IR Sensor network.

I was thinking about making a sensor network. I considered just making every sensor fat with Ethernet. Ethernet modules run around $25 + $0.50 for a MAC address eeprom. That can really add up fast if you have no budget. Then there are ip addresses, configuration code, local interfaces, cables, and power, and wait…a cable, what if I don’t want cables in the way.

XBee’s are about the same cost as the Ethernet modules. Maybe a little more if you’re using prototype boards and need adapter boards. XBee’s might be easier to deal with on dumb sensors without a bunch of interface for configuring network addresses. Not needing buttons and LCDs on your nodes saves a lot of code and cost too.

An IR sensor (38kHz) is around $2.00 and IR LEDs are cheap, perhaps use a preloaded MAC address eeprom to give unique addresses, or just code them in, or a set of jumpers and you’re around $4.00 for address and emitter/receiver. Range isn’t great so maybe a mesh/repeater algorithm needs to be developed on the nodes. You still need power, but this might work well in a computer room to log environmental data.

Seems like this could all be built onto a breakout board like the Evil Mad Science target board: Then maybe some casework, sensors and power for a total in the range of $30 + sensors and labor. Temperature is cheap, maybe $2. Humidity seems to start around $7 and go up. Perhaps a budget figure around $50/node for end units. Double or triple for the controlling node with Ethernet, local interface and maybe some more micro controller speed.

Here’s a starting point, just a TX and RX unit. Not sure if it’d work out, but it’s something to play with later.

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