Advice needed on motion sensor (PIR style)

T Chap

I installed a motion sensor on a door in NY, and it is false triggering now on a regular basis. The system has been in since June, but now the temps are near 40F. The sensor on the exterior is working fine so I am told. It is the sensor on the inside that is acting up. It is located just above a 6' wide x 7' glass door that slides open when triggered. I am told the inside sensor is located very close to a heater vent. The sensor works well when triggered by a person walking up, but is false triggering on the door closing. The device I use has a rotating lens, and it is not aiming at the door, and they have tried aiming it at all extremes, I have used this device a lot and never seen a false trigger like this. My thoughts are that the device is triggering when the temperature changes rapidly, as it is in a room that is above 70F, but when the large door opens it exposes the sensor to a cold rush, then back to normal. I was thinking that a quick fix might be a small acrylic box around the unit to semi insulate against quick air temp changes. Other than that, I need to look at some type of more industrial device. The reason I use this one is that is can be aimed to produce the best response. I don't like being stuck with a device that has a fixed field of view. Any suggestions on how to solve this would be greatly appreciated. The link is to the Bosche device in use at the moment.

http://www.pcrush.com/product/Motion-Sensors/682176/Bosch-DS150i-Motion-Sensor

kwinn

I am pretty sure you are correct as to the cause of the false triggering being caused by the temperature difference between the inside and outside air. I doubt that putting an acrylic box around the sensor will help, but it is simple and inexpensive enough that it is worth a try.

I have had a similar problem with PIR sensors used for lighting when they were placed too close to the heating diffuser. The turbulence created when the hot air from the heating system mixes with the cooler ambient air looks like a moving IR object to the sensor. The cure for our problem was to relocate the sensor, and when that was not practical to replace it with a dual mode PIR/microwave sensor.

T Chap

Thanks Kwinn for that info. I had a few Xbands laying around so I decided to test out the hybrid concept. Although I cannot replicate the project in my shop, at least I can simulate it with the same parts. The Hybrid method will watch for inputs from the PIR + Xband, so far it is working great.