Safety Switching Devices
Emergency-Stop Relay
PI 0067-0703 E
SNO 2012
4/6
Application Example
Two-Channel E-Stop Application with Cross Monitoring ,
Manual START and RESET Switch Monitoring (anti tie-down)
This application example shows the necessary connections for the
monitoring of the RESET switch. For this E-Stop application the
switch has to be connected to terminals S12/S34 and terminals Y1/
S37 have to be jumpered. In this case the device is enabled only when the
RESET switch is closed and released (falling edge of the signal ). This
feature allows a manual START of the device. The two-channel E-Stop
control circuit switches off the device even if one of the two contacts
in the E-Stop pushbutton does not open.
If a fault occurs ( i.e. the E-Stop contact connected to terminal S22
does not open), the second (redundant) contact S12 activates the
safety circuit. The 6 enabling current paths open, the control con-
tacts 71/72, 81/82 close and 91/92, 01/02 stay open. In case of a
short circuit in the lines leading to the E-Stop pushbutton, the inter-
nal supply voltage at S11, S21 is short circuited (cross monitoring).
The relays K1, K2 switch back to their off position and the electronic
protective fuse is triggered. If a line short circuit occurs in the RE-
SET switch after the device has been activated, it will be recognized
by the cyclical self-test when reactivating the device. This will inhibit
the enabling current paths (output safety contacts) to close again.
If the number of enabling current paths is not sufficient , external
contactors can be used for expansion ( 2 in this example). They are
driven through one of the enabling current paths of the device. The
function of the external contactors is monitored by their own NC
contacts connected in series to the feedback circuit Y1/Y2. The
contactors K4 and K5 must have positive guided contacts.
Two-Channel Protective Gate Application with Cross Monitoring
and Automatic Start
This sliding protective gate applications shows the necessary con-
nections for an automatic START (without monitoring of the RESET
switch). Terminals S12 and S34 have to be connected, terminal S37
stay open. The position of the sliding protective gate is monitored via
channel 1 (S12) and channel 2 (S22). The SNO 2012-xx is activated
by the automatic START. If the sliding protective gate is opened the
E-Stop relay goes back to its off-position (the 6 enabling current
paths open and the 4 control contacts close). When the protective
gate is closed again, the device is reactivated by the automatic
START.
The two-channel control circuit allows the synchronous check of the
position switches. The synchronous time is performed when closing
contact S1 (terminals S11/S12) before contact S2 (terminals
S21/S22). If contact S2 is closed before contact S1 the synchronous
time is t
S
=
∞
.
