9. Connector Decision Examples

The useful part here is the reasoning, not the answer in the last column. Jump to the closest scenario, then look at which families made the list, which specs actually decided it, and what got rejected before it became an expensive mistake.

For a step-by-step walkthrough of the most common scenarios, see the Decision Paths. Family-level depth behind these choices lives in the deep dives: MIL-DTL-38999, MIL-DTL-26482, M12/M8, DEUTSCH, and Molex Micro-Fit 3.0.

Quick map

Scenario	Families to consider
Sensor cable on a robot	M12 A-coded; M8 for small sensors
Motor power	M12 L/T-coded, industrial rectangular, high-current circular, Anderson SB, 38999 (sized/derated)
CAN bus	M12 A-coded (CAN pinout); 38999 in defense
Ethernet in a rugged enclosure	M12 D-coded (10/100), X-coded (GbE/10G); rugged RJ45 only if protected
External service port	Sealed service M12, Micro-D, 38999 maintenance; USB only behind a cover
Internal PCB harness	Molex Micro-Fit (power), PicoBlade/JST-GH (signal), TE, Harwin
Sealed enclosure feedthrough	38999 jam-nut/flange, sealed M12 panel, hermetic/potted penetrator
High-vibration military payload	MIL-DTL-38999 Series III; Micro-D internal
Removable control box	Industrial rectangular / Han-Modular; 38999 size-23 hybrid; M12 bundle
Test / debug port	Keyed shrouded header, Tag-Connect, Micro-D, D-sub; 38999 if external

Sensor cable on a robot

• Families to consider: M12 A-coded; M8 for small sensors.
• Specs that matter most: IP, vibration, cable flex, pinout, current, replaceability.
• Reject / why: JST/XH externally — no sealing/locking.
• Mistakes to avoid: Ignoring bend radius and strain relief.

See also: Industrial sensor decision path.

Motor power

• Families to consider: M12 L/T-coded, industrial rectangular, high-current circular, Anderson SB, 38999 size 12 (only where derating supports the load) or size 8/larger / dedicated power contacts (HCP/RADSOK).
• Specs that matter most: Contact current rating, wire gauge, loaded-contact count, ambient temperature and derating curve, heat rise, duty cycle, touch safety.
• Reject / why: XT60/90 hobby — not IP/professional; small signal circular paralleled.
• Mistakes to avoid: Paralleling contacts unless the manufacturer/application explicitly supports it and the design is reviewed; undersizing the contact.

See also: High-current DC power decision path; for a servo axis, where the motor's receptacles set the series and feedback rides alongside, the Motor + feedback cable path.

CAN bus

• Families to consider: M12 A-coded (CAN pinout); 38999 in defense.
• Specs that matter most: Shielding, termination, pinout consistency, daisy-chain.
• Reject / why: USB connector — wrong ecosystem, not rugged.
• Mistakes to avoid: No termination plan; pigtail shields; can't T-tap a single drop.

See also: the Connector Selection Packet — a fully worked CAN + power module interface.

Ethernet in a rugged enclosure

• Families to consider: M12 D-coded (10/100), X-coded (GbE/10G); rugged RJ45 only if protected.
• Specs that matter most: Speed, shielding, IP, cable category, serviceability.
• Reject / why: Consumer RJ45 outdoors; D-coded for GbE.
• Mistakes to avoid: Unshielded cable on X-coded; no shell bond.

See also: Rugged Ethernet decision path.

External service port

• Families to consider: Sealed service M12, Micro-D, 38999 maintenance; USB only behind a cover.
• Specs that matter most: Access level, dust cap, mating cycles, ESD, sealing.
• Reject / why: Bare USB-C on an exposed panel.
• Mistakes to avoid: Same keying as the operational port; no dust cap.

See also: Debug / service port decision path.

Internal PCB harness

• Families to consider: Molex Micro-Fit (power), PicoBlade/JST-GH (signal), TE, Harwin.
• Specs that matter most: Current, latch, TPA, wire gauge, vibration, tooling.
• Reject / why: Loose 0.1″ headers; bare solder joints.
• Mistakes to avoid: Hobby connector beyond its rating; no keying in volume production.

See also: Internal PCB harnessing decision path.

Sealed enclosure feedthrough

• Families to consider: 38999 jam-nut/flange, sealed M12 panel, hermetic/potted penetrator if pressure.
• Specs that matter most: IP/depth, gasket, panel thickness, torque, internal termination.
• Reject / why: Standard IP67 for 3 atm; RTV as "sealing".
• Mistakes to avoid: Confusing IP67 with IP68; no unmated cap; undersized wire seal.

See also: Sealed enclosure feedthrough decision path.

High-vibration military payload

• Families to consider: MIL-DTL-38999 Series III; Micro-D internal.
• Specs that matter most: Vibration, anti-decoupling, shielding, contact retention, service class.
• Reject / why: Reject consumer circular/RJ45; avoid bayonet coupling unless the specific connector is qualified for the vibration profile and has an appropriate anti-decoupling/retention strategy.
• Mistakes to avoid: Untorqued/under-engaged coupling; wrong crimp tool; no rear seal.

See also: Defense / rugged external I/O decision path.

Removable control box

• Families to consider: Industrial rectangular / Han-Modular; 38999 size-23 hybrid; M12 bundle.
• Specs that matter most: Mixed power/signal, serviceability, panel space, latch robustness.
• Reject / why: Many unlabeled individual pigtails.
• Mistakes to avoid: No keying; no ground-first sequencing where needed; connectors too close for hands.

See also: Removable machine module decision path.

Test / debug port

• Families to consider: Keyed shrouded header, Tag-Connect, Micro-D, D-sub; 38999 if external.
• Specs that matter most: Mating cycles, ESD, pin protection, access level.
• Reject / why: Tiny hobby connector for repeated lab use.
• Mistakes to avoid: Letting a debug port become an undocumented production interface.

See also: Debug / service port decision path.

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