Room Sensor

My original idea was to have a sensor in each room that recorded:

  • The temperature
  • The light level
  • The sound level
  • Occupancy of the room

I could then detect if lights were left on in unoccupied rooms, or if music or other media was playing, and if the temperature of the room was optimal for its current occupancy state.

With LightWaveRF control of lights, control over media devices, and LightWaveRF control of individual radiators, I could return everything to its correct state using OpenRemote rules.

I have built such a room sensor:

The latest one includes a humidity sensor, but no sound meter. I had a problem building a sound meter using an electret microphone or a piezo-electric buzzer, but will have another go soon. I don’t currently have a way to control humidity.

The main problem with the room sensor is that it uses too much current, and runs the batteries down far too quickly. I think it needs a design more like then emonTx sensor from OpenEnergyMonitor. I plan to buy a kit for an emonTx and experiment with that design. It runs at 3.3v, has no wasteful voltage regulator, and uses the Hope RFM12B module to turn off the power on the AVR when it is not taking measurements. This makes the batteries last far longer.

The other problem with the room sensor is that I have not yet got control over lights and radiators, and my control over media devices is incomplete.

Lighting: I have mainly LED GU10 lights in my house ad they are not dimmable. LightWaveRF only controls dimmable lights (as far as I can tell). There are dimmable LED bulbs but they are currently expensive. The ones room that has dimmable lights is my bedroom, and that uses halogen 50w dimmable bulbs. These are vary wasteful of electricity, but do not get used very much. I will get some LightWaveRF light switches for my bedroom and try them there first. I will then try some dimmable LEDs. The extra problem with dimmable LEDs is that they may not supply sufficient load for the LightWaveRF switches. This needs some experimentation.

Radiators: I have bought a LightWaveRF radiator valve, thermostat and window switch. These operate an 868MHz, not 434, so I need different RF transmitters and receivers to control and monitor them. They are currently quite hard to get hold of. I have bought a breakout board for the Arduino with an 868MHz Hope RFM12B transceiver. When I have soldered this together, I will build an RF Sniffer wth this, so that I can capture the LightWaveRF packets.

The only suitable room for this is the guest bedroom. Most of my radiators do not have thermostats on them, but the one in the guest bedroom does. The LightWaveRF motorised radiator valve replaces a standard thermostat radiator valve. So, I will fit the radiator valve, wall thermostat, and window switch in the guest bedroom. The window switch can be paired with the radiator valve to turn the radiator off when the window is open. If I capture the signal and send it to OpenRemote, I can fire rules when the window is open. The wall thermostat can also be paired with the radiator valve, Again, I can do more flexible things with OpenRemote but the (very small) wall thermostat could be useful for manual override. If any of this proves effective and useful, I will get thermostats fitted to the rest of my radiators, so I can implement this in all rooms.

LightWaveRF seems to have some cheaper window and door switches. That is cheaper than the window switches that control the radiator. I am hoping that these work at 434MHz. I will get one to experiment with. I quite like the idea of monitoring how often the fridge is open as in the bwired house.

Media devices: I just need to install an RF to IR remote in the guest bedroom and the dining room both of which have TVs with Virgin Media set top boxes, to get control of all TVs in the house. If I find a high sound level in an unoccupied room, it is likely to be a TV (or attached or built-in DVD player), or a computer, or the Xbox. Finding which to switch off could be difficult. I can turn the volume down in any computer using OpenRemote, and I can do this for TVs etc. I could try turning the volume down in the various devices to see which one causes the sound level in the room to go down, and I would then know which device needs switching off. This all seems rather complex. I have not yet investigated remote control of the XBox.

Humidity: As I say I have no way to control humidity, but it is not currently a problem. I mainly added a humidity sensor to the room sensor, just to play with it.

Room Occupancy: I am currently using a PIR sensor from Cool Components to check for motion in a room. This works, but I am not sure how reliable it will be. I may need more than one sensor in some rooms to reliably check for occupancy of a room (by a person who is awake). LightWaveRF have a PIR sensor which I could possibly use an alternative to my own device.

Flexibility: I am beginning to think that one room sensor per room may not be enough. As well as needng more than one PIR sensor, I want to monitor windows, doors, washing machine, electricity usage, plants, etc. Adding audio jacks to my room sensor like emonTx, would allow extra sensors to be added, which might satisfy some of the need, but sometimes I will need more than one room sensor, so calling it a room sensor is probably not sensible.

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4 Responses to Room Sensor

  1. tomkerswill says:

    Hi! I know this is quite an old post now, but thought I’d comment anyway. I currently have a load of LightwaveRF radiator valves in operation (they’re actually rebadged Technoline units I think). These are the first generation ones, rather than the more recent 2014 controls.

    I bought one of the LightwaveRF window switches — I think probably the cheaper ones you mentioned (£11.99 at Maplin). I’d originally planned to pair these directly, but the radiator valves operate on 868Mhz, and the switches on 484, so they can’t actually talk to each other directly! I think with Lightwave’s WifiLink, this could be made to work (as it can communicate on both bands).

    But I’m keen to do the control of the switches using an Arduino with your RF library rather than getting a WifiLink. Is there a part of your LightwaveRF code that can talk to radiator valves on 868MHz?

    Another option is to get a Technoline window switch, which I think *would* simply talk to the radiator valve or wall thermostat directly – no need for Wifi link or Arduino – … Bit more expensive though.

    Many thanks!


    • Geek Grandad says:

      I have one of the old radiator valves but I have never got round to trying to talk to it with an 868Mhz transmitter. Why do you think the Technoline switches will talk to it? If all you want to do is to switch the radiator off, then the 868Mhz LightwaveRF switch should do it (if they are still available). Personally, I would want them all integrated with by home automation software. I was planning to look at the new range of LightwaveRF radiator valves. I have not been doing much home automation for a while, but am just starting again. Sorry I can’t be of more help.

      • tomkerswill says:

        Hi – thanks for the reply! The Technoline switch should talk to it because they are basically the same system — eg. the old LightwaveRF radiator stuff is a rebadged Technoline (here’s a link to someone who is using them interchangeably: ) … The LightwaveRF 868 window switch could be a good alternative too — do you have a link? I couldn’t seem to find them anywhere!

        Yes, better to link them all in, though – so I’ll have a play with your library and see if I can get them all talking via that. Thanks for the great site!


  2. Geek Grandad says:

    I don’t know if the protocol that LightWaveRF uses for 868Mhz is the same as the 434Mhz protocol, or even if it is an on off keying protocol. I was wondering if they use a different radio such as a frequency shift keying one at 868Mhz, but I have no idea. I don’t know if the new range uses the same protocol as the old heating range. The LightwaveRf switch was probably the same as the Technoline one as they look similar.

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