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24 VDC POWER SUPPLY WIRE ASSEMBLY INSTRUCTIONS
Assembly Components
ENCLOSURE WIRING SUB-ASSEMBLY COMPONENTS
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1 × one-piece open-face enclosure (E-01)
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American flag circuit board (KIT-01)
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1 × panel-mount 2.1mm DC barrel jack
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1 × prewired inline 5×20 mm fuse holder
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1 × 1 A 125 V fuse (5×20 mm)
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Black 18 AWG stranded wire
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1 × Wire Clamp
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Zip Tie's
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Optional - Heat‑shrink 3/16 tubing (for insulation)
Assembly Equipment/Supplies
EQUIPMENT/SUPPLIES
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Safety glasses
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Soldering iron
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Soldering iron stand
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Flux-core solder
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Solder wick
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Wire cutter tool
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Wire stripper tool
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Small needle nose pliers
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Optional - Helping hands tool
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Optional - Small Vise
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Optional - Tin foil
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Optional - Hot air gun, if using heat shrink tubing
Common Barrel Jack Connector Dimensional Specifications
What "2.1 mm and 5.5 mm" Refers To
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The 2.1 mm dimension specifies the inner diameter (ID) of the barrel jack’s center pin receptacle.
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This center contact usually carries the positive voltage (V+) in most standard DC barrel power connectors (center-positive is the most common convention).
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A female barrel jack labeled as 2.1 × 5.5 mm (or more commonly 5.5 × 2.1 mm) typically has an outer sleeve diameter of about 5.6 mm. This tiny oversize (0.1 mm or so) is intentional: it allows the mating male plug (with a nominal 5.5 mm outer diameter) to insert smoothly, maintain good spring tension, and ensure reliable electrical contact without being too loose or too tight.
Typical Barrel Jack Dimensions
Barrel connectors are almost always specified by two key measurements:
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Inner diameter (ID) → the diameter of the plug’s center pin (e.g., 2.1 mm).
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Outer diameter (OD) → the overall width of the barrel sleeve (most often 5.6 mm nominal).
So, when you see a female connector described as 5.5 × 2.1 mm, it means:
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≈ 5.6 mm OD → the outer sleeve diameter (with slight oversizing for fit).
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2.1 mm ID → the inner pin receptacle diameter.
Mock‑up Illustration of Barrel Jack Connector
—Transparent View
Typical Panel Mount 2.1 mm Barrel Jack
Construction & Components
(Construction May Vary Depending on Manufacturer)
STEP BY STEP INSTRUCTIONS
Soldering the +24 VDC Red Fuse Wire & Black Ground Wire
to the Panel‑Mount 2.1 mm Barrel Jack
Tinning the Barrel Jack Connector Electrical Contacts
Safety Warning -
Soldering the Barrel Jack
Do not place the barrel jack connector directly on a tabletop and attempt to tin the contacts or solder wires. The connector must always be held securely in a small vise or holder designed for electronics work.
If you do not have a small vise or suitable holder for the barrel jack connector, you can simply install the barrel jack into the enclosure’s panel‑mount hole and use the enclosure to hold it steady while soldering, as outlined below.
Never ask another person to hold the connector for you while soldering. The barrel jack and wires will become extremely hot during the process and can cause serious burns.
Secure the barrel jack connector in a small vise or holding device so that its electrical contacts are fully exposed and easy to access. If using a vise, be careful not to over‑tighten, as this may deform the connector.
If you do not have a suitable holder, follow the alternative steps outlined below.
Securing the Barrel Jack Connector for Soldering Using the Enclosure
Insert the panel‑mount 2.1 mm DC barrel jack into the opening in the enclosure. Place the lock washer and nut onto the jack and thread them into position. Tighten the nut just enough to hold the barrel jack securely, but not so tight that it cannot be rotated. Leave it slightly adjustable so you can later rotate the jack to the orientation that makes wire installation and soldering easiest.
Enclosure
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DC Barrel Jack Mounting Hole
Identify Terminals on the Barrel Jack
(see Illustration below)
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Center contact (center pin): Inner contact of the jack, the positive (+) connection. On panel‑mount jacks this is usually a solder cup terminal.
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Outer contact (barrel/sleeve): The outer contact, the negative (–) connection. This is usually a solder lug/terminal.
Outer contact: The outer contact,
the negative (–) connection.
Usually a solder lug/terminal with slot for black ground wire.
Center contact (center pin):
Positive (+) connection.
With a solder cup terminal for red +24 VDC wire.
Tinning the Barrel Jack Connector Electrical Contacts
Soldering Steps
1. Safety First
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Put on your safety glasses.
2. Secure the Barrel Jack
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Use a helping hands tool or vise to securely hold the barrel jack — to prevent movement during tinning.
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If using a vise, be careful not to over‑tighten, as this may deform the connector.
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Orient the barrel so that it is easy to access the terminals.
Preparing the Soldering Iron
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Wet your soldering sponge so that it feels completely wet to the touch but is not soaking wet, it should only release only a few drops water (if any) when squeezed firmly.
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Turn-on the Soldering Iron and give it 2-3 minutes to heat to working temperature (around 320–350°C for leaded solder, 350–380°C for lead-free).
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Clean and tin the tip of your soldering iron.
2. Tin the center solder cup (positive):
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Heat the solder cup with the iron (See Illustration 1 below).
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Feed solder per Illustration 1 until the cup is filled with molten solder and the terminal tail is coated with a thin, even layer.
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Remove heat and let it solidify.
Illustration 1
Allow 1 second for the contact pin to reach soldering temperature and then feed a small amount of solder directly into the solder cup.
Feed Wire Solder Here
Heat the center pin as shown by placing your soldering tip lenght-wise lying flat on the terminal tail.
3. Tin the outer lug (negative):
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Heat the lug with your soldering iron (See Illustration 2 below).
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Feed solder to the lug until it completely coated with solder, but not so much as to close the hole for the wire with solder.
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Remove heat and let it solidify.
Illustration 2
Allow 1 second for the ground lug to reach soldering temperature and then feed a small amount of solder where the tip and the lug meet.
Feed Wire Solder Here
Place your soldering tip flat lengthwise against the ground lug for best heat transfer
After Tinning the Barrel Jack
The solder-cup is completely full, and the terminal tail is completely wetted
Possible minor wetting issue—not serious enough to require rework. It will most likely be resolved when the ground wire is attached
Ground lug is fully wetted
Minor burrs on the inside edge are normal, a result of the lug fabrication process, specifically when the slot was punched out of the metal
4x Magnification Using a Smart Phone Camera
Soldering the Black Wire to the Barrel Jack Connecter Solder Lug
1. Cut the Black Wire to Length
Using wire cutters, cut the 18‑gauge black wire so that it is equal in length to the red wire, as shown below.
2. Prepare the Black Wire
Using an 18 AWG wire stripper, strip about 1/8 inch (≈3 mm) of insulation from one end of the black wire — just enough bare conductor to form a secure hook and create a reliable solder joint in the ground lug/terminal slot.
Pinch the exposed strands and twist them clockwise (looking from the stripped end) into a tight, rope-like bundle. The end should appear smooth, compact, and pointed, with no frayed or stray strands protruding.
TINNING WIRES WITH YOUR SOLDER IRON
Factually Professional Electronics Manufacturers -
Do Not Use Soldering Irons to Tin Wires
Tinning Wires with a Soldering Iron
Although a soldering iron can be used to tin wires with acceptable results, it is generally not considered the best method. There are several reasons for this, he primary two being quality consistency and production throughput.
In professional electronics manufacturing, solder pots are the standard tool for tinning wires, since dip‑tinning provides the most reliable and efficient results. A soldering iron is typically reserved for special circumstances such as prototyping, some types of installations, field work, rework, and repairs
That said, for hobbyists working at home—a soldering iron is the ideal tool for tinning wires.
I’m going to show you how to do it safely and achieve good soldering results.
Proper Set-up for Tinning Wires at Home
When tinning wires at home, it is important to use the correct methods and tools to ensure safety and achieve the best results. Never attempt to tin a wire by placing it directly on a tabletop, as this can damage the surface and will also lead to poor soldering quality.
