DIY Power‑Converter Build Using Modular Rectangular Connectors – Full Parts List & Wiring Tips

If you’ve ever tried to solder a power‑converter board only to find the wires looking like a tangled mess, you know why a clean connector system matters. A good set of modular rectangular terminals can turn a chaotic prototype into a tidy, service‑friendly project – and you can do it without spending a fortune.

Why modular rectangular connectors matter

Rectangular terminals are the unsung heroes of power electronics. They give you a solid mechanical grip, low contact resistance, and the ability to pull a board apart for testing or repair. Unlike tiny screw‑type terminals, the rectangular style spreads the force over a larger area, which means less wear on the wire and a more reliable connection over time.

I first discovered this when I was building a 12 V to 5 V buck converter for a home‑brew LED driver. My first attempt used standard barrel plugs and a handful of crimped spade lugs. After a few weeks of intermittent flickering, I swapped to a set of 4 mm pitch rectangular terminals. The difference was night and day – the voltage stayed steady and the whole assembly looked like something a professional would ship.

Parts you’ll need

Below is the complete list I used for a 12 V to 5 V, 3 A converter. All parts are easy to find on major electronics sites or at a local hobby store.

Connector system

• 4 mm pitch modular rectangular terminal blocks, 2‑row, 8‑position (part #TB‑8‑4MM)
• Matching crimp pins, 22‑AWG (part #CP‑22‑4MM)
• Screw‑type terminal block for the input side (part #TB‑4‑IN)

Power stage

• LM2596‑based buck regulator module (rated 3 A, 4.5‑40 V input)
• Input filter capacitor: 470 µF, 25 V electrolytic
• Output filter capacitor: 220 µF, 10 V electrolytic
• 0.1 µF ceramic decoupling capacitor (x2)

Passive components

• 10 µH inductor, 3 A rating
• Schottky diode, 3 A, 40 V (e.g., SS34)
• 1 kΩ resistor (for the enable pin, optional)

Miscellaneous

• 22‑AWG silicone insulated wire, assorted colors
• Heat‑shrink tubing (2 mm and 3 mm)
• Small piece of perfboard or a 2 × 4 cm PCB for mounting the terminal block
• Soldering iron, lead‑free solder, wire strippers, crimping tool

If you prefer a tighter layout, you can replace the perfboard with a 2‑layer PCB that has the terminal block footprints already placed. The parts list stays the same; only the mounting method changes.

Step‑by‑step wiring guide

1. Prepare the terminal block

Strip about 5 mm of insulation from each wire that will go into the block. Use the crimping tool to attach the 22‑AWG crimp pins – you’ll feel a solid “click” when the pin is fully seated. Insert each pin into the appropriate slot on the terminal block, making sure the metal part is fully inside the cavity.

2. Wire the input side

• Connect the 12 V source positive to the input screw terminal (TB‑4‑IN). Add the 470 µF electrolytic capacitor across the input pins – positive to the source, negative to the ground.
• Run a short piece of 22‑AWG wire from the same source to the “VIN” pin on the LM2596 module. Use a heat‑shrink sleeve to protect the joint.

3. Connect the regulator

• The LM2596 module has three main pins: VIN, VOUT, and GND. Tie the GND pin to the ground rail on the terminal block.
• Attach the 10 µH inductor between the “SW” pin (switch output) and the VOUT pin. This inductor is the heart of the buck action.
• Solder the Schottky diode across the inductor, cathode to VOUT, anode to the switch node. This diode catches any reverse current and improves efficiency.

4. Output filtering

• Place the 220 µF electrolytic capacitor across the VOUT and ground pins. Add the two 0.1 µF ceramic caps in parallel – they clean up high‑frequency noise.
• Finally, run a short wire from VOUT to the “+5 V” terminal on the rectangular block. Ground the “‑5 V” terminal to the same rail you used for the input ground.

5. Optional enable control

If you want the converter to be turned on and off by a microcontroller, add a 1 kΩ resistor from the enable pin to ground and drive the pin with a 3.3 V logic level. This step is not required for a simple always‑on design.

6. Secure everything

Mount the terminal block on the perfboard or PCB using the provided mounting holes. Double‑check that no stray wires are touching each other. Slip heat‑shrink over each crimped joint and apply a gentle heat gun – this adds mechanical strength and prevents accidental shorts.

Tips to avoid common mistakes

• Check polarity twice. It’s easy to flip a capacitor or diode, especially when you’re working with a lot of small parts. A reversed electrolytic capacitor will bulge and leak, while a backward diode will cause the regulator to overheat.
• Don’t over‑crimp. Squeezing the pin too hard can crush the wire strands, raising resistance. Aim for a snug fit that holds the wire without flattening it.
• Leave a little slack. When you route wires into the terminal block, give each one a millimeter or two of extra length. This makes it easier to re‑work the board later if you need to change a value.
• Use proper gauge. For a 3 A output, 22‑AWG is fine for short runs, but if you plan to run the output cable a foot or more, step up to 18‑AWG to keep voltage drop low.
• Test in stages. Power the input first and measure the voltage at the regulator’s VIN pin. Then add the inductor and diode, and finally check the VOUT. This way you catch any fault early before you load the converter.

Testing and final thoughts

Once everything is wired, plug the 12 V source into the input terminal. Use a multimeter to verify that the output reads close to 5.0 V under no load. Then connect a small resistive load – a 10 Ω power resistor works well – and watch the voltage hold steady. If you see a dip below 4.9 V, double‑check the inductor orientation and make sure the Schottky diode is not installed backwards.

I’ve been using this exact build to power a Raspberry Pi Zero and a handful of LED strips for months now. The rectangular terminals make swapping out the power cable a breeze, and the whole thing fits inside a 2 × 3 inch project box without crowding.

If you follow the parts list and wiring tips above, you’ll end up with a clean, reliable converter that can be serviced in minutes – not hours. That’s the kind of practical, hands‑on result we aim for at Rectangular Terminals Review.