Photocell Group Linkage¶
Overview¶
Group linkage normally works by motion. When one sensor sees motion, the other lights in its group respond. Photocell group linkage lets a photocell sensor lead the group instead. When the sensor's photocell turns its light on at dusk, it tells the rest of the group to turn on. At dawn, when its photocell turns the light off, the group follows.
Use it where a group of lights should switch together with daylight, such as an outdoor site. Without it, each light switches on its own photocell reading, so lights come on and go off at slightly different times.
Key Facts¶
| Item | Detail |
|---|---|
| Where the setting is | "Group link setting" on the photocell sensor's settings page |
| Choices | "By motion" (the default) or "By photocell" |
| Sensors | EFS106-PC, and later sensors with a photocell on/off function |
| What it needs | Linkage turned on for the group, and "Threshold" turned on for the sensor |
| Firmware | The sensor needs firmware that supports Group link setting. If you do not see the setting, contact support. |
| Do not | Put photocell sensors and daylight harvesting sensors in the same group |
How It Works¶
The photocell has two states:
- PC ON: the light level drops below the On threshold, and the photocell turns the light on.
- PC OFF: the light level rises above the Off threshold, and the photocell turns the light off.
With "By photocell" selected:
- While the photocell holds its light on, the sensor keeps sending linkage messages to its group. It stops when the photocell turns the light off.
- The other lights in the group go to the linkage level. A light's own T1 level takes priority over the linkage level.
- When the messages stop, what a light does next depends on its own settings:
| The receiving light has | After the linkage messages stop |
|---|---|
| Photocell turned on | Holds its T2 dim level and ignores the T2 timer, until its own photocell turns it off |
| Photocell off, motion turned on | Dims to its T2 level, then turns off when the T2 timer ends |
A linkage message does not say whether motion or a photocell sent it. The lights that receive it treat both the same way.
If "Threshold" is turned off on a sensor set to "By photocell", that sensor neither sends linkage messages nor responds to them.
Setting Up Photocell Group Linkage¶
This is the typical setup: one photocell sensor leads, and the other lights in the group follow it.
- Commission the photocell sensor and the other lights into the same zone.
- Add them all to one group. See Creating and Managing Groups.
- Turn on linkage for the group and set the linkage level to 100%. See Multiple Group Linkage.
- Open the photocell sensor's settings page.
- Turn on "Threshold". Enter the "On threshold" and "Off threshold" values and tap "Send" after each. See Photocell Settings and Calibration.
- Under "Group link setting", select "By photocell". Tap the (i) button to read the notice about what the setting needs.
- Set the sensor's dim level and task level to 100%, then tap "Save".
- On each of the other lights in the group, turn on "Motion Sensor", turn off daylight harvesting, and set the task level to 100%.
What to Expect¶
| Time | What the group does |
|---|---|
| Dusk | The photocell sensor turns on and turns on every light in the group |
| Night | Every light stays on |
| Dawn | The photocell sensor turns off, and the group turns off |
Setting It for a Whole Group¶
When every sensor in a group is an EFS106, "Group link setting" also appears on the group's sensor settings page. Tapping "Save" there sends the choice to every sensor in the group.
If the group mixes sensor types, the group page does not show "Group link setting". Each sensor keeps its own choice, so set it on each sensor's own page.
Templates can also carry this setting, along with the photocell On and Off thresholds. Thresholds in a template are entered in fc. See Understanding Templates.
Do Not Mix Photocell and Daylight Harvesting Sensors¶
Keep photocell sensors and daylight harvesting sensors in separate groups. Mixing them may cause unexpected results.
The two kinds of light end their linkage differently. After linkage stops, a photocell light holds its dim level until its photocell turns it off. A daylight harvesting light turns off when its T2 timer ends. In one group, some lights would stay on while others go off.