Dewalt 18V/20V Battery Powered Portable Soldering Iron

While browsing Home Depot I saw that Ryobi had a tool similar to this one in their battery tool line, but Dewalt unfortunately did not. Since I do a lot of mobile solder repair work on lab equipment and 3D printers I opted to make my own. Due to my working on sensitive equipment occasionally I have added the option for grounding of this device is necessary via a banana plug. It also accepts a 24V barrel jack power supply if the battery dies, or user is near an outlet for an extended period while using this.

While I know there are portable options out there such as the TS80 and Pincecil (of which I do have the TS80), I vastly prefer the handpiece of my benchtop Hakko iron, as well as the huge array of tip shapes and sizes available for it. In addition, by keeping the compatibility with my Hakko FX-951, it allows me to swap out handpieces, grips, and tips as I want without having to worry about multiple different ecosystems.

Supplies

Parts:

• T12 Soldering Iron Tips
• T12-952 Soldering Iron Controller Board
• Dewalt 18V/20V Li-Ion Battery Pack
• Brass Crimps (I used these I found on Amazon. The largest male size worked well for this project)
• M3 x 5.7 Heat Set Inserts
• M3 Countersunk and Button Head Screws
• Hakko 599B Brass Wool Holder
• Panel Mount Banana Jack
• Stacking Banana Plug Cable (optional)
• Banana Plug ESD Wriststrap (optional)

Electrical Components:

• Custom PCB (board files and gerbers provided in step 1)
• 100nF 50V 0201 Ceramic Capacitors
• 100uF 35V D6.3 x L5.8
• 10uF 35V D4 x L5.4
• 1nF 50V 0201 Ceramic Capacitors
• 1uF 35V 0805 Ceramic Capacitors
• 2.2uF 6.3V 0201 Ceramic Capacitors
• 4.7pF 50V 0201 Ceramic Capacitors
• 22uH Inductor
• 10k Ohm 0201 Resistors
• 10M Ohm 0201 Resistors
• 165k Ohm 0201 Resistors
• 1M Ohm 0201 Resistors
• 2.7M Ohm 0201 Resistors
• 39k Ohm 0201 Resistors
• 71.5k Ohm 0201 Resistors
• 470 Ohm 0201 Resistors
• Analog Devices LT3007-5 TSOT23-8 Linear Regulator
• Analog Devices LT8334 DFN12-4x3 Adjustable Boost Regulator
• Maxim Devices MAX835 Latching Voltage Supervisor
• SS54 SMA Diodes
• STL260N4LF7 Powerflat (5x6) MosFET
• TS-1045-A13B3-D2 SMD Switches
• 24V Relay
• DPST Switch
• Barrel Connector
• SMD Cable Connector
• SMD Cable Shell
• SMD Cable Crimps

Misc Materials:

• 3D printer filament of choice (I used Nylon PA11 and recommend something with some temp resistance like ABS, ASA, or Nylon; but PLA will work)
• Solder Wire/Solder Paste
• Flux/Flux Cleaner (or IPA)
• Between 18-22 AWG copper stranded wire (do not use copper plated aluminum, make sure it is solid copper. Aluminum does not conduct as well as copper, and cannot carry enough current at this wire gauge)

Tools:

• Wire Snips (flush cut is best)
• Pliers
• Allen Keys
• Crimping Tools
• Soldering Iron
• Hot Air Soldering Station
• 3D Printer
• Heat Insert Tips
• Hot Glue Gun
• Fine Tip Tweezers
• Exacto Blade
• Wire Strippers
• Magnifying Glass/Microscope
• Cotton Swabs
• Putty Knife/Scraper

Step 1: PCB Ordering

I ordered my board through JLCPCB, but ultimately any fab house should work with the provided Eagle/Fusion360 eCAD files/gerbers. The important part when you order this board is to specify at least 2oz copper weight due to the current running through the board. Under worst case scenarios I expect around 3-5A to be running through the traces on the board and ordered 2oz to be able to better handle that with some thermal/current headroom. Due to the size of the several of the components on this board I would recommend ordering a stencil with the board at a minimum or possibly opting for an assembly service. I assembled it by hand myself, but that will require steady hands and a magnifying glass.

This board serves three purposes. The first purpose is to protect the battery, as for some reason Dewalt integrates the battery protection into the tool and not the battery unlike most other manufacturers. The second purpose is to ensure the soldering iron control board receives a constant 24V instead of the 16.5V-20V range of the battery. The third purpose is to allow for switching between a wall wart power supply or the power tool battery to increase the usability of this device.

• Fusion 360/Eagle Project File
• Gerber Zip

Step 2: PCB Assembly

Assuming you did not opt for assembly of the board, make sure both the board and stencil are clean of any and all contaminants. When applying solder paste to my boards, I put the boards on a piece of magnetic material (a printer with a magnetic bed will work) and use strips of magnet around the board to hold the stencil down. Before applying the solder paste make sure it is well mixed and add IPA or flux to it if necessary. I generally apply a generous pile (a teaspoon or so) and spread it onto the board with a putty knife, scraping off excess as necessary. Be careful lifting the stencil off the board as any lateral movement can smudge the paste.

