Ideas wanted for car proximity sensor.

[Russell Griffiths]

Greetings group.
I am planning to design a driveway alarm.
The aim is to install some kind of sensor to detect a vehicle
in the driveway up to 100m from the house.

If possible the sensor should be hidden from view.

I have made my own very detailed indexes of schematics in the magazines.
If you would like a copy, email me direct.

From the indexes, I have found many possible sensors,
ie:- infrared beams, PIR sensors, Ultrasonic etc.

The one I like the most at the moment was sent in by
David T. Francis from Cannonvale Qld. Electronics Australia 06/99.

This uses a 3 turn coil buried in the driveway with associated
detection circuit.

I would like to know if the detection circuit needs to be located
close to the coil, or if it could be located up to 100m from it.

And how deep the coil can be buried.

Would more turns make it more sensitive?

Does anyone have any suggestions?

Does anyone know David Francis?

Thanks in advance.

Russell Griffiths
Rochester Vic.

 

[Philip]

Sounds like a metal detector!
The sort of thing they use at Trafic lights.
Best to keep depth les than 20mm if you want to detect small bikes as well
as cars.
The number of turns will be related to the frequency the oscillator is
running at.
When a meta object come it to range the resonate frequency is pulled. Which
is what is detected.

"Russell Griffiths" <rg26ce1991@hotmail.com> wrote in message
news:13cdb672.0404102117.1536c29b@posting.google.com...

Greetings group.
I am planning to design a driveway alarm.
The aim is to install some kind of sensor to detect a vehicle
in the driveway up to 100m from the house.

If possible the sensor should be hidden from view.

I have made my own very detailed indexes of schematics in the magazines.
If you would like a copy, email me direct.

From the indexes, I have found many possible sensors,
ie:- infrared beams, PIR sensors, Ultrasonic etc.

The one I like the most at the moment was sent in by
David T. Francis from Cannonvale Qld. Electronics Australia 06/99.

This uses a 3 turn coil buried in the driveway with associated
detection circuit.

I would like to know if the detection circuit needs to be located
close to the coil, or if it could be located up to 100m from it.

And how deep the coil can be buried.

Would more turns make it more sensitive?

Does anyone have any suggestions?

Does anyone know David Francis?

Thanks in advance.

Russell Griffiths
Rochester Vic.

 

[Russell Griffiths]

Thanks Philip.
Would the range be increased if I put more current through the
3 turn coil?

The circuit in E.A. 06/99 uses a +- 9v to 15v supply with a 324 op-amp.
The coil has 10k in series.

Russell.

 

[Philip]

Had to say without seeing the circuit.

These circuits work either by detecting the change in DC current that occurs
in the present of metal or by the change in resonant frequency of the tunned
circuit.
The resonant frequency method is likely to be more sensitive. However there
is a trade off between sensitivity and stability.


"Russell Griffiths" <rg26ce1991@hotmail.com> wrote in message
news:13cdb672.0404122203.431d9191@posting.google.com...

Thanks Philip.
Would the range be increased if I put more current through the
3 turn coil?

The circuit in E.A. 06/99 uses a +- 9v to 15v supply with a 324 op-amp.
The coil has 10k in series.

Russell.

 

[Andy]

rg26ce1991@hotmail.com (Russell Griffiths) wrote in message news:<13cdb672.0404102117.1536c29b@posting.google.com>...

Greetings group.
I am planning to design a driveway alarm.
The aim is to install some kind of sensor to detect a vehicle
in the driveway up to 100m from the house.

If possible the sensor should be hidden from view.

I have made my own very detailed indexes of schematics in the magazines.
If you would like a copy, email me direct.

From the indexes, I have found many possible sensors,
ie:- infrared beams, PIR sensors, Ultrasonic etc.

The one I like the most at the moment was sent in by
David T. Francis from Cannonvale Qld. Electronics Australia 06/99.

This uses a 3 turn coil buried in the driveway with associated
detection circuit.

I would like to know if the detection circuit needs to be located
close to the coil, or if it could be located up to 100m from it.

And how deep the coil can be buried.

Would more turns make it more sensitive?

Does anyone have any suggestions?

Does anyone know David Francis?

Thanks in advance.

Russell Griffiths
Rochester Vic.

G'day Russell,

Here is a link to a product that will do the job:

http://www.elsema.com/md99.htm

Let us know how you go.

Cheers,
Andy