or FedEx ground. If you would like to choose a specific method I can do that and just pass on the exact cost to you, no markup.
Q: What about the other parts of the system like the main board, AC rectification & filtering, liquid cooling setup, etc. Can I get one of those?
A: Although I do have fairly complete designs worked out on the rest of the system I don’t have a stock on the parts. I am going to start making posts on the individual components starting with the matching transformer to give you what you need to duplicate each part. The main board schematic and board design are on GitHub although I will be making some changes to it on the next go around.

Driver Kit Update & $400 AA Battery Accident

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Broken MacBook Pro LCD

Driver Kit Update

It’s been a busy couple of weeks, both with my day job and working with suppliers to get the best price and quality on parts for the hybrid driver but I do have a driver kit update. I have finalized the supply chain and received all but the passive components and packaging materials. I expect everything to be here by the end of January. Once I have all the parts I’ll take the photographs for the plans, which will be available for free.
I also want to make a test rig for the hybrid driver ICs and the isolated DC to DC converters. They are critical components and cost a decent amount. I want to know that they are performing as expected before they go out in the kits or machines. I have a couple of ideas for building a simple but detailed and accurate Arduino based performance curve profiler similar to those used for testing transistors, diodes, and other electronic components. In the meantime, I’m getting back into the code using the two new driver boards I build from the spare components.

$400 AA Battery Accident

I dropped a harmless little AA on my desk while changing the batteries in my mouse. The battery bounced and rolled away, I didn’t think much about it. A few minutes later I noticed my screen took a hit… awesome. The outer glass isn’t even cracked. It was one of the substrate layers that broke and let out all the magic liquid crystals. Looking around for a replacement LCD for my MacBook Pro Retina, 15-inch, Mid 2014 it seems like $300-$390 is the price range, ouch! I saw some cheaper off brands but this is a beautiful Retina display, and I don’t want to change it out for some knockoff junk LCD.
I have been looking at the new MacBook Pros, but I genuinely don’t like them. The taskbar is a POS gimmick, and the keyboard feels like a toy. I switched to using MacBooks around 2009 when I got fed up with Windows interfering with my work. An [NTFS file system error] blue screen of death the night of a large network activation for AT&T Lightspeed/U-verse was the last straw. I went out and bought my first Mac the next day.
Yes, Mac hardware is costly, but it JUST WORKS! It is always something with Windows. I was tired losing valuable time fixing issues, updating, reinstalling, etc. The MacBooks I have used have ALWAYS worked rock solid. I run CleanMyMac to keep things tidy and a Time Machine at home which is the most intuitive and real world usable backup system ever, for a personal computer at least.
I didn’t mean for this to be a MacBook fanboy review or a windows roasting session, I still use windows too. Personal my favorite OS is Debian, maybe I’ll get a Linux computer. Probably not though, I just run VMware when I need it locally. Besides, I do love the integration between all my devices that Apple affords i.e., desktop, laptop, tablet, phone, TV, etc… It’s just that this is the first physical problem I’ve ever had with a Mac and honestly I’m sort of surprised how easy it broke considering how rough I’ve been on them over the years.
I’m going to order a screen today. I just tell myself, “Don’t worry, you can sell this Mac for about a grand when you upgrade!” Still, what a disappointing accident.

IGBT Driver – Out With The Old, In With The New (Year)

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First off, happy New Year! I hope that everyone is doing well in 2018. The first batch of IGBT Driver boards (Hybrid Driver v1.3) from PCBWay came in today, and they look great! 🙂

IGBT Driver Old And New - PCBWay

PCBWay Manufacturer

This order was my first time using PCBWay and I am blown away by how seamless from end to end the entire process is! I love the technological process tracking, it’s funny, but it reminds me a bit of how some pizza places track the progress of your pizza. My order was accepted, manufactured, shipped and in my shop in no time at all!

The quality of the boards, through-hole plating, silkscreen, bottom side tinning, and everything is a definite A+. I received excellent communication and engineering cooperation from the beginning. Although there are other PCB manufacturers that I like, I am going to use these guys going forward! I’d recommend them for prototyping or production.

PCBWay Technological Process Tracking

Open Source Advocate

I especially like that they encourage open source projects by allowing you to share your board designs, schematics, and project details after ordering. Here is the Hybrid Driver v1.3 in PCBWay’s project sharing section.  They make it easy for others to order boards since all the Gerber files are already there and pre-approved. They even give a 10% back to the project creator. Check it out and take a look at there projects, there are some impressive ones. I like OpenReflow, a control board to convert a simple toaster oven into an accurate reflow oven for soldering SMD components.

IGBT Driver

The new driver boards look great. I like the high gloss black solder mask and the highly visible white silkscreen over it. The slots for the IGBT gate connections turned out great. The board edges are clean and completely burr free. The only mistake I’ve found is that I forgot to set the OSH logo font to vector, so it expanded a bit and overlapped the G2 silkscreen. I also tweaked a few device name silkscreen positions to improve visibility.

IGBT Hybrid Driver v1.3

I’m waiting for the bulk orders of the VLA106-15242 isolated DC to DC converters and the M57962L gate drivers. After that, I’ll stuff the boards and get them in the ReactorForge to continue refining the firmware.

IGBT Driver Stuff Board

The First Kit

I’m planning on making the IGBT Driver (Hybrid Driver v1.3) the first complete kit. Of course, it will be standalone, apart from the rest of the induction heater. I’m ok with having the major components of the induction heater available individually as well as part of the whole machine kit.

I have never made a kit like this, but I am entirely confident that I can put together a great one. Still, this will give me the chance to test that confidence on a smaller scale. I’ve already established a supply chain for the parts and the PCB. What’s left is ordering consumables such as antistatic shielding bags, labels, and packaging. Then, of course, the written plans or instructions for the kit.

Bluetooth Telemetry Link

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Bluetooth Telemetry

This Bluetooth serial link is nothing new. I had it working on the existing setup to send data from the ReactorForge control board to the Processing visualization program. The HC-06 Bluetooth module enabled me to see the live telemetry coming from the ReactorForge. That helps you to understand what is going on and tweak parameters such as the PID settings.

Consolidation of Development Process

I’m excited to get the entire development process in one operating system. Before, I was bouncing between macOS, Windows in VMWare Fusion on the Mac, and a separate Windows machine. It’s a long story, but this was partly due to the Windows-only compiler I used at the time. Other shortcuts I made early in the process just to get things working enough to get the induction heater to Daniel’s shop also helped put me in that spot.

Problems Connecting to the HC-06 Bluetooth Module on Mac

Getting the HC-06 Bluetooth to Serial module working on macOS wasn’t hard, but I did have one issue. The HC-06 seemed to just disconnect randomly after a minute or two of being connected. Then when I would try to reconnect to it, the port would be busy. I knew it wasn’t busy or open using lsof | grep HC-06 or whatever your’s is named, Reactor-Link in my case.

I fired up Windows in VMware Fusion and paired the HC-06 Bluetooth module. Then I opened a connection to it using a terminal program. I also began a screen session (terminal) on the Mac side with a USB to serial adapter. The USB serial adapter was connected to the HC-06 Bluetooth module to monitor it (and send data from it).

Anyway, this worked fine, and the HC-06 Bluetooth module never lost connection on the Windows side. I did notice that on the Windows side, the HC-06 Bluetooth module asked me for asked me for the pin number during the pairing process, but it did not ask on the Mac side. I removed the device from on the Mac side in the Bluetooth manager and re-Paired it. To my annoyance and relief, this fixed the disconnecting issue. Maybe I changed the pin in the past since the last time it had been connected to the Mac.

Bluetooth on macOS

So this is the simple test setup. The photos say it all I think.

Bluetooth Telemetry

Bluetooth Telemetry

Bluetooth HC-06.pdf

Libraries, Drivers, Etc.

With that working, I’m going to work on the libraries now. I’m looking at whether or not to get the existing libraries working in the new environment or use new libraries.  I’m leaning toward new libraries because there are quite a few compiler warnings and even some errors from the old ones. I’ll have to update function names and setup code, but I’d prefer to start with something cleaner and updated. I’m pushing it all to GitHub as I go!

Addition Terminal Jargon

The astute reader might notice that I am using the /dev/tty.* version of the device rather than the /dev/cu.* version. So, what’s the difference? TTY devices are for calling into UNIX systems, whereas CU (Call-Up) devices are for calling out from them (e.g., modems). We want to call-out, so /dev/cu.* is the correct device to use.

The technical difference is that /dev/tty.* devices will wait (or listen) for DCD (data-carrier-detect) e.g., someone calling in, before responding. /dev/cu.* devices do not assert DCD, so they will always connect (respond or succeed) immediately. Since neither the HC-06 Bluetooth module or the USB to serial adapter support DCD it’s not an issue. Still, following best practice, you should use the correct port.

So why did I use the wrong one in the photos? I switched to /dev/tty.* when I was having the connection issue and just forgot to switch back before documenting it.

