Connectors, crimping and wire management

A connector is a planned break in a wire — which makes every connector a place the robot can fail. Robots rarely lose matches because of exotic electrical faults. They lose them because a plug wiggled loose, a crimp pulled out, or a cable got caught in a mechanism.

Team 26336Wiring and routing on a real robot· How we run power and signal so nothing chafes, snags, or pulls out mid-match.

The connectors you will meet

Connector	Where you find it	How it is attached	Holds itself in?
XT30	Batteries, the main power switch, hub power in/out, REV grounding strap	Soldered	Friction only
JST VH (2-pin)	Motor power ports on the hubs; REV motors	Crimped	Yes — a small latch
JST PH (4-pin)	Encoder, digital, analog and I2C ports; REV sensors	Crimped	Keyed, friction-locking
JST PH (3-pin)	RS485 link between hubs	Crimped	Keyed, friction-locking
JST XH (4-pin)	Encoders on goBILDA and AndyMark motors	Crimped	Friction — needs an adapter to the hub's JST PH port
3.5 mm bullet	Power on goBILDA Yellow Jacket motors	Soldered	Friction — needs an adapter to the hub's JST VH port
Anderson Powerpole	AndyMark NeveRest motors; many teams' battery leads	Crimped	Friction, but very reliable when genuine
0.1" servo plug	Servos and servo extensions	Crimped	Usually not — and often not keyed either

A few specifics worth knowing, from REV's documentation:

The JST VH motor connector is rated about 10A continuous with 16 AWG wire and has a latch you press to release.
The JST PH connector is rated about 2A and accepts very thin wire (24–32 AWG). It is keyed so it only goes in one way, but it holds by friction.
Each hub has one male and one female XT30. REV's convention is male for power in, female for power out to the next device.

Unplug by the plug, not the wire

Pulling on the wires is the fastest way to break a connector. REV specifically warns against pulling the battery out by its XT30 wires, which can expose the solder joints, and Game Manual 0 notes that goBILDA's bullet connectors hold tightly enough that teams fatigue the wires by yanking them. Grip the connector body every time.

Pre-made cables first

REV recommends pre-made cables for JST VH and JST PH in most cases, because a crimp made with industrial tooling is more consistent than one made by hand. For a rookie team, that is good advice: buy motor, sensor and servo extension cables in a few lengths and keep spares in the pit kit.

When you do need to make or repair a cable:

Use the right contact for the wire size. JST contacts come in versions for different wire gauges — check the part number against your wire.
Use a crimper made for that connector. A generic pliers-style crimper mangles small JST contacts. REV suggests a ratcheting crimper for JST PH; Game Manual 0 recommends a dedicated Powerpole crimper for Anderson connectors.
Strip only as much as the contact needs. Bare strands sticking out of the back of a contact can short to the next pin.
Do not tin the wire with solder before crimping. Game Manual 0 warns that solder can creep under crimp pressure, leaving a connection that loosens over time.
Pull-test every crimp. Tug the wire firmly. If it moves, cut it off and redo it — it will fail on the field if it fails in your hand.
Insulate. Heat-shrink soldered joints; never leave exposed copper.

Game Manual 0 also warns that off-brand Anderson Powerpole connectors often have reliability problems, so buy genuine Anderson parts.

Wire size and colour rules

The Competition Manual sets minimum wire sizes (rule R609 in 2026–27). Smaller AWG numbers mean thicker wire.

Circuit	Minimum wire size
12V main battery power, most motor power, circuits on an 11–20A fuse	18 AWG
Core Hex and TETRIX MAX motor power, servo/PWM, LEDs, circuits on a ≤10A fuse	22 AWG
Signal-level wiring (encoders, I2C, digital, analog, RS485)	28 AWG

Wires that came attached to a legal device from its manufacturer count as part of that device. You also cannot run two thin wires side by side to make up one thick one. FIRST's best-practices page goes further and strongly encourages going larger than the minimum on power wiring to reduce voltage drop.

The 12V main power and +5V auxiliary wiring must also be colour-coded along its whole length (rule R610): positive red, yellow, white, brown or black-with-stripe; negative black or blue. Motor, servo and signal wires are exempt. These numbers are season-specific — check the current Competition Manual.

Strain relief

FIRST's Robot Wiring Guide gives a simple rule: tie the wire down an inch or two from the connector, and leave a little slack on the connector side. The tie takes the tug from vibration and snagging; the slack means the connector itself never carries load and can still be unplugged for testing.

Do this at both ends of every important cable — at the hub and at the motor or sensor.

Wiring through a moving joint

Any cable that crosses a pivot or rides on a slide will be pulled, bent and pinched thousands of times. Plan it:

Leave a service loop — extra length bundled in a controlled loop — so the wire has room when the mechanism extends.
Anchor the wire on both sides of the joint so it bends in the same place every time.
Protect the bundle with split loom or spiral wrap, or run it in a cable chain on long slides.
Keep it out of pinch points, especially where an arm folds against the chassis.

Routing and labelling

Plan the routes before you build. Leave space for wiring in the design instead of squeezing it in at the end.
Keep runs short, but not so short that a moving part tugs them.
Keep signal wires away from motor wires where you can, and add ferrite chokes to sensor, encoder and USB cables — both help with electrical noise and static.
Keep connectors away from bare metal. FIRST's ESD guidance suggests an air gap of at least 10 mm, or a wrap of electrical tape, between exposed connectors and the frame.
Label both ends of every cable with what it is and which port it goes to: "FL drive — M0 / E0". When a cable comes loose at an event, a label turns a guessing game into a ten-second fix.
Use removable ties where you will need access — Velcro straps around the battery, zip ties along permanent runs.

Check yourself

You are making a new lead from the main power switch to the Control Hub. Which wire meets the 2026–27 manual's minimum and colour rules?

Check yourself

Where should you put the zip tie that strain-relieves a motor's encoder cable at the hub?

Check yourself

The XT30 plug into your Control Hub feels loose and the robot occasionally loses power when it hits something. What does REV identify as the most common cause?

Good wiring prevents most failures. The next lesson handles the rest: static electricity, Wi-Fi disconnects, and a troubleshooting order that finds the fault quickly.

Sources and further reading

REV: Cables and connectors — XT30, JST VH, JST PH
REV: Control Hub Troubleshooting — compressed XT30 pins
Game Manual 0: Connectors and Wires and Wiring Guide
FIRST Robot Wiring Guide — strain relief, moving parts, ESD wiring tips
FIRST Robot Best Practices — wire sizing beyond the minimum
FTC Competition Manual — rules R601, R609 and R610