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9. Connector Decision Examples

The reasoning is what transfers to your own problems. Use the quick map to jump to a scenario, then read the detail — families, the specs that decide it, what to reject and why, and the mistakes to avoid.

For a step-by-step walkthrough of the most common scenarios, see the Decision Paths.

Quick map​

ScenarioFamilies to consider
Sensor cable on a robotM12 A-coded; M8 for small sensors
Motor powerM12 L/T-coded, industrial rectangular, high-current circular, Anderson SB, 38999 (sized/derated)
CAN busM12 A-coded (CAN pinout); 38999 in defense
Ethernet in a rugged enclosureM12 D-coded (10/100), X-coded (GbE/10G); rugged RJ45 if protected
External service portSealed service M12, Micro-D, 38999 maintenance; USB behind a cover
Internal PCB harnessMolex Micro-Fit (power), PicoBlade/JST-GH (signal), TE, Harwin
Sealed enclosure feedthrough38999 jam-nut/flange, sealed M12 panel, hermetic/potted penetrator
High-vibration military payloadMIL-DTL-38999 Series III; Micro-D internal
Removable control boxIndustrial rectangular / Han-Modular; 38999 size-23 hybrid; M12 bundle
Test / debug portKeyed 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.

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.

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.

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.