If your lighting is only controlled by a switch on the wall, it’s time you added some sensors. It needn’t be difficult or costly – and could save you a lot of money.
Forget about the jargon, such as IoT, 'smart', mesh networks, platforms and protocols, this article describes simple ways to improve the efficiency of your lighting installation by using stand-alone controls.
We have included some very basic sensors and also more complex ones which can analyse data and connect to networks.
Briefly, there are two things you can do. Firstly, you need only switch the lights on when required. This is usually triggered by movement. This can save a huge amount of energy in spaces that are rarely used. Why are the lights on if there is no-one to benefit from them?
Secondly, you can make the sensor adjust the illumination to suit the location at any particular time. If a room is flooded with daylight, you don’t need the lights on.
All the sensors listed are standalone so you can install them into existing installations. Of course, the sensors can also be used in new installations but it might be easier to get them integrated in the light fittings when you order them.
One of the first things you need to do is to check what kind of driver or ballast is inside the existing luminaire. Some can only be switched on or off but many have extra terminals for control wires or a wireless signal. Read the label on the driver carefully and you will see what control signal they will accept. Typical ones are DALI, 0-10V and DMX.
You can fit a sensor next to each fitting but it might be more economical to use one sensor to control a group of luminaires. E.g a small office or a corridor. This can be done wirelessly but, at that point, you might need some specialist advice.
Most sensors are passive infra-red (PIR). These work by transmitting a beam and then detecting any change when it reflects back. They detect the warmth from a person or animal when it interrupts the beams.
The sensors are directional and often have optional blanking plates to limit the detection angle. For example, up and down a corridor. The beams are sometimes called switching zones.
Note that PIR works by line of sight. A small partition might block movement beyond it.
PIR detectors work less well in hot environments where the ambient temperature is similar to that of a person; typically, around 35C because there is little heat difference to detect.
You can have narrow beams and wide beams and the detection coverage is affected by the mounting height. It’s all down to the geometry of the installation.
An odd effect that you may have noticed is that you actually have to cross a beam to trigger the sensor. You sometimes find you can walk almost up to a PIR controlled door before it opens and that is because you are walking between the beams. The solution is to zig-zag your way towards the door but don’t blame me if you get breathalysed!
Microwave sensors work in a similar way but do not use beams. Instead, they look at changes to the 'echo pattern' of the space and detect movement by changes in the pattern.
Unlike PIR, they are not affected by temperature. There are two other aspects of microwave sensors that may, or may not, be an advantage. Firstly, they can detect movement through glass panes or stud walls. Therefore, movement beyond a glass partition or an adjacent office might trigger them.
Secondly, they are much more sensitive to movement – a draught causing a window blind to move may trigger the sensor.
Both these sensors can be used as presence detection or absence detection. These are similar concepts but differ in the way the lights are switched on and off. 'Corridor hold' is where nearby lights are also switched on. This gives a feeling of security to users who are working in nearly empty premises.
Light sensors can be used to dim the lights according to the amount of daylight available. I.e. the luminaires are dimmed when there is sufficient illumination from the daylight. This is known as daylight harvesting or daylight regulation.
Obviously, lights nearest the windows will dim the most (and may switch off completely) and the central luminaires in a deep plan office may not dim at all.
Light sensors should be positioned so that they do not receive direct sunlight. However, they can be used to detect the illumination on a floor or workstation caused by direct sunlight.
You should ensure that the dimming is done slowly so that it is not noticeable to people using the space. Also, you need to incorporate a delay period so that the luminaires do not respond to a short period of low illumination caused by a passing cloud.
Care should be taken about switching lights off completely. There is a natural tendency for users to manually switch the lights on again regardless of the illumination level.
Related to this is where the sensors are used to provide a constant level of illumination throughout the whole period of the installation. As the output from the LEDs slowly drops and dust accumulates on the luminaire surfaces, the sensor tells the driver to increase the output.
CP Electronics EBDRC
This long-established electronics company is now part of the Legrand group. CP Electronics has a huge range of sensors and we have chosen this particular one as a typical example.
The EBDRC sensor has a tiltable head, from 15 to 90 degrees so that you alter the detection distance. Together with its curtain lens, it is specifically designed for long range detection such as corridors and aisles. For example, it can detect movement at up to 24m from a 2.8m mounting height. This is a vastly greater distance than can be achieved with a fixed head unit.
