I am in need of a device that functions similar to game trail cameras that sense and take pictures of animals, except I want to sense a car going by and send a text message to alert me a car has gone by.
I can take the Arduino and use a GSM shield combined with a pre-paid texting plan, but I'm in the dark as to the right sensor. I don't want to sense using a beam-breaking detector, nor do I want to use a buried magnetic sensor. I was looking at the Passive Infrared sensors but I don't know the range on those things nor if they would detect the vehicle.
This device would be mounted to the side of a tree anywhere from 5-30 feet from the road. A truck or ATV would move past the device, and then I would get a text message.
I'm part of a small community watch, and some nights the patrols are so thin we can't be at all places at all times. Having a device to let us know we need to swing by and check out a potential trespasser would be amazing.
I assume this would be a tree that does not move in the wind to any significant degree.
I would suggest using a beam-braking detector. Now I presume you wish this to be battery powered (but use a solar panel to keep it charged).
The "trick" is to use a laser as the beam, and a retro-reflector mounted on the other side of the path. You arrange it to be pulsed so that on the one hand, it conserves power, and on the other, it allows synchronous detection - your receiver distinguishes the pulses from the ambient light though you still need the long black tubing on the receiver.
(You can use an infra-red laser - you align it by providing a rapid pulsing mode in your system and observing it through a pocket camera.)
The laser beam (infrared beam, etc) with retro-reflector creates a situation where installing this device becomes a bit of a pain. I want to be able to just attach this to a tree and be in and out. A fully contained device with no reflector to mount across the road or no magnetic sensor to bury is going to be the solution that works for us.
The tree will be big enough where even in high winds it won't move, so the device itself will be motionless in the wind.
That long rang ultrasonic sensor looks like it might fit the bill, but that plus the GSM shield, the arduino itself, and other ancillary parts and I'm probably looking at around $300 USD to make this work. That's a bit outside the budget we had in mind but if that's the perfect solution then we'll just have to work with that dollar amount.
Check out eBay for the GSM. If you buy from China, you'll wait 2-3 weeks. Also look at their track record for customer service. Generally the greater number of past sales, the greater number of complaints.
Pick one that has good reviews.
uptechsolutions:
I am in need of a device that functions similar to game trail cameras that sense and take pictures of animals, except I want to sense a car going by and send a text message to alert me a car has gone by.
Traffic monitors seem to use pneumatic tube sensing almost exclusively, and I suspect there's a good reason for that. The sensor is a tube placed across the road and secured at the ends, which produces a pressure change when a vehicle drives over it. It ought to be trivial to detect the pressure change with an Arduino, and if you want to minimise power consumption you could probably arrange a pressure sensor to generate an interrupt and wake the Arduino to do whatever you want.
I have another cheaper idea. I have never tried this so I don't know if it would work on the Arduino but what about a sound sensors?
You would have to run many test runs but I bet that you could get the average analog value that the sensor gives off when a car drives by. You might have some false trips, however, if you live in rule area this might work well. The best part is the price!
I would be really surprised if PIR sensors wouldn't work - especially considering exhaust heat. They have a range of up to about 50 feet. Of course, they would detect animals and people, but perhaps the sensitivity could be dialed down such that only exhaust heat would trigger an event. It would be easy enough to do the experiment.
It seems like most of the solutions mentioned would also trigger on people and bicycles.
Which ones? The sound sensor would not (probably). And the Ultrasonic sensor, with proper program, wont triger unless something as large as car drives by.
PIR does not sound like a good idea alone. There would be lots of false alarms, however if paired with a sound sensor they could be very accurate. Eg if sound level is met and motion is detect send text.
You're correct in that, the thing about sensors is, it's best to use several "different" kinds and check that the readings complement and confirm each other.