Motion Sensor Leaves Office Workers in the Dark

David Mery works in an office where the light is controlled by a single motion sensor that is relatively far from most of the desk-bound employees. When he wrote to the people managing his office to complain that one had to stand and flail about or lob a basketball at the sensor else work in the dark, particularly in the short days of winter (and sent this photo in to prove it), he received this illuminating explanation:

"The sensitivity of the sensors is set centrally for the whole building and is fine for most.

Oh well, David, there's always night vision goggles! Here's a look at David's office with the lights on and the mal-positioned sensor:




  1. Blimey. It would be a brave man who messed around with the electronics in their bosses office. I can see many possible ‘conversations’ but none of them end well! (Though your point is very valid. Theoretically!)

  2. I had the same problem. As the office was open plan the only real time I could work was when everybody had left for home.
    I solved the problem by making up ten darts out of paper. When the lights went out one dart at the sensor.
    One morning I came in and the cleaners were asking about all the darts over the office. I had forgetten to pick them up before going home. I worked in that office for six months.

  3. Fit a motion detection switch in place of the switch in the manager’s office. There are motion detectors that are direct replacements for standard switches so this is a simple DIY task. Use non-removal screws to fix it. Once the manager experiences the problems he will see things in a new light ( or with less managerial darkness )

  4. We had the same problem at my previous employer, they also fitted motion sensors in the toilets above the urinals. Unfortunately when the cubicle door was shut, the sensor became obscured by the door and the lights would go off. The only way to get the lights on was to open the door and jump about, not necessarily recommended when your trousers are around your ankles.

  5. We had a similar situation in the toilets.
    Nominally a location where short visits are expected, but the timing was set unduely short, and, well, while darkness raining (sic) wasn’t a problem, but you could sometimes hear darkness falling.

  6. > When the lights go out, the motor kicks in and spins the blades.
    Very ingenious, but not the sort of thing you should have to do in an office! Health & Safety would be down on you like a tonne of bricks :-)

  7. We fixed this issue with an old solar garden light!
    We took the solar powered garden light apart and replaced the buld with a low-powered electric motor with a cardboard “blade” attatched. When the lights go out, the motor kicks in and spins the blades. this is attached to the ceiling (hooked into the frame that holds the ceiling tiles in place) and the blade moves directly past the sensor, and the lights on go. As a result of the new light, the motor stops and we’re back to square one!!!

  8. If the lights aren’t staying on when you’re working at a computer your employer may be in breach of Health and Safety. HTH

  9. In a blog post here awhile back, I related this story from an expert witness who testifies in cases where automatic doors fail. It really underscores how lame David’s maintenance department was in claiming they had a solution that was satisfactory for most everyone, and the diabolical challenge in adjusting sensor sensitivity: “Technicians had been called in almost on a monthly basis to make simple adjustments to the sensitivity of a door’s control system. ‘Somebody would complain that the door was “ghosting” or opening for pedestrians and vehicles simply passing by at a distance, so a technician would reduce the sensitivity or tilt the sensor downward,’ he recalls. ‘Then somebody else would complain that it wasn’t opening every time a person wanted to pass through, and a different technician would come back and increase the sensitivity or tilt the sensor upward. The cycle would repeat all over again, until the adjustment was over-corrected and an individual was injured.’ I assume they switched over to a manual door at that point!

  10. @Karen, thanks for publishing this story.
    @Ray, as these are motion and not heat sensors I haven’t considered burning the place down :-) I have been tempted by a remote helicopter but have managed to resist temptation so far.
    The ways these sensors are used is very much as if they are tools of a cult of technology for its own sake. They work great in places where people move and don’t feel any affiliation to, such as staircases and corridors, but in city offices using a combination of one light switch per room and (education if needed and) trusting staff to use the switch has a much greater efficiency in term of productivity, morale and energy savings.
    br -d

  11. Hi David,
    I pity you as I was in the same type of office with exactly the same problem about 8 years ago, and this lasted for two or three years until a dreadful thing happened.
    The firm was Thales in Crawley, and I designed electronic circuits.
    We fixed up pieces of paper on the ceiling connected to a string to pull when the light went out, which was distracting when in the middle of a train of thought.
    Writing to the maintainance department, they took no action, and desinging took much longer as a result.
    I then found that a cooling fan positioned on a closer desk kept the light on.
    Because of the noisy fan a collegue put thick carpet tiles round it (not my idea).
    Unfortunately I forgot one day to switnh the fan off as it was on the other unused desk, when I went home. My colleauge did not either.
    Late in the evening the security guy patrolling saw a fire starting from the desk; it was the fan, overheated due to the carpet tiles.
    The place would have burnt down if he had not seen it.
    Of course I got the blame and had to go to a diciplinary meeting with personnel, where I mentioned the other guy and his carpet tiles.
    I was glad when it was time to retire after the way I was treated, and the dreadful dimly lit with no windows building.

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