Gate Motor Controller Fault States


Created: ; updated: .


The Gate Motor Controller (GMC) device is designed to control a motor operated irrigation gate where the motor turns a threaded spindle to raise and lower the gate or valve plate.  An H-bridge card is required to drive the motor in each direction and must provide a feedback signal to indicate when its internal current limit has been exceeded.  A rotary encoder is required to establish a relative gate position from the closed datum.

The gate can be controlled and scheduled via Observant Global to move it to the fully closed or fully open position.  Fully closed is detected by the motor current limit being exceeded, fully open is established by counting encoder pulses to set a relative distance from the closed position.


Fault States

A number of fault states can be detected by the GMC driver.  If a fault state occurs the gate will stop and wait until another command is received from Observant Global or the manual movement buttons are pushed before clearing the fault code.  Any scheduled movements will be cancelled when a fault condition is detected.


Fault State


Possible Causes


Current limit trips within start timeout

Spindle or gate has seized, motor short circuit


Current limit trips unexpectedly outside of start timeout (ie. when gate is not closing, or is closing but is not within Threshold of datum)

Gate has been fouled or sticky spindle

No Movement

Fewer than three pulses have been seen from the encoder after start timeout (to allow for encoder powerup glitches)

Motor burnt out, H-bridge failure, encoder failure, blown fuse


Gate has moved past the closed datum by > Threshold. 

Note that the gate continues to run in this state until the Transition Duration is reached.  The fault state will be set to Overrun as soon as it is detected, however the system state will only enter In Fault once the gate stops.  Fault state will remain on Overrun regardless of whether current limit was eventually hit.

Gearbox failure, spindle not locked, encoder jitter/noise


No current limit hit after Transition Duration, no Overrun detected

Low voltage, sticky shaft (gate moving too slowly)

Start timeout is either one percent of the max gate cycle time or three seconds, whichever is longer.

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