Connectors and terminals: the number one field failure
A perfect circuit is no use if a connector falls out or burns. Current rating, pitch, locking, and preventing polarity mistakes.
What to look at when choosing
| Item | Reason |
|---|---|
| Current rating (per pin) | Contact-resistance heating melts it |
| Pitch | 2.54 mm, 2.0 mm, 1.25 mm and so on. The smaller, the lower the rating |
| Locking | With vibration, a latch is essential |
| Mating cycles | Life, if it is plugged and unplugged often |
| Polarity key | A shape that cannot be inserted backwards |
Commonly used families
- Pin headers: prototypes, debug ports. Weak against vibration
- JST (XH, PH, GH): small devices, batteries, sensor cables
- Molex Micro-Fit: power at a few amps
- XT60, XT90: high-current batteries for drones and electric scooters
- Automotive (TE, Yazaki): waterproof, vibration-resistant
Design habits
- Use power pins at 50% of their rating or less; if that is not enough, parallel several pins
- When power and signals share a connector, place ground pins next to the signals
- Two connectors of the same shape on one board invite swapped plugs. Make the pin count or colour different.
- Put a TVS and a filter next to the connector to stop incoming noise at the entrance.