In our current house, we have added wired contact sensors to pretty much every door in the house (internal and external), the garage door and even the garden gates. In all cases these are invisible and implemented using micro reed relays and tiny, powerful magnets fitted into the doors. The wiring all runs back to a central point, where our Home Control System (HCS) is located. This approach fits well with our Smart Home philosophy.
In a couple of instances we have had to use Everspring SM103 Z-Wave sensors. These are quite large and not very attractive, so we have hidden them behind skirting board and plinths, using the remote switch capability to hide a micro reed relay in the door frame and fixed a small magnet into the door. This too is invisible home automation.
This project aims to address the two remaining doors in our current home, that are yet to be networked and have door contact sensors installed. These two doors are on the ground floor and we can find no viable route for wired sensors. To address this we have decided to take the fairly radical approach of installing Everspring HSM02 contact sensors inside the door, with a magnet hidden in the door frame. This is the best way we feel we can 'network' these doors with the automation again be invisible to the eye. This is not ideal as the sensors are now in a moving object and will be subject to greater shocks but, we will cushion them with some foam which will also keep them firmly in place.
The Everspring HSM02 is the new replacement device for the SM103 above. It is a much more compact device at 70 × 11.5 × 44mm. Full details and specification. Our sensor was supplied by Swarm Automation. The LED and notches in the front of device indicate the location of the internal switch and magnets. This makes aligning another magnet mounted in the door frame a lot simpler.
This is covered in our design section on doors.
This approach works because the two internal doors are made of wood. We plan to use a router to cut a slot in the top of the door, in which to slot the HSM02 sensor. It could also be done using a hammer and chisel.
Firstly, we marked up the top of the door, to indicate where the slot needs to be cut. The position needs to be chosen such that the router bit with not hit any metal work. We used a metal detector to ensure the area was clear of nails and other metal items. In this instance the slot starts about 100mm in from the edge of the door and is 75mm × 12mm. You have to allow a little bit extra space, because the router cuts a groove with rounded ends.
Our router bit is 12.7mm in diameter, so we can cut the required groove with a single stroke, moving in one direction. The depth of the cut is kind of irrelevant. Although the picture above shows a solid piece of wood, a pilot hole shows it to be just 25mm thick and our router can easily cut through to this depth.
We created a stable platform and an straight edge to run the router along by clamping some wood to the door.
This is the slot cut in the opt of the door. you can see where it has cut right through. This means that any sensor inserted in the hole cut will drop down inside the door. To prevent this, we will fill the void with some expanding foam and then push our sensor into this.
The HSM02 sensor really is quite small and only 12mm thick. The bit that goes into the door is only 31mm deep (without the magnet part).
We are not using the supplied magnet and its plastic enclosure, as it is far too big. It is much easy and tidier to use a tiny but, very powerful round magnet and simply drill a shallow hole in the door frame, opposite the reed relay in the HSM02 sensor. These are readily available on eBay and other similar sites. Note: These magnets are very powerful and can damage electronic devices and storage media if they are placed too close to them. You could unscrew this part as shown above and just re-use the magnet inside though.
On the main sensor, there is a small plastic cover that slides off, to reveal the battery and tamper switch. This is used to include the HSM02 onto the Z-Wave network (also used for exclusion and reset functions). This is pressed rapidly three times to perform inclusion. Once included, pressing the tamper switch once, causes the device to wake up.
We started up the VeraLite web interface in a browser and under the 'Devices' tab, we chose to 'Add Devices'.
We then chose 'option 1', to include a device in proximity to the controller.
The new device was found and assigned a node ID. We then assigned it a name.
We also assigned it a room.
We then configured two scenes and triggers on the VeraLite, to handle door open and close events. These scenes use Luup code to send the events to our Home Control System (HCS) using socket layer comms.
We do not plan to use any Z-Wave associations with this device.
