By inserting the two commands in series to the circuit of the STO "safeties", the axis enable is
controlled only when the master (e.g., PLC) controls both the S1 and S2 signals, and all the safeties
of the machine are simultaneously closed.
CAUTION:Mechanical hazard.
Note that the opening of a "safety" contact may cause an axis to drop
uncontrollably. which could cause damage to equipment.
Ø In situations where this behavior is not compatible with the machine move-
ments (for example with interpolated axes or ones that interfere mechanically),
it is recommended to use appropriate delayed safety contacts to release the
axis only after full stopping of the movement in a position that will not cause
any damage to the machine.
The dual channel consists of two separate, independent circuits; each control line is independent but
acts on devices connected in series with each other. Both commands must be properly provided to
enable motor movements.
PN: L-MAM2-E-201
Moog Casella DM2020 Installation and Startup Guide
5.3.6.9 STO Signals Connection
By including the two STO commands in series in the “safety device” circuit, the axis enable command is
operated only when the PLC controls both S1 and S2 signals, and at the same time all machine safety
devices are “closed”.
When a “safety” contact is opened, the axis is released without control; in situations where this is not
compatible with machine movement (for example axes that are interpolated or cause mechanical
interference), appropriate delayed safety contacts should be used to release the axis only after
movement has fully stopped in a position that does not damage the machine.
The double channel comprises two separate, independent circuits; each command line is
independent but acts on devices connected to each other in series; motor movement can only take
place when both commands are supplied correctly.
Absorption on the S1 and S2 inputs is below 50 mA at 24 V.
As feedback of the two commands, the drive relays corresponding S1 and S2 feedback (3.3 V, 1 kOhm)
to the PLC to check that commands are correct and consistent, and to operate movements with an
adequate sequence.
The delay between Command application (S1 or S2) and Feedback, which signals that the command has
been executed, is below 50 ms; the delay between removal of the command and feedback signalling is
below 20 ms.
In any case, wait for at least 50 ms before moving the axes after executing commands, and 20 ms before
checking that the drive is in a “safe” condition.
The STO function is certified to SIL 3 (EN62061) and PL e (EN13849-1), and allows for simpler wiring of
machine safety devices.
WARNING
If the connection cables of the STO function are outside the installation site, they must be protected from
external damage (for example using a raceway) and laid in a fixed position.
ATTENTION
Si les câbles de raccordement de la fonction STO sont à l'extérieur du site d'installation, ils doivent être
protégés contre les dommages externes (par exemple en utilisant un chemin de roulement) et mis en position
fixe.
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