Securing Wires for Tinning at Home
When tinning wires at home, it’s important to secure the wire so both hands are free—one to hold the soldering iron and the other to feed solder.
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Do not ask someone to hold the wire; it will become very hot and could cause injury.
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The proper method is to use a helping hands device, which holds the wire firmly in place while you work. These are widely available and designed specifically for this purpose.
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If you don’t want to purchase a device just to tin a few wires, you can improvise:
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Crumple a sheet of aluminum foil into a small ball.
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Tape the wire to the top of the ball to keep it steady during tinning.
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Place another sheet of aluminum foil under the ball to protect the work surface from any solder drips.
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If you are using a helping hands device, also place a protective sheet of aluminum under it to prevent molten solder from damaging the table.
Examples of Helping Hands Devices Methods
You Can Use to Hold Wires While Tinning at Home
Examples of Helping Hands Products You Can Buy
DIY Aluminum Foil Ball with Wire Tapped to Top for Holding Wire Secure
Tinning the Exposed End of the Black Wire:
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Secure the black wire to be tinned.
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Clean your soldering iron tip and ensure it is well-tinned.
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Heat the twisted strands starting from the tip, working toward the insulation edge.
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Feed flux-core solder to the wire (not directly to the iron tip) so it flows evenly into the bundle.
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Aim to tin most of the exposed length (about 80–90% from the tip, leaving a tiny untinned section near the insulation if possible). This provides stiffness for easy hook forming and insertion while preventing excessive brittleness or solder wicking under the insulation.
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Use a minimal amount of solder only enough solder to fully wet and bond the strands without creating large blobs or excessive buildup.
Goal: A smooth, shiny, uniformly tinned bundle that holds its shape during bending but remains flexible enough for clean hook closure. Light tinning is the best practice for hook-style solder lugs in most electronics work — it reduces fraying during manipulation, without being too brittle when bending, and promotes fast, reliable solder flow during final attachment.
Removing excess solder blobs, if necessary
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Clean your soldering iron tip and ensure it is well-tinned.
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Reapply the iron to the wire and gently brush the surface of the wire with the iron tip, adding a very small amount of fresh solder during this process. The new solder helps clean oxides from the iron tip and encourages the excess blob to adhere to the iron.
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Repeat the clean‑and‑rub process, each time adding only a trace amount of solder, until the excess is removed and the wire surface is smooth.
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Clean the tip of your soldering iron.
3. Form the Hook
(see illustration below)
Using needle-nose pliers, bend the tinned end of the wire into a hook or “J” shape (ideally approaching a 180°–270° to wrap around the lug geometry).
Size the hook to fit snugly through the terminal slot/hole, ensuring it can be closed securely around the lug for strong mechanical retention before soldering.
Illustration of tinned wire bent into a small J-hook
4. Insert Wire Hook into the Solder Lug/Terminal Slot
(see illustration below)
Insert the hook through the lug slot (or hole) so the wire is mechanically captured and cannot pull free even without solder.
Use needle-nose pliers to gently squeeze/cinch the hook closed, clamping it firmly onto the lug body. This creates initial mechanical connection.
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Ensure all strands are captured inside the slot; no stray wires should protrude.
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Position the insulation edge as close as possible to the lug (gap ≤ 1 wire diameter, ≈0.5–1 mm per IPC guidelines) without allowing insulation to enter the joint area or melt during soldering.
Shows the hook on the end of the wire inserted through the lug/terminal slot and squeezed closed
Approximately 1 wire thickness
gap between the solder joint
and the wires insulation
5. Soldering
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Heat the lug/terminal and inserted wire hook together with the soldering iron (apply heat to both for good thermal transfer).
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Feed solder to the joint (not the iron tip) so it flows and wicks into the strands and around the lug.
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Use just enough solder to form a smooth, concave, shiny fillet that fully wets both the wire and lug surfaces — avoid excess blobs, bridges, or dull/granular appearance.
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Remove heat once flow is complete (typically 2–5 seconds depending on iron power and mass).
6. Cooling & Inspection
Allow the joint to cool naturally (do not blow on it, quench, or move it prematurely — this can cause fractures or dull joints).
Inspect visually:
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Solder should be smooth, bright/shiny (not dull or grainy), with full wetting (no dewetting or voids).
