February 2014
I live in the country on a side road that tee's into a busy arterial. The arterial curves sharply to the left, offering only about 100 feet of visibility. Most of my trips involve turning left, thus crossing one lane of oncoming traffic. A car coming around the curve at 60 MPH gives me a little over one second reaction time when it first becomes visible.
At night, I can see oncoming headlights reflecting off a guardrail which gives me plenty of warning. During the day, I roll down my window and listen. However, this is not the best method with my aging hearing. I'm looking for a clever electronic solution to detect approaching cars and provide an earlier warning.
There is a pole on the other side of the road about 75 feet away that could be used to mount a device to bounce a signal off of. I'm new to electronics but if “steered” in a useful direction I can do the research and make it work. Any ideas?
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Why not ask the city to place a mirror? In Belgium you see those on many places.
I see a couple of problems with your idea of a Traffic Detector. First of all, the "pole on the other side of the road" belongs to a utility company and they are usually pretty adamant about "devices" being installed on their poles (for years, my Father tried to wrap a pole with sheets of 16 gauge aluminum to keep squirrels out of a pecan tree and the power company had him remove the sheets pronto). If the company allows you to put up a "target" to bounce a signal from, there is still the problem of aligning the "target" such that any size vehicle would be picked up EVERY time (or your safety would be compromised by a missed vehicle). Using sonar to "bounce off a target" most likely would not work and using radar would get into issues with the FCC, plus the need for Doppler signal processing to ensure you detect only moving vehicles and not plants or stationary devices (aka very complicated digital signal processing and VERY costly).
Since you are using your hearing now to detect approaching vehicles why not use a Super Ear Listening device ($29.50 at www.amazon.com/SuperEar-Personal-Amplifier-Listening-Compliance/dp/B000X2H8G4/ref=pd_sim_hi_1/182-4508871-5045937) or the Bionic Ear and Booster set for even better results ($155.99 at www.amazon.com/Bionic-Ear-And-Booster-Set/dp/B0012N6GZ2). Building either of these devices would require lots of electronic/construction skills (not for the novice since the SuperEar uses a highly directional microphone and the Bionic Ear uses a parabolic reflector), adjustment/alignment of the device to ensure accurate identification of approaching vehicles would be critical, and the cost of construction more than likely would equal or exceed the cost of a proven manufactured device. I am an old school electronics person and love building, but when safety is a concern it is best to use a proven device rather than a home brew.
Curtis, contact your local road department. Around here in SE KY they put up fairly large convex mirrors for just the problem you asked about.
You might want to look at using a microwave doppler sensor which you can find at DX.com searching for: Jtron HB100 10.525GHz Microwave Doppler Wireless Radar / Detector Probe Sensor. It is less than $10.
A pair could be used to detect vehicles approaching from either direction. The sensor could have a solar panel charging a battery, a low power receiver which you would trigger with a transmitter when you approach the intersection, which then would turn on the two radar transmitters, one first, then the other. If traffic is sensed the unit could flash a bright red LED, otherwise it could flash the green LED and time out after a minute or so.
There is no need to be transmitting radar signals all the time, this wastes battery power. Powering a receiver which then turns on the doppler sensors offers much less constant power draw, thereby making the power demands less challenging. For the RF link, one could hack a receiver/transmitter that is intended as a mailbox monitor or driveway monitor. Each has a receiver circuit that has modest power draw and are available for reasonable cost.
How about mounting a box with a doppler radar module (ebay search "doppler radar module") mounted on the pole across the road, in a plastic box, with an LED to indicate when the doppler detects a car? The modules cost under $10 from the far east. Biggest problem I can see is providing power. If mains power is not available you could use a solar panel and rechargeable battery. You need to check local laws regarding possible licensing of the doppler transmitter and get permission of the pole's owner.
