A different kind of motion sensing security light?

What I was mentioning is that today, what used to be a security function - motion sensor, has become a 'courtesy' function - turning on walk lights for guests etc. Your description is accurate. It is like an AC coupled response.

What I was talking about was disabling the ability of an intentional intruder from 'testing' the sensor early. Walking the space, finding range, sensitivity to motion, etc. IF the sensor has immediate response, is easy. IF sensor has a delayed or weird response time, is very difficult to correlate the activity to the sensor's response.

Reply to
Robert Macy
Loading thread data ...

f

nic

et

,
e

I agree that he has the highest potential of success using microwave, or such. But what you describe is usually AC coupled output and you're back to standing still not showing up. You could DC couple the detector, 'remember' the level coming out when nothing is there, and simply go from there, with a cheap ADC and map back into a DAC that runs the lighting.

Reply to
Robert Macy

ich it

l
e
t
c

If you're going mechanical, why not make it a capacitive sensor. Chopping the field from the intruder. Since you kknow the speed of the chopping, you can synchronously detect and obtain EXACTLY the type of signal you want. ...I think.

Reply to
Robert Macy

--
Oops...  

That's wrong. 

A target with a high velocity far from the sensor could the elicit the 
same response from the sensor as a nearer, slower target, so range 
can't be resolved that way. 

Sorry 'bout that.
Reply to
John Fields

--
Then it's more than likely either a photodiode or a phototransistor. 

Can you post a schematic of the circuit you played with?
Reply to
John Fields

--
I've done long-range PIR detection before and 20 feet is pretty easy, 
but 100 feet is going to take some care. 

Can you tell us a little more about your application?
Reply to
John Fields

Google produces 280 results for my "Tonal Voltmeter". I'm sure it was just that, using a photodiode to vary resistance/voltage. It looked like a clear T1 LED. I have nothing left (except fond memories) from experimenting with electronics.

Reply to
John Doe

--
eternalseptember.org, huh? 

Bye.
Reply to
John Fields

eternal-september.org!mx05.eternal-september.org!mx04.eternal-september.org!feeder.eternal-september.org!news.glorb.com!border3.nntp.dca.giganews.com!Xl.tags.giganews.com!border1.nntp.dca.giganews.com!nntp.giganews.com!local2.nntp.dca.giganews.com!news.giganews.com.POSTED!not-for-mail

sv3-4nwdpJ1RnrsGTRlB+DeZt1XaQC4QYiVJVws/lO+WtUPQMicApRclqY4aWsH7DvfSElYVHl067Cbsayd!ZZFMinTjj65oSChkjPueCxBsHpGwgx+BWgecpKUTFXcJu7a0fCvIdy4O4A8Cc0dWuBZZ6w==

properly

sci.electronics.design:267761 sci.electronics.basics:34918

>
Reply to
John Doe

If you mean PIR motion detectors, they usually have twin element pyrometers (thin film thermistor) a motion of a IR source (person) is "grated" to produce a gross change from one element to the other - this is done in various ways such as Freznel type lenses (special IR transparent material) and faceted surface reflecting reflectors.

Reply to
Ian Field

Most of the examples I pulled apart and hand traced the circuit years ago, were based on the LM324.

Reply to
Ian Field

That's strange that you would call them thermistors? TO me a thermistor is a slow reacting device? But yet we have an application where we use a basic pyroelectric 3 wire detector for detecting vibration of small conductor as it exits from an induction heater. This vibration can get up to around 1khz or more when the wire snaps for what ever reason.

I would think a thermistor device would be a little slow for this wouldn't you?

Maybe the units I used have different smoke in side.

Jamie

Reply to
Jamie

AIUI they are closer to capacitor than resistor, the device does sense its own temperature though, they detect remote temperature by black-body radiation changing the temperature of the sensor.

TO me a thermistor

if you could make it thin enough it would work.

--
?? 100% natural 

--- news://freenews.netfront.net/ - complaints: news@netfront.net ---
Reply to
Jasen Betts

I have some continuity/voltage checkers with a thin film PTC in series with an inverse parallel pair of high efficiency LEDs (2mA rating) - the series PTC thermistor can react fast enough to protect the LEDs from application to voltages upto 450V.

Reply to
Ian Field

--
The sensor elements aren't thermistors, which are made from sintered 
metal oxides (NTC) or  a doped polycrystalline ceramic (PTC). 

They're made from gallium nitride, cesium nitrate, polyvinyl 
fluorides, derivatives of phenylpyridine, or cobalt phthalocyanine. 

Moreover, thermistors exhibit a static change in resistance with a 
change in temperature, while PIR elements generate a charge when 
abruptly heated or cooled below their ambient temperature.
Reply to
John Fields

--
Apples and oranges.
Reply to
John Fields

Your usual disingenuous self!

My point is that a thin film thermistor can have a very fast response time - there was no need to be specific exactly what material the thin film was.

Reply to
Ian Field

--
Identifying the materials was necessary in order to show you that 
PTC's can't be PIR sensors, and vice versa. 
    
Whether a thin-film PTC thermistor can have a very fast response time 
is irrelevant when the discussion is about PIR sensors so, as usual, 
you're befuddled. 

On the one hand, consider the PTC thermistor you described and, on the 
other, a PIR sensor. 

The PTC thermistor is designed to have its resistance increase 
spectacularly as it self-heats because of small changes in the current 
through it, while the PIR sensor is designed to generate a miniscule 
charge when the temperatures its elements are exposed to change 
abruptly, ergo apples and oranges.
Reply to
John Fields

Wriggle wriggle!

Reply to
Ian Field

--
In which way?
Reply to
John Fields

ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.