Keychain detector
by electron
For a while now, I have been trying to figure out how to detect when the wife is at home, or 'on the road'. I needed something that was fairly accurate, and inexpensive as I was planning on triggering home automation functions based on this 'occupancy' status. For various reasons, I could not rely on the car occupancy detection method, and other solutions were too costly or not accurate enough. The solution? Detect when my wife is home by looking for the presence of her keys on the keychain storage hook located in our kitchen. She will never leave the house without her keys, so this was the best methodology to use as an occupancy sensor. Most people always have their keys on them, and usually place them in the same location when at home.
Concept
There probably is no simpler solution than this one. Think of a simple door/window contact, but the magnet/sensor combination are replaced with two metallic eye hooks. When a metal keyring is placed on these two hooks, it will close a circuit between them, and trigger an 'alarm' just like a regular door/window contact would.
Build it yourself
Step 1
Find two metallic hooks or nails which can hold the weight of your keys. It is up to you on the aesthetic details (keep the WAF in mind though). I used an existing key hanger board, and simply added 2 brass eye hooks to the bottom. It is important that these hooks/nails are conductive, so when in doubt, make sure you use your multimeter to confirm their conductivity (using the resistance settings of your multimeter). You could also wrap the leads from a wireless door sensor (i.e., DS10A) around each hook, and touch one hook with the other. If the light blinks, you know you are all ready for the next step.
Step 2
Decide how you want to interface this 'sensor'. There are many ways of doing this, such as using a spare pair in your Cat5/phone wire, wireless alarm sensor such as the GE wireless sensors, or in my case, a spare X10 DS10A. These sensors are very inexpensive, and their status can be monitored by my Elk M1 alarm panel (using the W800RF32 wireless receiver).
I disconnected the wires leading to the magnet, by undoing the 2 small screws, and pulling the wires out.
Step 3
Install the hooks, and connect them to the sensor wires. Since I am using the typical brass eye hooks you can find at any store, I predrilled 2 holes, about .5" apart. Since these hooks have to be screwed in, make sure you have enough clearance so they can turn! Also make sure that the holes are drilled as straight as possible (use a drill press if you have one), or it will look strange, and might cause false positives if the hooks aren't aligned.
I stripped approximately one half inch of insulation from the DS10A wires, and inserted them carefully into the holes. While holding the wire there, I carefully screwed the hooks into the wood. This seems to create a very solid connection, so there is no need for soldering.
Step 4
Last but not least, configure your sensor if needed, and make sure your home automation system sees the on / off signals by hanging your keyring on the hook. If everything works, then mount the key hanger and start programming. Make sure that other keys won't obstruct the hooks, as you don't want to generate false positives.
What's next?
When the wife isn't home, the system knows, and forwards any important reminders/notifications to her cellphone. Please keep in mind that certain applications might require the use of a timer (in case your keys get bumped when someone else hangs up their keys). There are other interesting things you can do (e.g., announce new messages when you arrive home), but there are too many to list here. While some might wonder if it is worth it, think of how inexpensive and easy this method is (especially when compared to RFID solutions), and if everyone in your household puts their keys on the hook when home (and many do, I have asked around), the benefits can be huge.
If you have any suggestions, or comments regarding this article, please don't hesitate to share!
by electron
For a while now, I have been trying to figure out how to detect when the wife is at home, or 'on the road'. I needed something that was fairly accurate, and inexpensive as I was planning on triggering home automation functions based on this 'occupancy' status. For various reasons, I could not rely on the car occupancy detection method, and other solutions were too costly or not accurate enough. The solution? Detect when my wife is home by looking for the presence of her keys on the keychain storage hook located in our kitchen. She will never leave the house without her keys, so this was the best methodology to use as an occupancy sensor. Most people always have their keys on them, and usually place them in the same location when at home.
Concept
There probably is no simpler solution than this one. Think of a simple door/window contact, but the magnet/sensor combination are replaced with two metallic eye hooks. When a metal keyring is placed on these two hooks, it will close a circuit between them, and trigger an 'alarm' just like a regular door/window contact would.
Build it yourself
Step 1
Find two metallic hooks or nails which can hold the weight of your keys. It is up to you on the aesthetic details (keep the WAF in mind though). I used an existing key hanger board, and simply added 2 brass eye hooks to the bottom. It is important that these hooks/nails are conductive, so when in doubt, make sure you use your multimeter to confirm their conductivity (using the resistance settings of your multimeter). You could also wrap the leads from a wireless door sensor (i.e., DS10A) around each hook, and touch one hook with the other. If the light blinks, you know you are all ready for the next step.
Step 2
Decide how you want to interface this 'sensor'. There are many ways of doing this, such as using a spare pair in your Cat5/phone wire, wireless alarm sensor such as the GE wireless sensors, or in my case, a spare X10 DS10A. These sensors are very inexpensive, and their status can be monitored by my Elk M1 alarm panel (using the W800RF32 wireless receiver).
I disconnected the wires leading to the magnet, by undoing the 2 small screws, and pulling the wires out.
Step 3
Install the hooks, and connect them to the sensor wires. Since I am using the typical brass eye hooks you can find at any store, I predrilled 2 holes, about .5" apart. Since these hooks have to be screwed in, make sure you have enough clearance so they can turn! Also make sure that the holes are drilled as straight as possible (use a drill press if you have one), or it will look strange, and might cause false positives if the hooks aren't aligned.
I stripped approximately one half inch of insulation from the DS10A wires, and inserted them carefully into the holes. While holding the wire there, I carefully screwed the hooks into the wood. This seems to create a very solid connection, so there is no need for soldering.
Step 4
Last but not least, configure your sensor if needed, and make sure your home automation system sees the on / off signals by hanging your keyring on the hook. If everything works, then mount the key hanger and start programming. Make sure that other keys won't obstruct the hooks, as you don't want to generate false positives.
What's next?
When the wife isn't home, the system knows, and forwards any important reminders/notifications to her cellphone. Please keep in mind that certain applications might require the use of a timer (in case your keys get bumped when someone else hangs up their keys). There are other interesting things you can do (e.g., announce new messages when you arrive home), but there are too many to list here. While some might wonder if it is worth it, think of how inexpensive and easy this method is (especially when compared to RFID solutions), and if everyone in your household puts their keys on the hook when home (and many do, I have asked around), the benefits can be huge.
If you have any suggestions, or comments regarding this article, please don't hesitate to share!
