In a past home, I have had the ability to crack a window open by as much as 4 inches without triggering a security warning. That allowed me to crack the window at night and get fresh air in the house and still keep the security system armed.
Can an open/close sensor be mounted in a way that will allow a window to not fire an “open” trigger if it is closed or cracked open?
One way you could fool the system would be to mount a secondary magnet so that the sensor would still report being closed.
Exactly what I was going to suggest. Just add some magnets to that when the window is cracked, it’s still showing as closed.
I’ve thought about doing things the opposite way too… mounting the magnet on the part that moves and then multiple sensors on the window frame. This would be quite expensive of course, but then depending on where the magnet is it would trip one of the sensors. This would allow me to know if it’s closed, open a little bit, or open a lot.
Again, potentially very expensive, but could provide some interesting uses.
For example: Make sure that if my whole home fan is on that there are enough windows open AND they are open far enough to provide adequate air flow… and turn off the whole home fan if there isn’t enough open.
Or: if rain in coming, report if windows are open alot so I can close them, but if they are only open a little, then don’t report on those.
@chrisb- great, now you got me thinking… how else can you know if the window is open or closed (without using two sensors) 
One way to be able to setup multiple sensors at a reduced cost would be to setup an Arduino UNO, with ST Shield and connected to multiple reed/magnetic sensors. Of course you would need to setup the device and SmartApp code, but much of that can be re-used from other projects.
For example(one of my favorites):
Yeah… what @DavidCreed said. If I were to go down this road it would likely be a custom hardware creation thing. I’m almost tempted to do it just to force myself to learn Arduino and devicetypes and such… But realistically I just down’t know if I’d the gains would be worth the effort, and costs, involved.
I just don’t know if the costs involved on a per window basis would be worth it to me. (Arduino… think shield… multiple reed/magnet sensors… that’s going to add up quick!)
The only other way I though about doing it was make with a laser range finder. But again, I don’t know if costs would be any less than the other way.
@chrisb I’m in the same place. I’m currently working(slowly) on this type of project, learning coding along the way.
In terms of pricing you are looking at:
ST Shield $35
Arduino Uno ~ $10
Reed sensor ~ $1 each
But you could also then add other sensors and controls to perform additional tasks and information:
4 Channel relay ~$4 - Could be used to control lights, ceiling fans, outlets, motorized window blinds etc
Temperature and Humidity sensor ~$2
PIR (passive Infra Red) Sensor ~$2 - motion sensor
Tho more things you add, of course the more complicated it can get, but also the value starts to increase. You can also add capabilities that aren’t native to standard ST or other zwave products.
Another option is if you have the ability to run wires through attic, floor or other spaces, you could have one controller, monitoring/controlling multiple rooms.
@DavidCreed Wow, please keep us in the loop on this project. I am looking to do similar things once Time allows, and I am excited about what you are building here.
Let us know how it turns out, and even better please share the results.
So, we might have highjacked this thread a little - - but, I’ve been thinking how to use the multi with two magnets to tell if the window is open.
I guess one way is to try using some of the other sensors inside the multi - - could it be possible to mount the multi, so when the window is open, the orientation changes? (thinking of the garage door monitor) I guess at it’s simplest form, mount the multi with velco; when the window is closed, the multi is at the bottom of the vertical sliding window. If the window is open, mount it on the side of the window (next to the second magnet).
That takes the fun out of the HA (SMILE) but @emilm I think we see a need for w window sensor that also shows positional information.
Could a sensor be made to first determine that the window has been opened, then have some sort sensor that can be mounted in the track of the window that detects the amount of opening. Magnetic or perhaps some sort of resistive based sensor to track how far the window has opened.
The problem is that this doesn’t exist, and unless you put the sliding sensor on the outside frame of the window, it will be difficult to make look nice (SMILE)
Taking this further, what we need is a window that does:
So anyone else want to add to the dream window?
Please keep in mind - the last thing I want to do is move the multi manually; was really trying to describe the concept.
So, if the multi actually had two magnet switches inside; one along the long side (as it does) and the second 90 degrees away from the long side - - this would help with using two magnets.
@chrisb @DavidCreed Glad you like my project. Let me know if I can help you in any way. I am hoping someday to free my project from the ST shield but haven’t worked out the specifics yet… depending on how I do that, it could bring the price per location down. I can say that it lends itself well to places like kitchens and bathrooms where you can hide wiring in cabinets. When you consider the fact that you can get lighting, a reed switch, a temperature sensor, a piezo/siren module, and a motion sensor in one location, it does make the project more economical than if you only use one of the capabilities.