SENLL & Indirect Lighting

Trouble shooting an install with SENLL light level sensor a 4ch relay and PCI. Unfortunately the SENLL sensors are installed in the ceiling above direct/indirect lighting. The only place they were able to move the sensor was between two rows of lights. So the problem is that with an on/off function the lights cycle on/off rapidly at different points in the day. Target is set at 630 Lux and Margin is 21%. This was the most stable I could get when on site. I am wondering even though I am using a relay if I could set the SENLL up as Light Level (dimming) instead of Light on/off, and in the relay adjust turn on threshold to try and build some kind of time factor into this to help prevent the cycling.

Dodge1

 

It sounds like you're stuck with an install with SENLL's in bad locations.

If the difference in Light Level that the SENLL sees when the lights turn either On or Off is greater than the Margin parameter, then you will get oscillation like this, as the sensor constantly flicks between being too bright and too dark for the nominal light level.

The Level control output from the SENLL will dim up and down a group address, using a 1 minute ramp rate. It will do this in a closed loop fashion, under the assumption that a change to the level of the group will result in a change to the brightness of the light it is measuring.

Assigning the light level output to a logic group in a Relay unit, and then adjusting the Turn-On Threshold in the relay unit is going to only delay the switching by a few seconds at best. You also have the added complication of trying to set the Turn-On Threshold to a value that works, but I suspect it might create a few strange "Why aren't the light's on?" moments for the occupants.

If you can't dim the lights and you can't move the sensors then widening the Margin parameter is going to be your best option.

 

Even if the lights are controlled by relays, if you have individual control of more than one light, you could use Light Level (dimming) instead of Light on/off as you suggested, but set the thresholds for turning on to different levels for each light. This would allow finer control of the light and might allow you to reduce the margin of the SENLL

 

Thanks I am going to try testing these avenues next week when I return there. I might try using the restrike delay as well if I keep everything as an on/off.

Dodge1