Problem, Solution = gerbils??

I and probably a lotta other people have a chronic problem that is in need of a simple solution. We're about to move into a new bldg and I have to do a lotta install'ns of PCs, etc., so I'm under the desk a lot. Every room in the new bldg has the motion sensors that turn off the lights after a few minutrd, and I have to continually get up and wave my arms to reactivate the sensors.

Some of the sensors are PIR motion detectors, and some are ultrasonic. The US ones could be fooled with a fan in front of the sensor, But how can I fool a PIR motion sensor? I have to have a warm, moving body in front of the sensor, maybe a caged animal? Or a long wave IR generator that moves or generates an intermittent output. I've ruled out candles or other flames for safety reasons. A friend suggested a Lavalamp might work, but I don't think I want to wait ten or twenty minutes to warm it up. Maybe one of those old lamps with the rotating picture and fan blades on top, that turns by convection currents from the light bulb heat. I know that the IR output from IR LEDs is much too short a wavelenght. Any ideas? Thanks.

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My email address is whitelisted. *All* email sent to it goes directly to the trash unless you add NOSPAM in the Subject: line with other stuff. alondra101 hotmail.com Don't be ripped off by the big book dealers. Go to the URL that will give you a choice and save you money(up to half). You'll be glad you did! Just when you thought you had all this figured out, the gov't changed it:

3' long board with incandescent light bulbs on each end, plus a timer to cycle them appropriately ???

...Jim Thompson

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|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
|  Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    |
|  Phoenix, Arizona            Voice:(480)460-2350  |             |
|  E-mail Address at Website     Fax:(480)460-2142  |  Brass Rat  |
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I love to cook with wine.      Sometimes I even put it in the food.

^That would work. I would put two or three bulbs in series ay each end to reduce annoying visible light output and to make the bulbs last practically forever.

--
Guy Macon, Electronics Engineer & Project Manager for hire. 
Remember Doc Brown from the _Back to the Future_ movies? Do you 
have an "impossible" engineering project that only someone like 
Doc Brown can solve?  My resume is at http://www.guymacon.com/

As I stated, and you deleted, I would *not* consider candles and flames because of safety and fire concerns. Thanks, anyway.

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I take it you mean an astable flip-flop that drives the lamps alternately. I'm wondering if the abrupt switching will keep the PIR sensor triggered. I'm thinking that long wave IR would come from a lamp that's not even glowing visibly. Maybe just a dull glow. Since the IR all goes into the same sensor, are two separate IR sources really needed? Maybe I should experiment with just a single lamp..

[snip]

Oops. That'll teach me to skim a bit more closely...

Now I am not quite sure what devices are being used, but all the PIR movement sensors for lights I ahve seen can be toggled into an 'always on' mode by quickly switching the light switch off the on.

I suggest trying a single automotive tail-lamp bulb modulated at 2-3Hz (555 + MOSFET driver). You don't really need to simulate motion with the pyroelectric sensors- in fact they have to turn motion of the target into an AC signal with their Fresnel lens.

Best regards, Spehro Pefhany

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"it's the network..."                          "The Journey is the reward"
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Well, thank you for that information. The usual new bldg has these sensors installed by the electricians, and then all the instructions are discarded along with the leftover packaging, so absolutely *no* one has a clue as to how these work and what to do with them. Isn't that crazily amazing..

I've got an IRF630 and a 2SK2135(?) laying around, maybe I'll make up a power flasher. I guess a 555 isn't really needed, just a flip-flop. I don't need full brightness, so I guess 6 to 9V would be enough supply V, assuming that the FETs will turn on enough at that voltage. The bulb should last about forever. Maybe a wall wart would handle the power. I might connect two lamps in series to get lower brightness.

What about one of those lamps that flicker like a candle?

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Steve Sousa

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A 100 watt incandescent lamp turned on and off periodically will do
it.  The trick is, you have to locate the lamp on one side or the
other of the PIR motion detector's sensitive region so that the heat
from the lamp will only get focused on one of the PIR sensor's two
detectors.

There's no manufacturer's name on them to lead you to a web site where you can find or ask for information about them?

Jeff

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Jeff Wisnia  (W1BSV + Brass Rat '57 EE)

"My luck is so bad that if I bought a cemetery, people would stop dying."

Well, I went out there today and went on a walk-thru of the new bldg with the other honchos. I found that the light switches have _two_ small buttons, side-by-side, labeled "I" and "II". These are set up so that one of them lights the center tube of the three-tube fluo light, and the other lights the two outer tubes of the fluo light. So you can press both buttons for all three. Unfortunately there's no way to rapidly toggle these on and off, because they're like a ball point pen, they're click on, click off. And they're small enough so that if you're trying to hit them quickly, you're likely to press the wrong one, or both of them.

So it looks like your idea of rapidly toggling these, sadly, isn't going to work. And _every_steenking_room_ has them! Damn!

The ones I've seen have two electrodes in neon gas, and don't produce enough IR to do the job.

For the last half hour, I've been googling for motion sensing light switches, and I still haven't come across anything that looks remotely like the ones in this new bldg. I'm going to keep searching until I find one that at least _looks_ like them. So far, I know that they're not Leviton, Zenith or GE.

Ah-HAH! I'm finding out more and more about these sensors. So even tho they're only three leads, ground, power and output, they have more than a single sensor inside? That's good to know, thanks. Maybe that's why J.T. suggested two lights spaced 3' apart.

Yes. AFAIK there are three types of materials used in the sensors: lithium niobate, poled polyvinylidene fluoride, and a ceramic of some sort. Almost all of them internally use two tiny rectangular sensors which generate an electrical signal when they're heated, (or cooled) and they're connected differentially so that if they're both heated or cooled at the same rate the net output from the pair will be zero. A lens is used in front of them so that as a warm object moves across them the image will be focused when it hits them, and as the spot traverses the pair it generates the desired output, which is usually cap-coupled and severely bandwidth limited and eventually used to makes the yes-no decision about whether to turn on the lights, or detonate the bomb, or whatever.

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That's good to know, thanks.

I have done a lot of work with security system PIR sensors. The typical design uses a single sensor and a molded multiple lens array so that the sensor "sees" what you would see if you punched a few holes in a sheet of cardboard and held it a couple of feet in front of you. The "motion sensing" is really a warm body either being in front of the "hole" or between two of them. The sensor then takes the signal. low pass filters it so that no 60Hz gets through, takes out the DC with a series capacitor, then rectifies the signal and runs it into a comparator threshold detector.

--
Guy Macon, Electronics Engineer & Project Manager for hire. 
Remember Doc Brown from the _Back to the Future_ movies? Do you 
have an "impossible" engineering project that only someone like 
Doc Brown can solve?  My resume is at http://www.guymacon.com/