My friend Phil sent me an e-mail saying “I'm currently looking around for a device that I can install somewhere on my driveway that will send a wireless signal to my living room letting me know when a vehicle is coming up my way and set off a mild chime rather than a loud siren.”
This is a relatively common need, particularly for anyone with a long driveway, but it is also handy for a retailer with a drive-in customers.
There are a number of ways to approach the problem and the costs can range from $100 to $300 or more depending on the quality of the device and the nature of the installation.
Your first decision is whether to go with a wireless or hard-wired system. As a rule any hard-wired system is more reliable and it has the added advantage of allowing you to power the device without having to use batteries that will eventually have to be replaced. The cable is not expensive and there’s no concern about interference because it is only sending an on/off signal.
But if you want it to last in an exterior installation it should have a weatherproof (direct burial) jacket and (ideally but not always) be installed inside a conduit. Burying that conduit over a long length is where the expense comes in. If you already have wires run to the end of the lane, maybe for a gate motor or an intercom, and there is a spare pair, you may have a quick and easy solution.
A wireless system can transmit long distances if there is a clear sight line, but trees, hills and buildings will all interfere with it. And it runs on batteries that will eventually have to be changed.
The least expensive sensing device is a motion detector. Of course it has to be weatherproof but there are many available, including some self-contained packages specifically designed for this application. Compared to other devices it draws less current so if it’s wireless the batteries will last longer. You have more flexibility in locating it; it can be set back from the driveway rather than on it or immediately beside it.
Because it detects motion indiscriminately, it will send a signal if people or vehicles cross its beam, but it will also detect rabbits and squirrels, and depending on how it’s aimed it may also pick up street traffic. If you specifically want to detect vehicles, one of the other options might be a better choice.
Remember in the days before self-service when all gas stations had a rubber hose in the parking lot that rang a bell in the station when a car drove over it? Well you can get the same thing to detect vehicles in your driveway. It has the advantage of no false alarms because it requires something heavy like a car to set it off. The wireless version is very easy to install and the indoor chime can be plugged into a regular power outlet, while the transmitter by the hose runs on a regular 9 volt battery.
The disadvantage is that it won’t work reliably in snow and ice and the hose is subject to wear and tear, reducing its lifespan. You would want to install it on a hard surface, like pavement, that won’t give under the weight of a car.
The next level of cost is a metal detection probe. It is buried a few inches under grade beside the driveway. The wireless version connects the buried probe to a weatherproof transmitter that can be mounted on a nearby post while the hard-wired version has a cable that runs back to the house, also (ideally) buried just below grade. It has the advantage of only detecting metal, eliminating false alarms entirely (but, of course, it won’t detect pedestrians).
Phil had said that he’d like a “mild chime” to notify him. His best solution is probably a self-contained package that includes a chime. Some devices offer a variety of chime sounds at the receiver, so that you can set up more than one detector and differentiate between them.
But there are many other options at the receiving end. If you have a security system you can tie the sensor into it, programming it to set off a siren, a chime, a buzzer, or even call the monitoring station. You can connect it to a doorbell or a device that will make the lights flash in the house. You can tie it into your phone line, setting it to ring a distinctive tone, which allows you to hear it on your cordless phone even if you’re out at the pool.
Some devices have a hand-held receiver that you can carry around with you, ideal for farmers. You can link the detector to an auto-dialer that will call out to your cell phone, or to an annunciator that reacts to a trigger with your own pre-recorded voice saying something like, “They’re here!”. Some of these devices will add one or two hundred dollars to the cost, but there are also kits available that combine features.
Like anything in home electronics, the solutions are completely customizable to suit your specific needs and budget.
Bill Monahan is a “smart home” specialist who has been in the construction industry for thirty years, with the last twelve devoted exclusively to residential electronics. While he provides and installs products he sees his main mission as making homeowners comfortable with the new technologies.
