RF 433 MHz and BLE with OpenMQTTGateway and ESP8266 – Cheap Home Automation on a budget

Adding an RF/BLE gateway to your Home Assistant setup opens up a multitude of low-cost automation opportunities, making your setup incredibly versatile. This project configures OpenMQTTGateway, giving you the ability to add cheap RF devices to your Home Assistant setup.

Wifi-enabled IoT devices such as weather stations, door sensors, motion sensors, alarm systems, and driveway alert systems, can be very expensive. This is due to additional functionality included such as mobile app support and the cloud services required to support them.

RF devices are low-powered devices that emit a single integer code. This can be read by a gateway device to be translated into a Wifi-based format your home automation server can understand.

Requirements for RF Gateway

For my use cases, the device should capture any incoming radio frequency (RF) signals at 433/315MHz and emit an MQTT message on the WiFinetwork with the original RF payload. This MQTT message can then be consumed by other WiFi-enabled entities such as Home Assistant or my MQTT Payload Processor.

The device should have a range of at least 20 meters, which should cover my house just fine. Walls and interference might reduce this range.

Lastly, the gateway must be reliable. This is very important because it will be a central part of the home automation system. If you are having problems with smart home reliability check out my post on best practices for smart home monitoring.

RF Door/Window Sensor

RF Door and window sensors are a reliable addition to smart home and batteries last for a long time.

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Advantages of RF devices

Radio-controlled devices — particularly on the 433MHz frequency – are incredibly cheap, and battery-operated and there’s a huge variety of devices available on Ebay.

• Cost: they are orders of magnitude cheaper than their Wifi equivalent. Approximately \$15 each, depending on the device. Meaning you can outfit all rooms in your house with a motion sensor for \$100.
• Affordability: since they are cheaper, you will be able to afford more
• Open protocol: they are hackable and independent of manufacturers (no locked to a particular vendor’s cloud service.
• Low power: they are low-power, battery-operated devices (Wifi is power-hungry, RF is not)
• Local: RF devices are local devices

Known Limitations of RF signals

Lack of Error Correction

RF is not as reliable as a WiFi connection because it does not have built-in error correction. The protocol caters for this by sending the same signal multiple times (which can hardly be called error correction and it actually causes more problems because signals need to be deduplicated by the client. Again, my MQTT Processor takes care of this among the many other benefits.)

Mitigation: Run RF devices at the rated voltage, keep batteries charged, place multiple RF gateways around the house if you find the signal range to be a problem

Signal quality diminishes as the battery goes flat

Some motion sensors can be operated on batteries or by supplying power via micro USB.

Mitigation: I recommend implementing monitoring for all battery-operated devices in your smart home. Check out my detailed post of system monitoring for an in-depth discussion on the topic and a plug-and-play solution.

RF is not Stateful

RF devices are very dumb… all they do is emit a single piece of data (a large integer number), and in most home automation use cases this is completely fine. There is no way to maintain a persistent state on the RF device for two reasons:

1. The firmware does not support it. It simply sends an RF code when an event happens (for motion sensors that is “motion detected”).
2. The state cannot be queried by Home Assistant. (Again, the devices do not maintain state and a very basic).

Mitigation: Use Home Assistant to track the state of RF devices, this is much easier than it sounds and you’ll have to do this anyway to make the RF device available in Home Assistant. Check out my post Setting up stateless RF Motion Sensors as binary_sensors for more information.

Limitation Summary

For a post raving about the greatness of RF (it truly is!!!), I have admittedly given you a ton of reasons not to use it. I think it’s important to know its limitations as the extremely low cost outweighs them more often than not. Here are some more tips:

• Run RF transmitters and receivers at the max rated voltage to increase the range
• Solder a custom antenna to the chip (see the optional item in the parts list)
• Use the recommended RF modules
• Create a custom HA component to manage state in memory on the home automation server (give the illusion of state from an automation perspective)

Motion Sensor

Kerui RF Motion Sensor

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Instructions for Open MQTT Gateway

Parts

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• OpenMQTTGateway, a free MQTT gateway supporting RF, Bluetooth, infrared and many more transport layers
• MQTT broker like Mosquitto
• WiFi Enabled Arduino chip such as ESP8266 or ESP32
• RF receiver/transmitter: STX882 & SRX882 (affiliate link)
• ESP32
• (optional) 433MHZ Helical Antenna for Arduino Remote Control

Image	Product	Features	Price
	ESP8266	Built-in Wifi Chip Arduino Compatible ESP based	Purchase Now
	ESP32 (alternative)	Built-in Wifi Chip Arduino Compatible ESP based	Purchase Now
	RF Receiver	SRX882  Reliable RF receiver	Purchase Now

Future Improvements

This post discussed the advantages of 433Mhz devices, their limitations and ways to work around them. They present a fantastic opportunity for budget-conscious people!

Dockerising the RF to MQTT gateway

Let’s create a MQTT to RF gateway image and use it to control cheap RF devices in our home automation set up!

I recommend you check out this dockerised RF gateway or this ESP32 version of the same, reducing on the amount of hardware required to support your home automation setup! Check out this post to read more about the advantages of using docker and microservices in home automation.