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Festo — CMMT-AS-...-S1 — 2021-04d
Product overview
SBC request
If there are suspended loads, they usually drop if STO and SBC are requested directly before the
braking ramp is completed because the engagement time of the holding brakes must be considered.
For details of how to wire up safety sub-function STO with SBC, see
•
When selecting the delay time t
Delay
, make sure it is long enough to account for the maximum
braking ramp time and brake engagement time.
4.1.5
Cross wiring of several servo drives
For cross wiring, wire the diagnostic outputs as a ring. Route both ends of the ring to a 2-channel input
of the safety relay unit. The safety relay unit monitors for discrepancies. A maximum of 10 servo drives
can be wired in parallel.
Cross-wiring, example STA
Fig. 11: Cross-wiring, example STA
For cross-wired diagnostic outputs, the condensed state results from a logical AND link. An output of a
CMMT-AS is capable of pulling all other outputs to low signal. A high signal is present at the two inputs
of the safety relay unit only if all diagnostic outputs deliver high signals. The ring-shaped cross wiring
of the diagnostic outputs with sensing at the beginning and end of the signal chain makes it possible
to detect cable breaks in the cross wiring.
At this point, the diagnostic outputs deviate from the closed current principle. Cyclical automatic
testing of the diagnostic output by the safety relay unit is therefore highly recommended
feedback via STA diagnostic contact and
SBC feedback via SBA diagnostic contact.
4.1.6
Fault exclusion
Put suitable measures in place to prevent faulty wiring:
