The Smarter Way to Automate Your Home

Well-designed smart home systems may indeed be pretty smart, allowing their owners to adjust the lighting and temperature on a schedule, monitor the home for security, and get the exact information they need, right when they need it. However, some smart home ecosystems don’t feel very smart. Between bloated, unintuitive smartphone apps, and erratic voice assistants, users often feel frustrated with their setups.

YouTuber Made By Dennis experienced the downside of existing smart home ecosystems, and instead of complaining about it, he decided to do something about it. Starting from a single smart button, he ultimately built an entire DIY smart home system that can do everything from dimming the lights to detecting open doors and monitoring the laundry.

Dennis’ system was designed to be different. Instead of relying on Wi-Fi, Zigbee, Bluetooth, or popular microcontroller platforms like the ESP32, he designed a custom wireless solution centered around an nRF52 microcontroller. This decision enabled an extreme level of power efficiency, with the device consuming as little as 1.4 microamps in its lowest-power state.

Powered by a standard CR2032 coin cell battery, the system achieves a theoretical lifespan of up to nine years. This is made possible through a combination of hardware and firmware optimizations, including aggressively disabling unused components and leveraging a “wait for interrupt” sleep mode that keeps the device dormant until triggered by an event like a button press or sensor reading.

The hardware itself is built on a compact custom PCB designed in KiCad. Despite its small size, it supports a variety of sensors and modules through expansion headers. A 100µF capacitor helps stabilize the power supply during brief current spikes, such as when the device transmits data wirelessly.

Dennis demonstrated multiple use cases, including a vibration-based laundry monitor using an accelerometer, a magnetic door sensor using a Hall effect sensor, and a motion detector using a PIR module. Additional configurations include a temperature and humidity monitor and a “smart knob” using a quadrature encoder for precise control of lighting or volume.

One particularly interesting addition is support for an E Ink display. To prevent unnecessary power drain, the display is physically disconnected from power when not in use, ensuring that it consumes no energy while idle.

On the software side, the system prioritizes both efficiency and security. Communication between devices is encrypted using AES-CCM, with safeguards in place to prevent replay attacks. Rather than relying on over-the-air pairing, encryption keys are provisioned via a direct wired connection, simplifying setup while improving security.

Instead of connecting directly to the internet, the devices communicate with a dedicated receiver, which bridges the custom wireless protocol to a smart home API via a Raspberry Pi 5. This architecture keeps the low-power devices simple while still enabling integration with modern smart home systems.

For more on this project, be sure to give the video above a watch.