Post by thread:[EE] Magnetic driveway monitor

Hello all, I am working on a little project to help secure my home... I have a long driveway and would like to know when someone is approaching my house. I used to use a driveway monitor that had an IR motion detection sensor. This worked, but produced more false alarms than true alarms. Not that it was malfunctioning, but since I live in a rural area, it would detect every deer, groundhog, dog, whatever... I would like to design something similar to: http://www.smarthome.com/790908.html It uses magnetic probes to detect vehicles approaching. Unfortunately, I know nothing about metal detection. I've never even used a metal detector, let alone know how one works well enough to design one. Can anyone give me some pointers on how to go about making magnetic probes such as the ones used in the above system? Maybe a website explaining the basics of ferrous material detection and some simple schematics for a basic metal detection probe? Basically I just want to find a circuit that upon detection of the metal, it sends out a digital pulse. From there I'll use that to activate the alarm be it over wireless, wired, whatever... I'd appreciate any advice. Thanks, Brad

Brad, have you thought about those drive-over detectors that they use to count traffic sometimes? It seems to be just a cable that reacts to being compressed by the weight of a car. It's not as "magicky" as what you're proposing, but seems much simpler. Also, an acquaintance of mine once had a radar setup in his office, pointed out the window, and he could get a decent tracking of what cars were driving by. Just some thoughts. - Marcel On 10/15/07, Brad Stockdale <spam_OUTbrad_listsTakeThisOuTgreenepa.net> wrote: {Quote hidden}> Hello all, > > I am working on a little project to help secure my home... I have a long > driveway and would like to know when someone is approaching my house. I used > to use a driveway monitor that had an IR motion detection sensor. This > worked, but produced more false alarms than true alarms. Not that it was > malfunctioning, but since I live in a rural area, it would detect every deer, > groundhog, dog, whatever... > > I would like to design something similar to: > > http://www.smarthome.com/790908.html > > It uses magnetic probes to detect vehicles approaching. > > Unfortunately, I know nothing about metal detection. I've never even used a > metal detector, let alone know how one works well enough to design one. > > Can anyone give me some pointers on how to go about making magnetic probes > such as the ones used in the above system? Maybe a website explaining the > basics of ferrous material detection and some simple schematics for a basic > metal detection probe? Basically I just want to find a circuit that upon > detection of the metal, it sends out a digital pulse. From there I'll use > that to activate the alarm be it over wireless, wired, whatever... > > I'd appreciate any advice. > > Thanks, > Brad > -

The theory is pretty simple. You form a simple oscillator with a coil, only the coil in this case is very large. http://www.electronics-tutorials.com/oscillators/oscillator-basics.htm The frequency of the oscillator will change quickly as a car drives over the coil. Alternately, measure the inductance of the coil with a PIC and if it changes suddenly, you've got a lot of metal on top of it. You simple need to detect the frequency shift. In our world (PICs) this can be done fairly simply. Of course, the devil is in the details. Signal strength, shift magnitude, etc can be hard to deal with correctly, but for a one-off project that can be tuned, these shouldn't be overwhelming. This might get you started, or at least help you to know what questions to ask depending on how you want to proceed. -Adam On 10/15/07, Brad Stockdale <.....brad_listsKILLspam@spam@greenepa.net> wrote: {Quote hidden}> Hello all, > > I am working on a little project to help secure my home... I have a long > driveway and would like to know when someone is approaching my house. I used > to use a driveway monitor that had an IR motion detection sensor. This > worked, but produced more false alarms than true alarms. Not that it was > malfunctioning, but since I live in a rural area, it would detect every deer, > groundhog, dog, whatever... > > I would like to design something similar to: > > http://www.smarthome.com/790908.html > > It uses magnetic probes to detect vehicles approaching. > > Unfortunately, I know nothing about metal detection. I've never even used a > metal detector, let alone know how one works well enough to design one. > > Can anyone give me some pointers on how to go about making magnetic probes > such as the ones used in the above system? Maybe a website explaining the > basics of ferrous material detection and some simple schematics for a basic > metal detection probe? Basically I just want to find a circuit that upon > detection of the metal, it sends out a digital pulse. From there I'll use > that to activate the alarm be it over wireless, wired, whatever... > > I'd appreciate any advice. > > Thanks, > Brad > -

If I remember, it is not weight that triggers, it's a large coil and ferrous metal interacts with it, changing some frequency in the controller. Probably the same with the system in the link shown. You could probably find a cheap metal detector and mount the coil at the edge of the drive. I've found cheap ones that do detect ferrous stuff at gross sensitivities for less than $10. Get one with a light as well and you'll have a binary interface already set to go. ;) Even if the side of the driveway isn't good enough, you could bury it just under the surface and that would guarantee detection... Marcel Birthelmer wrote: {Quote hidden}> Brad, > have you thought about those drive-over detectors that they use to > count traffic sometimes? It seems to be just a cable that reacts to > being compressed by the weight of a car. It's not as "magicky" as what > you're proposing, but seems much simpler. > Also, an acquaintance of mine once had a radar setup in his office, > pointed out the window, and he could get a decent tracking of what > cars were driving by. > Just some thoughts. > - Marcel > > On 10/15/07, Brad Stockdale <brad_listsKILLspamgreenepa.net> wrote:

----- Original Message ----- From: "Brad Stockdale" <.....brad_listsKILLspam.....greenepa.net> To: "Microcontroller discussion list - Public." <EraseMEpiclistspam_OUTTakeThisOuTmit.edu> Sent: Monday, October 15, 2007 1:38 PM Subject: Re: [EE] Magnetic driveway monitor {Quote hidden}> Hello all, > > I am working on a little project to help secure my home... I have a long > driveway and would like to know when someone is approaching my house. I > used > to use a driveway monitor that had an IR motion detection sensor. This > worked, but produced more false alarms than true alarms. Not that it was > malfunctioning, but since I live in a rural area, it would detect every > deer, > groundhog, dog, whatever... > > I would like to design something similar to: > > http://www.smarthome.com/790908.html > > It uses magnetic probes to detect vehicles approaching. > > Unfortunately, I know nothing about metal detection. I've never even > used a > metal detector, let alone know how one works well enough to design one. > > Can anyone give me some pointers on how to go about making magnetic > probes > such as the ones used in the above system? Maybe a website explaining the > basics of ferrous material detection and some simple schematics for a > basic > metal detection probe? Basically I just want to find a circuit that upon > detection of the metal, it sends out a digital pulse. From there I'll use > that to activate the alarm be it over wireless, wired, whatever... > > I'd appreciate any advice. > > Thanks, > Brad > -- Brad, A search for magnetic vehicle detector produced many results. Maybe something like these? www.sensourceinc.com/PDF/SS-MS30%20Vehicle%20Sensor.pdf http://www.ssec.honeywell.com/magnetic/mark_det.html Good luck, Richard

Hi Brad, I'm doing something similar for my Dad who has had similar problems with the X10 infrared system he uses. Try using the NXP (formerly Phillips) KMZ10B or KMZ51 detectors. These are what the traffic systems usually use. They have a bridge resistor inside that changes when a change in the surrounding magnetic field is detected. You can check out the web page at http://www.nxp.com. You will need an op amp on the output but it all works on 5 volts so that helps. I'm running the output of the op amp into a PIC which just watches for significant rises over the normal level. From there the world is your oyster for what you do with the signaling from there. Regards, Andy {Quote hidden}> From: brad_listsspam_OUTgreenepa.net > To: @spam@piclistKILLspammit.edu > Subject: Re: [EE] Magnetic driveway monitor > Date: Mon, 15 Oct 2007 13:38:50 -0400 > > Hello all, > > I am working on a little project to help secure my home... I have a long > driveway and would like to know when someone is approaching my house. I used > to use a driveway monitor that had an IR motion detection sensor. This > worked, but produced more false alarms than true alarms. Not that it was > malfunctioning, but since I live in a rural area, it would detect every deer, > groundhog, dog, whatever... > > I would like to design something similar to: > > http://www.smarthome.com/790908.html > > It uses magnetic probes to detect vehicles approaching. > > Unfortunately, I know nothing about metal detection. I've never even used a > metal detector, let alone know how one works well enough to design one. > > Can anyone give me some pointers on how to go about making magnetic probes > such as the ones used in the above system? Maybe a website explaining the > basics of ferrous material detection and some simple schematics for a basic > metal detection probe? Basically I just want to find a circuit that upon > detection of the metal, it sends out a digital pulse. From there I'll use > that to activate the alarm be it over wireless, wired, whatever... > > I'd appreciate any advice. > > Thanks, > Brad > -

The units I have used have been pre-built. The coil specs are for about two-three turns, and then doing a twisted pair back to the sensor. They use an LC circuit, and a frequency counter - when a vehicle enters there is a delta Hz due to the change in L, above a certain threshold and fiddle with an output. Search for vehicle loop detector... http://emxinc.com/vehicle-loop-detector-d-tek.html http://www.neverfail.com/NewFiles/Products.html http://renoae.com/traffic/files/AX/Model%20AX%20Operating%20Instructions%20%2003-30-04%20(551-0106-01).pdf >>> KILLspambrad_listsKILLspamgreenepa.net 15 Oct 07 13:38:50 >>> Hello all, I am working on a little project to help secure my home... I have a long driveway and would like to know when someone is approaching my house. I used to use a driveway monitor that had an IR motion detection sensor. This worked, but produced more false alarms than true alarms. Not that it was malfunctioning, but since I live in a rural area, it would detect every deer, groundhog, dog, whatever... I would like to design something similar to: http://www.smarthome.com/790908.html It uses magnetic probes to detect vehicles approaching. Unfortunately, I know nothing about metal detection. I've never even used a metal detector, let alone know how one works well enough to design one. Can anyone give me some pointers on how to go about making magnetic probes such as the ones used in the above system? Maybe a website explaining the basics of ferrous material detection and some simple schematics for a basic metal detection probe? Basically I just want to find a circuit that upon detection of the metal, it sends out a digital pulse. From there I'll use that to activate the alarm be it over wireless, wired, whatever... I'd appreciate any advice. Thanks, Brad

Hi Brad, there was a PIClist thread exactly a year ago called [EE] Vehicle detection - magnetic sensors? which you could look up > I have a long driveway and would like to know when someone > is approaching my house. I used to use a driveway monitor that > had an IR motion detection sensor > http://www.smarthome.com/790908.html I suggested http://www.siliconchip.com.au/cms/A_102998/article.html Was available as kit KC5402 from http://www.jaycar.com.au , way less than the $500 smarthome unit. They have sales reps in the US or a broken-beam system using a laser pointer

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 On Tue, Oct 16, 2007 at 10:32:54AM +1300, Jinx wrote: {Quote hidden}> Hi Brad, there was a PIClist thread exactly a year ago called > > [EE] Vehicle detection - magnetic sensors? > > which you could look up > > > I have a long driveway and would like to know when someone > > is approaching my house. I used to use a driveway monitor that > > had an IR motion detection sensor > > > http://www.smarthome.com/790908.html > > I suggested > > www.siliconchip.com.au/cms/A_102998/article.html > > Was available as kit KC5402 from http://www.jaycar.com.au , way less > than the $500 smarthome unit. They have sales reps in the US How much current did the device consume? I have an project where that'd be useful, but it has to be fairly low power so I can run it off batteries. - -- http://petertodd.org -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.6 (GNU/Linux) iD8DBQFHE9333bMhDbI9xWQRAu/fAKCfmM13hWLudcgFWzKJA5Xqa93YzQCgnq55 DKhNguRp9wantRtUKG5fJ8U= =dEcV -----END PGP SIGNATURE-----

You don't even have to do that.. A car driving by a coil, distorts the earth's field by a surprising amount. With a simple differential amplifier (three op-amps and some 1% resistors) you can see traffic going by on the third floor of an apartment building, 10-20 feet from the street below, using a "telephone pickup" coil. Been there, done that. With a larger coil, especially one with a large area, and closer in, the signal is much larger. A loop of wire in the road is good too, but you don't need to go to that extreme. The "metal detector" approach works, but you'll be better off, if you must go that route, to use the balanced field type, that won't be sensitive to heat, cold, rain etc. A pair of coils are used, with the larger one in a shape that's hard to describe in text, but basically such that the smaller coil can be placed right over it in a spot where it gets no, or almost no signal when the large coil is driven with a fairly large signal. External metal, ferrous or not, distorts that field, and imbalances the system resulting in a larger signal in the small coil. Boxcar integrator or other synchronus detection can be done, to reject noise, and the amplitude and phase of the signal will tell you something about the target.

