logo@gorn.santa-cruz.ca.us (David Kiviat) (07/08/89)
I have just started work somewhere where the lights are controlled by a system of motion sensors-if nothing moves in a pre-determined amount of time the lights go off. I find this system most annoying as I am often sitting at my desk working when the lights decide to go out and I have to wave my arms to get them to go back on again. What I would like to do is to build a device with a timer where when the timer was wound some sort of signal would be broadcast that would fool the motion sensors into thinking something was moving. When I left the room the timer would run down and the device would shut off so the lights could go out. What I need is some basic information on what frequencies to use and any other general tips on building such a device. Please note I am not against saving energy and the device I have in mind will not cause the lights to stay on very long if I forget to turn the timer off when I leave. Thanks in advance for any help you can offer.
barry@hprmokg.HP.COM (Barry Fowler) (07/10/89)
Without trying to sound sarchastic..... Try a "switch". That is, bypass the switch inside the motion sensor with a SPST (single pole, single throw) switch when you wish to override the motion sensor.
jeffj@pedsga.UUCP (Jeff Jonas) (07/11/89)
In article <358@gorn.santa-cruz.ca.us>, logo@gorn.santa-cruz.ca.us (David Kiviat) writes: > > I have just started work somewhere where the lights are controlled by a system > of motion sensors-if nothing moves in a pre-determined amount of time > the lights go off. You didn't mention how the motion was detected. The most popular kind of detection these days for non-critical applications (like lighting control) is using the Passive Infra Red (PIR) detectors. It's an infrared detector on a chip, usually with a fresnel lens over it to give a better range of view. You can see these things up close at most hardware/home imprevement centers: they have a milky plastic window. It works by sensing changes in infrared light. What I'd do is look up the frequencies of sensitivity of the detector (possibly on one of the brochures that I can't reach until the weekend), and build a little box as follows: there's an infrared LED on the top, aimed at the sensor. There's a momentary pushbutton. Push the button and for 30 minutes, the LED blinks at a slow rate (once every 10 seconds), just enough to trigger the motion detector. The timer is a 'pop up' timer (resettable one shot), so pushing the button gives you 30 more minutes. Battery powered, a walkman sized case would be generous. __________ UNIX policeperson: "HALT! You're under arrest!" User: "Huh?" UNIX policeperson: "You have 25 CPUS in a residentially zoned area. The limit is 10. VCRs and microwaves count" Jeffrey Jonas INTERNET: jeffj@pedsga.tinton.ccur.com USENET: allegra!io!mtune ---------> petsd!pedsga!jeffj decvax!mcnc!rutgers _____/
erk@americ.UUCP (Erick Parsons) (07/13/89)
From: logo@gorn.santa-cruz.ca.us (David Kiviat) Message-ID: <358@gorn.santa-cruz.ca.us> >I have just started work somewhere where the lights are controlled by a system >of motion sensors-if nothing moves in a pre-determined amount of time >the lights go off. I find this system most annoying as I am often >sitting at my desk working when the lights decide to go out and I >have to wave my arms to get them to go back on again. What I would >like to do is to build a device with a timer where when the timer was >wound some sort of signal would be broadcast that would fool the >motion sensors into thinking something was moving. When I left the >room the timer would run down and the device would shut off so the >lights could go out. What I need is some basic information on what >frequencies to use and any other general tips on building such a >device. Please note I am not against saving energy and the device I >have in mind will not cause the lights to stay on very long if I >forget to turn the timer off when I leave. Thanks in advance for any >help you can offer. Heres a little something that I whipped up in a similiar situation :-) mech oooo / / /-- light sensor arm o| | \/\/ / \ / / ----- / \ / / | | <--- interface / / --- |------|/ |O| | | |little| | | | ----------------|black | | | -------------------|box |------------------| | | |------------------|O| Desk Top... |------| / \ ------------------------------------------------------------------ | | Sorry couldn't resist.. -- ------------------ // -----------Cut-Here---------------------------------- Erick Parsons // Words for the wise: *If it works don't fix it.* Sacramento Ca // mail to: ...pacbell!sactoh0!americ!erk ------------- \\// --------------------------------------------------------
root@swituc.UUCP (Admin) (07/18/89)
> >I have just started work somewhere where the lights are controlled by a system > >of motion sensors-if nothing moves in a pre-determined amount of time > >the lights go off. I find this system most annoying as I am often If the motion sensor is an infrared detector, which it probably is, try using a 755-type timer IC firing an IR LED once every few minutes, seconds, etc. You can pick up all the parts at Radio Shack for under $10. including a small enclosure and battery to power it with. I leave it up to the reader to design the (trivial) circuitry.
