Right... What I want to do is a fun project to report back the locations of my two cats within the house. I was first thinking of fitting them with RFID tags and then dotting wireless RFID readers around the house, but those things are so expensive I would only be able to afford a small number.
So.... What else could I use to detect which room the cats are in and which part of the room? The location doesn't need to be precise, as long as it can detect they are in a room or on one side of a room that would do.
How about one of the cheap wireless receiver kits, a microcontroller, and IR LED collar. Send out a command for one of the cats to start blinking a certain pattern, and then you receive the flashes on an array of IR phototransistors in each room. You could set up each phototransistor to see a specific zone. This could be a very lightweight system.
passive RFID wouldn't really work for this method anyway as its range is way too tiny. what about xbee nodes? the newer ones are pretty powerful. If you get 4 nodes you can use 3 at set positions and triangulate the location of the 4th node (i.e. the cat).
You might have to do a little calibration though and create a lookup table, cause you might have some interference with all the walls in the house.
Best bet is if you could get a Zigbee evaluation kit. This system is designed to do just this sort of thing and is able to locate a position based on the signal strength from several different nodes. The hardware to do this is built into the receivers. TI do one that will work with this situation.
Webcams = Complicated and also means lots of wires or PC/Laptops in each room
I am looking for a simple and cheap solution.
I think possibly some kind of IR beacon would do the trick.
If I could make a tiny IR beacon that the cats could wear on their collar that is powered by a button cell and sends an IR burst only every 5-10 seconds to conserve battery life, that mat be a solution.
xbee is really the way to go for this task. the xbee modules are quite small, especially with the chip antenna. its not as expensive as you think, for what they're capable off.
Hmm... you need something small and without a battery source.
you could look into active RFID but the recievers are expensive. The tags are small even though some of them have batteries in them.
you could also look at visions systems. There are some cameras that are stand alone with TTL ouputs. You can adjust the HSL/RGB scales to find the colour you are looking for and then teach the camera to send a high signal when it finds that output. You are looking at >$100 per cam though
The more I think about it the more I think something is going to have to give. I again will bust the Xbee. You can get them quite small and have them running off a small coin sized battery. The adafruit Xbee Breakout board or the Lilypad Xbee should do you wonders in conjunction with a coin cell breakout board or the lilypad power supply.
Switches or buttons will only work if teh cat goes to that specific area and will not be able to differentiate between the two.
I was thinking about maybe a sensor that picks up different wavelengths of light and having different reflective patches on the collars, e.g. One with an IR reflector and one with an UV reflector and then send out a pulse of IR and UV and see what comes back. What do you think? Is that possible?
The same board could also be used to receive transmissions for triangulation and then send data back to a central point. This would be like the XBEE triangulation idea, bit these units are far smaller and consume less power. A tiny button cell powered tag, with a life of several months, could easily be attached to a cats collar.
