How do PIR Sensors work?
PIR sensors (passive infrared) detect infrared light (heat energy) which radiates from objects in its field of vision, such as a human body. This makes them great for protecting ute canopies, or for van security where a solid cargo barrier prevents ultrasonic sensors covering the load area.
PIR installation methods
There are two ways to connect PIR sensors can be wired up to an alarm. The first method is to wire the sensor up to the alarm’s AUX input.
Most decent car alarms give the user the option to disable the AUX input on the alarm. This keeps the door and bonnet triggers active so that the vehicle can be locked and armed with the PIR sensor turned off if desired.
OEM Upgrade Method
One common issue when installing a PIR sensor in a ute is that when the vehicle is unlocked (alarm is disarmed), the vehicle will re-lock and in turn re-arm the alarm if a door is not opened after a set time (normally about 30 seconds).
This can then catch the owner out if they only wish to access the canopy without opening the main vehicle. As soon as they trigger the PIR sensor, then the alarm sounds!
Whilst the user could simply open and shut one of the doors to stop this from happening, most people don’t find this very convenient.
Wiring the PIR sensor via a relay to one of the doors will trick the vehicle into thinking that a door has been opened as soon as the PIR sensor detects movement. This will then prevent the vehicle from re-locking and re-arming, and getting triggered by mistake.
The downside to the method is that you need to be aware and remember how it works. Also, having a dog in the back would cause the door open warning light to flash each time the dog moved, which would also turn the internal lamp on and off! There is a better solution:
How many amps does a PIR Sensor draw?
Most PIR sensors draw about 8mA, whilst this is not a high current it worth remembering that the current drain of all the accessories in a vehicle can add up.
N/O or N/C PIR sensor?
Remote Double Tap Module
The Remote Double Tap Module works with the existing remote and simply prevents the vehicle from re-locking if the remote unlock button is pressed twice. It can also be used to unlock the canopy where electronic locks are fitted. More details here…
Wireless PIR
Autowatch make a wireless PIR sensor which eliminates the need to run cables to the sensor. Details can be found here.
PIR Sensor Installation Cost
Adding a PIR Sensor to an aftermarket car alarm
$180.00 for a standard installation when added to an aftermarket alarm. *Price does not include the alarm.
Adding a PIR Sensor to an existing factory alarm system
$300.00 to integrate into a factory alarm (vehicle dependent).
More alarm sensors
I install security systems into a wide range of vehicle. What makes my installations effective, is knowing what alarm sensors are suitable for your vehicle and needs.
