Dual T-12 station

Notes about making a dual T-12 soldering station.

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After having access to a Metcal MX5200 with the full 2 soldering pencils, the lion kingdom became aware of its limitations & advantages.  The mane problems: changing temperature required changing tips & having the right tip.  There wasn't enough room for 2 stands.  Most of the time, only the copper wool in 1 stand would be used for cleaning while the other was behind a pile of cables.  The connection to the base station was also constantly glitching out.  The smartheat/curie point system is all but obsolete, nowadays.  

It was luxurious having tips that fine.  It was much easier to pick & place surface mount parts with 2 fine tips.  It could heat ground planes effortlessly.  The base station was a very compact way to power 2 tips.  Unfortunately, it was a loaner.

The lion kingdom's previous irons were the Hakko FX-888, Weller WES51, & for the 1st 15 years, the $8 Radio Shack iron.  The Hakko FX-888 was the duck's guts in 2012, for soldering 0603's & bigger, but its mane problem was the lack of any tips for it as small as the Metcal.  The finest tips were conical.  These required turning up the heat to get the very end hot enough & risking burning up components. 

The quest for an affordable & modern alternative to the Metcal revealed this Jeri Ellsworth video showing 2 JBC stations.

Dual JBC's were obviously a sign of someone who had arrived.  That was what people were using for the newest components.  The next step was figuring out what made a JBC better & trying to clone it in a smaller, dual iron package.

 The thermal inertia of a very fine tip is too low to rely on a wide heater separation.  To make the tip finer, the heater has to be closer to the end.  The curie point was the original way of doing it, but better manufacturing has proven good enough to use active temperature control.

The lion kingdom really needs a single controller feeding 2 tips & a single stand for holding 2 tips with 1 copper cleaner.  There's no commercial solution at any price.  The idea of making your own soldering station didn't exist 7 years ago when the FX-888 arrived.  It only seems to have appeared in the last 3 years.

The Hakko FX-951 is the cheaper version of the JBC & uses T-12/T-15 tips.   It has an impossible user interface.  They have a thermocouple in series with the heater.  The thermocouple makes a voltage when the heater is off, which is proportional to the temperature difference between the copper leads & the heating element.  It's heated by 24V AC.

Cold junction compensation:

They're basically measuring the temperature where the copper connects to the thermocouple with yet another thermister & using a table that factors in the copper temperature.  The trick is a thermocouple only senses difference between the copper & the alloys while a thermister senses absolute temperature.  This is not actually used anywhere but internet comments.  Assuming the copper temperature is 72F has proven good enough.

Chinese pinout diagram:

It's quite clear that the internet doesn't really know what the pins do.  They all just copy the same wiring diagram from China.

Universal solder controller with typical voltages & wiring patterns for the various tips, but no functional description:

This is incredibly overcomplicated, but it shows how recently it wasn't trivial to make your own soldering station.


Analog circuit for reading the thermocouple & powering the heater:

The mane problem is getting the op-amp to handle the 24V when the heater is on.   There's also a current flowing out of the op-amp input, which affects the voltage reading if a large current limiting...

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  • Upgrading to the Hakko FX-9501

    lion mclionhead01/19/2020 at 21:10 0 comments

    Based on the internet, people just assemble their cheap Chinese soldering irons & put them away, it seems.  At most, they keep buying upgrades for their cheap Chinese irons until they cost as much as a JBC.  Then, after a few years, they have enough home equity to buy a JBC & use that instead.

    As one does, the next installment on the way to costing as much as a JBC was made & 3 weeks later, some Hakko FX-9501's arrived from ebay.  These were choked up & much more accurate.  The good old days of Metcal were almost back.  On the other paw, the Hakkos were all plastic, the tips were mashed in rather than being securely bolted on, & they couldn't be changed when they were hot.

    There was just the problem of replacing the 3 wire cables with the 5 wire cables, installing the motion switch, building a stand, & grounding.  The Hakkos had a capacitor between the DC+ & DC- but still nothing connected to the GND.

    Drawing sketches & randomly bending metal sheets for a while yielded this.

    The switches were mashed in.  

    The new stand was assembled.

    Single paw soldering has returned, as the T-12 tips were meant to be used.

  • You need to ground the T-12 tips

    lion mclionhead01/01/2020 at 05:21 0 comments

    After an uneventful year, some 1.1V chips started turning up zapped.  The prime suspect was the T-12 not having grounded tips.  Previously, the tips were connected to each other but not a ground.  This caused glitching temperatures when both tips were on, so they were made floating.  Decided to ground the tips to Earth ground like other irons & the chips stopped getting zapped.  So the answer is yes, the tips need to be Earth grounded.

