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'[PIC] Microwave sensor for PIC?'
2005\09\21@220641 by Crayola

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I am looking for an off the shelf microwave
sensor that I can easily interface with a PIC.
Something similar to Parallax's PING Ultrasonic
sensor. Any ideas?

Thanks,
Mike


2005\09\22@010921 by Robert Rolf

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Motor vehicle police radar detector.
Covers lots of bands (X,K, Ka) and is already interfaced
to a PIC.

You'll have to be a LOT more specific about what frequency
of microwaves you want to detect. The wavelength
affects how big the sensor has to be.

Robert

Crayola wrote:

> I am looking for an off the shelf microwave
> sensor that I can easily interface with a PIC.
> Something similar to Parallax's PING Ultrasonic
> sensor. Any ideas?
>
> Thanks,
> Mike
>
>

2005\09\22@064706 by Vasile Surducan

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On 9/22/05, Robert Rolf <spam_OUTRobert.RolfTakeThisOuTspamualberta.ca> wrote:
> Motor vehicle police radar detector.
> Covers lots of bands (X,K, Ka) and is already interfaced
> to a PIC.
>
> You'll have to be a LOT more specific about what frequency
> of microwaves you want to detect. The wavelength
> affects how big the sensor has to be.

 Not how big, but what is the principle will use. A tunable detector
will work different than a wide band detector. There are plenty wide
band detectors covering from 100KHz to 1GHz or from 50 MHz range up to
7GHz and up to -60dBm detection range. Look at AD and Linear
Technology sites.
If you need a doppler effect microwave detector this is different.

cheers,
Vasile

{Quote hidden}

> -

2005\09\22@091244 by crayola

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> Motor vehicle police radar detector.
> Covers lots of bands (X,K, Ka) and is already interfaced to a PIC.
>
> You'll have to be a LOT more specific about what frequency of
> microwaves you want to detect. The wavelength affects how big
> the sensor has to be.

I am planning on using it as a proximity sensor similar to the
microwave field sensors found in car alarms used in convertibles.
Is this called a doppler effect sensor?

It should be small 3"x3" tops, and be able to sense up to a 360 deg
field around it.. up to maybe 8 or 9 ft.

Any ideas? I guess using a car alarm sensor would work but they
are kinda pricy. There must be a cheaper way to get one out there
or a schematic I could build from scratch.

Thanks,
Mike

2005\09\22@113355 by David Van Horn

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> I am planning on using it as a proximity sensor similar to the
> microwave field sensors found in car alarms used in convertibles.
> Is this called a doppler effect sensor?

Yes. It senses motion and reflectivity. It won't tell you how far away
anything is.  I've used these sensors many times.

A cockroach at 6" looks the same as a man at 20'
An RF absorbing surface can move all it likes and not be detected.
It also can't discriminate between it's own motion, and the motion of
anything else.

> It should be small 3"x3" tops, and be able to sense up to a 360 deg
> field around it.. up to maybe 8 or 9 ft.

Not actually achievable, but you can get close.

> Any ideas? I guess using a car alarm sensor would work but they
> are kinda pricy. There must be a cheaper way to get one out there
> or a schematic I could build from scratch.

Schematics won't help much with microwaves. The PCB and enclosure ARE
part of the circuit. For some of these devices, the antenna is also
etched right into the board. Trace widths and lengths, and type of
material are critical.

The ARRL UHF and Microwave handbook will give you a good idea of what
you're up against, you'll be looking probably between 0.9 and 24 GHz.




2005\09\22@182837 by Crayola

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> > I am planning on using it as a proximity sensor similar to the
> > microwave field sensors found in car alarms used in convertibles.
> > Is this called a doppler effect sensor?
>
> Yes. It senses motion and reflectivity. It won't tell you how
> far away anything is.  I've used these sensors many times.
>
> A cockroach at 6" looks the same as a man at 20'
> An RF absorbing surface can move all it likes and not be detected.
> It also can't discriminate between it's own motion, and the
> motion of anything else.

That's okay.. I am planning on using it to trigger a animatronic
when something comes walks into its field. I understand they actually
cant do 360 deg since it radiates out in a directional pattern based
on the antenna orientation.

>Schematics won't help much with microwaves. The PCB and enclosure ARE
>part of the circuit. For some of these devices, the antenna is also
>etched right into the board. Trace widths and lengths, and type of
>material are critical.

Hmm, since I am not an EE I'll stick with a premade
sensor I guess. Any ideas where I can get them the cheapest?

Thanks,
Mike


2005\09\22@184634 by David Van Horn

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> Hmm, since I am not an EE I'll stick with a premade
> sensor I guess. Any ideas where I can get them the cheapest?

You don't need to be an EE, but it helps :)

Bulldog makes some 12V powered ones, about $30 for car alarms.
1.2 or 2.4 GHz, I forget.  Useful range probably 10' or so.

Higher end car alarm shops sell them.
You can get used 10 GHz Solfan or similar units on Ebay, but they are
rather large.  

Passive IR might work for you, they get very small and very inexpensive.

Also power consumption is much lower. Slow response, and a room full of
warm bodies would put it to "sleep".
They don't see through windows, or walls, like microwave does.




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