7-2
7-1 Safe Torque OFF (STO) Function
OMNUC G5-SERIES AC SERVOMOTOR AND SERVO DRIVE USER'S MANUAL
7
Safety Function
I/O Signal Specifications
Safety Input Signal
There are 2 safety input circuits to operate the STO function.
When safety input 1 or 2 turns OFF, the STO function will start operating within 5 ms of the input,
and the motor output torque will be reduced to 0.
Connect the equipment so that the safety input circuit is turned OFF to operate the STO function.
Use Stop Selection for Alarm Detection (Pn510) to set the operation when the safety input is
turned OFF.
Precautions for Correct Use
L-pulses for self-diagnosis of safety equipment
When you are connecting a safety device, such as a safety controller or a safety sensor, the safety
output signal of the device may include L pulses for self-diagnosis. To avoid malfunction due to the
L pulses for self-diagnosis, a filter that removes the L pulses is built into the safety input circuit. If the
OFF time of the safety input signal is 1 ms or less, the safety input circuit does not recognize it as
OFF. To make sure that OFF is recognized, maintain the OFF status of safety input signal for at least
5 ms.
Signal name
Symbol
Pin
number
Description
Control mode
Position
Speed Torque
Fully-
closed
Safety input 1
SF+ CN8-4
• The upper arm drive signal of the
power transistor inside the Servo
Drive is cut off.
√√√ √
SF− CN8-3 √√√ √
Safety input 2
SF2+ CN8-6
• The lower arm drive signal of the
power transistor inside the Servo
Drive is cut off.
√√√ √
SF2− CN8-5 √√√ √
For self-diagnosis L pulse
Within 1 ms
Within 5 ms
Normal operation
STO status
Safety input signal
Servo amplifier operation
5 ms or more
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