makeuseof.com — Discovery (discovered via Homelab) — Thu, 27 Aug 2026 16:30:13 GMT
Summary
The article argues that inexpensive sensors become significantly more useful when connected to Home Assistant, since the value lies in automating actions from their data rather than the hardware itself. It highlights five examples: magnetic door sensors that control air conditioners and trigger lights or open-door alerts; temperature and humidity sensors that function as a roughly $10 climate control unit, trigger dehumidifiers, or monitor 3D printer enclosures; and power-monitoring smart plugs that act as energy audit tools by revealing standby power draw and aging appliances. It also describes ultrasonic distance sensors, paired with ESPHome microcontrollers, that detect whether a car is parked in a garage or measure water levels in tanks. Finally, the article notes that installing the Home Assistant Companion app turns an old smartphone into a sensor hub, using its light sensor, GPS, and battery status for automations such as adjusting blinds and triggering arrival or departure routines.
Smart home sensors always seemed gimmicky to me, the kind of thing you buy, get excited about for a week, and then forget they exist. On top of that, most of these sensors sell with incredible markups, meaning you can buy the actual sensor for much cheaper and use a microcontroller to pull that data into Home Assistant.
And when you start doing that, you'll quickly realize that a boring sensor, one that sometimes costs under a dollar, or even an old smartphone collecting dust, can be incredibly useful when used right.
A basic magnetic contact sensor is about as simple as smart home tech gets: just two pieces of plastic that know whether they're touching or not. On its own, it's boring. But once it's feeding data into Home Assistant, it can easily open up automations you didn't even think were possible.
I now have door sensors that control my ACs and only turn them on when all relevant doors are closed, turn on hallway lights only when the door opens after sunset, notifies me if the front door stays open for too long. None of this required expensive gear, just a cheap sensor, a $5 microcontroller, and some automation logic that's far easier to write than you'd expect.
Standalone temperature and humidity sensors usually sit around showing numbers on a tiny screen nobody checks. Link them with Home Assistant though, and you'll have your own climate control unit that costs less than your coffee order. They become eyes for climate decisions you would otherwise make manually and inconsistently.
This is exactly how I made my $10 climate control unit that measures the temperature and humidity of the room I'm in, and controls the air conditioning to maintain a predefined temperature. However, there are plenty of other ways you can use them. You can have humidity spikes trigger dehumidifiers automatically, or put one in your 3D printer's enclosure and get warnings before a print gets ruined by warping. The sensor itself doesn't change, but giving it a place to report to makes all the difference.
A power monitoring smart plug seems like a convenience feature at first, just a way to check if a particular appliance is drawing too much power. But once that power reading is sent into Home Assistant, it turns into a full energy audit tool.
I found out my old space heater was quietly adding more to my energy bill than I imagined. Now, I get alerts when standby power on certain devices creeps higher than it should, which usually means something is about to fail. It's one of the few sensors that pays for itself just by revealing how much electricity everything else is secretly using; not to mention, it's one of the easiest ways to add smart control to appliances that won't otherwise give you that option.
I have half a dozen cheap ultrasonic distance sensors lying around from old projects, and at first, I didn't think they'd be of much use when it comes to home automation. But hook them up to a cheap microcontroller running ESPHome, and it becomes a surprisingly effective presence and distance detector.
You can have one mounted above your parking spot in the garage, and now Home Assistant can tell you exactly how far you pulled in. Now that might sound silly until you realize that it also means the garage light and door automations only trigger when a car is actually there, not just when something moves nearby. You can even use them to measure water levels in rain barrels or tankers to know when you've got enough water for the house. It's not glamorous tech, but it's incredibly cheap and can often fix problems that would otherwise require expensive commercial presence sensors.
If you install the Home Assistant Companion app on your old Android or iOS smartphone, you can access most, if not all, of your phone's sensors to trigger automations around the house. Anything from the accelerometer, ambient light sensor, microphone, GPS, battery status, and even the camera can be used in various ways as standard Home Assistant entities.
I use the light sensor to adjust blinds based on actual sunlight. The GPS can trigger certain going-away or returning-home automations when my phone leaves or comes back within a certain radius. I even have automations based on my phone's battery level that can remind me to charge my phone or shut off the charger if the phone reaches a certain charge percentage to ensure battery longevity.
Taken together, these cheap sensors won't just make your home feel smarter; they'll make it feel like you're finally paying attention to things you used to have to notice yourself. None of them are individually impressive pieces of hardware on their own, but that's kind of the point.
The real upgrade isn't the sensor itself; it's plugging them into a system that can do actually useful things with that data. Knowing what's going on in your house is one thing, but unless you can use it to take action, those sensors and your Home Assistant instance are just wasted potential.
Original article: https://www.makeuseof.com/cheap-sensors-ridiculously-useful-connected-to-home-assistant/ Source: makeuseof.com (discovery)