Connection Mistakes: WAGOs, Crimps, and Strip Lengths

Most 'electrical gremlins' are bad physical connections. They add resistance (voltage drop and heat), back out under vibration, or fail inspection. Here are the specific mistakes and the correct technique for each connector you will actually use.

WAGO lever/spring terminals (on the REV PDH):

• Mistake: tinning or twisting the wire before insertion. Tinned solder cold-flows under the spring and the wire works loose; twisting reduces contact area. Fix: insert bare, straight, untinned copper. WPILib explicitly recommends against tinning to maximize pullout force and minimize resistance.
• Strip length matters. Strip to the length WAGO specifies for the terminal so the full conductor is clamped without leaving bare copper exposed; too short clamps only part of the conductor, too long leaves exposed copper that can short. Only one wire is permitted per WAGO terminal under the FRC rules.

Weidmuller terminals (roboRIO power, VH-109 radio power): these are spring-type connections (like WAGO) that work best with standard stranded wire — WPILib specifies 18 AWG stranded wire inserted directly for the roboRIO power input, and ferrules can be added to stranded wire elsewhere in the system to prevent fraying. Solid-core wire is actually more prone to breaking under vibration. The roboRIO power input and the VH-109 radio's 12V Weidmuller input both land here, and they are mission-critical, so get them right.

Crimped ring/lug terminals (battery, motor leads, main breaker):

• Mistake: a cold crimp done with pliers. Fix: use a proper ratcheting crimper, tug-test every crimp (it should not budge), and for high-current lugs many teams add a dab of solder after crimping. Battery and PD lugs are 6 AWG and carry the full robot current.
• Insulate. Battery terminals, the main breaker, and their connections must be fully insulated at all times (rule R607). Use heat-shrink, not just tape, on exposed battery lugs.

Fuses and breakers:

• Mistake: a fuse or breaker that looks seated but is not. Fix: push hard; a properly seated PD fuse is difficult to remove by hand. A half-seated fuse causes intermittent dropouts that mimic a CAN problem.
• Use only legal breakers in PD slots: Snap-Action MX5 series or VB3-A / AT2-A, 40A rating or lower (R619). ATC/ATO fuses on the low-current channels must be 10A or lower (R620).

SB-50 Anderson connectors: secure them with clips or cable ties so they do not pop apart on impact. The battery connector popping mid-match is an instant robot death.

Maintenance cadence: rotational fasteners (battery lugs, PDP screw terminals) loosen and should be checked every few matches; spring connections (WAGO, Weidmuller) are more stable and typically need checking only once per event. The highest-priority lines to verify are Battery -> Breaker -> PD and PD -> radio.