The Light sensor view can be accessed by navigating to the grid view and clicking the Instance types perspective at the top-right of the grid and then clicking the Light sensor tab.

There are instance and primary target settings that can be changed along with all of the profiles that are assigned to a control system on the right side of the grid. This is where light sensor applications can be created for each profile on a control system.

Row Harvesting

Is a way to instruct the controller to adjust its target at individual rates. When row harvesting is off, each target of the light sensor receives one step command per adjustment. Whilst this is useful for rooms with uniform lighting, this may be problematic when a window contributes much of the light in a room. In this instance, the ideal scenario is that lights closest to the window are dimmed more by lux adjustment than lights that are further away. We can achieve this by turning row harvesting on which adjusts targets (generally groups) based on a configurable ratio.  

Please note that there is no reason to run a single row row harvesting - this does not work and will be removed from the options in the cloud soon.  If you require lux monitoring with a single target or you want to run your targets at the same illumination, simply set row harvesting to disabled.

Row harvesting strength and targets for a Normal dimming direction

Target placement for different row counts

Each row will be a group.  It is not necessary to also run an "all lights group" that has all rows in.  Simply give any pushbutton or occupancy sensor controlling the room, all of the row group targets. 

For example, if your rows are Group 0,1,2,3, you would give the same targets to the push buttons / other sensors.

If you wish for the light to turn on to the level that they were at, when turned off via switch / sensor, use the memory dim functionality of switches.  For sensor occupancy sequences, there is a template for memory dim available when you create a sequence.

Twilight Mode

Twilight mode is used by the light sensor to determine what action is to be executed when the twilight lux levels have been reached by the light sensor's current lux reading. If it is disabled then it will have no effect.

Each of the twilight modes specify what time of day is set up for to be run at, which will be either nighttime or daytime, as well as the action to perform.

Twilight mode can be configured to do the following actions:

It can turn a light on, off or go to minimum.

It can enable/disable PIR triggers (that is, all occupancy sensor hits will be ignored until the PIR triggers enabled - at which point a pir trigger will be able to trigger a sequence).

It can trigger a target itself (ie, it can trigger a target which you can set up a sequence to run against).

The levels are determined by the Twilight on and Twilight off columns. The Twilight on and Twilight off columns form a hysteresis, for nighttime mode, the action will not be taken until the light level falls below Twilight on, similarly the off action will not be called until Twilight off has been reached.

Daytime twilight modes require the Twilight on lux to be higher than the Twilight off lux otherwise it will not work as expected. This behaviour is reversed for the nighttime twilight modes meaning the Twilight on lux must be lower than the Twilight off lux.

For instance, a light sensor can be deployed into a car park and configured (through the Nighttime recall max twilight mode) to turn the lights on if the lux goes under the Twilight on threshold (ie. when the sun sets). It will also turn the lights back off once the Twilight off threshold has been reached.

If the user requires a custom light command such as a scene, you can run the twilight sensor in trigger mode, which sends sensor triggers to its target whilst the threshold is not met (requiring a sequence to be configured in the trigger map).  In this configuration, in night time trigger mode, a trigger is sent if the lux is lower than the Twilight On threshold.  In daytime, the trigger is sent if the lux is higher than the Twilight On threshold.

It should be noted that in trigger mode, triggers are sent frequently as long as the condition is met.  This allows you to create a timeout sequence, much the same as one would with a PIR sequence.  The following sequence is an example twilight trigger without an eventual timeout to off.

Timeline:
Lux is detected as above / below Twilight On threshold, trigger is sent. 

Sequence is started and the scene is sent.  Sequence begins counting the 1200 seconds before sending the OFF
Controller receives another lux update from sensor (updates are sent periodically and if lux changes).

Controller decides lux is still not satisfactory and sends another trigger.  If sequence is still running, sequence will obey override setting of the current action it is on, otherwise, the sequence will be started.
In this case, already running sequence obeys override setting for the action it is in (that is, the action it should jump to if it receives another trigger) and goes to action 1 and sends scene 0 again.  Sequence begins counting to 1200 seconds again.

