Your complete guide to electrical systems in FIRST Tech Challenge — from wire management and static mitigation to custom sensors and PCB design.
In FTC, mechanical design gets the spotlight — but electrical systems are what make everything actually work. A perfectly built arm is useless if its motor controller browns out mid-match. A well-tuned intake fails if its encoder wiring is loose. Electrical problems are consistently among the top causes of match failures, and they're almost entirely preventable.
Unlike mechanical failures that are often visible and diagnosable in the pit, electrical faults can be intermittent, subtle, and catastrophic at the worst moments. Static discharge can reset a Control Hub during autonomous. A poorly crimped connector can pass inspection and fail on the field.
The goal of this resource is to give FTC teams — from rookies to veterans — a thorough understanding of every layer of the electrical stack, so you spend less time debugging and more time competing.
Key insight: Electrical issues are rarely random. Every brownout, disconnect, and sensor glitch has a root cause. Understanding the fundamentals makes you a better troubleshooter and a better builder.
This guide is organized into four major areas of FTC electrical. Click any card to explore a section.
Cable protection, routing for static and moving systems, and building custom wires with proper crimping technique.
How ESD can silently destroy a match, mitigation with Staticide and grounding, and the real physics behind it.
Encoders, distance sensors, color sensors, cameras, and localization — types, uses, and our top picks for FTC.
Why teams design custom circuit boards, the tools and workflow, real FTC use cases, and key considerations.
An orientation to the hardware you're working within before diving into each section.
| Component | Role | Common Examples |
|---|---|---|
| Control Hub | Main robot controller, runs OpModes | REV Control Hub |
| Expansion Hub | Additional motor/servo/sensor ports | REV Expansion Hub |
| Battery | 12V main power supply | REV Slim Battery, TETRIX 12V |
| Power Distribution | Fused power routing | REV Power Distribution Block |
| Motors | Actuators with built-in or external encoders | goBILDA, REV, NeveRest |
| Servos | Precise angular positioning | Axon, REV Smart Robot Servo |
| Sensors | Perception and feedback | Encoders, ToF, IMU, cameras |
| Custom PCBs | Team-designed boards for specialty functions | LED drivers, sensor breakouts |
Cable protection, management, and building custom wires — the foundation of a reliable robot.
FTC robots take a beating. Cables get pinched by mechanisms, abraded by aluminum edges, and jerked during quick movements. Protection keeps insulation intact and prevents the slow degradation that becomes a match-ending short.
Expandable braided sleeving bundles multiple wires together and provides excellent abrasion resistance. It's flexible, easy to install, and looks professional. Use it for harnesses that need to survive repeated mechanical stress — cables running along a lift or arm. Sizes range from ¼" to 1" diameter; choose based on bundle size.
Tip: Use heat-shrink at the ends of braided sleeving to prevent fraying and lock the bundle entry point cleanly.
Silicone self-fusing tape bonds to itself without adhesive, leaving no sticky residue. It's excellent for wrapping connector entry points, preventing cable jacket cracking, and providing extra insulation at stress points. Standard electrical tape should generally be avoided for permanent bundling — it loses adhesion over time and leaves residue.
Spiral wrap coils around a bundle and can be added or removed without disconnecting anything. Great for runs that need occasional access — sensor harnesses you might swap mid-season. Less abrasion-resistant than braided sleeving but more maintainable.
Cable chain (drag chain / e-chain) is linked plastic conduit that guides cables through moving axes. It constrains cables to bend only within a defined radius, preventing over-flexion and fatigue cracking. Essential for any repeatedly-moving mechanism. Covered in detail in Section 1.3.
Braided expandable sleeving. Withstands contact with sharp edges and repeated friction.
Spiral wrap or cable chain. Easy to open for rerouting or swapping cables mid-season.
Self-fusing silicone tape. Creates a residue-free barrier at stress points.
Standard electrical tape as a long-term bundle method. It degrades and leaves residue on connectors.
"Static" refers to cables on fixed structure — the chassis, Control Hub mounting plate, battery area. Good static management prevents pinch hazards, speeds up debugging, and impresses judges.
The workhorse of FTC cable management. Cut them flush — leftover tails are inspection red flags and field hazards. Use nylon zip ties sized to the bundle; over-tightening deforms insulation. For bundles needing periodic removal, use releasable zip ties or hook-and-loop straps instead.
