Twilight Photos vs. Occupancy Sensors

[David E. Rose]

I have a question for the architectural photographers in our forum. I am shooting a recently completed project that has a sustainable focus and therefore uses occupancy sensors for the lighting in most rooms. A twilight shot is desirable, but the building is never fully occupied, so the lights go off in the un-occupied spaces, leaving parts of the facade dark. The lighting designer confirms that there is no override switch for the lights. The sensors are the latest technology (PIR) and require movement to trigger them. Have you run into this and does anyone have a solution for activating the lighting short of having a person stationed in each room?

[Kirk Gittings]

Small world.......see the latest entry in my blog.

[spiky247]

how long do you plan on exposing? maybe have an assistant "drive" remote controlled car through the corridor?

[Vaughn]

Rig up a little pendeleum (sp?) in front of each sensor (a machine nut on a string suspended out form the sensor if wall mounted)?

[Marko]

Tie a balloon - the kind you can buy in most supermarkets - to a small fan in front of every sensor you want to keep active.

[argos33]

I like the gerbils idea - just release a couple hundred in the building and you shouldn't have to worry about them going off!

Really I think it depends on how long they stay on once motion has stopped. Vaughn's idea sounds like a good one to me.

[David E. Rose]

Guys,
Thanks for the suggestions, humorous and otherwise. Kirk, thanks for the link to your blog. I was not aware that you were doing that and your efforts to share knowledge are very much appreciated!

The intent for this twilight shot is a series of exposures of one view over the course of a half hour or so. The individual exposures will be bracketed, and probably not run any longer than a couple of seconds. The idea of placing some moving object in each room was my initial thought. I keep looking at my son's toys for likely candidates. One of the problems is that the sensors have become more difficult to fool as they have become more sophisticated. The other issue is that the latest designs have the ability to learn the use patterns of the room and adjust the turn-off time to achieve the best energy efficiency and convienence for the normal occupancy. This means that the shut-off time after no movement varies.

As sustainability and energy efficiency become normal design criteria, I believe that we will face this challenge frequently. We need to find the perfect cheap wind-up or battery driven moving object (toy) that will keep the lights on!

[Kirk Gittings]

I like the fan idea, perhaps a small cheap oscillating type, but I think I will test it with a piece of crepe paper or ribbon attached rather than hassling with balloons. Something like this:

http://www.jr.com/holmes/pe/HMS_HACP9/

[Paul Metcalf]

So what do the owners do when they want to sit quietly and read a book? Wave their arms every few minutes? I can't imagine why there isn't an override, and if I were king (for the day) I'd make it part of the electrical code to have a manual override. (And how long will it take for criminals to figure out that a "sustainable" house is unoccupied when the lights are out. Sheez) But of course I'm never king.

Does the house have central air or heat? You could turn the fan on the air/furnace (assuming it has a manual switch unlike the lights) and have crepe paper attached to each outlet in each room.

[Arne Croell]

Guys, with respect to the ideas with fans, ballons, etc.: Not all, but most motion detectors are based on the change of IR radiation in their field of view, such as when a human body with a higher temperature than the surroundings passes by (see: http://en.wikipedia.org/wiki/Passive_infrared_sensor). If the moving fake object has the same temperature as its surroundings, nothing will happen. Otherwise, any movement of, say, a curtain due to airflow would trigger it.

[Marko]

Guys, with respect to the ideas with fans, ballons, etc.: Not all, but most motion detectors are based on the change of IR radiation in their field of view, such as when a human body with a higher temperature than the surroundings passes by (see: http://en.wikipedia.org/wiki/Passive_infrared_sensor). If the moving fake object has the same temperature as its surroundings, nothing will happen. Otherwise, any movement of, say, a curtain due to airflow would trigger it.

So, use a hot air balloon? :D

[Arne Croell]

So, use a hot air balloon? :D
Yup, that would work - probably after eliminating the smoke detectors? ;-)
The gerbil idea mentioned above would work, or a hamster wheel in each room...

On a more practical side, for these sensors some temperature change needs to be there, so I would think along the lines of maybe using a fan with some heating built in, or some erratically moving cheap toy like the "Weazleball" with a heat pack (like the ones in gloves or ski boots) attached to it, in a transparent plastic box in view of the sensor. Testing is mandatory beforehand; the cost of lets say 60 Weazleballs, 60 heat packs and 60 plastic boxes adds up...

[Steve M Hostetter]

shut off the main power supply and then back on right as you are ready to make the exposure,, they should all activate for 10 sec. then repeat as needed

[David E. Rose]

The subject in question is a Law School. I won't be cutting off the power, and it wouldn't buy me enough time anyway. Kirk, those fans look great and would probably work with some sensors, but not the IR type, which are the current technology and were used in this project. The issue of the lights going off while the room is in use has been an issue in the past, which is the reason for the sophisticated IR sensors. This is a challenging problem!

[Gary Beasley]

Thats what law students are for. Pay a bunch to watch you from the windows and run back into the room and sit down when you blink a flashlight at them.

[Kirk Gittings]

I wonder if the heat of the motor of the fan would do it?


The subject in question is a Law School. I won't be cutting off the power, and it wouldn't buy me enough time anyway. Kirk, those fans look great and would probably work with some sensors, but not the IR type, which are the current technology and were used in this project. The issue of the lights going off while the room is in use has been an issue in the past, which is the reason for the sophisticated IR sensors. This is a challenging problem!

[David E. Rose]

Those that followed this thread might be interested in the final product. I was lucky to find an evening when most of the rooms were occupied. I tested the shut off time for a sensor in an unoccupied classroom- it was around 15 minutes. After setting up the camera, I did run in to two of the classrooms that were not occupied to bring the lights on. The dark rooms were locked and not yet occupied, so I was OK with the lights being off there.

I still don't have an answer for controlling the lights, but if I come up with something, I will let you know. I may pick up the fan that Kirk suggested and test it. A small oscillating heater may be another possibility.

[argos33]

Nice work David. Perhaps the pendulum idea but instead of a bolt/random weight use a cheap hand warmer? If you bought them in bulk it might be a cheap yet effective solution; that is assuming you can get to the sensor in each room.