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Post by kiwicraig on Apr 3, 2010 21:23:41 GMT -8
I like the vehicle loop detector circuit a lot. well done!!
i was wondering as my drive way is already laid and i do not wish to cut into it what other types of effective inductive sensors could be used.
i have thought of mounting it on the fence beside my driveway but think that the temperature changes during the day will affect the stability. also the distance might become an issue.
i have seen a probe version for sale that has an impressive 15ft radius. (might even pick up the neighbors driveway!!)they measure between 6-12 inches long and can be buried beside the drive way.
i would like to attempt to build this could anyone give me any suggestions or details how?
do you think it could run on the same circuit?
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Post by Gary Lecomte on Apr 4, 2010 5:33:51 GMT -8
I like the vehicle loop detector circuit a lot. well done!! i was wondering as my drive way is already laid and i do not wish to cut into it what other types of effective inductive sensors could be used. i have thought of mounting it on the fence beside my driveway but think that the temperature changes during the day will affect the stability. also the distance might become an issue. i have seen a probe version for sale that has an impressive 15ft radius. (might even pick up the neighbors driveway!!)they measure between 6-12 inches long and can be buried beside the drive way. i would like to attempt to build this could anyone give me any suggestions or details how? do you think it could run on the same circuit? i have seen a probe version for sale that has an impressive 15ft radius. (might even pick up the neighbors driveway!!)they measure between 6-12 inches long and can be buried beside the drive way. 15 Foot Radius? 6-12 inches long? SORRY this Doesn't make any sense to me.As to any Coil working, Its all About the "Inductance" of the Coil. Beside the driveway MAY Work. But yes, Distance can be a Problem.
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Post by Deleted on Apr 23, 2010 21:14:21 GMT -8
I am also interested to get suggestions for vehicle coils I wish to bury in the roadway of a new acerage home. I want one coil to be perhaps 900 ft from the house and another at about 300 ft. I would likley use 2 at each locaction to deterimin direction. I'd lke advise of the coil construction (I am thinking I would likley make them 6 ft as suggested by others). I am wondering about encasing the cols in plastic to prevent corrosion. I would use burial cable (likey a Cat5) to run to the house, where it would connect to an input module.
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Post by Gary Lecomte on Apr 24, 2010 5:24:20 GMT -8
That going to require some Expermenting!
As That Distance will add a Lot of Capacitance in parallel with the coil.
If Using Magnet Wire for the Coil, It Shouldn't require any further protection.
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Post by Deleted on Apr 28, 2010 22:22:03 GMT -8
I am also interested to get suggestions for vehicle coils I wish to bury in the roadway of a new acerage home. I want one coil to be perhaps 900 ft from the house and another at about 300 ft. I would likley use 2 at each locaction to deterimin direction. I'd lke advise of the coil construction (I am thinking I would likley make them 6 ft as suggested by others). I am wondering about encasing the cols in plastic to prevent corrosion. I would use burial cable (likey a Cat5) to run to the house, where it would connect to an input module. I'm new here, but I thought I'd take a pitch at this and see what you guys think. Jump right in, as they say. I think this could work, but you'd have to put the circuit out by your coils to keep the sensitivity up due to the capacitance Gary mentions. Cat 5 Electrical Characteristics for reference. Cat 5 would give you eight conductors to work with, so you might naturally be inclined to drop a pair on each of four coils. Cat 5 has excellent crosstalk immunity for high frequency (MHz), weak, low voltage (<1V), and most importantly digital signals, mainly due to the twisted pair arrangement of it's conductors. I'm uncertain what would happen with a lower frequency (hundreds of KHz) signal that's intended to transmit subtle changes in analog value. Why not instead use two conductors to run power out to 'box A' and 'box B', each of which contain the circuitry for two coils. You can use the remaining six wires to pass back the output of each box how you see fit, you'll just have to share a ground somewhere as you're down two conductors. You could use some discreet transistor gate circuitry if you wanted to send direction of travel information if you wanted as well. Doing it this way will spare you a lot of grief in tuning your coils (or getting them to work at all), but has it's own pitfalls as well. Cat 5 is standardized as 24AWG, so you must keep your power supply current low to avoid a large voltage drop. For example a 12V source will be down to about 9.5V across a 50mA load at 900 feet ( calculated here). You'd have to ask Gary (or test) if the circuit will work unmodified at lower voltages, and test the current consumption of the one you build. You can simulate the wire drops to some degree with a bit of tinkering and math. Also note that Cat5 is not often rated for more than 500mA on any one conductor, and sometimes the buried versions are less than the 'tray' versions (more insulation means less heat dissipation for I2R losses). If you're forced to deliver more than that you should use more than one conductor and a lot of care. If carrying the power out there seems daunting, you might consider putting together a simple solar station. Done properly you could probably fit the entire thing in a solar powered lawn lamp housing. It's actually a fairly elegant solution, allowing you to use the cable completely for signal and minimal grief for long term sensor reliability. If you're looking for wire for the loops, I've found that CRT degaussing coils are a great source of heavier gauge magnet wire. I'm on an extremely low budget, so I get almost all my parts from salvage, and this looks like a perfect recycle opportunity. I'm not sure of the gauge of the stuff I salvaged but it looks like 22 or 24AWG and it's red lacquer laminated. One 27" television degaussing coil had more of this stuff than I'll likely ever use, I'd guess over one hundred feet easy. The coil can be found in a plastic sheath wrapped around the large end of the picture tube of any CRT. I must warn though, CRTs are dangerous to disassemble if you're inexperienced or unaware of the hazards. As for it's durability, it's hard to say to be sure. If you're using a lacquered magnet type wire in a hoop there are a bunch of different ways you could bond the wire together: zip ties, tape of various sorts (nothing metallic!), paint (make sure it doesn't dissolve the lacquer insulation), a length of non-metallic hose, etc. Heck, you could cut a 18' 3/4" length of garden hose and feed the wire through repeatedly to make a roughly 6' coil, then use plastic hose fittings (a 'T' fitting to close the loop, and splices elsewhere) and more hose to lead the wire back to your box or tie point. Don't forget to feed the wire through the 'T' fitting as you go, that sounds like a gotcha waiting to happen. The hose and the fittings will compress when you pile on the roadway (and the cars), but you really don't need a completely watertight seal. The big worries are probably mechanical force damaging or shearing the coil and corrosion where bare copper meets wet soil. I'll stop, I think I've run on a bit much. I have a tendency to babble. Hope that helps
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Post by Gary Lecomte on Apr 29, 2010 5:41:30 GMT -8
It is Not good to put the Circuit Outside as suggested.
Such Temperature changes will result in Instability of the Frequency.
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Post by Deleted on Sept 11, 2010 5:48:35 GMT -8
Hi,
As a hobbiest in mainly digital electronics, I have just built this circuit with the intention of integrating it with my home automation system (will ultimately open a pair of gates). What I'm not sure about though is how to 'tune' it to actually work!
What am I expecting the voltage to be on LM393 pin 6? As I understand it this should reach the voltage on pin 5 (and sink the pin 7) when the resonant frequency in the coil (with the car on top) effectively induces the voltage increase?
So what would it be normally at pin 6 when the is no vehicle on top? Very close, or essentially sunk to ground? It seems to sit at around 0.06v
Also, how can I determine what the frequency of the coil would be or otherwise select the right Cx? I have a scope, so is there a way I can measure it?
At a bit of a loss as to how to get it to do anything just twiddling the 50k pot - certainly don't get the LED alight!
I suppose I was expecting that twiddling the pot would at some point light the LED and you trim it with the 2k5 pot to just at the point the LED is on/off then with the vehicle on top, it would fire the other way? Voltage no way near it doing that!
Any help much appreciated!
Regards,
Richard.
