This post is the second example of how to make a 110 volt temperature controlled soldering station. Please refer to the previous post for information on materials used, their costs and where they can be obtained. The steps for modifying the soldering iron are very similar to the previous post but a few things are different for this version.
The steps for making the controller are virtually the same. As a result, most of the details for the controller have been omitted in this post. The main difference is the addition of a green ground wire to the 4-pin female DIN socket.
This build also conforms to international standards for positive and negative DC wire colors (red and blue) vs. USA standards (red and black).
The soldering iron chosen for this build is similar in design to the one used in the original version. It a replacement handle for the Mini Solder Station 15860 TL (ZD-99). The cost was $4.95 USD and was obtained from this link.
The main reason I chose this unit was because a selection of tips was available for it. Like most soldering irons sold today, it comes standard with a conical tip. A chisel tip is shown in the photo below.
Part I: Modifying The Soldering Iron
This soldering iron has a mica tube heating element and adapts well for this project. It is a 110 volt, 58 watt unit with a ground wire and a 3-conductor cord. More info on a mica tube heating element can be found at this post.
In order to adapt it to work with a temperature controller, a thermocouple is inserted into the the rear of the heating element. The power cord was also replaced with a flexible 5-conductor cord and 4-pin DIN connector.
The unit is a replacement handle for a dimmer control type soldering station similar to the DIY Analog Soldering Station featured in an earlier post. Although it is not sold as a plug-in unit it could easily be converted into one simply by connecting a replacement electrical plug to the cord. A 3-wire plug like the one shown below can be obtained at most hardware stores:
The screws that secure the handle are three pronged fasteners called “tri-wing” screws. You will need a tri-wing screwdriver or bit set plus a standard quarter inch bit driver to disassemble this soldering iron. The bit set (shown below on the left) was obtained from Amazon.com. The ratchet driver was from a basic computer tool kit.
The head of a tri-wing screw is sort of like a Phillips except with three slots instead of four. Shown below is a closeup of the screw heads and the bit driver.
Removing the tri-wing screws will allow the two halves of the handle to be separated (see photo below). The three Phillips screws that secure the tip enclosure to the black plastic collar would also need to be removed.
Replacing the Power Cord
An RG58 strain relief boot needs to be fitted into the recessed area of the soldering iron handle. First it must be trimmed with a precision utility knife.
There is a small plastic anti rotation stud inside the recessed area of each half of the soldering iron handle that needs to be removed in order for the RG58 strain relief boot to fit properly (see photo below). They can be filed or trimmed down by hand with a precision utility knife or with a power rotary tool.
The connections between the power cord and heating element leads are secured with brass crimp splices. Remove the heat shrink tubes and carefully pry each splice open to disconnect the heating element wires and the ground wire.
The power cord is separated from the tip enclosure and the heating element (see photo below).
The power cord will be replaced with a 4 1/4 foot length of 5-conductor silicone extension cord. The silicone extension cord was purchased in 9 1/2 foot lengths so one piece was simply cut in half for two soldering irons.
The 4 pin male DIN connector has a small metal retaining tab which is visible through an opening in the plastic cover. The connector is disassembled by pressing down on the metal tab with a small screwdriver.
The metal parts will disengage the from the plastic cover and the unit can be disassembled for soldering.
The pinout of the 4 pin DIN connector is shown in the diagram below. This is the same pinout as in the previous post so the soldering irons can be interchangeable with the controllers. The black wire was soldered to pin 4, white to pin 3, blue to pin 2 and red to pin 1.
Note: The reason I chose the 4 pin DIN connector instead of a 5 pin DIN connector was to avoid accidental plugging in of a wrong soldering iron into the controller. Both DIN 5 180 degree and DIN 5 240 degree variants have already been established for existing 24 volt soldering stations. If one of those irons were to be accidentally plugged into the 110 volt controller it would destroy the iron.
The wires were stripped and soldered to the connector pins. Note that one of the halves of the circular metal skirt has a crimp connector for securing the cord. The green wire is held with a surgical clamp and then soldered to the inside of this part. The blue gummy stuff in the photo below is called Blu-Tack reusable adhesive. It comes in handy for holding small parts for soldering.
The metal part was crimped down over the cord with a pair of long nose pliers. Soldering the green wire to the inside of the metal skirt was a way to connect 5 conductors to a 4-pin connector. The female connector has a 5th solder lug for the ground wire (shown further down in this post).
The connector is shown reassembled in the photo below.