    A voltage test showed 5V AC between the tips & ground.  A current test showed the tips sending 100uA AC to ground when they were both heating.  The problem is there's a capacitance between the heater & the surface.  It conducts current when the heater is driven by pulses.  This is the downside to having the heating element integrated in the tip, instead of a ceramic piece in the venerable FX-888.  

    The temperature readouts once again glitched around when the tips were connected to earth ground.  When grounded, the glitching was equal if 1 or 2 were on.  When the heating element was off & the temperature was freefalling, 1 or 2 tips still glitched.    Removing the ground immediately stabilized the temperature of either 1 or 2 tips freefalling.

    With no earth ground & both tips connected, the glitching only happened if both tips were on.

    So the effect of earth ground is the same as the effect of another tip being powered.

    When the tips were floating, their mane use case was soldering 2 pins of the same component.  Most of the time, they were conducting through the component & glitching the same as if they were connected to each other.  So there was no practical benefit to having the tips floating.

    The internet as usual was random.  The eevblog recommended replacing the pin header with direct soldering to get the temperatures to stabilize.

    Helas, the eevblog revealed a lot more problems than just what lions experienced.

    Installed caps & directly soldered the wires, but it didn't show any improvement.  The irons do indeed get more unstable the higher they go, until they're completely useless at 450C.  

    The eevblog blamed cable length for some of the instability, but lions think the PID gains are off & they're not lowpass filtering the temperature.    There was also an idea of shorting the STC 12's DC- & earth ground instead of using manes earth at all.  Meanwhile,

    recommended connecting STC T12's  DC- to manes earth ground & manes neutral while not using the STC T12's earth ground at all.

    The lion kingdom has an isolated DC- which can't be used for grounding the tips.  

    He documented the menu system, but it doesn't allow changing the PID gains.

    Newer irons are always emerging, with choked up handles & maybe fixed temperature sensing, but the trend is for guys to keep buying upgrades for these low cost JBC replacements until they've spent as much as a JBC.

    The op-amp gain & op-amp offset were signs of a voltage to read the temperature off of.

    The STC T-12 has also been used on 12V battery power.  It's extremely slow on 12V & can't heat much mass, but still suffers from the instability.  There's also the problem of grounding it on battery power.  You'd need a bodged ground wire.

    Given the fact that current is leaking from DC+ to earth ground from capacitance in the tip, lions want all the current from DC+ going down DC- instead of earth ground, & DC- is isolated from manes neutral, the best solution is just shorting earth ground, DC-, & the tip.  DC- won't be isolated anymore, but that's physics, marriage, & taxes.

    With that solution, they did 450C with no glitching, no extra capacitors, & no special cables.  Most power supplies are floating, so grounding DC- might be the most...

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  • Rudung rework

    lion mclionhead11/16/2019 at 23:38 0 comments

    After living with only a single Rudung for a while, the decision was made to replace the other one with a front power switch.  The rear power switch got to be a pain in the mane.  It also arced.  The front switch has the same Chinese quality, but has a rubber covering up the pixies.

    The Bang Bad switch proved unsuitable for soldering.  The contacts are some kind of pop rivets & melt through very easily.  There's no special alloy or heat resistant plastic like the Japanese switches.  Managed to get 1 to work by soldering the very ends & heat shrinking.  

    The lion kindom specifically ordered 250V 15A versions

    but they're visually very similar to a 12V model

    Wouldn't trust them with 250V 15A.  The most they'll see is 120V 3A.

    The bang bads continued to get stuck in the on position, at random times.  Replaced one, tore it down, bent some of the metal pieces to keep the rocker more snug.  It's hard to believe China flies stealth jets & rockets using these switches, but how much software valued at over $80 billion works?

    A Rudung was more useful as a portable battery powered regulator.  The day job can't do that.  They have to lug around an inverter & Agilent to get a measly 1A.

  • T-12 problems

    lion mclionhead04/07/2019 at 04:20 0 comments

    After using the T-12 for a while, the honeymoon was over.  It has a very short timeout for the complete powerdown.  You'll be frequently seeing 000 & power cycling it to turn it back on.

    For the 200C powerdown, the timeout is shorter & it relies on a tilt sensor rather than a full motion sensor.  It always senses being pulled out of the stand, but during a long solder job with little movement, a part with high thermal mass, & lead free solder, it usually times out.  You have to frequently take it off the part & shake it again.

    The tip length is so long, the ages old technique of holding down a part & soldering with the same paw doesn't work anymore.


    Old tip

    A handle can technically choke up around the tip, but it would be expensive.  The long tip also makes it shake more.  The lion kingdom is forever missing the Metcal in this department.

