Bill Killick, Technical & Quality Manager at Finder, highlights some of the weird and wonderful ways that PIR technology is being utilised in modern day applications.
“You’re never more than 6m from a PIR movement detector”, so the saying goes. Well, it does at Finder anyway! We seem to be making more and more of them as our customers find ingenious ways to use them.
Originally developed for military and security applications, these clever little sensors have had several major technological advances that have turned them into a vital part of any automation and control kitbag.
Beating the cistern
You and I never did this of course, but some school pupils have been known to block bathroom sinks and leave the taps on to flood the bathroom – hilarious for a 15 year old. For those less amused, the solution is to connect a PIR detector to the water system via a solenoid valve and then, when mummy’s little darling flees the area, the PIR detects no human presence and turns off the water supply. Very clever!
I have felt his presence
PIR stands for Passive Infra-Red and is the technology used to detect change in thermal radiation as a person moves across a sensor’s view. In the 70s ultrasonic and microwave detectors were popular but were a bit specialist (and caused lots of false alarms). Then someone invented the Segmented Mirror (not actually a children’s fantasy film), transistor-based sensors, and then the Fresnel lens; the modern PIR detector was born.
The first PIR detectors were pretty basic, had short ranges and would only trigger on big movements (hence the boardroom wave every 20 minutes to get the lights back on), but these days manufacturers such as Finder have movement detectors with ranges up to 15m either way, and can sense movements so small that they’re often called ‘presence’ or ‘occupancy’ sensors – suited for areas where the movement is more limited.
The spy who stayed out in the cold
The colder the ambient temperature the better the sensors tend to work and recently we were able to put this effect to good use in a set of warehouse freezers where the temperatures were around -22°C. A typical ceiling PIR can sense up to 6m down, but in the freezing conditions the relative heat of the warehouse team was detected at over 8m and, once connected via a Finder mini-contactor, the detector was able to manage the entire warehouse lighting system without any manual switching.
Of course, you have to be careful with energy saving. It’s no good turning the lights off so much that no one can see anything. These days car park lighting is often on a 90/10 rule – the PIRs turn on the main lights when someone needs them but keeps some low light on all the time for a bit of feel-good and security. Using this idea the other way round, some hotel rooms use a PIR under the bed to activate a soft light when someone gets up in the night. It looks very cool indeed!
Smart’ has the answer Activating cameras, door bells, heating and ventilation systems can all be easily achieved with a PIR but now there is a new word in the PIR world: connectivity. And it changes everything.
Imagine you have set up an entire system of ceiling PIRs controlling the lights in a building and two weeks later the client rings back: “Can you just change the settings on them slightly please…all of them”. “That’s easy”, you say, “All my PIRs have Bluetooth and I can control them from my smartphone”.
Turns out you’re right – there’s a new breed of PIRs now with Bluetooth, KNX and DALI connectivity.
PIRs are now very easy to install, simple to set up (and alter two weeks later), connect to almost anything and are IP-rated. Welcome to the new world of PIR automation. You’ve got a couple ready to go too, right?
