The Best Magnetic Driveway Alarm With No False Alarms

If you are wondering what is the best magnetic driveway alarm for the money, let me offer my years of experience having installed and used all sorts of different wireless devices for my own home security.

I have installed what I believe is the best value magnetic driveway alarm.

Actually there are two. I have both systems installed. However this review covers my installation experience with the first one, the Mighty Mule FM231. (I’ll review the other more expensive one, the Dakota Alert, later on).

1. Mighty Mule (FM231)
2. Dakota Alert

(view on amzn)

The Mighty Mule is comparatively the most affordable magnetic driveway alarm, and doesn’t require a professional installer (neither dose the Dakota Alert).

Briefly stated, it’s a vehicle sensing driveway alarm. It uses a metal sensing probe. It only detects moving metal. You can bury the probe, or simply place the probe near the area to be monitored (that’s what I did with one of mine on the edge of the driveway, which works fine).

It will alert when a VEHICLE is approaching – without false alarms (see below for what to do if this happens).

Know when vehicles approach your home, property entrances, business, or farm. 

(UPDATE 1 year later – read at end of post)
(UPDATE 2 years later – read at end of post)

#1 Reason Why I like This Magnetic Driveway Alarm:

Security. It does not issue false alarms for animals, blowing tree branches, or other non-metal objects that move past it. I only want to be alerted of VEHICLES approaching on my long driveway road.


The ‘Mighty Mule’ company (no affiliation with this blog) designs devices for automatic gate openers. They also design a driveway alarm using their same electromagnetic sensor technology.

Why the Mighty Mule Magnetic Driveway Alarm is the Best for the Money

No False Alarms

The reason why most ordinary motion sensor alarms issue false alarms (animals passing by or the wind blowing tree branches or bushes, etc..) is because of the type of sensor that’s used. Such as those which throw an interruptible ‘beam’ or the type that senses IR (infrared) thermal heat signature. The Mighty Mule uses another type of sensor…

Sensor Detects Surrounding Magnetic Field

Some might call this a magnetic driveway alarm. The Mighty Mule utilizes a sensor ‘wand’ specially designed to ‘sense’ its surrounding magnetic field and any disturbances to that magnetic field in the driveway. It senses metal.

The sensor wand is designed to be buried out of sight – several inches deep, up to 12 inches deep – along side the roadway or driveway. It is connected by way of a weatherproof cable to a transmitter device which is also weather proof.


Driveway Alarm Transmitter

The driveway alarm transmitter uses two ‘AA’ batteries (use these Lithium batteries for best performance!) to send its signal to the receiver which is located inside the home.

How It Works

When a vehicle passes by within 3 – 12 feet of the electromagnetic sensor, the disturbance in the magnetic field (via the metal of the vehicle) triggers the transmitter to send an alert / alarm back to the receiver.

Driveway Alarm Indoor Receiver

An alarm sounds from the indoor receiver which has an adjustable volume control – letting you know that a vehicle has passed by the sensor.

There is also a low-battery indicator on the indoor receiver which lets you know when the transmitter batteries need to be replaced (a nice feature!).

The receiver also has an LED that lets you know that the device has been triggered (in case you missed the audible alarm due to being somewhere else), and it will remain lit until you press a ‘reset’ button. This is another nice feature letting you know that a vehicle has passed by the sensor when you were away.

Great Security For Private Driveway Or Private Road

I happen to live at the end of a private road. It’s nice to know when a vehicle is coming down the road. Having this driveway alarm is especially comforting for ‘the middle of the night’ when there certainly should be no vehicle approaching. If the alarm is ever triggered in the wee hours of the morning, it will ‘buy time’ to get prepared for whatever may be heading this way…

Driveway Alarm Transmit Distance

The ‘Mighty Mule’ specification indicates that this magnetic driveway alarm will transmit up to 400 feet (ideal conditions). My testing reveals closer to 300 feet in general.

(If you need more range, see the alternative equivalent product at end of article – the Dakota Alert)

My own installation is at a distance of 330 feet line-of-sight to the receiver. There are a number of trees in the way, and it works solid from there. I tried further out, but the road dips down and becomes out of ‘the line of sight’ with the receiver (and there are lots more trees in the way) at the 400 foot mark.

When I tested the distances (do this before digging the trench!) the 400 foot distance was marginal for me so I brought it in closer to be assured of a consistent signal.

For a longer distance (sooner driveway alert), I also installed the “Dakota Alert” which transmits a lot further. But it costs more (another review for later).

Mighty Mule Magnetic Driveway Alarm Installation Tips

Sensor on the Right Side of the Road

Given it’s sensitivity radius, install the magnetic sensor wand on the right side of the road. This will better detect vehicles driving “in” to your property.

Magnetic Sensor Orientation With The Road

Orient the sensor wand parallel with (in line with) the driveway.

Best Line Of Sight

Try to get best ‘line of sight’ between the transmitter location and the receiver. The more trees, buildings, walls, the less effective distance. For example, my receiver is setting on the bedroom window sill which faces the general direction of the transmitter.

Inserting the Transmitter Batteries

The moment when you insert the ‘AA’ batteries into the transmitter, it ‘takes a snapshot’ of the surrounding magnetic field via the sensor wand’s current position.

It uses this reference ‘snapshot’ to detect subsequent differences in the magnetic field which will trigger the alarm.

So, when inserting the batteries for testing (and when inserting the batteries for the last time after you’ve completed the installation) be sure that the environment within at least a 15 foot radius does not include ‘non-typical’ metal objects. For example, a shovel setting nearby, etc…). Just make sure the area is clear when you insert the batteries.

Transmitter Support Post

Once I had determined the location for the transmitter and after I dug the trench for the wand, cable, and support post, I set the plastic support post (of the transmitter) in a shallow dug hole and added a puddle of ready-mix concrete for longevity and support. Then I covered the concrete with some dirt on top for the grass to grow.

Paint the support post and the transmitter cover to match your surroundings. I used a ‘forest green’ spray paint.

Mighty Mule Driveway Alarm False Alarms?

If your Mighty Mule keeps giving you false alarms, it is most likely because someone else within range has one too. Or there’s some form of radio frequency interference with another device using the same frequency. It’s easily fixed. All you need to do is change the little micro-switches on the transmitter AND the base unit to something else. Just make sure they match each other.

Mighty Mule FM231 Manual

( Here’s a link to the manual )


An important aspect of overall preparedness is security. Depending on where you live and the layout of your property, the Mighty Mule Driveway Alarm might be just the thing you need for your own security.

 UPDATE 1: My magnetic driveway alarm has been installed for more than a year and I felt compelled to followup with how it has been working out for me:

The driveway alarm has been working great! The performance of the product has been flawless and I continue to strongly recommend it.

It has been very beneficial to be notified of a vehicle approaching on our private road – no surprises when a visitor shows up…

UPDATE 2: I now have had the Mighty Mule FM231 magnetic driveway alarm installed for several years. I simply replace the batteries once a year and it keeps on working!

I have also installed a Dakota Alert further down the road (it has longer range, but it costs a lot more). So now I have a double alert. It’s nice because if the 2nd alarm doesn’t go off, I know they’ve turned around (usually after the ‘Private Drive’ sign).

I’ve also replaced the batteries with these – better for cold weather performance: Lithium AA Batteries

For your interest, here’s an alternative driveway alarm which is specified for up to 1/2 mile away. It’s more expensive, but if you’re looking for distance beyond 400 feet (the Mighty Mule), then this one’s for you:

Dakota Alert DCPA-4000
(view on amzn)

[ Read: Security Tips For Rural Property ]