Rule of thumb: Zip tie every 3–4 inches on hub wiring, every 2–3 inches near connectors, and every 6 inches on longer runs. Tie to structure, not to other cables.
Route cables along the interior of frame channels where possible — cables on the outside get hit by field elements. Run power wires (battery, main power) separately from signal wires (encoder, I2C, sensors) to reduce electromagnetic interference.
Plan for future access: don't bury the motor controller you'll need to swap in a match under five layers of zip-tied harness. Route so critical components can be replaced with minimal re-wiring.
Bundle cables going to the same destination before mounting. Group by function: drivetrain, arm, sensor harness.
Use frame channels, mounting plates, and existing structure as guides. Don't bridge open air more than a few inches without a midpoint anchor.
Leave 2–3 cm of slack near each connector. Prevents tension on pins and allows reconnection after cuts.
Zip tie at regular intervals. Trim tails flush, tuck ends, verify nothing can reach a moving part.
Moving cable management is one of the hardest problems in FTC mechanical design. Every mechanism cycle flexes cables. Over hundreds of cycles, this causes fatigue failure — the conductor inside the insulation cracks, causing intermittent faults that are nearly impossible to diagnose without specialized tools.
Cable chain is the gold standard for moving axes. Links articulate within a defined bend radius (typically 25–50mm for FTC-scale chains), preventing the tight bends that cause fatigue. Cables are laid inside and anchored at both ends.
Key points: Fill no more than 60–70% full. Mount both ends with proper strain relief. Account for the full travel arc — the chain needs complete clearance at all positions.
For scissor lifts, cables can be routed diagonally across the linkage arms using guides at pivot points. Cable length must be precisely matched to travel — too short and it yanks at full extension; too long and it sags into moving parts at full retraction.
A badge retractor is a small spring-loaded spool that takes up cable slack automatically. Used for short-travel axes where a full cable chain is overkill — rotating turrets and small wrist mechanisms. Use thin, flexible wire only — heavy gauge will overpower the spring.
For linear slides or spool-based mechanisms, cables can be loosely tied alongside the drive string or cord. As the string winds and unwinds, the cable follows. A simpler approach that requires careful matching of cable slack to mechanism travel. Use flexible, small-gauge cable to minimize tension buildup.
Critical: Never let a cable contact a moving mechanism without constraint. A cable that slips into a gear or bearing can lock up an entire drivetrain mid-match.
Custom wires are one of the highest-leverage upgrades you can make. They eliminate excess length, match gauge to application, and give you precise connector placement.
No extra slack. Wires reach exactly where they need to go with a service loop, and no further.
Match wire gauge to current load. Oversized wire wastes weight; undersized wire heats up and loses voltage.
Build Y-cables, T-taps, and connector adapters that aren't available off the shelf.
If you built it, you can fix it. Custom wires are faster to replace and easier to trace.
| AWG | Max Current | Typical FTC Use |
|---|---|---|
| 10 AWG | ~30A | Main battery lead, power to hubs |
| 14 AWG | ~15A | High-current motor power |
| 18 AWG | ~7A | Standard motor wiring, servo power rails |
| 22 AWG | ~3A | Servo signal, general sensor power |
| 26–28 AWG | ~1A | I2C/SPI signals, encoder data, badge reel cables |
Crimping mechanically deforms a metal terminal around a wire to create a gas-tight, low-resistance connection. A proper crimp is stronger and more reliable than solder for vibrating applications — which describes every FTC robot.
Strip 3–4mm of insulation. The wire barrel grips only bare conductor; the insulation barrel grips only the jacket.
For fine-stranded wire, lightly pre-tin the conductor end to prevent strand splaying. Don't solder through — the crimp must deform metal, not solder.
Insert wire until conductor is visible at the front. Crimp the conductor barrel first, then the insulation barrel. Use the correct die for the terminal size.
Pull the wire firmly. A correct crimp won't pull out. If it does, redo it — a loose crimp on the field is worse than no wire at all.
Buy a connector assortment kit. Having JST-PH, JST-XH, and Anderson Powerpole connectors on hand means you can build any wire you need at competition.
Pre-make spare harnesses. Build a duplicate of every custom wire before your first competition. Swap the spare in a match and diagnose later.
Label everything. Heat-shrink label tubing on connectors. "INTAKE MOTOR L" takes two seconds to read and saves ten minutes of tracing at 7am.
The invisible threat that resets Control Hubs and corrupts autonomous runs — and how to fight it.