Have you thought about using piezo cable? This is the same type of cable that in road traffic light sensors and roadside speed recorders use. This stuff can be quite sensitive. Colin :: I am working on a little project to help secure my home... I :: have a long :::: driveway and would like to know when someone is approaching my :::: house. I :::: used :::: to use a driveway monitor that had an IR motion detection :::: sensor. This :::: worked, but produced more false alarms than true alarms. Not :::: that it was :::: malfunctioning, but since I live in a rural area, it would :::: detect every :::: deer, :::: groundhog, dog, whatever... -- cdb, RemoveMEcolinTakeThisOuTbtech-online.co.uk on 16/10/2007 Web presence: http://www.btech-online.co.uk Hosted by: http://www.1and1.co.uk/?k_id=7988359 Even if faith is lacking, and hope is non existent, you always have charity and compassion to offer. -- No virus found in this outgoing message. Checked by AVG. Version: 7.5.488 / Virus Database: 269.14.12/1073 - Release Date: 10/16/2007 8:22 AM

On 10/15/07, Brad Stockdale <spamBeGonebrad_listsspamBeGonegreenepa.net> wrote: > Hello all, > > I am working on a little project to help secure my home... I have a long > driveway and would like to know when someone is approaching my house. I used > to use a driveway monitor that had an IR motion detection sensor. This > worked, but produced more false alarms than true alarms. Not that it was > malfunctioning, but since I live in a rural area, it would detect every deer, > groundhog, dog, whatever... > > I would like to design something similar to: > > http://www.smarthome.com/790908.html > > It uses magnetic probes to detect vehicles approaching. And you're supposing they will approach using a car and never by foot, right ? It seems your burglars have leak of imagination... {Quote hidden}> > Unfortunately, I know nothing about metal detection. I've never even used a > metal detector, let alone know how one works well enough to design one. > > Can anyone give me some pointers on how to go about making magnetic probes > such as the ones used in the above system? Maybe a website explaining the > basics of ferrous material detection and some simple schematics for a basic > metal detection probe? Basically I just want to find a circuit that upon > detection of the metal, it sends out a digital pulse. From there I'll use > that to activate the alarm be it over wireless, wired, whatever... > > I'd appreciate any advice. > > Thanks, > Brad > -

On 10/16/07, Vasile Surducan <TakeThisOuTpiclist9EraseMEspam_OUTgmail.com> wrote: > And you're supposing they will approach using a car and never by foot, right ? > It seems your burglars have leak of imagination... Engineering is just another form of applied economics - the allocation of scarce resources. One method to manage decision making is to simplify the problem. 1. Assume the burglar is a spheroid... :-) -Adam -- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - Moving in southeast Michigan? Buy my house: http://ubasics.com/house/ Interested in electronics? Check out the projects at http://ubasics.com Building your own house? Check out http://ubasics.com/home/

It wouldn't be too hard to intercept and modify the throttle signal. When the immobilizer is activated, it simply starts reporting lower and lower values for the throttle position. The engine will slowly get starved of gas, slowly lose power, and no damage will occur to the vehicle or the occupants. It could be hard to remove or modify depending on placement, but without modifying the ECU itself it can always be jumpered. -Adam On 10/17/07, Peter P. <RemoveMEplpeter2006TakeThisOuTyahoo.com> wrote: {Quote hidden}> Robert Rolf <Robert.Rolf <at> ualberta.ca> writes: > > Apparently vans are a very popular theft target so they can haul > > their break in booty away, and then ditch it. > > Perhaps this is a STRONG hint towards the need to install immobilizer type > alarms buried deep in the engine and transmission ? I have no idea how I'd go > about fitting such a thing to a car that is not prepared for it but I'm sure it > is no impossible at all. It could even involve a pic or ten. > > Peter P. > > > > -