    The only useful tip for through hole has been the hoof tip.  The chisel tip provided is too wide.  The knife tip is useful for feeling powerful, but doesn't transfer as much heat as the hoof.  Of course, most people only have the stock tip for it & only 1 iron.  The lion kingdom got a complete set of tips & 2 irons.

  • Soldering with the T-12

    lion mclionhead01/27/2019 at 00:43 0 comments

    It starts up much faster than the MX-5200 & comes out of sleeping much faster, but thermal regulation isn't as fast.  Soldering a ground plane is still painful.  The LED goes out, indicating its thermocouple is at the required temp, but the tip is still cold.  It's an incremental improvement from the FX-888, but nowhere close to the Metcal.

    Conical tips on the T-12 are incrementally better but still suffering from FX-888 problems.  The point tends to stay cold, while the heat comes from the side.  Temperature has to be increased to get a hot tip.  Never did measure the Metcal's temperature, so it might have relied on a hotter temperature.  It might have always been 340C.  Lions use 280C as much as possible, to avoid lifting a pad & burning flux.

    The rattling of the motion detecting switch is bearable & it's sensitive enough to keep it on with normal motion.  The tip being longer than any other iron ended up not being noticeable.  They might have done that to get a cold side for the thermocouple.

    We've traveled far, in the last 30 years.  The 30W Archers & Wellers are long gone, though the very 1st stand from the lion kingdom's 1st Archer kit is shown.  Lions spent a lot of time grinding down the Weller tips as they eroded.  Time to discard the 15W.  Lions never got burned after switching to the regulated ones, because they had real stands.  

  • Complete bench in a box

    lion mclionhead01/03/2019 at 21:14 0 comments

    It took 6 weeks for the boat to arrive from China.

    Bang shiny before they're used.  The legendary hoof tip finally arrived.

    Step 1 was fabricating the power supply.  2 Rudung buck converters & a direct 25V connector powered by a single 300W.  The Rudungs have independent grounds, but the lion didn't try shorting anything yet.

    There was much tinning of 14 gauge silicone wire.  It was a better wiring job than anything money could buy.  There's room for fans on the Rudungs, but no plan to need high current until the next major LED project.  With pixies now available,

    The irons could be fired up.  It was easiest to hot glue the boards on the outside.  Forget about using jumpers to connect the connectors.  Just solder them into the boards.

     Still need a stand, since they don't fit in the Hakko stands.  Tested it at 280C with the Fluke & the temperature was already calibrated in the factory.  Not sure how high the Fluke can go before it melts.  

    The soldering station used just the cheapest soldering & a wall wart to weigh it down. 

    A note on grounding the tips:

    Ideally, the tips would be Earth grounded, but this was intended to be battery powered.  The lion kingdom didn't want to connect the tips to negative supply because they could fry a gadget if the same supply was powering the circuit.

     The tips were originally connected to each other but not to Earth.  This was a failure.  The tips must not be connected if they're powered by the same 25V.  They must be on isolated supplies in order for the tips to be connected, otherwise they'll be unstable when simultaneously heating.  The tips are a current path for the heater but don't connect to negative supply.  When using a common 25V, the tips have to be floating. 

    The 2 irons heat up bang fast on 25V.  The power supply fan briefly spins up when it heats up or solders something.  It's quite a powerful feeling, making a fan spin up by soldering.  It could run on a 12V battery, but there wouldn't be a fan.

    Absolutely none of the buttons or switches ordered were used.  The switches were failed short circuiting switches from the mastech which the lion kingdom repaired.  The Mastech may be used 1 more time in the lion kingdom's lifespan.

  • Bench in a box begins

    lion mclionhead01/03/2019 at 07:18 0 comments

    1 month after ordering, parts started arriving from China, manely top of the line RUIDENG DPS5005 50V 5A's  with communication support.

    What Dave couldn't do was done.

    Revealing it was 2 boards soldered together with 2 pin headers & a display on a 3rd board, itself soldered by a 1 pin header.  Its only attachment to an enclosure was the liner.  The standoffs were loose fitting.

    16 pins with conformal coatings ensnared the 2 boards.

    So there would be no replacing the display or the buttons with any ease.  It was already decided that the bluetooth & USB support wasn't worth it.  That was only ordered in case someone needed to test a voltage ramp.  At least there's alternative firmware.

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ivan003003 wrote 04/11/2019 at 00:49 point

However,what do you think about Unisolder 5.2 ?

  Are you sure? yes | no

David H. wrote 01/23/2019 at 17:13 point

I remember seeing someone comparing these T12 controllers and the one pictured with the segmented LED display wasn't the best, for a bit more money, you can get a completed OLED T12 mini station without the PSU and if one's on a budget, the one without the LED display performed better.

  Are you sure? yes | no

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