Electrostatic discharge (ESD) is a sudden flow of electricity between two charged objects. In FTC, it most commonly occurs when wheels build up a charge through triboelectric contact with carpet tiles, and that charge discharges through your electronics when it finds a low-resistance path.
The most common ESD symptom. The robot stops, waits a second, then resumes — losing critical seconds of autonomous or teleop.
Encoders read incorrect positions. I2C sensors go offline. ESD mid-auto can corrupt odometry and throw off localization entirely.
Repeated or severe ESD can permanently damage sensitive ICs. CMOS logic inside sensors and microcontrollers is especially vulnerable.
The USB connection between the Control Hub and its internal computer can be disrupted by ESD, causing the OpMode to crash entirely.
Real scenario: Teams have lost autonomous runs to ESD-triggered Control Hub reboots at critical moments. This happens regularly at competitions, especially on dry-air days with carpeted fields.
Staticide is a topical anti-static agent that makes surfaces slightly conductive, allowing charge to dissipate slowly rather than building up to a discharge threshold. Spray or wipe a thin, even coat on wheels and chassis surfaces. Reapply between matches. Don't apply to connectors or PCB surfaces. Check with your local rules — generally allowed, but confirm with the current season's game manual.
Staticide is the easiest first line of defense. A $15 bottle lasts an entire season and can be the difference between a reliable autonomous and a coin-flip.
A grounding strap connects the robot chassis to the electrical ground of the power system. The theory: charge that accumulates on the chassis dissipates into the power ground rather than through sensitive components. A thin wire (22–26 AWG) from a chassis bolt to the negative terminal or REV Hub ground port accomplishes this. The connection must have metal-to-metal contact — anodized aluminum is an insulator, so the bolt must bite into bare metal.
Insulating the Control Hub from the chassis with plastic or rubber standoffs breaks the direct conductive path between chassis charge and electronics. A piece of UHMW or Delrin between the Hub mounting plate and the chassis can help significantly. Shielded cable for critical signal lines (encoder, I2C) provides an additional barrier against ESD-induced noise.
Static electricity arises from the triboelectric effect: when two dissimilar materials contact and separate, electrons transfer between them. FTC fields with rubber or foam wheels on carpet are textbook triboelectric generators. Charge accumulates on the robot's aluminum structure because the robot isn't in continuous contact with ground — it's rolling on insulating wheels.
Here's where it gets counterintuitive. A grounding strap connects chassis to the electronics ground. In theory, this provides a dissipation path. In practice, it can create a ground loop — multiple paths to ground at different potentials. Small voltage differences cause currents to flow through signal wires referenced to both, injecting noise into encoder signals, I2C buses, and analog outputs.
Additionally, a poorly implemented strap can make ESD worse: instead of slowly dissipating charge, it creates a low-resistance path that facilitates a faster, more violent discharge directly into the electronics ground rail.
Our finding: Grounding straps without additional filtering (bypass capacitors on power rails, ferrite beads on signal lines) produced inconsistent results in our testing. A strap alone is not a guaranteed fix — it must be paired with proper decoupling to be effective.
We've been investigating ESD behavior using an electrostatic fieldmeter and logging Control Hub reset events across different surface conditions and humidity levels.
ESD events below 30% RH are 3× more common than above 50% RH in our logs. Very low humidity = very high risk.
Softer rubber compounds (~40A durometer) generate less charge than harder compounds on standard FTC carpet.
Staticide on wheels combined with plastic-standoff Control Hub isolation has been our most reliable mitigation so far.
I2C sensors are significantly more ESD-susceptible than UART or SPI, likely due to the open-drain bus topology.
This is an area of active investigation. We'll publish our full methodology and data as we gather more. If your team has data to share, reach out.
Every type of sensor used in FTC — what it does, which variants exist, and what we recommend.
Sensors are how your robot understands its own state and the world around it. Without them, you're open-loop: you can command motors but can't react to where things actually are. Good sensor integration is what separates consistent autonomous routines from hopeful approximations.
Signal quality matters. Even the best sensor is useless if it's wired with the wrong gauge, placed in a noisy environment, or polled at the wrong rate in software. Hardware and software are equally important.
Encoders measure rotational position and velocity. They're the foundation of reliable motor control — without encoder feedback, you can only run motors open-loop (by time or by joystick), which is inconsistent match to match.