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Concave fillet around the hook and lug.
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No stray strands, insulation in the joint, cold joints, cracks, or excessive solder obscuring the connection.
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Mechanical security: Gently tug to confirm the hook holds firmly.
(Optional- Heat-Shrink Tubing)
If using heat-shrink for strain relief or insulation:
Important Safety Warning: Do not attempt to heat‑shrink wires while the barrel jack is installed in the plastic enclosure. The enclosure material SLA 9600 cannot withstand the high temperatures required for heat‑shrink tubing and may warp or melt.
SLA 9600 resin enclosure has a heat deflection temperature of about 59 °C, which means it will begin to soften if exposed to temperatures above that. Since heat‑shrink tubing typically requires 90–200 °C, you do need to be concerned about accidentally warping or damaging the enclosure if you apply heat directly.
Key Facts About SLA 9600 Resin
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Technology: SLA (stereolithography) photosensitive resin
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Heat Deflection Temperature (@0.45 MPa): ~59 °C
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Strengths: Good surface finish, toughness, hardness
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Weaknesses: Not suitable for high‑temperature environments, sunlight, or UV exposure
Always remove the barrel jack from the enclosure before performing any heat‑shrink operation. Once the tubing has been properly shrunk and cooled, you can reinstall the barrel jack into the enclosure.
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Slide 1/2-inch piece of tubing onto the wire before soldering (critical if the other end is already terminated, e.g., on the red/fused wire).
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Position it away from the joint during soldering, then using a heat gun shrink after inspection of the solder joint.
Soldering the Red Wire to the barrel Jack Connecter Solder Lug
1. Optional - Heat‑Shrink
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To cover the barrel jack connections, cut heat‑shrink tubing 1/2 inch which will be long enough to fully cover the exposed solder joints and overlap onto the wire insulation. Slide the tubing onto the wires before soldering the red wire to the barrel jack. This step is especially important for the red fuse wire, since its other end is already attached to the fuse contact, which will make doing so after soldering impossible.
2. Red Inline Fuse Wire (Positive)
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Important: If the inline fuse wire comes already stripped and tinned from the manufacturer, you can skip the stripping and tinning steps for the red fuse wires.
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Note: The inline fuse assembly has two red wires; either one may be connected to the power source side, as they are electrically identical.
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Strip about 1/8 inch (≈3 mm) of insulation, keeping the exposed length short.
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Pinch the exposed strands and twist them clockwise into a tight, rope‑like bundle. The end should look smooth and pointed, with no frayed or stray strands.
3. Tin the Wire
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Heat the twisted strands with the soldering iron.
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Apply solder to the wire (not directly to the iron) so it flows evenly into the strands.
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Coat lightly — just enough for a thin, shiny layer that binds the strands together.
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Remove heat and let the wire cool naturally.
4. Appearance After Soldering
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The wire tip should look smooth, shiny, and solid.
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The strands should be fully bonded together with no gaps or loose ends.
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The solder should cover the exposed copper evenly, without blobs or dull, grainy spots.
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The finished tip should resemble a neatly sealed, metallic point ready to be soldered into the barrel jack connector.
Removing excess solder blobs, if necessary
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Clean the tip of your soldering iron.
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Reapply the iron to the wire and gently brush the surface of the wire with the iron tip, adding a very small amount of fresh solder during this process. The new solder helps clean oxides from the iron tip and encourages the excess blob to adhere to the iron.
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Repeat the clean‑and‑rub process, each time adding only a trace amount of solder, until the excess is removed and the wire surface is smooth.
5. Attach the red wire to the center cup:
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Reheat the filled cup until solder is molten.
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Insert the stripped red wire into the molten solder.
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Hold steady until the joint cools and solidifies.
7. Optional Heat‑Shrink
Procedure for Soldering Power Supply Input Wires to the Circuit Board
Step: Preparing Power Input Pads (See Illustration below)
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Locate the solder pads marked +24 VDC and Ground on the circuit board.
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Tin the pads:
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Heat each pad with a clean, tinned soldering iron tip.
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Apply solder to the pad until the surface is fully wetted.
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Ensure a small, smooth solder bump remains on each pad.
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