larry@kitty.UUCP (Larry Lippman) (07/19/89)
In article <163@swituc.UUCP>, root@swituc.UUCP (Admin) writes: > > >I have just started work somewhere where the lights are controlled by a > > >system of motion sensors-if nothing moves in a pre-determined amount of > > > time the lights go off. I find this system most annoying as I am often > > If the motion sensor is an infrared detector, which it probably is, try > using a 755-type timer IC firing an IR LED once every few minutes, seconds, > etc. You can pick up all the parts at Radio Shack for under $10. including > a small enclosure and battery to power it with. > > I leave it up to the reader to design the (trivial) circuitry. While the circuit design is rather trivial, it is unlikely that the circuit will work for the intended purpose. IR LED's of the variety you mention are near infrared (NIR) devices, and typically have an emission wavelength ranging from 810 nm to 980 nm, depending upon the particular LED specification. Passive infrared detectors (PIR) for use in security and energy management systems detect MUCH longer wavelength IR, with typical spectral sensitivity in the range of 2 to 12 microns (2,000 to 12,000 nm). The actual characteristics of these sensors depend upon the sensor manufacturer and the bandpass of the protective cover. The cover will, for example, typically NOT pass any energy below 2 microns so as to preclude interference from ambient light. After all, the function of a PIR is to detect body heat, and NOT be influenced by the effects of ambient light. NIR is too close to ambient light to be detected. <> Larry Lippman @ Recognition Research Corp. - Uniquex Corp. - Viatran Corp. <> UUCP {allegra|boulder|decvax|rutgers|watmath}!sunybcs!kitty!larry <> TEL 716/688-1231 | 716/773-1700 {hplabs|utzoo|uunet}!/ \uniquex!larry <> FAX 716/741-9635 | 716/773-2488 "Have you hugged your cat today?"
howardl@vice.ICO.TEK.COM (Howard Luce) (07/20/89)
How about an incandescent lamp instead of the LED for some longer wavelength content?
brian@ucsd.EDU (Brian Kantor) (07/20/89)
Point a high-intensity ("tensor") lamp at an oscillating electric fan
in view of the motion sensor.brad@optilink.UUCP (Brad Yearwood) (07/21/89)
larry@kitty.UUCP (Larry Lippman) writes: >sensitivity in the range of 2 to 12 microns (2,000 to 12,000 nm). The This suggests that the gentleman's problem could be solved (one way or another) by aiming a CO2 laser (10.6 microns) at the motion detector. Brad Yearwood {pyramid, tekbspa, pixar}!optilink!brad
michael@xanadu.COM (Michael McClary) (08/05/89)
In article <358@gorn.santa-cruz.ca.us> logo@gorn.santa-cruz.ca.us (David Kiviat) writes: > >I have just started work somewhere where the lights are controlled by a system >of motion sensors-if nothing moves in a pre-determined amount of time >the lights go off. I find this system most annoying as I am often >sitting at my desk working when the lights decide to go out and I >have to wave my arms to get them to go back on again. What I would >like to do is to build a device with a timer where when the timer was >wound some sort of signal would be broadcast that would fool the >motion sensors into thinking something was moving. Motion detectors are x-band doppler radar. I don't recall the exact wavelength, but it's well under an inch. So a corner reflector a couple inches on a side will do a dandy job of spoofing it. Imagine a hollow metal cube, and you cut off one corner, so you have three triangular metal plates at mutual right angles - a triangular pyramid. Microwaves going in through the open base of the pyramid have one component of their direction vector reversed by the bounce off each surface, so they emerge going right back at the source. Just like roadside reflectors do to light. At any significant distance from the transmitter, a small corner reflector returns as much signal as a very large object, because it reduces the signal loss from inverse fourth power of distance to about inverse square. (It would be exactly inverse square if the reflector were perfect and diffraction were neglected.) But this is a MOTION detector. You must move the corner reflector around a little bit to doppler shift the radar signal. So build one out of heavy foil (like TV dinner trays) and mount it on a moving thing of some sort. (Nitinol "space wings" are ideal.) Motion toward/away from the detector is what counts, and it doesn't take much. Much easier to build than an active microwave gadget.
