Homemade Magic Makes The Metcal Go

First soldering irons are often of the Radioshack or Maplin firestarter variety. They’re basically wall power shorted across a nichrome heater or similar with some inline resistance to make it harder to burn down the house. You plug them in, the current flows, and they get hot. Done.

If you stick with the hobby for a while, these eventually get replaced with something like the venerable HAKKO FX-888D or that one Weller everyone likes with the analog knob. These are much improved; having temperature control leads to a more consistently heated tip and much improved soldering experience.

Entering the electronics workplace one comes across the next level of quality soldering iron: high end HAKKOs, Metcals, JBCs, and the like. Using one of these irons is practically a religious experience; they heat in a flash and solder melts while you blink. They even turn off when you put the handpiece down! But they’re expensive to buy (hint: think used). What’s a hobbyist to do?

[SergeyMax] seems to have had this problem. He bit the bullet, figured out how the Metcal works, and made his own base. This is no mean feat as a Metcal might look like a regular iron but it’s significantly more complex than ye olde firestarter. The Metcal magic is based on a oscillating magnetic fields (notice the handpiece is connected via BNC?) interacting with a tip bearing a special coating. In the presence of the changing field the tip heats up until it hits its Curie temperature, at which point it stops interacting with the magnetic field and thus stops heating.

When the user solders, the tip cools by sinking its heat into the part and drops below the Curie temperature again, which starts the heating again. It’s like temperature control with the sensor placed absolutely as close to the part as possible and a nearly instant response time, without even a control loop! [SergeyMax] has a much more thorough description of how these irons work, which we definitely recommend reading.

So what’s the hack? Based on old schematics and some clever reverse engineering from photos [SergeyMax] built a new base station! The published schematic is as rich with capacitors and inductors as one could hope. He didn’t post source or fab files but we suspect the schematic and photos of the bare board combined with some tinkering are enough for the enterprising hacker to replicate.

The post contains a very thorough description of the reverse engineering process and related concerns in designing a cost efficient version of the RF circuitry. Hopefully this isn’t the last Metcal replacement build we see! Video “walkthrough” after the break.

Edit: I may have missed it, but eagle eyed commentor [Florian Maunier] noticed that [SergeyMax] posted the sources to this hack on GitHub!

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A USB -C Soldering Iron For Weller Tips

There was a time when a decent temperature controlled soldering iron took the form of the iron itself and a box of electronics, but now it’s just as likely to be a miniaturised affair with the temperature controller built into a slim and lightweight handle. Irons such as the Miniware TS series have become firm favourites, displacing a traditional soldering station for many.

[Thomas.lepi] has combined the best of both worlds, with a TS-style microprocessor-driven handle driving the familiar Weller RT elements. Its interface is very simple, but through its USB power socket a serial port provides opportunities for adjustment. Providing control is an STM32F042G6U6 ARM Cortex M0 microcontroller, with USB power control coming from an STUSB4500QTR .

If you are used to irons such as the Miniware TS100 then this one with its smartly 3D-printed case will be very straightforward to use. Whether or not the ready availability of the TS100 or its USB-C sibling would remove the need to build this iron is up to you, but then again that’s hardly the point. The Weller tips are some of the better ones of their type, so perhaps that might make this project worth a second look.

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Auction Finds Combined For A Unique Desoldering Station

If you are in the market for a high-quality soldering iron, a rewarding pursuit can be attending dispersal auctions. It is not unusual to see boxes of irons, as anything remotely iron-like is bundled up together by the auctioneer into a lot with little consideration for what combination has been gathered. [Stynus] found himself in this position, the proud owner of a Weller DSX80 desoldering iron from an auction, but without its accompanying solder station required for it to work. Fortunately, he had another Weller solder station, not suitable for the DSX80 as it stood, but which provided a perfect platform for a home-made Weller DSX set-up.