If lux stabilises and does not cause triggers, off will be sent and sequence will complete.

Note: You can override action 2 on action 2 if you do not want to have the scene sent again - it will instead only start the action 2 delay again.

Custom Twilight Sequences

If custom functionality for twilight is required, you can opt to give your light sensor a system variable target, and create an On System Variable Change sequence that acts on value to your requirements.  

Example trigger:

Example sequence:

This sequence turns the light on to a scene if the light falls below 300 and then requires light to go over 600 to turn the light off

Timeline for this sequence:

Each time the lux sensor reports, the system variable (0) is changed, which causes a trigger.  
Action 1 checks if the target is on and if it it, the sequence will jump to action 3, which checks our value against a higher lux value.  If the condition of action 3 is met, the lights go off.
If the light isn't on, the lux is checked in action 2 to be below 300 and note in the post action behaviour that the sequence has End Sequence which means that action 3 is NOT checked.

Target lux 

The Target column is used to specify the target lux setting for the sensor. The target lux is used to determine how quickly arc levels step up or down based on what the current lux reading of the light sensor is. The further away the current lux value is from the target lux the faster the arc levels will step up or down.

Behaviour 

The Behaviour field specifies the type of harvesting the lights in the targets list will use, to be able to use row harvesting strength, row harvesting direction or internal lux, you must first enable lux harvesting under the Target column. If the twilight mode is disabled the Twilight on and Twilight off fields will also be disabled.

• Internal lux
  • If the device supports an internal sensor, you may use this option to track each device individually.
  • If this option is not available, or is not enabled the light level will have to be tracked by an external sensor.
• Row harvesting strength
  
  • Sets the severity of the row harvesting
  • High strength means the lights closest to the window will dim at nearly the the same rate as lights further from the window, this leads to the effect of a lot of the rows dimming.
  • Low strength means the lights closest to the window will dim at a much faster rate compared to lights further from the window, this leads to the effect of only the rows closest to the window dimming.
  • Disabled will dim all lights in the targets list at the same time

• Row harvesting dimming direction
  • Sets the direction of the row harvesting
  • Use Normal, if the targets are listed from the window to the inside of the building (Row 1 closest to window)
  • Use Inverted, if the targets are listed from the inside of the building to the window (Row 1 is closest to the inside of the room)
• Row harvesting row count
  • Specifies the number of rows to use for row harvesting

• Twilight mode
  • Specifies the twilight mode

Calibrating light sensors 

There are two reasons to calibrate a light sensor:

1.  So that the lux reading is more easily standardised (light sensors will read quite different values, depending on installation).

2.  So that you can change multiple lux sensors to a new value, ie via the tuneable white sequence mechanism without it having unexpected results, depending on installation.

If you only want lux levels to be from the perspective of the sensor itself then you can skip calibration.

There are 5 fields that must be set in grid view in order for calibration to be completed.

The mode column must be set to meter POV if you want the calibration values to be used otherwise they will be ignored. There are 2 sets of readings that must be taken for the calibration. One when the lights are at their minimum level (lower calibration) and one at their maximum level (upper calibration). For each set of readings you will need one reading from the sensor's perspective and one reading at the desired point where you want the lux levels to be read from which is usually a desk or something similar.

The reading from the sensor's perspective can be easily done by right-clicking the cell and clicking set to current sensor level. This will only work if the control system is online otherwise it will have to be done manually.

After the calibration levels have been set and the mode is correctly set then the lux levels that are used for light sensor configurations will now be calculated based on the where the meter POV readings were done from. 

Light sensor values with an slx suffix signify a light sensor level reading from the sensor. This is usually shown before a sensor has been calibrated. After calibration a light sensor level will appear as lx or if the light sensor is set to meter POV, it may also appear as mlx.