How are you going to jumper the signals to 6 fuel injectors or time the ignition. The key is coded, and the computer is looking for that code, where when you get an extra key, the dealer needs to know you are the owner, and if I know Ford's IT systems, the coding for the new key comes from a server, and isn't local generated. M. Adam Davis wrote: {Quote hidden}> It wouldn't be too hard to intercept and modify the throttle signal. > When the immobilizer is activated, it simply starts reporting lower > and lower values for the throttle position. The engine will slowly > get starved of gas, slowly lose power, and no damage will occur to the > vehicle or the occupants. It could be hard to remove or modify > depending on placement, but without modifying the ECU itself it can > always be jumpered. > > -Adam > > On 10/17/07, Peter P. <plpeter2006EraseME.....yahoo.com> wrote: > >> Robert Rolf <Robert.Rolf <at> ualberta.ca> writes: >> >>> Apparently vans are a very popular theft target so they can haul >>> their break in booty away, and then ditch it. >>> >> Perhaps this is a STRONG hint towards the need to install immobilizer type >> alarms buried deep in the engine and transmission ? I have no idea how I'd go >> about fitting such a thing to a car that is not prepared for it but I'm sure it >> is no impossible at all. It could even involve a pic or ten. >> >> Peter P. >> >> >> >> --

I was responding to the question, "How hard is it to make/install an immobilizer". One could make an immobilizer by making the engine controller think that there's no throttle/air, therefore causing the engine to slow down to idle power and essentially immobilizing the car. It seems you believe I was suggesting a way to get around existing immobilizers. The key coding in my 1998 ford is locally generated. As long as you have two keys that the controller accepts, then programming an additional key is straightforward. When you have one key, then it has to be a "primary" key, and then you can program another key. If you've lost all your keys you have to go to the dealer to have it reset. They have undoubtedly strengthened this over the years. You are correct that attempting to bypass this type of system is difficult. So much so that insurance companies apparently are turning down some claims of stolen cars because they believe the system is foolproof. It is, however, not impossible. Some cars even have relatively simple override procedures for the system, or so I've read... -Adam On 10/17/07, Carl Denk <EraseMEcdenkalltel.net> wrote: {Quote hidden}> How are you going to jumper the signals to 6 fuel injectors or time the > ignition. The key is coded, and the computer is looking for that code, > where when you get an extra key, the dealer needs to know you are the > owner, and if I know Ford's IT systems, the coding for the new key comes > from a server, and isn't local generated. > > M. Adam Davis wrote: > > It wouldn't be too hard to intercept and modify the throttle signal. > > When the immobilizer is activated, it simply starts reporting lower > > and lower values for the throttle position. The engine will slowly > > get starved of gas, slowly lose power, and no damage will occur to the > > vehicle or the occupants. It could be hard to remove or modify > > depending on placement, but without modifying the ECU itself it can > > always be jumpered. > > > > -Adam > > > > On 10/17/07, Peter P. <RemoveMEplpeter2006EraseMEEraseMEyahoo.com> wrote: > > > >> Robert Rolf <Robert.Rolf <at> ualberta.ca> writes: > >> > >>> Apparently vans are a very popular theft target so they can haul > >>> their break in booty away, and then ditch it. > >>> > >> Perhaps this is a STRONG hint towards the need to install immobilizer type > >> alarms buried deep in the engine and transmission ? I have no idea how I'd go > >> about fitting such a thing to a car that is not prepared for it but I'm sure it > >> is no impossible at all. It could even involve a pic or ten. > >> > >> Peter P. > >> > >> > >> > >> --

--- Carl Denk <RemoveMEcdenkspam_OUTKILLspamalltel.net> wrote: > How are you going to jumper the signals to 6 fuel > injectors or time the > ignition. The key is coded, and the computer is > looking for that code, > where when you get an extra key, the dealer needs to > know you are the > owner, and if I know Ford's IT systems, the coding > for the new key comes > from a server, and isn't local generated. You are giving them way too much credit. The car has eeprom space for up to 16 trusted keys. When the dealer wants to add another key, they plug their Rotunda analyzer into the car and tell the car to add the next key put in the ignition. The security is by obscurity and nothing more. By the way, you don't have to go to the dealership to add a new trusted key. If you already have two trusted keys, start the car with both of them and then the new key, which will automatically be added to the list of trusted keys. Of course, you have to plan ahead to make it work, which most people don't do. But when I got my car I bought 2 spare keys ($38 each if you know where to look) and ran through the add-a-key process using the 2 keys that the car came with. Cheerful regards, Bob

