Home security system

[sbj_ee]

I created my own home security system.  We bought this house 9 years ago and the previous owner had a security system.  All of the sensors were present (a combination of wired and wireless sensors). I figured the wired sensors would be trivial, but I had no idea how the wireless sensors worked. I quickly determined that all the wireless sensors were transmitting on 319.5MHz. So, I bought a Software Defined Radio for ~$35 and with a little code was seeing all of the wireless sensor messages.  I had the decoded messages outputting as json and some simple python code to implement some intelligence and viola.

The wired sensors were trivial.  I simply connected them to the GPIO of a Raspberry Pi Zero W.  Then I just monitor for state transitions and send UDP messages to a central server which does all of the higher level logic and alerting.  I even send notifications to my Apple devices for whatever criteria I determine.

 

 

[Aaron Moncur]

Stephen, that's an awesome project! Thanks for sharing here. Super impressive you were able to get it all working on your own. Do you have a software background?

[sbj_ee]

On 12/15/2024 at 3:52 PM, Aaron Moncur said:

Stephen, that's an awesome project! Thanks for sharing here. Super impressive you were able to get it all working on your own. Do you have a software background?

I used to think of myself as more of a hardware engineer and writing software to utilize the hardware features… Then I found myself spending more time in software than the electronics. Today, I deal with systems using whatever hardware or software solutions that are appropriate. The best software is one that solves a personal need.

 

[sbj_ee]

I'm about to put an extension onto my home security system.  I recently created a mechanism for detecting woodpeckers pecking on a surface of our house. I just finished the code to incorporate it into my security system where it alerts all of the panels (well - it will only make the one on my desk beep 5 times until I flush out some minor details).  The key thing is to absolutely minimize false alerting. You have to be able to ignore ambient sounds. My plan is to place the piezo mic in direct contact with a window near a wall the woodpeckers tend to favor. If the piezo is flush with the surface, then it does not pick up people speaking or even the music I'm playing. However, it detects me tapping on my desk (the piezo is currently flush with my desk), it detects me tapping on my mouse pad which is a cushion type, and it even picks up my typing as I type this.

Now here's where you ME's can laugh at an EE.  Physically positioning the sensor to remain flush with the window.  I do not want to have anything between the piezo and the glass dampening the vibrations. I also need something with mass to keep the piezo from moving.  I just happen to have some steel rectangle blocks which are 15mm x 15mm x 388mm that I used to help with some thermal smoothing in my toast oven solder re-flow profile (a story for another day). So I used the steel block and some mounting putty - I'll add a photo for a better visualization of my device under test. I can even add additional steel blocks if needed to keep the sensor positioned properly.

Now I just have to wait for my youngest daughter to return to college and vacate her bedroom. You can imagine an 18 year old's reaction to me putting this in her bedroom... Then it will go into the real life testing stage/trial.

Oh - woodpeckers... If you have ever had to deal with them, then this will resonate (pun intended). If you have never had to deal with them destroying your house, then consider yourself very fortunate. They cause ~$1000/year in stucco damage to our house.