Parameter 2 enables a delay to be set before the device reports close events. By default, there is no delay and we have no changed this setting.
We don't recommend that you use contact sensors in this way, if you have the choice. It is much more cost effective and reliable to use wired sensors where possible. This project shows that if you can't install the required wiring, then you have a viable alternative using Z-Wave technology.
It doesn't matter how beautiful the manufacturers of home automation equipment make their devices, in most of the scenarios we have come across, you just don't need or want to see them. Sticking or screwing sensors to internal doors is never going to look good in our view, so making them disappear is definitely the way forward. There are no Z-Wave contact sensors specifically designed with an invisible installation in mind.
Because these devices are hidden out of sight within the door, it is essential that they can report battery status remotely. Our Home Control System (HCS) collects this and sends out notifications when batteries need changing. The lack of batteries is another advantage of a wired installation.
These two sensors are now installed and in operation. They work very reliably and well. Our only concerns are with the battery levels reported and the battery life expected from the Everspring MSM02 device. Battery level changes recorded so far are:
- 12/11/2012 Lounge door battery = 60% (new battery).
- 28/11/2012 Lounge door battery = 50%
- 30/11/2012 Kitchen door battery = 60% (new battery).
- 20/12/2012 Lounge door battery = 40%
- 26/02/2013 Kitchen door battery = 30% - at this point we got an SMS message from our HCS.
- 09/03/2013 Kitchen door battery = 40% - the device died from loss of power.
- 14/03/2013 Kitchen door battery = 80% - New battery installed.
- 05/04/2013 Kitchen door battery = 30% - Must be a duff battery? This one lasted less than a month!
The battery level reporting on these devices is a bit rubbish. Not only is 80% battery life the best we have seen with a new battery but, the battery level varies by ~20% over time too.
26th November 2012
We didn't think much of it before now but, both of these new sensors report a battery level of 60% and show up in the VeraLite UI with orange battery levels. We will change one with a known new battery and see what happens.
28th November 2012
The low battery has been a useful test of our existing code and XML-based configuration. We received a text message from our Home Control System (HCS) this morning, informing us that the Lounge Door sensor had alarmed due to the battery capacity hitting 50%. This is something that just automatically happens with our design and implementation.
We have bought some new batteries and this should also allow us to measure battery life starting with a new battery.
30th November 2012
Tried a new CR2450 battery in both sensors and they still only report 60% battery capacity. We can only imagine that this is a flaw in the Everspring HSM02 sensor. We have asked the question on some Internet forums and so far, our view is backed up by the experience of others.
17th January 2012
The Kitchen Door reports a battery level of 40% for the first time.
26th February 2012
We got an SMS message from our Home Control System (HCS) telling us that the Kitchen Door battery level had hit 30%.
14th March 2013
We noticed that our Kitchen Door was no longer reporting. The batteries have gone completely flat and the last reported battery level was at 40% on the 9th March 2013. We wouldn't normally let things get to this stage but, we wanted to test the absolute limits of battery life. We then installed a new battery and the battery level reported was 80%. We still have some concerns that we are usign a duff set of replecment batteries. To remove this possibility, we have also bought new Duracell branded CR2450 from two different shops.
The Lounge Door is reporting a battery level of 40% and we expect it to die soon too. We will then try one of the new Duracell branded batteries in this sensor.
If we can't resolve the CR2450 battery issue, we then plan to try a twin AA battery holder. There is plenty of space in the door to hide this and this will mean we can use much cheaper batteries and they should also last much longer.
5th April 2013
We received another SMS message this morning informing us that the Kitchen Door battery level had reached 30%. We are beginning to think we have some duff batteries.
15th September 2013
We received another SMS message this morning informing us that the Kitchen Door battery level had reached 30%.
27th July 2014
A quick analysis of our Home Control System (HCS) logs shows that our lounge door can report over 1200 open and close transistions per month. At the weekend, this one door will report over 100 open and close transistions in a day.