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Post by Dale Frizzell on Sept 11, 2010 20:19:30 GMT -8
hay swinfen Gary is working on a Cat Flap and on the frist one it had a heat and cool problems from temp. He was thinking that it could work on the Vehicle Loop Detector too
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Post by Gary Lecomte on Sept 14, 2010 6:01:44 GMT -8
Hi, As a hobbiest in mainly digital electronics, I have just built this circuit with the intention of integrating it with my home automation system (will ultimately open a pair of gates). What I'm not sure about though is how to 'tune' it to actually work! What am I expecting the voltage to be on LM393 pin 6? As I understand it this should reach the voltage on pin 5 (and sink the pin 7) when the resonant frequency in the coil (with the car on top) effectively induces the voltage increase? So what would it be normally at pin 6 when the is no vehicle on top? Very close, or essentially sunk to ground? It seems to sit at around 0.06v Also, how can I determine what the frequency of the coil would be or otherwise select the right Cx? I have a scope, so is there a way I can measure it? At a bit of a loss as to how to get it to do anything just twiddling the 50k pot - certainly don't get the LED alight! I suppose I was expecting that twiddling the pot would at some point light the LED and you trim it with the 2k5 pot to just at the point the LED is on/off then with the vehicle on top, it would fire the other way? Voltage no way near it doing that! Any help much appreciated! Regards, Richard. Richard, If you use the Coil Size as Suggested (4 Turns of 20 AWG, 6 Feet in Dia.) and use a .47 Cap, this Circuit should work OK. My Only Complaint with this circuit is Poor Temperature Stability.As Dale Said, I now have designed a Much more Stable Circuit for the Cat detector, BUT it requires winding Dual Coils and with Considerably More Turns of wire. This Circuit can also detect a car, But I don't think these Larger Coils would be very practical to be buried for detecting a car. Too Date, I have Not Posted this circuit on my Website. But I will do that at some later date. Gary
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Post by Deleted on Oct 14, 2010 7:30:47 GMT -8
Hi Gary. Thanks for getting back. Finally got round to looking at this circuit some more, but my lack of understanding is frustrating me!
Can you help me understand the theory a little more?
What should I expect to see on a scope at various points. E.g. the 555 output obviously generates a nice clean pulse of whatever frequency. After the 150ohm resistor (actually used 3 x 470ohm in parallel to handle the current) I get a very feint oscillation of the same frequency (ranging from sinusoidal to sawtooth in shape) but at much lower voltage and alternating (+/- 20mV). The voltage of that actually varies with the frequency. Perhaps that's just some noise, but is it possible to measure what's 'happening' in the coil?
I'm expecting to see a change in the oscillation somewhere with the presence/lack of the metal object? How is this weak voltage ever brought up to the >+12v required to fire the LM393?
Am I expecting the output of the LM393 to oscillate as well? I.e. the compounded oscillations of the 555 output and the coil that trip slightly over the +12v line will cause an oscillating output on LM393:7 perhaps?
Anything I can measure with my scope to help me understand what's going on would be great.
To clarify I have made the 6ft coil from 4 turns of 20AWG enamelled wire. I have used a Metpoly .47uf cap for C1.
Should I expect no significant voltage on LM393:6 _without_ the metal object?
Regards,
Richard.
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Post by Gary Lecomte on Oct 15, 2010 4:03:09 GMT -8
Hi Richard, Judging by your IP Address, I believe you live in the UK.
If you have a LAND BASED PHONE, I can call you for FREE to discuss this MUCH Easier than a bunch of Typing!
Gary
UPDATE: As a Result of our discussion and what his intentions were in using this circuit, I have Revised the Cicuit Board and Mailed one to Richard for FREE.
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Post by Jan on Nov 20, 2014 18:56:12 GMT -8
hi Gary, is there any substitute IC I could use instead of CE 04 in the revised schematic? we're building a small scale vehicle loop detector for our project. thanks!
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Post by Gary Lecomte on Nov 22, 2014 12:46:30 GMT -8
Use Two 2N3904 Transistors. Ideally Placed Face to Face and Glued Together with Crazy Glue.
So they both are at the Same Temperature.
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Post by Jan on Nov 23, 2014 3:35:11 GMT -8
Oh, thanks. Another question: which pins of the transistors are connected where? Or rather, what are the connections of the transistors' pins basing on your schematic?
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Post by guest101 on Nov 23, 2014 5:11:32 GMT -8
Using 2N3904 transistor in behalf of ce 04 ic for the vehicle loop detector, how will i connect the pins of the transistor so that it will have the same function as the ce 04 ic? What is the function of ce 04 ic in the circuit? Thanks!
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