The old station had a side-mounted valve and a 24V input, so he had to install a toroidal mains transformer and move the valve frontwards. Fortunately, this style of Weller station case was frequently available with just such a transformer installed, so there was plenty of space in the enclosure. A custom board was then created for a temperature controller centered upon a PIC microcontroller, and a new front panel was crafted to accommodate a Nokia 5110-style LCD display.

The resulting unit with its upper half repainted, is a pleasing and professional-looking project. Heated desoldering irons are an extremely useful tool that anyone should consider for their arsenal, but not all of them are as good as this Weller-based one. We recently reviewed a much cheaper example, with comedic results.

Is It A MagLite Or A MagnaStat?

[David Schneider]’s love affair with Weller temperature controlled soldering irons began many years ago, but when he came to the point of needing a cordless iron he had problems finding one that replicated his trusty mains-powered soldering station. His solution was simple, to build his own, and in a stroke of genius he did so with an odd combination of a Weller MagnaStat element and bit, and a repurposed MagLite flashlight.

The Weller parts are all available off-the-shelf as spares, and the MagLite was easy to source. But its D cells would never give the required 24 V for the iron, so he had to incorporate a set of 14500 Li-ion cells with built-in electronic protection. The element protrudes from the front of the flashlight, giving an iron that seems to do the business but to our eyes looks rather unwieldy. Still, it does the job, and provides a far more sturdy and reliable iron than any cordless one we’ve yet seen, so we think that’s a result.

We’ve reviewed a Weller MagnaStat in the past,with a special look at availability of bits for older models.

One Soldering Controller To Rule Them All

If your favourite programming language is solder, they you’ve surely worked your way through a bunch of irons and controllers over your hacker existence. It’s also likely you couldn’t pick one single favourite and ended up with a bunch of them crowding your desk. It would be handy to have one controller to rule them all. That’s just what [sparkybg] set out to do by building his Really Universal Soldering Controller. His intent was to design a controller capable of driving any kind of low voltage soldering iron which used either an in-line or separate temperature sensor (either thermocouple or resistive PTC).

This project has really caught on. [sparkybg] announced his build about two years back and since then many others have started posting details of their own Unisolder 5.2 builds. [zed65] built the version seen to the right and [SZ64] assembled the boards shown at the top of this article.

The controller has been proven to work successfully with Iron handles from Hakko, Pace, JBC, Weller, Ersa, as well as several Chinese makes. Getting the controller to identify one of the supported 625 types of iron profiles consists of connecting two close tolerance resistors across the relevant pins on the 9-pin shell connector. This is a brilliant solution to help identify a large variety of different types of irons with simple hardware. In the unlikely situation where you have a really vague, unsupported model, then creating your own custom profile is quite straightforward. The design is highly discrete with an all analog front end and a PIC32 doing all the digital heavy lifting.

To get an idea of the complexity of his task, here is what [sparkybg] needs to do:

“I have around 200 microseconds to stop the power, wait for the TC voltage to come to its real value, connect the amplifier to this voltage, wait for the amplifier to set its output to what I want to read, take the measurement from the ADC, disconnect the amplifier from the TC, run the PID, and eventually turn the power back on. The millivolts to temperature calculation is done using polynomial with 10 members. It does this calculation using 32bit mantissa floating point numbers and completes it in around 20 microseconds. The whole wave shaping, temperature calculation, PID and so on is completed in around 50-60 microseconds. RMS current, voltage and power calculations are done in around 100 microseconds. All this is done between the half periods of the mains voltage, where the voltage is less than around 3 volts.”

The forum is already over 800 posts deep, but you can start by grabbing the all important schematic PDF’s, Gerbers, BoM and firmware files conveniently linked in the first post to build your own Unisolder5.2 controller. This Universal Controller is a follow up to his earlier project for a Hakko T12/T15 specific controller which gave him a lot of insight in to designing the universal version.

[sparkybg] has posted several videos showing the UniSolder5.2 controlling several types of Irons. In the video after the break, he demonstrates it controlling a Weller WSP80.

