I had a project fall in my lap for a local campground for a one-way signal light for their new road (it is only wide enough for one vehicle to come through at a time, and they want to avoid people going through both ends at the same time. Road has been open only 4 days, and this has happened 3 times!)
Looking at some Waterproof Ultrasonic Sensor with Separate probes (Arduino store TPX00079 - Sensor link on Arduino.cc store ) And I would like to convert the cable to CAT6 and run that for a few sensors about 200-300ft. What sort of problems may I encounter with this possible setup? Will it even work?
The idea for my project is I would have 5 ultrasonic sensors across the 15 ft wide and 500ft long driveway/road. 2 of them would be near both ends separated by about 50 ft each. When the first sensor is triggered, it would turn on a STOP red light on the other end of the road, indicating to traffic on that end to NOT proceed, that a vehicle is coming along the road. A timer would start (initially 20 seconds) and if the 2nd sensors is not triggered before that time-out it would extinguish the STOP red light and go back into standby wait mode. But if that sensor is tripped, it would indicate that a vehicle truly is coming through and keep the light on, and continue to monitor as it passes the mid point and then the exit. At which point the STOP red light would turn off. I have the basics of the concept figured out, it is the practical side if the ultrasonic sensors would work from those distances. Thank you
I don't think that the sensor signals would work over those distances, but it may be worth it to experiment to see what happens.
If going with wired, have each sensor to a small Arduino compatible like a tiny85. Each Arduino would have a rs485 node. RS485 is a serial data link made for long distance and multiple drops. RS485 modules.
For wireless have an Arduino compatible like a Nano connected with a sensor and aNRF24L01 radio transceiver module. Several of those radio modules can talk to 1 central module connected to the Master Arduino. Use these adapters to supply sufficient 3.3V power to the RF24 modules.
Interesting idea! I REALLY like it. (The NRF24L01 idea) Thank you @groundFungus. Now another question. What is the practical range of the Ultrasonic Sensors? Will they accurately measure a vehicle passing by over the width of a 12-15ft wide driveway?
I imagine that that spec is for a more or less ideal target which would be a hard flat surface perpendicular to the ultrasonic "beam". That sure could be a motor home or car. Another consideration is the "beam" divergence. It is not really a beam it is a divergent cone of sensitivity. There is no information in the linked page on the angle but the width of the sensitive area increases with distance. It could be quite wide at 19 feet.
Illustration of cone of sensitivity.
There may be other sensors out there with better range. I would expect so, anyway, since the old Polaroid camera auto-focus sensors would work out to 30 feet.
You may want to consider something like IR light gates where there is a IR beam across the road and a sensor on the other side that will detect when the beam is broken. Modulate the IR light so that ambient light does not effect the sensor. The sensor is a special IR sensor that is only sensitive to IR light modulated at a specific frequency. Vishay make such sensors. The IR source and sensor are recessed in tubes to shield them from most of the ambient light.
Or the old tried and true hose across the road like in the old time gas stations. Easily done with solid state pressure sensors.
