433 MHz devices - Overview

433 MHz devices have their place in today's home automation space. Simple and straightforward technology enables low-cost devices, but is also vulnerable to security and reliability issues. These problems can often be avoided, as long as you keep in mind a few basics.

In the autumn of 2015 Cozify added support for a selection of Nexa and Proove sensors and smart plugs that operate on the 433 MHz frequency. That lead to a steep increase in the sales to consumers. At the beginning of 2016 we were very happy with the choice we had made: our customers were able to reap more benefits from the devices they had already acquired and it significantly lowered the threshold to start using the Cozify Smart Home. In appropriate use, they are handy and worry-free.

However, as always, there are reasons for low cost. The 433 MHz devices are not based on any common protocol as all manufacturers have to come up with their own protocol or loan it from their neighbour. Partly due to inexpensive components there is quite a bit of variation in the implementation of the protocol even between two devices that should be the same. This has resulted in significant amount of unexpected work, which has in turn delayed some other projects. Implementation of Z-Wave support is one of them, unfortunately.

All 433MHz devices that we have encountered so far are only capable of one-way communication. I.e. the smart plug can only receive a command to turn on or off, but cannot acknowledge that the command has been executed. Therefore, the Cozify Hub must assume the state of the device, which is not optimal. In practice, hub commands plug five times "Turn the plug on", but cannot verify from the plug if the message was really received.

Some 433 MHz devices only send their status into the air. For example, the thermometer transmits the data once every minute regardless of the traffic in the same frequency at that moment. This leads to mixing of the messages as more 433MHz devices are added to the system. Hub cannot ask from the thermometer what the temperature is, but have to wait until the value is sent next time, meaning after a minute or so.

Cozify Hub prioritizes listening to the traffic instead of sending. We recently visited the home of a customer where the 433MHz devices were practically unusable. They randomly worked, but always with a significant delay. Using a sniffer, we found out that the cable modem wall mount sent disturbance on a wide frequency band, thus jamming Cozify to listen to possible messages. By moving the Hub by 1,5 meters the system became fully functional.

433 MHz frequency devices work well, as long as the technology used by the restrictions are taken into account. Positioning the motion sensor is careful, because if the motion detector continuously detects motion, it covers other 433 MHz devices signals thus making it impossible for the hub to receive or send commands to other 433 MHz devices. Positioning devices is important, because signal must go through from the hub to the device, and vice versa. Depending of the device type. Changing hub or device place a bit, might make a huge difference in reliability. In general, the case survives by experimenting and observing the situation on the ground.

Pros

• Inexpensive devices
• Simple technology to implement
• Widely used technology
• Devices been in the market for some time

Cons

• One-way signal traffic (hub is not able to confirm or ask device state
• No agreed standard between device manufacturers
• Sensitive to interference
• Signals to and from the device cannot be encrypted

List of Cozify supported 433 MHz devices can be found here.

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Support for Proove and Nexa devices, and Verkkokauppa.com as a new retail partner

We are announcing support for wireless devices from Proove and Nexa. The list of new supported hardware includes devices such as inexpensive outlets, temperature sensors, motion sensors and remote controls. Here is a summary of the new devices and a few examples of fun and interesting applications. The devices and the Cozify Hub are now available for purchase at Verkkokauppa.com.

Proove and Nexa have had smart home devices on the market for several years. They are often controlled by wireless remote controls, but they are equally compatible with other smart devices as part of a smart home controlled by Cozify Hub. By combining the functions and features offered by different devices, you are able to elevate your life to a new level of comfort and security.

A few examples of new applications

• Remote controls and wireless wall switches can be used to conveniently access lighting and music to suit different moods and different times of the day.
• The lights in the shower turn red when the relative humidity of the air exceeds 90%. The smart lights signal that it’s time to finish – a good function for a family where teenagers seem to lose track of time when taking a shower.
• Cigar aficionados no longer need to guess the relative humidity of the air in their humidor, and wine enthusiasts are always aware of the temperature in their wine cabinet. A thermo/hygro sensor sends a notification to your mobile phone if the temperature or the relative humidity of the air rises above or falls below your predetermined limit.
• A swimming pool thermometer can also be placed at the end of the jetty in a lake, allowing you to check the water temperature even before you drive to your summer cottage.
• A thermometer and a fan heater connected to a socket are the perfect combination for heating your greenhouse in the autumn. Using one simple rule, Cozify will ensure that the temperature stays at 15 °C or above, leaving your tomatoes unharmed by any night frosts.
• Your car can be warmed up in the morning by using a remote-controlled outlet, in accordance with your weekday morning schedule and the temperature.

A few words on technology

Devices that use 433 MHz radio are usually cheaper than ZigBee or Z-Wave devices, for example. The lower prices are due to the devices’ economical design and simple technology. Communication is one-way and unencrypted, which is why the equipment cannot be recommended for critical applications, such as locking. On the other hand, the equipment works smoothly and without delay in good conditions.

My experiences of Proove devices connected to Cozify Hub are very positive. Motion sensors, daylight sensors and door sensors have worked smoothly with Nyce Zigbee sensors and Osram Lightify bulbs and lights. The Hub makes it easy to set up the devices and the connection covers the entire house, through several structures, even reaching outside. The range can be expanded even further with “range extenders”, but in my case they have not been necessary. 

What’s next?

Proove devices are already supported by Cozify Hub today. Nexa devices are very similar to Proove devices, and we will extend our support to cover Nexa equipment in the next few days. Our support for Nexa also means the introduction of new device categories, such as a daylight sensor, wall switch and doorbell.

Once we have released support for Nexa, we will turn our focus to adding support for devices such as IP cameras. We are always happy to receive feedback and ideas on new devices to support. Join the discussion on new devices on the Cozify discussion forum.

Our list of supported devices is available at http://support.cozify.fi/support/solutions/articles/8000034917-technical-information

Where can I buy these new devices?

Our support for 433 MHz equipment is based on our newly launched cooperation with Verkkokauppa.com. The smart devices they sell include Cozify Hub as well as Proove and Nexa products. Check also our own web store http://en.cozify.fi/pages/shop.

Wishing you a cozy autumn,

Kimmo / Cozify