| Blink Code | FCT Software Message | Root Cause Analysis | Corrective Action | | :--- | :--- | :--- | :--- | | | Overcurrent (Power stage) | Short circuit in motor cable; defective motor winding; incorrect motor phase resistance. | 1. Disconnect motor cable. Reset error. If error persists, controller is faulty. 2. If error clears, check cable for shorts (continuity test). | | 2 flashes | Overvoltage | DC link voltage exceeded max threshold (typically > 80V DC for CMMO-ST). Regenerative braking from decelerating a large load too fast. | 1. Increase ramp-down time (deceleration). 2. Ensure power supply is regulated (48V +/- 5%). 3. Install an external braking resistor (if supported by your model). | | 3 flashes | Undervoltage | DC link voltage dropped below minimum operating threshold (approx. 16-18V DC). Underpowered PSU; long, thin power cables causing voltage drop. | 1. Verify power supply outputs 24V (logic) and 48V (power). 2. Measure voltage at the controller terminals under load. 3. Increase wire gauge for power lines. | | 4 flashes | Excess position error (Following error) | The motor’s actual position deviated too far from the target position. Mechanical blocking; acceleration too high; motor undersized. | 1. Manually turn the lead screw/actuator by hand. 2. Reduce acceleration ( Fieldbus Acceleration parameter). 3. Increase Position Error Monitoring tolerance (if acceptable). | | 5 flashes | Overtemperature | Internal controller temperature > 85°C. Ambient temp too high; PWM frequency too high; obstructed cooling vents. | 1. Install a cooling fan on the control cabinet. 2. Reduce motor standstill current (Idle current reduction). 3. Move controller to a cooler location. | | 6 flashes | Motor phase failure | One of the two motor phases (A or B) is disconnected. Broken cable; damaged connector pin (M17 or M23). | 1. Visually inspect the stepper motor cable. 2. Use a multimeter: Measure resistance between pins 4 & 5 (Phase A) and 8 & 9 (Phase B). Should be low ohms. 3. Replace cable. | | 7 flashes | Encoder error (Missing encoder) | The feedback encoder (optional on CMMO-ST) is not communicating in closed-loop mode. Wrong encoder type selected in FCT; broken encoder cable. | 1. Check FCT settings: Ensure "Sensorless" is selected if no encoder is present. 2. If using encoder, check 5V supply and A/B track signals. | | 8 flashes | Illegal Hall state | (Less common for stepper) Hall sensors (if used) provide invalid logic combination (e.g., 000 or 111). | 1. Check wiring of Hall sensor interface connector. 2. Replace motor or feedback board. | | 9 flashes | Limit switch error | Both positive and negative limit switches are active simultaneously. Hardware short; incorrectly wired N/O vs N/C switches. | 1. Check DIN inputs for limit 1 and limit 2. 2. Verify logic polarity (Active High vs Active Low) in FCT software. | | 10 flashes | Software overtemperature | The calculated temperature model (based on current and time) exceeds limit, even if actual sensor is cool. High RMS current over long periods. | 1. Reduce duty cycle. 2. Lower the "Motor Peak Current" parameter. 3. Increase pause time between moves. | | Continuous red | Internal device fault (EEPROM/CRC) | Non-volatile memory corruption; firmware crash; severe electrical noise on 24V rail. | 1. Power cycle the entire cabinet (disconnect mains). 2. Reload factory parameters via FCT. 3. Return unit for service. | | Slow blink (1Hz) | Warning: I²t limit reached | The motor is overheating electrically. You are running at peak current for too long. | Reduce acceleration, speed, or load. Allow cooling. The drive will shut down if ignored. | | Fast blink (5Hz) | Start-up error / STO active | Safe Torque Off (STO) function is active (DIN 5 & 6 not receiving 24V). | Apply 24V to both STO inputs (pin 18 & 19). The drive will initialize. |
Includes "Drag error monitoring" (following error) and "Software end-position detection" if the motor cannot reach its target or hits a software limit.
| Flashes | Meaning | |----------|-----------------------------| | 1 | Overvoltage / Undervoltage (24V DC power supply) | | 2 | Overcurrent / Motor short circuit | | 3 | Overtemperature (internal controller) | | 4 | Following error / position deviation | | 5 | Encoder error (if encoder feedback used) | | 6 | Software limit switch exceeded | | 7 | Parameter error (invalid config) | | 8 | IO-Link communication timeout |
safety function. The STO is the controller's ultimate shield, designed to cut power to the motor to prevent accidental movement. Elias realized someone had accidentally bumped an emergency stop button. He cleared the area, reset the safety relay, and watched the STO diagnostic LEDs return to green. 3. The "C5" Battery Blues Acorn Stairlift Codes: Understanding and Resolving
Here is a structured checklist to guide you through general troubleshooting steps. cmmo-st-c5-1-diop error codes
When a diagnostic message appears, it provides a clear path to resolution. Here are the recommended steps to follow:
If the error persists after a power cycle, the internal EEPROM may be damaged, and the unit will need to be replaced. 2. Error 0x17: STO (Safe Torque Off) Active 0x00 (STO channel discrepancy)
Occurs when the deviation between the target and actual position exceeds the defined tolerance.
Adjust your position window and acceptable following error tolerances in the FCT parameterization menu. | Blink Code | FCT Software Message |
Damaged motor cable, short circuit between motor phases, or faulty motor. Troubleshooting:
| STO1 | STO2 | DIAG1/DIAG2 Status | Description | | :--- | :--- | :--- | :--- | | | 1 | High resistance (open) | Normal operation – Power stage is switched on. STO function is inactive. | | 1 | 0 | High resistance (open) | Single-channel failure – The STO function has been requested on a single channel. Power stage is switched off on 1 channel. Motor can no longer be operated. STO function is inactive. | | 0 | 1 | High resistance (open) | Single-channel failure – The STO function has been requested on a single channel. Power stage is switched off on 1 channel. Motor can no longer be operated. STO function is inactive. | | 0 | 0 | Low resistance (closed) | STO active – The STO function has been requested on two channels. Power stage is switched off on 2 channels. Motor can no longer be operated. The STO function is active. |
A typical scenario in pick-and-place applications: The CMMO-ST-C5-1-DIOP drives a belt actuator. Suddenly, the motor vibrates, loses torque, and the drive trips with .
: Signals a Bootloader error , typically occurring during a failed firmware update. The primary fix is to power-cycle the device; if it persists, it may require a Festo Service intervention. Common Diagnostic Categories Reset error
: Digital I/O interface featuring PNP (positive switching) logic. The Hexadecimal Error Code Format
The motor controller communicates diagnostic information through a integrated 7-segment display and more detailed hexadecimal codes accessible via the Festo Configuration Tool (FCT) or the device's web server. Display-Based Diagnostics
Errors are shown as: