I need help in finding the best approach towards a stealth project. I am operating a mission in my home where I need to ensure that I cannot get flanked / approached by someone from behind and not notice. Basically I will need to construct a couple of motion detectors that:
Are reliable and won't trigger randomly.
Are very small and easy to deploy.
Aren't expensive, so if they get destroyed or lost it wouldn't be the end of the world.
Work in the dark.
Are able to send a message / notification to a device REMOTELY. I can't use anything that makes a noise like buzzers etc.
I've thought of trying to interface an RF system where as soon as the motion sensor detects motion, it uses a connected RF transmitter and sends a signal. But how would I interpret the RF message, and on what device?
A second idea that came to me which I think is more realistic is to set up a raspberry pi server, hosting a simple webpage on my home network. I could then use an esp8266 Wi-Fi board together with a small arduino and motion sensor to send a packet of data to the webserver whenever the motion detector is triggered. I would be connected to my home network from my mobile and be viewing the page, so I will get informed whenever there is motion detected.
What are your thoughts about the potential solutions I have described? Are there any alternative methods that I should consider?
I once built motion detectors using HC-SR04 boards and ATTiny85s.
The idea was to initially measure the distance that the SR04 "sees" and then trigger an alarm once that distance changes.
They were pretty cheap to build and worked reasonably well.
The whole thing easily fit inside 7x7cm boxes with lots of room to spare.
There are several RF transmitters that you can simply hook up to a serial interface on the arduino side of things, so receiving the messages should not be that much of an issue.
ESP8266 would probably work as well, but personally I do not like using WiFi for things like alarm systems.
Shuzz:
I once built motion detectors using HC-SR04 boards and ATTiny85s.
The idea was to initially measure the distance that the SR04 "sees" and then trigger an alarm once that distance changes.
They were pretty cheap to build and worked reasonably well.
The whole thing easily fit inside 7x7cm boxes with lots of room to spare.
There are several RF transmitters that you can simply hook up to a serial interface on the arduino side of things, so receiving the messages should not be that much of an issue.
ESP8266 would probably work as well, but personally I do not like using WiFi for things like alarm systems.
Shuzz:
I once built motion detectors using HC-SR04 boards and ATTiny85s.
The idea was to initially measure the distance that the SR04 "sees" and then trigger an alarm once that distance changes.
They were pretty cheap to build and worked reasonably well.
The whole thing easily fit inside 7x7cm boxes with lots of room to spare.
There are several RF transmitters that you can simply hook up to a serial interface on the arduino side of things, so receiving the messages should not be that much of an issue.
ESP8266 would probably work as well, but personally I do not like using WiFi for things like alarm systems.
Thanks for your reply, sounds interesting. Also I do agree with you regarding RF vs WiFi for security. Could you give some links to the main parts used?
Also, I think you misunderstood me regarding the WiFi vs. RF thing: RF will have more "security" issues than WiFi, with WiFi being encrypted as a standard.
BUT if your "attackers" or whatever can unplug your WiFi-AP you're boned. With RF based communication, your single point of failure would be the receiver that collects the alarm messages - and you'll probably have that one close to you, right?
Drawback is that you need to take care of encryption yourself, if you think it is necessary. Also, some thought will probably be required for thinking up useable message formats, complete with checksums and so on and so forth.
Just put loads of plant pots, crockery and glassware on shelves everywhere around you and tie everything to everything else with fishing line. And throw a handful of corn flakes on the floor all around you, and switch the lights off. You'll know when someone comes anywhere near!
Seriously though... Is this some sort of game? Or what? It sounds fun.
As mentioned, local RF is more reliable. Xbee or similar, and build a mesh network. That way if anything breaks the signal will just reroute. Ultrasonic should be good enough for what you are doing for proximity sensors.
Also, the beauty of ultrasonic sensors is that it is almost impossible to move them in order to sneak by, because that would likely also change the distance the sensor "sees", thus triggering the alarm.
I am thininking a combinatin of heat sensors, ultrasonic motin sensors, in-floor weight sensing tiles, inplanted RFID chips, video-processors.
you scan the video, note any changes and log them
scan the IR sensors, log them
scan the ultra sonic, log them
scan the floor tiles, log them
scan your implanted RFID chip
overlay all the above on a floor plan with values of closeness to your location as values of 1 to 100
as you move, the sphere of caution would move with you and would stop you from walking into a trap.
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