It's Not Motion Sensing Its Heat?

re: “Zones” or the “Beam pattern” (wikipedia.org)

The plastic window covering may have multiple facets molded into it, to focus the infrared energy onto the sensor. Each individual facet is a Fresnel lens.

As a result of the focussing, the detector view is actually a beam pattern. Under certain angles (zones), the PIR sensor receives almost no radiation energy and under other angles the PIR receives concentrated amounts of infrared energy. This separation helps the motion detector to discriminate between field-wide illumination and moving objects.

When a person walks from one angle (beam) to another, the detector will only intermittently see the moving person. This results in a rapidly changing sensor signal which is used by the electronics to trigger an alarm or to turn on lighting. A slowly changing signal will be ignored by the electronics.

The number, shape, distribution and sensitivity of these zones are determined by the lens and/or mirror. Manufacturers do their best to create the optimal sensitivity beam pattern for each application.
120px-Motion_Detector_with_Beam_Pattern
Motion detector with superimposed beam pattern. The length of the beams is a measure of the detectors sensitivity in that direction.

2 Likes

I know many cameras use the two detection methods in conjunction with each other. What I don’t know for sure is which ones do so. I believe that the majority of systems do. As pointed out above Ring does, and Eufys battery powered cameras do as well.

I think most line powered cameras forgo the PIR sensors entirely and use Pixel Change analysis and algorithms to detect and quantify motion. But I also think it depends on the intended application and of course cost.

1 Like

Initally Wyze was to use Pixel Change but was dropped due to power requirements.

Dual IR Sensor are used in Differential detection

Pairs of sensor elements may be wired as opposite inputs to a differential amplifier. In such a configuration, the PIR measurements cancel each other so that the average temperature of the field of view is removed from the electrical signal; an increase of IR energy across the entire sensor is self-cancelling and will not trigger the device. This allows the device to resist false indications of change in the event of being exposed to brief flashes of light or field-wide illumination. (Continuous high energy exposure may still be able to saturate the sensor materials and render the sensor unable to register further information.) At the same time, this differential arrangement minimizes common-mode interference, allowing the device to resist triggering due to nearby electric fields. However, a differential pair of sensors cannot measure temperature in this configuration, and therefore is only useful for motion detection.

Yes, the focus of each facet is “baked” or molded into the PIR sensor. But the number, shape, distribution and sensitivity of these facets is set by the manufacturer … they’re not selectable by users. That’s why RING offer three (3) separate PIR sensors that can be turned on or off by users … they are not changing the PIR lens or each facet … users are only deciding which PIR sensor to turn on/off. Blink and WYZE do not offer anyway to change the focus of the PIR lens. Granted, there are differences between manufacturers in how to select pixel disruption detection.

1 Like

So Ring’s multiple sensor is only selecting one of three in order to steer the detection field. It is not a differential arrangement.

Yes, some battery operated RING cameras allow users to turn on/off left, center and right (any combination of 3) PIR detection sensors. Wyze and Blink are fixed PIRs that require users to position camera so that the PIR lens covers the desired PIR detection zone. Blink then allows users to select zones for pixel disruptions. Wyze allows sensitivity adjustment for pixel disruptions.

1 Like

Wyze users can always use duct tape to mask out an undesired detection area.

1 Like

Ha! But also remember that PIR detection is based on IR radiation heat detection moving across a field of view defined by the camera’s electronics. While duct tape fixes a lot of evils, covering part of the field of PIR view would probably screw up the required heat detection. I also doubt if @WyzeGwendolyn would approve of using duct tape for anything except shutting me up.

2 Likes

Personally I think Wyze and other camera vendors could use the vastly underemployed Monkey population. Tether a monkey to each camera. For a correct detection they get food, for each incorrect or missed detection a minor electrical shock.

This would be like learning AI systems and over time would result in very accurate detection rates. Faster detection could award a tastier morsel where slower rates would result in tasteless morsels.

Just think of the PR campaigns Wyze could offer. Monkeys throwing poo at intruders! It would be the PR coup of the millennium!

3 Likes

You mean WYZE beta testers? Or wait, they aren’t monkeys … they’re guinea pigs. Hopefully WYZE won’t employ electro-shock therapy.

2 Likes

You would need a pre-trained monkey to prevent excessive battery drain on the WCO.

3 Likes

True, I had not thought of that. Wyze could offer a bonus to users who were willing to submit their trained monkeys!

1 Like

image

4 Likes

Just heard on the radio there is a shortage of Monkeys for testing the vaccine.
Maybe Wyze users have been scooping them up for motion detection training. . .

Wyze pays more. The smart Monkeys are all hanging with the Wyze Guys!

1 Like

You may have something there. All the Monkeys who want to be injected with a test vaccine form a line on the left :grimacing:, those who want training by Wyze nerds form a line on the right. :cowboy_hat_face:

1 Like

Clearly the better option!

2 Likes

(Updated) The fixed detection zone is arguably the most disappointing feature of the WCO. I guess that’s because you can’t move the heat sensors, in contrast to selecting any part of the field of view for detection as you can do with the other Wyze cameras, Combine the fixed detection zone with the relatively short detection distance (25-30 feet?), and you’re really constrained in where and how you use the camera. I moved it about five times before I found a location that gave me useful detections.

One more point: The delay in it waking up after detecting a heat signature has occasionally resulted in the 12-sec video only capturing the top of a visitors head has he/she approaches our porch. It missed one person completely, apparently because she moved into the detection zone quickly. That’s not useful. It just happened again. The mail person delivered a package to our front door. The 12-sec clip catches the top of his head as he goes under the camera, even though he should have been detected 20-30 feet earlier.

1 Like

I can agree. I’m sure that they will think of ways to fix this or create a new motion detection for a possible v2 outdoor camera.

1 Like

I see similar behavior with my WCO pointed at gravel road & vehicles. Just barely catches it at end with sensitivity set to 100%.