Hardware troubleshooting

Canonical source: openamr-platform-hw/electrical/motor_control/motor-driver-fault-codes.md Applies to: the documented OpenAMRobot reference mobile base; verify repository revision before changing hardware or firmware.

Experimental project documentation

These instructions describe the current reference build and its measured behavior. Use physical safeguards, test with wheels clear of the floor, and revalidate after changing parts, wiring, firmware, battery chemistry, or geometry.

How to read the driver's LED blink code and the full fault-code table. Driver: ZBLD.C20-120L2R (Ningbo Zhongda Leader / ZD), 24 V ±20 %, 7.5 A, 120 W. One per wheel (LEFT = M1, RIGHT = M2).

Last updated: 2026-06-26.

When a driver detects a fault it STOPS the motor and blinks an error code on its LEDs. So a red LED is not cosmetic — the motor will not turn until the fault is cleared, even though the Teensy keeps sending PWM (you can confirm the Teensy side is fine: /debug/pwm still shows the commanded value).

Reading the LED blink code

Each driver has a green and a red indicator. On a fault they flash a repeating pattern:

ERROR CODE = (number of GREEN flashes × 5) + (number of RED flashes)

Count one full cycle: the green flashes first (each green = 5), then the red flashes (each red = 1), then it repeats. Count green and red separately — do NOT add them into one running count.

⚠️ The encoding is NOT a clean base-5 code, so green×5 + red can alias (e.g. 1 green + 5 red and 2 green + 0 red both arithmetic to 10). Do not "carry" a 5th red into an extra green — read the actual emitted pattern the driver blinks. Below are the patterns observed on this robot (field-confirmed); for any code not seen here, read the pattern off the driver and cross-check the fault-code table.

You see (emitted pattern)	Code	Meaning	Confirmed
1 green, 5 red	10	busbar under-voltage	✅ seen on this robot (2026-06-26)
2 green, 4 red	14	locked rotor	✅ seen on this robot (2026-07-01, wheel jammed on wall)

(Other codes in the fault-code table below are from the manufacturer manual and have not been observed here — read the blink pattern off the driver, then look up the code. Green contributes 5 each, red 1 each, but trust the pattern the driver actually shows, not a computed sum.)

Fault-code table

Code	Fault	Typical cause
1–6	Over-current (during acceleration / deceleration / constant speed)	short on the motor phases, motor stalled/jammed, wrong wiring, current limit too low
7–9	Over-voltage (different operating phases)	supply > 28.8 V, or regenerative braking spikes (decel) with no bleed
10	Busbar under-voltage	24 V too low: flat/weak battery, voltage drop under load, supply can't hold the current spike at fast acceleration, or driver HW fault
11	Motor overload	motor drawing too much for too long (load too high, gearbox binding)
12	Driver overload	driver output beyond its rating (7.5 A / 120 W)
13	Hall sensor error	Hall connector loose/miswired/disconnected → driver can't commutate
14	Locked rotor	motor blocked / can't turn (mechanical jam, brake on)
16	Driver over-temperature	heatsink too hot — sustained high load / poor cooling
19	Current sense error	internal current-measurement fault
27	Data storage error	driver parameter/EEPROM error
29	Over-current feedback error	current-feedback path fault
30	Lack of input phase	a motor phase (U / V / W) is missing — phase wire disconnected

(Codes grouped 1–6 / 7–9 cover the same fault type at different motion phases; exact sub-code detail is in the manufacturer's manual, ZBLD.C20.pdf.)

Clearing a fault

Fix the cause first (see the table — e.g. for code 10, recharge the battery to ≥ 25 V).
Power-cycle the 24 V (cut, wait a few seconds, restore). Faults latch until a power cycle.
The red LED should go out and the motor respond again.

Most common on this robot — code 10 (under-voltage)

Both drivers showing code 10 at once = a shared cause = the 24 V bus is too low (they share one battery). The ZBLD.C20 needs 24 V ±20 % (≈ 19.2–28.8 V); below that → under-voltage → both stop. - Diagnosis: measure the battery at rest — if < ~22 V (let alone < 19 V), that's it. - Note: a charged but weak battery can still trip code 10 under load ("voltage drop / fast acceleration") — the pack sags at the current spike. Same root as the Pi 5 brown-outs (raspberry-pi.md / power.md): keep the battery healthy + ≥ 25 V, with short, thick 24 V wiring. - Fix: charge to ≥ 25 V → power-cycle the 24 V → red LED off → wheels turn (ros2 topic pub --rate 15 /debug/openloop geometry_msgs/msg/Vector3 "{x: 100.0}" with the robot lifted).

If it is NOT under-voltage (battery confirmed good)

Code 13 (Hall error) / 30 (missing phase) → a motor connector is loose/disconnected (check the Hall and U/V/W wiring; brown = +, blue = − for power leads).
Code 1–6 (over-current) / 14 (locked rotor) → the motor is jammed or shorted — check the wheel turns freely and the phase wiring isn't shorted.
Code 16 (over-temp) → let it cool; reduce sustained load.

See also: motors-drivers.md (driver model, DIP switches, pots), power.md (battery / 24 V), and the openamr-platform-sw troubleshooting doc (docs/troubleshooting/diagnostics.md in that repo).

Engineering handoff

Record the repository commit, hardware revision, supply voltage, and test configuration with every result.
Stop if observed wiring, component labels, geometry, or topic behavior differs from this page; resolve the discrepancy in the owning repository first.
Report documentation or implementation defects through the repository issue tracker.