Control Systems – Sensor Control

Lighting has come a long way from 100 FC on a task plane while burning 24/7/365.  Now, we’re lucky if we can provide the client 30 FC, a task light, and some form of automatic shut off without the Power Police descending on our doorstep.  The days of supplying a light switch to grant just the user control of a space have dwindled and gone.  I’m not saying there’s anything wrong with a switch, I’m just saying that you better have some sort of automatic backup. 

With the advent (and in some cases, enforcement) of ASHRAE 90.1, very few spaces in building are mandated without a required “automatic off” function for the lights.  Whether by time-based or occupancy-sensing control, ASHRAE doesn’t care as long as the lights switch off by themselves after the set time limit.  Good news for the world’s energy store, bad news for designing engineers, only codes that are more stringent are being introduced to the masses.  And technology, it is quickly advancing past what most would consider to be the “simple” control solution. 

So where is this rambling going?  I want to achieve two separate goals through a number of posts over the next couple days.  First, I want to make you more aware of the different “tiers” of control system that is available at your fingertips.  Control solutions range from simple to complex (or perceived to be simple and perceived to be complex).  Systems have emerged to simplify user control or contractor installation (and a lot of times both), and it is important to understand these tiers so you can provide proper recommendations for specific applications.  The second goal is to better acquaint you with the palette of control tools that is available to you through the Federated line card.  Made of all flavors and sizes, the controls manufacturers were selected so that you can mix and meld to meet those simple or complex applications that are placed before you. 

Let’s start with some systems overview. 

When looking at systems logically, there are three separate tiers where the majority of systems fall.  Okay, so according to my logic there are three tiers that these systems fall into.  Now, of course there will always be exceptions, but the majority of systems can be broken down into these three types:  Sensor Control, Centralized Control, and Individual Fixture Control. 

Let’s start simple. 

And Sensor Control is really as simple as it sounds.  With this control type, you are providing local control to rooms and lighting zones.  No fancy processors, no fancy connections, just low voltage wiring and a sensing device. The easiest way to look at this solution is to look at an individual room.  If you want to turn the lights on/off based on human presence, then you install an occupancy sensor.  If you’re looking to control lights because of the amount of daylight in the space, we’re talking about a photocell.  These are individual devices that will be attached to a group of lights or all the lights in the room, and those lights will be controlled off of the sensor inputs/outputs. 

The control of this type of system is achieved through the wiring.  Sensors are either wired in line with the lights or they are wired to power packs via low voltage wirings.  With low voltage sensors, the power pack is then placed in line with the lights. 

A Sensor Controlled system is not stupid; it is just limited by the intelligence of the sensor itself.  Sensors can do many different things, including having different sensing capabilities, control multiple zones, and even dim  zones to different levels.  Control is always limited by the way the system is wired.  If a light is wired separately from a sensor, the only way to control it by the sensor is to rewire the zone or sensor.  I don’t want you to call me a liar later, so I’m going to give you a sneak peak.  I said sensors are limited by their intelligence and wiring.  Systems can be provided that allow the sensors to do both, we are just no longer talking about a sensor controlled system. 

Sensor control is really the most common form of lighting control, and its necessity is often dictated by one thing: cost.  Of all the options, this solution is by far the least expensive way of meeting all code requirements with regards to automatic shut off.  However, this system has the most amounts of limitation.  The sensors will control what they are wired to, and they will only operate to the level the sensors can operate at.  Yes, the sensors can be adjusted, but they must be adjusted individually and it is recommended those recommendations are made during installation.  Full building adjustments can only be made by reprogramming every sensor individually.  You will not make any friends with the contractor or building manager explaining that one…

So Sensor control is the simplest type of lighting control.  We’re going to break here, and come back a little later with the next tier of control, a centralized lighting system.

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