Interlock¶

What is Interlock ?¶

Interlocks developed at ESRF is a way to use Wago PLC to continuously monitor for some input conditions and trigger a relay output when those conditions meet a thresholds.

What is the purpose?¶

Let’s imagine that some hardware of a beamline has to maintain a temperature between 20 and 80 degrees. Going under 20 degrees or over 80 may cause a hardware damage and imagine that in that case we would like to shutdown the power supply.

This is the typical case of use of interlocks.

More details¶

On the same Wago controller, one or more interlock instances can be defined.

The controller stores the configuration in its internal non-volatile memory.

One interlock instance is made by:

One PLC’s digital output normally associated with a relay
One or more control conditions (input/output channels of the PLC)

Each control signal of an interlock instance has a defined “alarm condition”. This condition is a defined logic value (ON or OFF) for digital signals and a value range (defined by MIN/MAX thresholds) for analog signals. Whenever one of the control signal reaches an alarm condition, the interlock instance goes into tripped state and the alarm relay switches to the alarm position.

By default the alarm position is OFF (relay open) but this can be inverted in the configuration of the interlock instance.

The configuration is at first created in Beacon and then managed through Bliss.

The configuration of the interlock instances can be displayed, uploaded and checked (from the controller itself).

Steps to to make it works¶

To have this kind of interlocks system working:

An interlock program isgmain should be loaded on the WAGO normally by ESRF Electronic group, this program is generic (always the same for all WAGOs)
Conditions have to be defined in the Beacon YAML configuration for that PLC
Conditions have to be uploaded to the WAGO using the command wcidXX.interlock_upload()
From here on the WAGO will operate by himself checking inputs and eventually activating relays; no need for Bliss to be active.

Warning

The interlock_upload() method does not work if the tango device server is declared in config.

YAML configuration for interlocks¶

interlocks keyword must be added to the Wago configuration file and a list of interlocks can be specified.

interlocks:
    - relay: intlckf
      flags: STICKY
      description: Interlock 1
      channels:
          - logical_name: esTf1
            type: TC
            min: 10
            max: 50
          - logical_name: esTf2
            logical_channel: 1
            type: TC
            min: -10
            max: 50.5
    - relay: intlckf
      relay_channel: 2
      flags: STICKY
      description: Interlock 2
      channels:
          - logical_name: esTr1
            type: TC
            min: -10
            max: 50.5
          - logical_name: o2
            type: OB
    - relay: relay012
      flags: inverted
      description: monitor test
      channels:
        - logical_name: th011
          type: TC
          min: -201
          max: 850
          flags: MONITOR
          dac: dac1
          dac_scale: 2.2
          dac_offset: 30

Configuration of the relay¶

relay: (Mandatory) is the logical name that will be activated in case of triggering
relay_channel: (default is 0) is the logical channel that will be triggered. The same name can be assigned to more than one input/output. The first will be 0, the second 1 and so on.
flags: (Optional)
- STICKY: once conditions are meet and the relay is activated, the command interlock_reset must be manually send through Bliss to reset it.
- INVERTED: the behaviour of the relay is Inverted: normally the relay is closed (letting current to pass) during operations and if triggered it will open (avoiding current to pass). If this flag is set, the behaviour will be inverted.
- NOFORCE: by default when there is no alarm condition, the alarm relay is forced to the normal position and cannot be switched externally. The NOFORCE flag relaxes this constraint. In any case when the instance trips, the relay is always forced into the alarm state.
description: (Optional) is simply an user description of the purpose of the interlock condition.

Configuration of the channel¶

Digital or analog channels can be used, the following are common config:

logical_name: (Mandatory) is the logical_name of the input/output that will be check, this has to be defined in the mapping.
logical_channel: (Optional, default is 0) is the channel that will be read in case of defined logical channel with same name.
type: (Mandatory)
- IB: Input Binary type (digital input)
- OB: Output Binary type (digital output)
- IW: Input Word value
- OW: Output Word value
- IV: Input Voltage
- OV: Output Voltage
- TC: Termocouple
flags: (Optional)
- INVERTED: The logic of alarm condition can be inverted with the INVERTED flag. By default digital control channels are normally ON and switch into alarm condition when they become OFF, and analog channels trip when their value is out of the min/max thresholds as explained above.
- STICKY: The STICKY flag has the same function than when it is used as an instance flag, but in this case it is associated to a particular channel and only takes effect when this channel is the one that trips.
- MONITOR: The MONITOR flag allows: val(dac1) = dac_scale*val(th11) + dac_offset This is typicaly used with the cryocooler racks for displaying the temperature (or the pressure) on a LCD display. Remark: dac mnemonic has to be dacxx like dac1.