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How To Make Your Weller Wireless

On occasion I have encountered portable soldering irons and my impressions of them have ranged from nearly usable to total rubbish. While using a popular butane powered model and pondering if it was really any better than a copper wire and a candle a thought occurred to me. A regular old Weller station runs on 24 volts AC and performs all of its temperature regulation in a magnetically activated thermostatic fashion and all of that goodness occurs within the hand piece itself. It stood to reason that it could perform just as well with a DC source.

In this instance we are ignoring the negative effects of switching DC current over AC current on mechanical contacts. After all we are “In the Trenches” wherever we might have need for such a device. Using a couple of gel cell 12 volt 7 amp hour batteries freshly removed from a UPS I strung them up, and there you have it, a totally battery operated  iron with performance equal to that of the one at my bench.

Connecting SMPS to the Weller Iron
Connecting Power to the Weller Iron

Right at 24 volts the iron Thermocycles at the same rate as it would be while using the bench top supply for it. Just sitting under no load it cycles about every ten seconds and there was no perceptible difference in heat capacity or performance. A fully charged pair of batteries will last all day. The on state current draw from a full charge (13.5 volts on each of the batteries) yielded about a 2 amp draw. As the voltage began to decrease the current off cycle would get shorter as one would expect, but no drop in heat transfer was noticed until the batteries were well depleted and that took most of a work day.

For this instance I used the hand piece from the venerable Weller WTCPT station. For ongoing use I would not recommend this due to the use of a mechanical contact within the unit and switching of DC can reduced the life of most mechanical switches. Currently I am awaiting the arrival of some cheap eBay Hakko handpieces; I am sure they are knockoffs, but fine to experiment with a simple PWM with a feedback loop controller as the basic Hakko design also utilizes a 24 volt source. An automatic shut off timer would also be handy to avoid premature battery abuse due to a forgetful operator.

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Long-Term Review: Weller Magnastat Soldering Iron

One of the things you find yourself doing as a young engineer is equipping yourself with the tools of your trade. These will be the foundations upon which your career is built in a way that a diploma or degree certificate will never be, for the best degree in the world is less useful if the quality of your tools renders you unable to capitalise upon it. You may be lucky enough to make some of them yourself, but others you’ll lust after as unaffordable, then eventually put the boat out a little to buy at the limit of your meager income.

Your bench may have a few of these lifetime tools. They could be something as simple as screwdrivers or you may have one of those indestructible multimeters, but in my case my lifetime tool is my soldering iron. At some time in 1992 I spent about £60($173 back then), a lot of money for a student, on a mains-powered Weller Magnastat. The World Wide Web was still fairly fresh from Tim Berners-Lee’s NeXT in those days, so this meant a trip to my university’s RS trade counter and a moment poring over a telephone-book-sized catalogue before filling in an order slip.

The Magnastat is a simple but very effective fixed-temperature-controlled iron. The tip has a magnet on its rear end which holds closed a power switch for the heating element. When the tip has heated to the Curie temperature of the magnet, it loses its magnetism and the switch opens. The temperature falls to below the Curie temperature and the magnetism returns, the switch closes, the tip warms up again, and the cycle repeats itself. The temperature of the tip is thus dictated by the magnet’s Curie temperature, and Weller provides a range of tips fitted with magnets for different temperatures.

The result is an iron with enough power to solder heat-sucking jobs that would leave lesser irons gasping for juice, while also having the delicacy to solder tiny surface-mount components without destroying them or lifting tracks. It’s not a particularly small or lightweight iron if you are used to the featherlight pencil irons from today’s soldering stations, but neither is it too large or heavy to be unwieldy. In the nearly quarter century I have owned my Magnastat it has had a hand in almost everything I have made, from hi-fi and tube amplifiers through radio transmitters, stripline filters, kits, and too many repairs to mention. It has even been pressed into service plastic-welding a damaged motorcycle fairing. It has truly been a lifetime tool.

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