Automotive microwave motion detector at home

I have an automotive microwave motion detector 2.4 GHz. However, I use it at home, powered from the mains. It has a drawback - it is sensitive to glitches occurring at the time of turning on and off electrical devices (mains powered) located near wires going to the sensor. Is there a way to make the sensor (mains powered) insensitive to this?


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Don't know, could be something external coming in. Could be the switching transient on the line itself [like the incandescent bulbs get upset, until your eyes adjust], or could be a switching induced transient [spikes of energy].

To check for external coming in. Run off battery, completely isolated from mains, operate with transients. If no effect, connect one line to the mains and do again.

If still no effect, get a MULTI-stage EMI Line filter. Make certain you use the line filter well, short connections etc.

If THAT doesn't block a transient response, then you need to control your power supply better, which seems odd, since you say this comes from an automobile application. And everyone knows automobile power is really awful.

I guess I'm back to "just HOW did you power this thing from the mains?" Doesn't sound like something got preserved here.

What did you do? Use a lousy brick? One of those cheap thingies with absolutely NO filtering? If so, maybe plugging the brick into a multistage EMI Line Filter may work just right. ...I say multistage, because in my experience a single stage [like those most sold] are not very adequate and in some cases can be useless making NO difference whatsoever!

If you're adventuresome, try taking the filter out of a dead PC supply.

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The 2.4GHz band is crowded as hell so I wouldn't trust it. Why not use an IR motion detector module? You can buy 3-pin sensors the size of your finger tip that include a lens of your choice, line noise rejection, and a buffered output.

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The output signal is in the microamps range so they need another output buffer. They can technically conduct more current but you'll get thermal feedback between the innards of the detector. A 555 chip works great as a combination buffer and timer for driving something else.

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Kevin McMurtrie

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