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Window open sensors


dnb

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As part of my home automation ideas, I am considering "instrumenting" all of the opening windows in the house. Ideally I want the sensors to be extremely unobtrusive, preferably invisible, and definitely not be wireless or require batteries. Oh, and each sensor needs to be fairly cheap because there are quite a lot of opening windows!  I'm not against carefully drilling the frames during window installation to fit the sensors so they are totally invisible with the windows closed. I have all the cross section drawings and assembly data for the windows so can do this without fear of compromising anything.

 

I found some ideally suited small sensors (based on reed switches and magnets I believe) lurking on Amazon early last year, but they appear to have disappeared without much trace. So I wondered what people here had done? A quick search yeilded nothing much, other than an interesting thread about fire safety systems. (Still useful, but for a different thing...)

 

I must confess to not being totally sure what the house system will be asked to do with the information. Currently thinking along the lines of displaying security warnings and to give a bit of intelligence to the HVAC.

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Humm..

 

I doubt you want a separate wire from every sensor back to the HA controller, it would make much more sense to have multiple sensors on one cable. That means they need to identify themselves to the HA so that the controller can tell which window is open. This must have been solved by alarm/HA companies years ago.

 

Which HA system are you looking at?

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Google suggests the Texecom CQR FC505 series might be suitable but they look like simple window switches with no identification capability so you would need to walk around to find which window was open if they were all in series on one wire. Need a 20mm hole so not very small.

 

https://cpc.farnell.com/cqr-security/fc505-wh/contacts-flush-mount-white/dp/SR08422

 

http://www.farnell.com/datasheets/1700911.pdf

 

image.png.f8c046c12064a63fbd93a67b72251db9.png

Edited by Temp
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34 minutes ago, Temp said:

I doubt you want a separate wire from every sensor back to the HA controller, it would make much more sense to have multiple sensors on one cable.

 

I would indeed prefer not to have hundreds of cables around the place. It's not the end of the world to have a microcontroller sat in each room to report to the HA about open windows. The uC is going to be there anyway to report on temperature, ambient light and probably some air quality measure (etc - add features until there's no spare input pins...) anyway. So why not give it another job. This should divide up the problem a bit.

 

24 minutes ago, Temp said:

Texecom CQR FC505 series

I saw these too and thought they were a bit big.  Ideally I would like something about half the diameter, but I could probably work with them. I found them once so I will do it again!

 

1 hour ago, Temp said:

This must have been solved by alarm/HA companies years ago

Identification is probably possible with not too many windows using a resistive ladder and an A to D converter. In theory at least - the voltage drop of the long cables probably spoils things a bit.

 

46 minutes ago, Temp said:

Which HA system are you looking at?

Let's say probably Loxone. SWMBO likes their light switches and I think the product scheme looks well thought out.

But in all fairness I'm not all that impressed with any of what I have seen in the market sector. It's still the land of early adoptors with all the problems that go with it.

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A bit of early morning lateral thinking.

How about a 1Wire light sensor with a very small LED as the light source.  This can be powered from the same source as the 1Wire.

 

Actually, thinking about it a bit more, just the cheapest 1Wire DS18B20 and a contact switch. Then sense when they DS18B20 is connected or not.  You can collect the temperature data when it is connected to i.e. when window is closed.

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Have you already ordered windows?  Much simpler and less risky to have window manufactuers supply windows with sensors pre-installed.

 

We have two sensors pre-installed in each window (one for tilt and one for turn).  Sliders also have two sensors, one which tells you when it's locked (for security) and one that tells you when it's open/closed (to disable blinds).

 

Some are simple reed contacts, but most are "Maco" sensors which work with the window mechanism.  See: https://www.maco.eu/en-GB/Products/Windows/TRONIC-sensors/Wired-sensors

 

The price of adding these sensors was nothing, compared to the overall window order.

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5 hours ago, Dan F said:

Have you already ordered windows?  Much simpler and less risky to have window manufactuers supply windows with sensors pre-installed

Yes. On order since October so too late to change things. It seemed a considerable cost uplift to me when we discussed it, but looking back now they might have changed the design of the opening section for a more expensive set of extrusions at the same time. I agree it's much less risky to have it all built in but since this is only a "toy" feature for the house I didn't want to commit too much resource to it when everything else is seemingly increasing in cost weekly. If all I end up with is something that tells me a window is closed, but can't tell if it is latched, then that's still a useful input to the HA.

 

4 hours ago, Temp said:

Not sure about the source but just 60p each. Not addressable.

Those are the exact ones I found on Amazon last year - even down to the same photos. They look very much like like unbranded versions of one of the Honeywell sensors.

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