michael@xanadu.COM (Michael McClary) (08/05/89)
Oops. Forgot about the new infrared motion detectors (and the very old ultrasonics). The corner reflector will spoof ultrasonics, too. (The sound waves work the same way, and are roughly the same size as the x-band microwaves.) Passive infrared is recognizable by a patterned whitish plastic lens. An infrared LED in a blinky-light circuit should do the job. (Put it in series with an ordinary LED for a pilot light.)
morris@jade.jpl.nasa.gov (Mike Morris) (08/07/89)
(Michael McClary) writes: >I have just started work somewhere where the lights are controlled by a system >of motion sensors-if nothing moves in a pre-determined amount of time >the lights go off. I find this system most annoying as I am often >sitting at my desk working when the lights decide to go out and I >have to wave my arms to get them to go back on again. What I would >like to do is to build a device with a timer where when the timer was >wound some sort of signal would be broadcast that would fool the >motion sensors into thinking something was moving. Tape some aluminum foil to the blades of a cheap desk fan. Mike Morris UUCP: Morris@Jade.JPL.NASA.gov #Include quote.cute.standard | The opinions above probably do not even come cat flames.all > /dev/null | close to those of my employer(s), if any.
tomb@hplsla.HP.COM (Tom Bruhns) (08/15/89)
larry@kitty.UUCP (Larry Lippman) writes: > Passive infrared detectors (PIR) for use in security and energy >management systems detect MUCH longer wavelength IR, with typical spectral >sensitivity in the range of 2 to 12 microns (2,000 to 12,000 nm). The >actual characteristics of these sensors depend upon the sensor manufacturer >and the bandpass of the protective cover. The cover will, for example, >typically NOT pass any energy below 2 microns so as to preclude interference >from ambient light. After all, the function of a PIR is to detect body heat, >and NOT be influenced by the effects of ambient light. NIR is too close >to ambient light to be detected. > ><> Larry Lippman @ Recognition Research Corp. - Uniquex Corp. - Viatran Corp. ><> UUCP {allegra|boulder|decvax|rutgers|watmath}!sunybcs!kitty!larry ><> TEL 716/688-1231 | 716/773-1700 {hplabs|utzoo|uunet}!/ \uniquex!larry ><> FAX 716/741-9635 | 716/773-2488 "Have you hugged your cat today?" >---------- The PIR detectors used in my house to turn on/off lights are sensitive to the heat of a woodstove and to direct sunlight (perhaps interrupted by swaying trees). This may give you some ideas: for example, you could pulse a 300W/120V lamp with, say, 10 or 20 volts, and get a lot of IR but not much visible light. If you know where the sensor is, you could focus the IR toward it. Also interesting to note: In the (real) old days of IR spectrometry, spectrometer rooms were lined with 100 watt lights; if you moved from one place to another, you were supposed to turn on a light where you left and turn one off where you went. That was supposed to cause the least disruption to the IR background. So you are probably roughly equivalent to a 100 watt lamp in an IR sense. (Experiments may show you can get by with something much smaller than the 300W lamp suggested; you could try a "heat lamp" with integral reflector envelope for focussing...)