Learn How to Control Old-Fashioned Smart Home Devices with a Cheap USB TV Tuner

If you see a home appliance or device advertised as “smart” today, then it is pretty safe to assume that it can connect to your WiFi network and be controlled through an app or some kind of hub. But older smart home devices, particularly those that were made before WiFi became commonplace, worked using simple radio transmitters and receivers. Because they don’t utilize WiFi, they implement very little security and don’t require complex digital signals. If you know how commands are encoded, you can control those devices using generic radio transmitters. River’s Educational Channel has a great video and article explaining how to control an old “smart” ceiling fan using a cheap USB TV tuner.

Most of those radio-controlled “smart” devices work at a frequency of 433MHz, because the FCC allows manufacturers to use that frequency without any tricky regulatory loopholes to jump through. But if you want to follow along with this tutorial, you’ll need to find the actual frequency that the device in question utilizes. You can do that with any cheap USB TV tuner that is built around the Realtek RTL2832U chip and that supports a wide frequency range. That can be connected to any computer, but a Raspberry Pi single-board computer is an affordable option. You can then use free, open source software called Spektrum to analyze radio signals across the supported frequency range. Then push a button on the remote and look for the signal spike to determine the frequency at which the remote’s radio transmits.

Now that you know what frequency the remote operates on, you need a way to determine how the data is encoded and what commands (usually a handful of bits) are required for different operations. That can be achieved with a second piece of open source software called Universal Radio Hacker. That software helps you decode various radio signals. Fortunately, most of these kinds of devices omit security entirely and there likely won’t be any kind of encryption to worry about. All you have to do is press the different buttons on your remote to identify what bits are being encoded into the radio signal. Now you know the correct frequency, the different command bits, and how those bits are encoded. With that information, you can transmit you own signals to control the device. You probably won’t receive any feedback from the device, which limits your ability to work with it. But this is a great way to experiment with radio signals and even to build your own smart home hub that works with older technology.