Correct me if I'm wrong on any of this, but... The motion sensor (part) output constantly varies. Only when its output reaches a certain level relative to its normal state, then it trips a switch that drives the light for some period of time. Then the lightbulb switches off and waits for another significant change in detection. What I would like to do is have a lightbulb or LED brightness/intensity follow the motion sensor output part. In other words... If a bird flies by, the lightbulb would momentarily dimly light. If a person walks into close range, the lightbulb would continuously shine brightly. If the person walked behind some object, the lightbulb would go off, and then when they reappeared, the lightbulb would come back on. Hopefully I'm not over describing this, but I'll be happy to provide more description if asked. Does such a device (or close) already exist for purchase in a store? The sensor output part typically could not be connected to an LED without putting an amplifier on it? Anybody do this before, any schematic? Thanks. -- Crossposted, feel free to delete the other group(s). BTW. I'm not suggesting that anybody else could use or enjoy this.

look at ultrasonic distance sensors. You can get outputs that are analog for a distance reading of an object infront of it or a switched output when an object is with in range. Jamie

A different kind of motion sensing security light?

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Robert Macy 13 years ago

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.

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Robert Macy 13 years ago

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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.

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Robert Macy 13 years ago

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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.

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John Fields 13 years ago

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.

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John Fields 13 years ago

Then it's more than likely either a photodiode or a phototransistor. Can you post a schematic of the circuit you played with?

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John Fields 13 years ago

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?

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John Doe 13 years ago

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.

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John Fields 13 years ago

eternalseptember.org, huh? Bye.

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John Doe 13 years ago

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

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Ian Field 13 years ago

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.

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Ian Field 13 years ago

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

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Jamie 13 years ago

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

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Jasen Betts 13 years ago

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 ---

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Ian Field 13 years ago

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.

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John Fields 13 years ago

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.

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John Fields 13 years ago

Apples and oranges.

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Ian Field 13 years ago

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.

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John Fields 13 years ago

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.

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Ian Field 13 years ago

Wriggle wriggle!

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John Fields 13 years ago

In which way?

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A different kind of motion sensing security light?

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