Dual PIR/Microwave Sensors Outdoors - Truck False Alarms

[BeachBum]

I recently installed three different wired outdoor motion sensors around my property and in my backyard. They are all dual technology PIR and Microwave. One is a DSC LC-151, another is a Hikvision DS-PD2-T10 (2 PIR + MW), and the third is a generic PIR/Microwave from China. My property sits up on a hill about 80 feet elevated with a road down below. I have the DSC in the backyard facing the house and not at all facing the road below. The other two are along the fence line but are still 100+ feet from the road.

They are all generally stable. The Hik and the DSC are very stable during the week (no false alarms), but Monday is trash day and the big trucks are rolling around are neighborhood. Today, I got about 5+ false alarms on all three when garbage trucks pass by on the road below my house.

All three are set to only trigger if the both technologies trip and two of the three are set to low sensitivity to limit the range to about 20 feet.

I could see that the microwave signal might travel all the way down to the road, but not the PIR. The backyard motion would also need to go through a foot of cement wall and hillside to get to the street below. I have cameras that verify that each of the false alarms were caused by the trucks passing.

My latest theory is that it isn't signal related, but vibration related. The trucks are heavy enough that it does vibrate the ground.

I also considered that maybe the trucks had powerful transmitters, but I doubt that.

Does anyone have any theories?

 

[electron]

Welcome to CocoonTech!

Big vehicles, especially ones with so much metal and thermal mass, are known to trip all kinds of security sensors. Do you have more details about the microwave feature (frequency, etc.)? I couldn't find any real technical data on how this sensor operates. But if it's a 2.4GHz sensor, then it could easily be wireless interference.

Might be time to start looking at a vision based approach (combined with some of these sensors).

 

[RAL]

Some garbage trucks now use microwave sensors to detect objects or people that might be in danger from the truck, as well as IR and cameras to allow the operators see in the dark. That might be causing problems with your motion sensors.

 

[BeachBum]

Do you have more details about the microwave feature (frequency, etc.)?

All three are on 10.25Ghz.

Some garbage trucks now use microwave sensors to detect objects or people that might be in danger from the truck, as well as IR and cameras to allow the operators see in the dark.

This is a really good theory. I don’t get false alarms when moving vans or fire trucks go down the road but for some reason the garbage trucks set them off. I considered using LiDAR but it has some issues and limitations as well.