Wire-to-Board vs Wire-to-Wire Connector: Selection Guide

Choosing between wire-to-board and wire-to-wire connectors is one of the first decisions in any electronics wiring design. The wrong choice creates assembly challenges, increases cost, or reduces reliability. Wire-to-board connectors terminate at a PCB, while wire-to-wire connectors join two cable harnesses together. Each family has dozens of subfamilies with different pitches, current ratings, and locking mechanisms. This guide gives Indian makers and product designers a clear framework for selecting the right connector for any application.

Table of Contents

• Wire-to-Board vs Wire-to-Wire: Core Differences
• JST Connector Family Guide
• Molex Connector Family
• Pitch Selection: 1.25mm to 5.08mm
• Current Ratings and Wire Gauge Matching
• Locking Mechanisms
• India Sourcing Guide
• Frequently Asked Questions

Wire-to-Board vs Wire-to-Wire: Core Differences

The fundamental distinction determines where the connection terminates:

• Wire-to-Board (WTB): One side is a PCB-mounted receptacle (through-hole or SMD); the other side is a wire-terminated plug. Used to connect external wiring to circuit boards: power harnesses, sensor cables, motor connections.
• Wire-to-Wire (WTW): Both sides are wire-terminated. Used to connect two cable assemblies or harnesses: extending cables, modular wiring harnesses, removable sub-assemblies.

Some connector families support both configurations — the same crimp terminal and housing can mate with either a wire-terminated plug or a PCB-mounted receptacle, providing design flexibility.

JST Connector Family Guide

JST (Japan Solderless Terminal) makes the most widely used low-current connector families in the maker and hobby electronics world. Each family has a different pitch, current rating, and mechanical profile:

JST-PH (2.0mm pitch)

• Current rating: 2A per contact
• Wire gauge: 26–32 AWG (0.05–0.13 mm²)
• Pin count: 2–16 pins
• Use case: LiPo battery packs (most common 2-pin LiPo connector), balance leads, small sensors
• India price: ₹8–20 per pair (plug + receptacle)

JST-XH (2.54mm pitch)

• Current rating: 3A per contact
• Wire gauge: 22–30 AWG (0.08–0.33 mm²)
• Pin count: 2–15 pins
• Use case: LiPo balance connectors (2S, 3S, 4S, 6S), servo extension cables, sensor harnesses
• India price: ₹5–15 per pair

JST-SM (2.5mm pitch)

• Current rating: 3A per contact
• Use case: LED strip connectors (3-pin JST SM for addressable LEDs), outdoor wiring with polarisation
• India price: ₹10–25 per pair

JST-EH (2.5mm pitch, older)

Similar to XH but with a different housing profile. Common on some older equipment and sensors. Sometimes confused with XH — check by measuring the pitch precisely.

Molex Connector Family

Molex connectors are the industry standard for higher-current wire-to-board and wire-to-wire connections in computer, automotive, and industrial applications:

Molex KK (2.54mm pitch)

• Current rating: 3A per pin
• Wire gauge: 22–28 AWG
• Use case: PCB power connections, internal computer wiring (older IDE, floppy connectors), sensor modules

Molex Micro-Fit 3.0 (3.0mm pitch)

• Current rating: 5A per pin
• Wire gauge: 20–28 AWG
• Use case: Power distribution in equipment (replaces older Molex connectors in modern designs), motor driver to motor connections

Molex Mini-Fit Jr (4.2mm pitch)

• Current rating: 9A per pin (13A for power pins)
• Use case: ATX power supply connectors (the 24-pin and 8-pin connectors in PC power supplies), high-current industrial applications

Pitch Selection: 1.25mm to 5.08mm

Connector pitch (the centre-to-centre distance between adjacent pins) determines both the physical size and the current-carrying capacity. Choose pitch based on board space and current requirements:

Current Ratings and Wire Gauge Matching

Current rating is determined by the smaller of: (1) the contact’s rated current, or (2) the wire gauge’s current capacity. Never mismatch — a high-current connector with undersized wire will overheat the wire. Always match:

Wire gauge to current capacity guide (single wire, 60°C ambient):
30 AWG (0.05mm²) → 0.86A max
28 AWG (0.08mm²) → 1.2A max
26 AWG (0.13mm²) → 2.2A max
24 AWG (0.20mm²) → 3.5A max
22 AWG (0.33mm²) → 5.5A max
20 AWG (0.52mm²) → 8.0A max
18 AWG (0.82mm²) → 12A max
16 AWG (1.31mm²) → 18A max

Rule: Always derate 20-30% for bundled wires (in harness,
wires run hotter due to mutual heating).

Locking Mechanisms

Connector retention is critical for reliability, especially in vibration environments (motors, vehicles, drones):

• Friction lock (no mechanism): DuPont/Dupont headers, JST-XH. Suitable for benchtop and low-vibration. Can pull apart accidentally.
• Latch lock: Most Molex and JST connectors have a positive latching tab that clicks into place. Requires deliberate press-and-pull to disconnect. Suitable for most applications.
• Secondary lock: A separate clip that locks over the latch. Used in automotive wiring (requires tool to remove). Maximum retention.
• Screw lock: Terminal blocks and some panel connectors use screws for permanent connections. Used in fixed installations, control panels.

India Sourcing Guide

Frequently Asked Questions

What is the most commonly available connector in India for maker projects?

The 2.54mm pitch DuPont-style headers and JST-XH connectors are the most widely available. DuPont headers are the classic prototyping connector (used in Arduino jumper wires, breadboard connections) and can be bought at any electronics shop in India for ₹2–5 per piece. For locked connections, JST-XH at 2.54mm pitch offers a latching mechanism and is available from Robu.in and similar suppliers.

Can I use DuPont connectors for motor wiring?

DuPont connectors (the standard 2.54mm black plastic headers) are rated for 3A per pin — acceptable for small motors (brushed DC motors up to 5W). For larger motors (BLDC, stepper), use higher-rated connectors: JST-XH (3A), Molex Micro-Fit (5A), or XT30/XT60 for high-current RC/drone motors.

How do I identify an unknown connector type?

Measure: (1) the pitch in mm using callipers or a ruler against a known grid, (2) the number of pins, (3) the housing width and height. Cross-reference with connector reference guides (Samtec, JST, or Molex online catalogues have dimensional drawings). Alternatively, post a photo to electronics forums (r/electronics, Hackaday, Indian electronics groups on Telegram) for community identification.

What connector should I use for battery packs in India?

For LiPo batteries in drones and RC: XT60 (up to 60A) or XT30 (up to 30A) — widely available at RC hobby shops in India. For 18650 cell packs in IoT/robotics: JST-PH (2A) or JST-XH (3A) for small packs; Deans/T-connector or XT60 for larger packs. For 12V lead-acid: ring terminals on the battery posts, then JST or Molex Micro-Fit for distribution to the PCB.

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