On our latest IoT Podcast episode, we take a question that Mark left on our IoT Voicemail hotline. Mark wants to use the sensors in a smart thermostat and other devices to detect the presence of people in his smart home. But he doesn’t want any automations or actions from those devices to fire up if a pet walks by the sensors. Mark has a cat that currently sets off some devices when they detect his feline friend.
We’re actually just on the cusp of new, smarter sensors that will help in this situation. Mark is using HomeKit in his house with Home Assistant to supplement it. The topic is relevant to any platform or ecosystem, however.
The newest Ecobee thermostats, announced last week, for example, use millimeter wave technology. This acts similar to radar and provides more data when a person, or a pet, is moving around. Older PIR, or passive infrared sensors, are better suited to tell you if something is moving.
Millimeter-wave provides higher-resolution scans and, when paired with the right algorithm, can accurately determine movement between people, pets, and other things. Other RF detection solutions include Wi-Fi sensing although that market seems behind the millimeter-wave products.
We checked with Ecobee on its new products and were told both the thermostat and the new remote sensor can tell the difference between a person and a pet. However, Ecobee says to ensure the best presence detection, sensors should be at least three feet above the floor, not pointing at blinds or curtains which can move. That’s actually a good rule-of-thumb for any sensors, in my experience.
Older devices that use PIR technology might discern pets and people moving around, but if you need pet detection, I’d hold out for hardware that uses newer radio solutions. As upgraded hardware appears, you’ll see more that rely on higher resolution sensors with more “smarts” in this regard.
It’s also worth noting that there’s a handy tip for people using webcams to detect motion or people. Most of the mobile apps that support webcams offer a masking feature. This is used to create a mask or zone for the camera and that’s the only area it will look for people or motion.
Given that I have pets too, I’ve used this approach on my indoor and outdoor cameras, specifying a zone that’s above floor or ground height. Aside from the very occasional false positive, this has worked well for me in the past.
To hear Mark’s question, along with our discussion in full on the topic, tune in to the IoT Podcast below.
The new sensor technology that’s coming out is definitely in interesting, and there are several different possibilities. And of course, to be honest, right now I’m waiting on almost all new device purchases for a year if I can, just to see what happens with matter.
Meanwhile, it’s helpful to understand that classic PIR (passive infrared) sensors work by measuring tiny changes in heat as it moves across the sensor. That is at 90° to the sensor, not straight on to it.
Because a cat is pretty small relative to even an eight-year-old child, you have a good chance of being able to find a sensor, or even reposition an existing sensor, so that it will detect people but not the cat.
Some Sensors have an adjustable “sensitivity“ parameter, and many of these have a “pet immune“ setting or something similar that won’t trigger until the body walking past the sensor is at least 40 pounds or so. It’s tricky, because again, this type of technology is looking for heat and many animals have a resting temperature higher than humans, so a 15 pound cat might be detected as similar to a 20 pound child in that sense. But almost all of the ones on the market are good at ignoring cats and dogs up to about 25 pounds. Larger than that, we come back to the first rule of home automation: “the model number matters.“ Some sensors can be fine tuned, many cannot.
The second thing is what ecobee told you: the detection zone. Dogs are usually close to the floor. With the cat, it depends on the cat, but you may be able to position the sensor so that it will pick up persons passing by at around their shoulder level, but not be triggered by the pet because the pet is too close to the floor. many people take a piece of plastic tubing and put it over the sensor opening to limit the area that it detects. With some models you can even just put a piece of opaque tape along the lower half of the sensor lens and it will no longer detect things on the floor. Some people put a little cardboard or wooden shelf under the sensor sticking out about 4 inches so that it can’t “see“ the floor, but personally I find the tape solution more aesthetic. Your choice.
Of course that kind of modification does mean that if a burglar came in and crawled along your floor the sensor wouldn’t realize they were there, so it all depends on the details of the use case. If you’re using sensors so that humans walking into the room trigger lights or the thermostat or music then not detecting someone on the floor is probably fine. If This is part of a critical security system then you may want to look for the “pet immune“ models instead.
( of course, if, as Fitz would point out, The evil doers send in a really smart little monkey first to disarm your security system with its little monkey hands, a pet immune sensor might miss them. But I suspect most people won’t be concerned about that.)
SOME OPTIONS
If you do want one of those fine tunable sensors, there are several options. Listed in no particular order:
1) one of the most configurable motion sensors anywhere for Home Automation is from Fibaro. This thing has an amazing number of parameters that you can set, including a wide range of sensitivity. It comes in two models, one that works only with HomeKit, and one that works only with zwave. Both models are available in both the US and Europe. Make sure you get the exact model that you need, in this case the HomeKit version. I’m linking to the manufacturer site, but you’ll be able to buy it at Amazon or most home automation retailers.
https://www.fibaro.com/en/products/motion-sensor/
The Homekit version isn’t as configurable as the Zwave version, but you still get low, medium, or high sensitivity, which is better than most HomeKit motion sensors. I would expect a Fibaro motion sensor set on low sensitivity at least 4 feet off the ground to ignore a cat pretty easily.
Do be aware that the more sensitive the setting, the faster it will use up battery life. But in this case, the question was about a less sensitive sensor setting, so that’s all to the good.
It can measure light level and temperature as well as motion, but if you want to use those as triggers in HomeKit, you’ll need to use a third-party app like Home+ or eve. Only the motion will show up in the basic HomeKit home app.
And it’s not cheap, usually listing at about $50. So if you already have a less expensive sensor, you might want to try the tape trick first and see if that’s enough to avoid the cat triggering it.
This is the smallest of the three sensors I’m listing today.
2) Eve Motion. Eve motion offers a pinhole setting on the back of the device for low/medium/high sensitivity. This device is supposed eventually use thread once matter is here, but I think it’s still using Bluetooth now. It costs about the same as the Fibaro. It’s hard to find right now, although the Apple store usually has it online.
3) Hue motion sensor used with a Hue bridge. This applies to both indoor and outdoor models. You can change the motion sensitivity in the hue app, and I think you could get it to ignore a cat. Comments on the hue Facebook page indicate that most people seem to be able to get it to ignore a pet 15 pounds or smaller, but once you hit 20, it tends to trigger even at low sensitivity. Hue’s recommendation is to mount the sensor higher on the wall.
Prices on this one vary a lot, so shop around. For some reason, Target is usually about five dollars cheaper on these models than the other big retailers, including Best Buy, so I have typically gotten mine there.
Again, you’ll need to use a third-party app for triggers other than basic motion.
I really like these devices and have several of them, but they are big and clunky looking indoors, and big and noticeable outdoors. So again it all depends on what you want to use them for.
————
I’m not aware of other HomeKit compatible motion sensors that offer sensitivity settings, and these three are among the more expensive, but they do all three offer at least basic high/medium/low sensitivity, and for a cat I think the low should work fine in most cases. Especially if combined with moving the motion sensor higher up and maybe the tape trick so the sensor isn’t even checking the floor. Choice is good. Good luck, and be prepared for some trial and error to find the exact right location.
Pet immune motion sensors have two IR sensor instead of one.
https://www.alarmgrid.com/faq/what-is-a-pet-immune-motion-sensor
Excellent article, thanks for sharing it!
As that article notes, “some” models labeled pet immune have two sensors.
Most don’t, as it adds cost in a category which is very cost-sensitive.
The two-sensor models are usually part of professionally-installed security systems.