When assembling this board, I recommend having the board file open on your computer as a reference for what value goes in what location. In addition, I recommend starting with the larger IC's and populating the smaller resisters and capacitors around those parts after. Leave the biggest parts (through hole, electrolytic caps, connectors, and inductor) for last. I recommend working in areas at a time and using the hot air station to reflow each area before you move onto the next one.

Step 3: 3D Print Enclosure and Install Heat Inserts

Print out all of the parts in the provided STL files. I have also provided the Fusion360 CAD project for anyone that wants to make modifications or changes to my design. Most of the parts will require some support material, but I have designed it that the support material should not be too annoying to deal with. The top, base, and contact parts will require the use of heat set inserts. When installing the heat inserts (locations shown in attached images) ensure that they go in a straight as possible.

The top will require 5 inserts, the bottom will require 2 inserts, and the shoulder brace will require 2 inserts.

Important note: I did design this part with about 0.2mm of tolerance, but you might need to adjust the horizontal expansion if the parts don't fit together quite right.

Step 4: Crimp and Install Cables/connectors

There are three (technically 3.5-4 I guess) sets of cables that need to be created. These sets of cables are the cables that go from the battery terminals to the BMS/regulator board, from the BMS/regulator board to the soldering iron control board, from the soldering iron control board to the handle connector, and the final one from the control board to the ESD banana jack. Depending on which version of the soldering iron control board you order, it might come with cables that have the JST-2.54 ends pre-crimped. These should be fine to use, but I definitely recommend making sure the crimp is done properly and makes a solid connection.

For the battery to BMS/regulator board connector, there will be two wires, the positive terminal and the negative terminal. One end of each cable will be terminated with the largest male spade connector in the linked kit and the other end will be terminated with the PH-T crimps linked in the materials section.

The cable that connects the BMS/regulator board to the soldering iron controller board will also be a two wire cable, also with a positive and negative cable. One end will consist of PH-T crimps as linked above in the materials section and the other end will consist of JST-2.54 crimps. For the JST side, the T12-952 uses a 3 pin connector with the middle pin being earth/ground. This middle pin is what we will use to connect to the grounding banana jack. One end of this cable for the banana jack will consist of a JST-2.54 crimp and the other end will consist of one of the medium female spade crimps from the kit I linked up above. The positive wire goes to port A pin 2 of the BMS/regulator board and the negative wire goes to port A pin 1.

The last cable is for connecting the DIN-8 connector for the soldering iron handle to the soldering iron controller board. This cable will consist of 4 wires, with one for earth/ground, one for the heater element, one for the thermistor, and one for the ball/vibration switch (which currently I am not using due to possibly looking to integrate something into the stand instead of modifying my Hakko handles). One end will consist of JST-2.54 crimps and the other end will be soldered directly to the DIN-8 connector as shown in the labelled pin out diagram. Following the numbering pattern in the datasheet pin 2 goes to earth/ground, pin 1 goes to O- of the soldering iron control board, and pin 3 goes to O+ of the soldering iron control board.

Step 5: Install PCB's\Cables in Enclosure

To install the cables that go to the battery, the spade terminals need to be inserted into the contact piece as shown in the picture above. I then filled the recess with hot glue to ensure they were held well in place and wouldn't shift. After this is done, the contact piece can be inserted into the bottom enclosure piece and screwed into place with one of the countersunk M3 screws.

The BMS/regulator board can then be installed on top of the base and screwed into place with the M3 button head or cap screw.

For the top section of the enclosure insert the soldering iron control board into its recess as shown in the picture above. You might have to put a little force on it to get the encoder fully through its hole. After it is in place tighten down the nut for the encoder using your fingers (or a socket wrench/pliers if you want to get it tighter).

You will then need to put the DIN-8 connector into shoulder brace piece as shown and then screw that into place with its corresponding cutout on the front. You can also insert the banana jack into the side of the top now and tighten down the nut for that by hand (or with a wrench if you want it to be a little more snug).

Step 6: Cable Management/cleanup

This step is mostly unnecessary, but if you want you can use hot glue to ensure the soldering iron control board is nice and snug in the top shell. I would also consider using either electrical tape or zips ties to hold the bunches of cables together, so they aren't as messy. Once everything is all good and plugged in, you can close up the shell and install the three countersunk M3 screws in the bottom to hold the bottom and top snuggly together.

After closing the enclosure, you can screw the tip holder and handle holder to the side of the case. I designed it for the tip holder to go on the left side and the handle to go on the right due to the placement of the on/off switch.

Step 7: Operating Instructions

• When inserting a fresh battery to reset the BMS the button on the side must be pushed. This is a limitation of the supervisor I used, that I was not able to come up with a more convenient workaround for
• If a DC barrel jack is to be used instead of a battery, the relay will automatically switch over and cut all contact with the battery
• The ON/OFF switch is connected directly to both the DC jack and the battery to be able to directly cut power at the source

Step 8: Possible Next Steps

While I am extremely happy about the outcome of this design, there are a few possible changes I would consider if I were to make another revision of this.

• Custom control board with open source firmware
• Possibly combine BMS/regulator and control board into one board
• Add switch/sensor to the handle holder to tell if the handle is being used or not

I am also considering adding a few more tools to this series of Dewalt battery tools. I am currently looking into making a hot glue gun and a hot air rework station that runs off of the Dewalt 18V/20V batteries

If you have any suggestions for future power tool designs based around the Dewalt ecosystem, please leave me a comment.