Development Environment

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Development Environment

If you follow the GitHub repository by clicking [Watch] you may have noticed work on the firmware. I’ve begun setting up the new development environment. Going forward, I don’t want to deal with switching to Windows to work in AVR Studio. I never liked that environment anyway. I had talked about possibly moving everything into the Arduino environment because of its popularity, however that has its own set of issues. For starters, support for the AT90PWM family of chips isn’t there, and I don’t want to spend the time to add it. Then there’s this: + = frickin awesome

Beginning Development Environment

Arduino is a great prototyping platform and IDE to get started on if you have never worked with microcontrollers. As a beginner, it can get you building projects faster than any other platform out there. But eventually, the features that make it convenient and easy to use can hold you back. It lacks many features which make writing code quicker, easier, and have become quite standard in modern text editors. There are also bits of code that get inserted into your code that can cause some very head-scratching issues.

Moving Beyond Arduino

The next logical step is to leave the Arduino IDE behind. We do that by working in a more fully-featured development environment. Atom + PlatformIO is my new favorite open source cross-platform IDE. It even comes with the Arduino framework among others. That lets you test drive it with a code structure you are familiar. When you are ready, you can remove the training wheels and go full native C++. There is so much more I could brag about with both of these tools. But I’ll let you discover the awesomeness yourself!

Development Environment

Next Steps

What’s next? I’m going to begin porting over the libraries used in the existing project. Then the main code, and start rewriting, optimizing, etc. The photo above is a test rig I used for setting up the new IDE. I will continue to use it throughout the porting process. Once the code is stable in its new environment, I’ll switch over to the ReactorForge!

I had also planned on using this setup to demo and explain the basics behind the AT90PMW software PLL setup. I’ll get to that but for now, it’s back to work in the new development environment!

Mains Power Feed Complete

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Mains Power

This is the last mains power update for the ReactorForge Induction Heater. It will be the last because it’s complete! Here is how the last couple days of that process went.

Mains Power

I started by connecting the jumpers from the custom splice connector to the 60 Amp 240-volt dual pole breaker and ground bus. The photo shows green hooked to the neutral bus. I later moved this as I did not need to tap 120-volt like I thought I would have to since the ATX power supply runs on 240-volt now. (I just forgot, it’s been a while.)

Mains Power

And here is the 240-volt quick disconnect assembly installed and ready. I will print another version of the slide lock. The slides should be solid so the splice connectors are not accessible while the wires are disconnected.

Mains Power

Next, I prepared the 2 AWG mains power feeder lines. These will connect the splice block directly to the input of the ReactorForge.

Mains PowerMains Power

The splice block side has thick metal tabs that are double layered with heat-shrink tubing. These provide a high current, high durability connection to the screw terminal that will stand up to multiple connect/disconnect cycles.

Mains Power

The Induction Heater side has heavy duty lugs that will accept the terminal post. These are also insulated with double layers heat-shrink.

Mains Power

Bringing It All Together

And here you can see the feeder lines connected to the input of terminal posts on the back of the ReactorForge. I also ran a USB extension with a small hub for connecting the Atmel ISP programmer. I put the Bluetooth dongle here as well. It communicates with the mainboard to send/receive commands and system telemetry.

Mains PowerMains Power

I then installed a variac between the mains contactor and the inverter input filter.

Mains Power Variac

When software activates the contactor, 240 volts directly feeds the inverter typically. Since I have a decent amount of testing to do, I severed that connection and installed the variac to allow lower power testing.

Mains Power

I taped up the small areas where 240 volts was accessible in the front to avoid accidental contact or tools shorting things out. Getting my fingers across 240-volt mains power is not something I want to experience twice!

Mains Power VariacMains Power

On To The CODE!

That’s it for cooling and mains power connections. The next step is to get the programming environment set back up. I will turn things up as is and do some testing to make sure everything is still good. Once that is done I will get right to the next big task, I’ve decided to port the entire thing to Arduino. This won’t be too difficult since the code is already in C and I will be glad to get away from AVR Studio, to be honest. I made the choice to move to Arduino due to is massive use and rise in popularity over the last few years. Since this is an open source project I want to use a platform that people are familiar with. Let’s put industrial level induction heaters right up there with open source 3D printer firmware!

Nylon 3D Print of the 240V Quick Disconnect

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3D Print 240V Quick Disconnect

In my last post, I showed a prototype 3D print of the 240V Quick Disconnect. Here are the results of the final 3D print.

Nylon 3D Print

I’ve got the final version of the 240V Quick Disconnect printed in in natural colored Bridge taulman3D industrial high strength nylon. It is insanely strong! The first nylon 3D print failed because I forgot to include a skirt, so the edges curled up slightly, and I didn’t notice until it was complete. It still worked, but it bothered my OCD, so I reprinted another, only took an hour anyway. I ran over that first nylon print with my truck (laying flat), and it didn’t get so much as a scratch on it.