On Wed, 2007-10-17 at 08:16 +0000, Peter P. wrote: > Robert Rolf <Robert.Rolf <at> ualberta.ca> writes: > > Apparently vans are a very popular theft target so they can haul > > their break in booty away, and then ditch it. > > Perhaps this is a STRONG hint towards the need to install immobilizer type > alarms buried deep in the engine and transmission ? I have no idea how I'd go > about fitting such a thing to a car that is not prepared for it but I'm sure it > is no impossible at all. It could even involve a pic or ten. No need to go "deep in the engine and transmission". I installed an immobilizer in my 87 Olds, simply a relay turning off the power to the ignition module. Instant dead engine with no damage. In my case I simply used an extra output from an aftermarket keyless entry module I installed when I got the car. TTYL

On 10/16/07, Peter P. <RemoveMEplpeter2006TakeThisOuTspamyahoo.com> wrote: > > > And you're supposing they will approach using a car and never by foot, right ? > > It seems your burglars have leak of imagination... > > They are *rich* burglars, Vasile ... If they are rich from burglary, they are not stupids. Meaning they know to fools an infrared pyroelectric detector, go inside the house and deactivated the car monitor system, go back end enter with the van, and empty your house. Which is a good point, because sometime you need to redecorate and starting from an empty room is always easiest. Think positive.

Hi Brad: I'd like to learn what you end up using and how it works. I've spent some time studying what I call outdoor intrusion detectors, see: http://www.prc68.com/I/ID.shtml I live in the forest where there are a lot of deer and other animals amongst the trees so seismic type sensors are of no value. There are a great number of ways that magnetic distrubances can be detected. The more sensitive ones will detect the metal eyelets in a pair of tennis shoes a few feet away. More on my sensors page: http://www.prc68.com/I/Sensors.shtml#Magnetic -- Have Fun, Brooke Clarke http://www.PRC68.com http://www.precisionclock.com http://www.prc68.com/I/WebCam2.shtml 24/7 Sky-Weather-Astronomy Cam

I used to use a switch in series withn the electric fuel pump. (I used the switch normally used to turn the instrument lights off). Without a fuel pump the car would only go for a few hundred metres. Seemed to work OK but was never actually required. (Fitted to a mini van - rough value ~$NZ250 in 1976). RP On 18/10/2007, M. Adam Davis <EraseMEstienmanspamspamBeGonegmail.com> wrote: {Quote hidden}> It wouldn't be too hard to intercept and modify the throttle signal. > When the immobilizer is activated, it simply starts reporting lower > and lower values for the throttle position. The engine will slowly > get starved of gas, slowly lose power, and no damage will occur to the > vehicle or the occupants. It could be hard to remove or modify > depending on placement, but without modifying the ECU itself it can > always be jumpered. > > -Adam > > On 10/17/07, Peter P. <RemoveMEplpeter2006KILLspamyahoo.com> wrote: > > Robert Rolf <Robert.Rolf <at> ualberta.ca> writes: > > > Apparently vans are a very popular theft target so they can haul > > > their break in booty away, and then ditch it. > > > > Perhaps this is a STRONG hint towards the need to install immobilizer type > > alarms buried deep in the engine and transmission ? I have no idea how I'd go > > about fitting such a thing to a car that is not prepared for it but I'm sure it > > is no impossible at all. It could even involve a pic or ten. > > > > Peter P. > > > > > > > > --

>More on my sensors page: > http://www.prc68.com/I/Sensors.shtml#Magnetic Gee, how do you get the time to put all this together ... ;)) That is a powerful list of sensors and stuff. but I couldn't get to the Honeywell Turbidity sensor page (came back saying couldn't resolve IP address). And you spelt Agilent wrong in the IRDA sensor notes. Under the turbidity sensor you might like to put a link to the page that someone posted here some time back. http://instruct1.cit.cornell.edu/courses/ee476/FinalProjects/s2005/jsa25_jyh25/TurbidityMeter.htm Found it eventually in the archives, I thought I had saved a link, but the archives saved me again.