In the case of an analog input/output signal, minimum and maximum can also be specified:

min: lower limit, going under will trigger the relay
max: higher limit, going over will trigger the relay

For thermocouples, the precision can be given in decimal, E.G. 50.7 Celsius.

Interlocks on Bliss shell¶

interlock_show() will display interlocks info concerning all Wagos already imported from yaml file or with config.get.

During the execution of this command the configuration loaded into Wagos will be downloaded and compared with the existing one in Beacon. If differences are found they will be printed in the shell.

interlock_show(wago): display interlocks info only for given Wago.
interlock_state() return a tuple containing the actual state of the interlocks, useful also in scripts or status bar for monitoring.
interlock_state(wagos) return states only for given Wago.

To use it inside a script it must be imported with:

from bliss.common.standard import interlock_state

Methods attached to Wago objects¶

wago_instance.interlock_reset(instance_num) it will reset a specific relay instance.

wago_instance.interlock_upload() will upload the configuration for the given wago_instance from beacon to the WAGO.

wago_instance.interlock_to_yml() will download the actual configuration from the wago and give back as an YML string. Very useful on an existing WAGO that you wish to convert from spec to Bliss.

wago_instance.interlock_state() will print the state of interlock relays for the given wago_instance.

interlock_show¶

BLISS [16]: wcid42hpps = config.get("wcid42hpps")
BLISS [17]: interlock_show()
Currently configured Wagos: wcid42hpps


Interlocks on wcid42hpps
Interlock configuration is not present in Beacon
On PLC:
1 interlock instance
  Instance #1   Description:
    Alarm relay = intlckhpps[0]  STICKY                             [ON]
    State = NOT TRIPPED
    10 channels configured:
      # 1  .... - hppstc1  TC  Low:0.0000 High:50.0000  STICKY      [23.5]
      # 2  .... - hppstc2  TC  Low:0.0000 High:50.0000  STICKY      [23.1]
      # 3  .... - hppstc3  TC  Low:0.0000 High:50.0000  STICKY      [23.2]
      # 4  .... - hppstc4  TC  Low:0.0000 High:50.0000  STICKY      [23.0]
      # 5  .... - hppstc5  TC  Low:0.0000 High:50.0000  STICKY      [23.1]
      # 6  .... - hppstc6  TC  Low:0.0000 High:50.0000  STICKY      [23.3]
      # 7  .... - hppstc7  TC  Low:0.0000 High:50.0000  STICKY      [23.3]
      # 8  .... - hppstc8  TC  Low:0.0000 High:50.0000  STICKY      [23.6]
      # 9  .... - pptc1  TC  Low:0.0000 High:50.0000  STICKY        [14.1]
      #10  .... - pptc2  TC  Low:0.0000 High:50.0000  STICKY        [14.4]

The same command can be used as a method of a the Wago.

BLISS [14]: wago_simulator = config.get("wago_simulator")
BLISS [15]: wago_simulator.interlock_show()
Interlocks on wago_simulator
Interlock Firmware is not present in the PLC

On Beacon:
2 interlock instance
  Instance #1   Description: Interlock
    Alarm relay = intlckf1[0]  STICKY                               [None]
    State = NOT TRIPPED
    4 channels configured:
      # 1  .... - esTf1  TC  Low:10.0000 High:50.0000               [None]
      # 2  .... - esTf2  TC  Low:-10.0000 High:50.5000              [None]
      # 3  .... - esTr1  TC  Low:10.0000 High:50.0000               [None]
      # 4  .... - esTr2  TC  Low:10.0000 High:50.0000               [None]

  Instance #2   Description: _Interlock 2
    Alarm relay = intlckf2[0]  STICKY                               [None]
    State = NOT TRIPPED
    2 channels configured:
      # 1  .... - esTr1  TC  Low:-10.0000 High:50.5000              [None]
      # 2  .... - esTr2  TC  Low:-10.0000 High:50.0000              [None]

The interlock show will check both Beacon configuration and Hardware configuration and will make evidence of any difference.