The slide lock completely prevents finger access to the Burndy splice connectors. Still, this is not something you should attempt if you are not familiar with electrical safety and codes. Your best bet is to higher an electrician to add a permanent outlet. This assembly setup is for testing purposes only, and I know what I’m doing. Don’t try this at home.

Safety First

Things you should understand if you do try this at home is the earth ground system in your home electrical wiring. You should also understand how NOT to overload circuits, that’s a significant fire hazard. The NEC can help here understand load maximums on a given wire gauge. Finally, understanding how transformers isolate you from the shocking truth will help you understand how the work coil is electrically separated from your home or shop AC grid.

Remember, Safety should always be first! The voltage and current coming from your wall outlets can kill and should always be respected.

Project ReCap and Photos

The updated CAD 3D print files are on on the Thingiverse Project. This assembly houses 3 Burndy splicers (PN: AMS2BAG2R). It does a few important things, it isolates them from each other, from the breaker box, and it snaps closed to prevent the lugs from sliding out (and attacking passer buys). On the side where the wires enter the assembly from the breaker, it is closed off except for holes just big enough for them, so it’s impossible for the splicers to slide out from that side. There are also ears on the front to keep the entire assembly from sliding all the way in the breaker box.

Power Progress – 240 Volt Quick Disconnect

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240V Quick Disconnect

In the photo below is my power test setup at home. Unfortunately, where my other shop is right now, I am unable to make changes like this. Here I explain what I did to get around that and make power progress!

DIY Induction Heater Power

Now that the ReactorForge is back on the bench it’s time to get it powered up!

This setup isn’t necessarily something that an inspector would like to see.  So don’t think this is my recommendation for a permanent solution. I’m just sharing what I did to make my current setup work. Keep in mind the breaker should always be OFF before connecting or disconnecting wires on the quick disconnect assembly.

To hook up 240 to the ReactorForge in this shop I have to run a temporary line. I don’t want to have to remove the breaker each time I do this, so I made an enclosure that mounts in a breaker slot. The assembly houses 3 Burndy splicers (PN: AMS2BAG2R). It does a few important things, it isolates them from each other, from the breaker box, and it snaps closed to prevent the lugs from sliding out (and attacking passer buys). On the side where the wires enter the assembly from the breaker, it is closed off except for holes just big enough for them, so it’s impossible for the splicers to slide out from that side. There are also ears on the front to keep the entire assembly from sliding all the way in the breaker box.

I printed a quick test in PLA, made a few changes and am ready to 3D print the final version in nylon after Thanksgiving. I’m sharing all the files here in case anyone else finds it useful. Be smart, be safe.

Power progress photos:

New Shop Power Panel

My problem is that I do not want to open up the panel and remove the breaker and wires every time I need to remove the temp line.

Power progress

Fusion 360 power splice quick connect

So I drew a simple small enclosure to house some common splice blocks made by Burndy.

The prototype:


The slide lock action:

Technical Drawing:

240V Quick Disconnect Drawing v10.pdf

*Tip: I usualy try to make a technical drawing before I 3D print a part. It’s quick and easy in Fusion 360 and saves me wasted prints and time redrawing later. I always catch a lot more looking at the drawing with multiple views and mesurements than just looking at the drawing in the viewport.

You can view and download the CAD files over at Thingiverse – 204 Volt Quick Disconnect Splice Housing 

Cooling is a GO

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Cooling - connected and flushed

I got the new fittings and hoses hooked up then flushed the water chiller and the induction heater. No leaks, cooling is a go!

Cooling - connected and flushed

Cooling - New metal base for cart

Before putting it back on the cart I replaced the top plastic liner with 16 gauge sheet metal that I cleaned and lightly wiped down with oil. I think I’ll go back and add a lip around 3 sides with the box break to catch any falling sparks and molten beads of metal that try to escape.

Back on the cart!

Cooling setup on cart

And here it is with cooling set up on the new cart.

Cooling setup on cart

Now to move on to power. I am making a quick disconnect near the breaker box. I will need to draw and 3D print a small enclosure for the 3/8″ dual splicers. More on that progress here.

Hooking up cooling water and power

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Hooking up cooling water - parts laid out

Hooking up cooling water, but first, fittings!

Hooking up cooling water - fittings

One trip the hardware store later and I’m ready to hook utilities up to the induction heater. 

Hooking up cooling water - parts laid out

Hooking up cooling water isn’t the only step… Power!

I also ordered a larger variac, a 5000VA 220V model to aid in testing and firmware optimization. I have a small 2000VA 120V variac but running it on such low voltage skewed a lot of the readings. The variac is nice because running full power while testing new features can a bit nerve-racking and wasteful.