A small 2mm x 100mm cable tie was attached near the end of the cord to keep it from slipping out of the strain relief boot. Note: An 8-inch cable tie was used for the IL12A soldering iron in the first build but the handle on this ZD-99 iron is a little bit different so a smaller cable tie was used.
The cord and cable tie position is checked for fit in the plastic handle (see photo below).
Using the two tri-wing screws, the handle is temporarily assembled to check the final fit of all the parts.
Preparing and Installing The Thermocouple
The tip enclosure and heating element are shown below with a K-type thermocouple rated for -50°C to 700°C. The thermocouple cable in the photo below is 2 meters long. Only a few inches are needed.
A length from the spot welded end of the thermocouple was cut and then some of the fiberglass insulation was stripped from the ends of each lead. The photo below shows that the thermocouple is trimmed to approximately the same length as the heating element leads. Please see the previous post for more details on this step.
Several pieces can be made from one cable. If there is no access to a proper thermocouple spot welder, they can be spot welded with a 12 volt car battery, a set of jumper cables, a claw hammer and a pair of long nose pliers. Please see this post for details.
The thermocouple was tested with a K Type thermometer to ensure proper functionality before it was installed inside the soldering iron. The polarity is indicated by the color of the stripe on the insulation. The positive lead has a red stripe and the negative lead has a blue stripe.
A length of 4mm ID fiberglass sleeve (rated at 600°C) plus lengths of 1/8 in and 3/16 in inch heat shrink tube are needed to prepare the thermocouple for installation. Please see the photo below. There is limited room on the thermocouple so the pieces must not be too long.
Use a heat gun to shrink the 3/16 inch heat shrink tube over the fiberglass sleeve. This piece has to be shrunk down first. The knife blade is pointing to the approximate position of the spot welded tip inside the fiberglass sleeve.
Next, use the heat gun to shrink the 1/8 inch piece of heat shrink tube over the 3/16 inch piece. This piece has to be shrunk down last because it holds the 3/16 inch piece to the thermocouple cable.
Position the fiberglass sleeve just inside the rear opening of the heating element and then use a small cable tie to secure the thermocouple to the heating element leads like the photo below.
Thread the black plastic collar over the thermocouple and heating element leads like the photo below and then replace the three Phillips screws that secure it to the tip enclosure. Take care to replace these screws straight in. The plastic is soft and it is easy to cross thread them.
Lengths of heat shrink tube were cut and threaded over each of the five leads like the photo below. Then each conductor was twisted to the appropriate lead. The black and white conductors were connected to the heating element leads and the read and blue conductors were connected to the positive and negative leads of the thermocouple (respectively). The green conductor was connected to the yellow and green ground wire.
This is where this modification got a little tricky. This soldering iron has ceramic insulators covering the heating element leads. Right here at this step I was having trouble routing all the wires so the handle could be reassembled because the ceramic insulators were rigid and inflexible.
I replaced the ceramic insulators with a couple of flexible insulators from a spare heating element that I had on hand. I disconnected the heating element leads and threaded the flexible insulators onto them and took this photo below:
Then I replaced the small cable tie securing the thermocouple to the heating element leads.
With the flexible insulation the wires were easy to route inside the handle. Before reassembly, a heat gun was used on the heat shrink tubing covering the connections. Don’t use a heat gun near the plastic handles. A piece of cardboard from an ordinary legal pad like the one shown in the photo below was used to shield the black plastic collar from the heat.
The photo below shows the soldering iron reassembled after modifications.
A test rig with a dimmer control was used to check the temperature of the thermocouple compared with the actual tip temperature. Instructions for making a dimmer controller can be found in this previous post. A set of alligator leads were plugged into a K type thermometer and connected to the thermocouple pins on the back of the female DIN socket. The photo below shows that it was within seven degrees C.
Part II: Building The Controller
Please see the previous post for step by step instructions for building the controller. The only differences for this build were the colors of the wires used for positive and negative DC conductors (red and blue) plus a ring terminal was crimped onto the end of the green (ground) wire in the photo below and attached to the chassis with the same screw as the green (ground) wire from the IEC power receptacle.
The photo above shows the colors of the wires that were soldered to the female DIN socket and the heat shrink tube over the soldered connections.
The photo below shows a view of the chassis before attaching the metal cover.
The finished unit is shown below ready for use.
When tuning the controller the soldering iron was taken apart about five times to adjust the position of the thermocouple for a more accurate temperature reading.
The photo above shows that both the thermocouple and the tip temperature were reading 343°C. It was worth the effort because the final adjustment didn’t require any temperature offset adjustment in the controller.
Please see the video links at the end of the previous post for instructions on adjusting the controller settings and for the auto-tuning procedure.