Quadrature encoders output two square wave signals (A and B channels) offset by 90°. The REV hubs count these pulses in hardware, giving you position (total counts) and direction. Velocity is derived from count rate. Higher PPR (pulses per revolution) means finer precision.
Magnetic encoders use a magnet and Hall-effect sensor instead of optical encoding. More robust to contamination (dust, oil) and have no moving wear parts. Available as standalone units like the REV Through Bore Encoder.
Absolute encoders report the exact angular position within one revolution — no homing required after power-on. Essential for arms and wrists where you need to know position immediately at startup without running a homing routine.
Dead wheel encoders are standalone quadrature encoders on unpowered tracking wheels. They don't slip under drive loads and are the backbone of precision odometry systems for competitive FTC robots.
Distance sensors measure how far the robot is from an object. Uses in FTC: approach control (slowing a drivetrain before hitting a wall), game element detection (is a sample in the intake?), and alignment against field elements without relying on odometry drift.
Time-of-Flight (ToF) sensors emit an IR or laser pulse and measure how long it takes to return. Accurate, fast, narrow beam angle — great for precise ranging up to ~4000mm. The VL53L1X and variants are widely used in FTC.
Ultrasonic sensors use sound pulses with a wider detection cone and slower update rate. Generally inferior to ToF for FTC applications but functional for coarse ranging and object detection tasks.
IR proximity sensors are simpler and less precise. Good for binary detection — confirming a game element is loaded in an intake, or detecting a field boundary.
Color sensors measure the wavelength composition of reflected light. In FTC, they're used to detect game element color (red vs. blue alliance pieces), line following, and confirming which zone a robot occupies.
Broadband RGB sensors output red, green, and blue channel values plus an ambient/clear channel. The REV Color Sensor V3 (APDS-9151 based) is the standard FTC option with built-in SDK support.
Spectral sensors like the AS7341 measure 8+ spectral bands — a more complete surface fingerprint. Useful for distinguishing subtle color differences under variable lighting conditions.
Key challenge: Ambient lighting at competition venues varies dramatically. Always normalize readings and test under multiple light conditions. Readings that work in your lab may fail under competition fluorescents.
Cameras provide rich visual information — far more data per frame than any point sensor. In FTC, cameras are used for AprilTag detection (localization and target identification), game element detection, and Team Prop identification during autonomous initialization.
The FTC SDK includes the Vision Portal, which supports AprilTag detection and TensorFlow Lite object detection out of the box — significantly lowering the barrier to camera-based automation.
USB webcams connect via USB to the Control Hub and are processed in software. Most FTC vision pipelines run well at 320×240 @ 30fps. Higher resolution increases CPU load significantly — benchmark your pipeline early.
Warning: Camera processing is CPU-intensive. Complex vision pipelines running alongside a full auto routine can cause loop time spikes. Always profile your pipeline's CPU and memory usage during development.
Localization is knowing where your robot is on the field at all times. It's a fusion of multiple sensor inputs into a reliable position estimate — the backbone of consistent autonomous performance.
Wheel odometry uses drivetrain encoders to track displacement. Simple to implement but suffers from wheel slip (especially on fast drives) and accumulates error over long paths.
Dead wheel odometry uses unpowered tracking wheels (small omni wheels on spring-loaded pods) with high-resolution encoders. Much more accurate because tracking wheels don't slip under drive loads. Three-wheel configurations provide full x/y/heading tracking and are the competitive standard.
IMU measures heading via gyroscope. The REV Control Hub has a built-in BHI260AP IMU. Useful for heading correction and turns. Drift is acceptable for single-match auto runs but should be fused with odometry for long paths.
AprilTag localization uses cameras and field-mounted tags to get absolute field position — immune to drift. Requires tag visibility and has update rate limits, but provides a powerful correction signal for odometry-based systems.
SparkFun OTOS uses optical flow (like a high-speed camera pointed at the floor) to track robot movement without contact encoders. Very promising for FTC — no encoder pods to build or calibrate.
Why FTC teams design their own circuit boards, how to get started, and what's actually possible.
Custom printed circuit boards were once exclusive to advanced teams, but accessible tools like KiCad and cheap fabrication from JLCPCB have made them realistic for any team willing to invest time in learning.
Replace a tangle of breakout boards and jumper wires with a single purpose-built board that fits your robot exactly.
Soldered PCB connections are far more vibration-resistant than breadboard assemblies. No jumper wires to pop loose mid-match.
