[impostervt]

I'm interested in making a door movement sensor with a remote alarm to wake me up if my sleepwalking daughter goes roaming.

As a software person who is just getting into electronics (played with a particle photon, just bought the Make: Electronics book & component kit to learn), what are the options when you want to have two pieces of hardware communicate inside a house?

- Bluetooth - limited range?

- Wifi - requires you to join each piece to the network, seems a hassle/expensive for simple electronics.

- Xbee - expensive!

- RF transmitter/receiver - seems cheap, but maybe distance is limited and there may be a lot of noise?

Anything else?

[slig]

Look up the ESP8266. It's a very cheap piece of hardware that you can program using the Arduino IDE. It can connect to your local WiFi easily and send a push notification to your phone.

So you can build something like this using a simple PIR sensor + ESP8266.

[gpribeiro]

Just made an account to say this and you beat me to it.

I built a garage door opening sensor using an ESP8266 (connected to my home wifi) and a magnetic contact switch. I'm also using TelAPI to send me SMS messages every time the garage door is opened.

It is very simple to do, and kind of cheap.

[andrey_utkin]

Could you please share any existing sources (schema, firmware)? Thanks in advance.

[impostervt]

Thanks, sounds similar to the particle photon + pir sensor I used for my version 1. It works, but i'm wondering if the phone part is overkill if I want to make this into a real product. Requires programming, an app on the app store, etc. If i have a second piece of hardware to receive and make noise, maybe that would be easier.

[andrey_utkin]

You didn't mention wires. And I think it's worth considering. Most probably your sensor is going to be connected to power plug (if it goes detached). So why not to situate mini-server (RPi-alike) nearby, with a sensor connected by wire?

[impostervt]

Not sure I follow. The door sensor is going to be hanging on my daughter's door, and the alarm would be in my room, probably 40 ft away.

[andrey_utkin]

Wherever you place the sensor, it most probably needs power supply. Batteries die, so I'd go with plugging into power socket. Since we use a nearby (to daughter's door) power socket, we could insert _right_there_ a mini-PC to control the sensor (because sensor just senses, and you need some "digital brain" to do something with results of sensing). Then mini-PC could notify you in a lot of possible ways.