You can also set the time delay and lux settings remotely via a simple IR handset. As well as simple on/off, it can also send DALI and 1-10V analogue signals to the luminaire.
Other sensors in the range include a sophisticated multi-beam unit for warehouses.
Enocean Easyfit EMDCB
This is different from many other PIR detectors because it is solar powered and wireless. You don’t need to replace batteries nor power it from the luminaire or separate supply. Instead, the EMDCB has an internal energy storage element which will operate the device for up to four days in absolute darkness. The signal from the sensor to the luminaire is transmitted wirelessly via Bluetooth and the Casambi platform. It means that you don’t have to mount the sensor adjacent to the luminaire. Typically, you could mount it up to 10m away indoors and even further with outdoor installations.
The detection radius is 5m when installed on a 2.5m high ceiling.
As well as motion detection, the sensor allows light level control which will operate from total darkness up to 65,000 lux.
LEDvance PIR sensor
This is a nice, simple, non-dimmable PIR sensor available in an IP20 recessed version or an IP44 surface mount version. You can set the time delay from 2 seconds to 15 minutes. This makes it ideal for stairwells, bathrooms, store cupboards etc. On a normal height ceiling, the detection range is 6m.
The light sensor can be adjusted to trigger from 1 – 1,000 lux.
What I like about this unit is its simplicity. It is easy to understand and you can see its capabilities and what it does without any complications.
Optex WX Shield
Optex specialises in sensors of all kinds from doors and access to vehicles and visual verification. The majority of their products are for outdoor use. This particular unit has just been launched and combines both PIR and microwave in one sensor.
The WX has twin PIR beams that can detect the difference between movement from an animal like a fox and that of a child. The WX also covers 180 degrees and the right and left hand sides can be controlled individually (sensitivity, alarm trigger etc).
There are shutters and masks so that you can limit the detection angle. It has the option of a day and night mode so that it will only operate when light levels are low.
There is also clever internal software that recognises when someone attempts to disable the sensor by masking it with tape.
Steinel IR Quattro HD
Steinel offers a huge range of sensors to suit just about any application. They can be used, indoors, outdoors, for loading bays, lecture theatres. They can detect the difference between human movement and that of animals or foliage blowing in the wind.
I chose the IR Quattro HD for two reasons. Firstly, the lenses on it provide a square detection pattern so it is much more suited to conventional applications such as large offices, lecture theatres, sports halls, factories etc.
Another reason is the high number of beams/switching zones. The HD suffix denotes high definition which is achieved with 4,800 beams. This compares with 500 – 1,000 for a conventional detector. This density of beams means that much smaller movements can be detected. For example, people typing or doing fine assembly work.
Sundrax Motion sensor
This is slightly out of the ordinary in that it is a motion sensor for a streetlight but I have included it to open up the possibilities of what can be done with sensors nowadays.
Sundrax is a developer and manufacturer of hardware and software for smart city lighting control. This particular motion sensor dims the streetlight up and down depending on vehicle and pedestrian traffic flow. You can automatically have full output at peak times and then dim down at quiet periods. When movement is detected, the luminaires will increase their output.
Like other streetlighting systems, the unit can transmit data to other lanterns so they respond in advance of the traffic. The lighting level varies with the pedestrian and vehicle traffic.
The system also has tilt and vibration sensors so that you can tell if the column has been hit or maybe oscillating too much in the wind.
Tridonic basicDIM Wireless
Tridonic is well known for its control systems and drivers and this unit is the basic movement and light level sensor. The basicDIM is really aimed at OEMs but any review of electronics for lighting needs to include this unit.
That said, it is highly scalable and can control a large number of luminaires wirelessly using Bluetooth and the Casambi platform. Your luminaires need to be fitted with a 24v constant voltage or DALI driver.
As you might expect, the basicDIM is the entry level unit and there are much more complex and sophisticated control options available.
The sensor can be mounted at up to 4m and has an 8m diameter detection range at 3m height. The light measurement detection at the sensor head is 1 – 2,000 lux.
Users can choose whether to control the lighting using a remote app or the basicDIM wireless user interface. It is set up to control, dim and provide scene setting for groups of luminaires.
- See the latest lighting control sensors at the LuxLive 2019 exhibition. The show takes place at ExCeL London on Wednesday 13 November and Thursday 14 November 2019. Entry is free if you pre-register. For more info, click HERE