Proper ground planes and decoupling caps placed right at the IC improve signal quality versus ad-hoc wiring.
Need an LED indicator board that fits a 20×30mm slot? A connector adapter? A current sensor? PCBs make these practical.
FTC Legality: Custom PCBs are legal in FTC as auxiliary electronics — indicators, sensors, power distribution, signal conditioning. They cannot replace the required control system. Always verify with the current season's game manual.
The PCB workflow: schematic capture → PCB layout → fabrication → assembly. Full tutorials for each tool are widely available — we'll orient you to what matters for FTC specifically rather than duplicate general guides.
Free, open-source, and the community standard for hobbyist and professional PCB design. Excellent documentation and a huge library. Version 7+ has a significantly improved interface.
Browser-based designer that integrates directly with LCSC components and JLCPCB fabrication. Lower learning curve than KiCad. Great for simple boards and teams new to PCB design.
Useful if your team already uses Fusion for mechanical design — the PCB can be co-designed with its enclosure or mounting structure.
Most popular for FTC teams. 5 boards for ~$2–5, ships in 7–14 days to the US. Also offers SMT assembly — they solder components for you at low cost.
US-based. More expensive but fast domestic shipping. Good for last-minute orders before a competition. Beautiful purple soldermask.
Competitive pricing, good quality, great customer service. Good alternative to JLCPCB with more options for flex PCBs and specialty materials.
A great first FTC PCB: a small board connecting to the Control Hub's digital I/O pins to drive high-brightness LEDs indicating robot state (autonomous phase, intake status, alignment complete). Teaches PCB fundamentals while producing something genuinely useful for match awareness.
Takes 3–5 digital GPIO signals from the REV Hub, uses a ULN2003A transistor array to drive higher-current LEDs than the Hub pins can source directly, and exposes a JST-PH connector for easy connection. LEDs mount near the board edge for outward visibility.
Add power symbols (5V, GND), GPIO input connectors (JST-PH 5-pin), ULN2003A transistor array, 330Ω current-limiting resistors, LED footprints, and 100nF decoupling caps on the power rail.
Use SMD 0402 resistors and caps. Place the IC centrally. Route power and ground first, then signals. Place LED pads near the board edge. Add a ground plane fill.
Run the Design Rule Check to catch spacing violations and unconnected nets. Export Gerber and drill files. ZIP and upload to JLCPCB. Order 5 boards (~$5 shipped).
Solder components. Test each LED channel on a bench supply with 3.3V before connecting to the robot. Measure current draw to confirm resistors are correct.
Robot status lights visible to drivers. Alliance color indicators. Autonomous phase displays. Under-robot illumination for camera tracking.
Convert between JST-PH, JST-XH, XT30, Anderson Powerpole. Replace fragile flying leads with solid, permanent PCB adapters.
Current sensing boards using INA219 to log motor current draw. Useful for detecting stalls and tuning PID current limits.
Custom breakouts for sensors without FTC-compatible connectors. Mount with the exact orientation and connector type your robot needs.
Use a TCA9548A to connect multiple same-address sensors on one I2C bus. Expand beyond the Hub's built-in port count.
Advanced teams have built stepper motor controllers, brushless ESC breakouts, and solenoid drivers for actuators not supported by the Hub natively.
JLCPCB standard service is 7–14 days to the US. Add time for assembly and testing. Do not order your first PCB the week before a competition. Design iteration is normal — budget for at least two rounds of ordering before you need the board in a match.
Add test points to every net you'll want to probe. A 1mm pad labeled "TP_5V" takes 30 seconds to add and saves hours of debug time. Add power-rail status LEDs so you can visually confirm the board is healthy before touching a multimeter.
Design the PCB shape around your robot's mounting constraints from the start. Export the board outline to DXF and import into CAD. Confirm M3 mounting hole placement before ordering. A PCB that won't fit your robot is a wasted board and wasted time.
Components handling significant current need a thermal plan. Copper pours, thermal vias, or small heatsink attachments. Competition halls are warm and pits get hot — don't design only for ideal lab temperatures.
Safety first: Before connecting any custom PCB to your robot, test it standalone on a current-limited bench supply. A short on a custom board connected to a 12V battery can cause fire or permanent damage. Always verify before integrating with the robot.
Start simple. Your first PCB should be passive — connectors, resistors, maybe a few LEDs. Master the fabrication workflow before adding complex ICs. Each project teaches you something new for the next one.