Computing stuff tied to the physical world

Meet the JeeNode "Pulse"

In AVR, Hardware on Mar 30, 2009 at 00:01

Here’s the first prototype of what I plan to install in several places around the house:

Pulse prototype

It looks a lot like the last post because it’s the same setup, with an SHT11 temperature/humidity sensor added on port 2. The current plan is to support the following hookups:

  • Either an ePIR via software serial or a PIR on DIO plus an LDR on AIO.
  • The SHT11 sensor, which requires a dedicated port.
  • Two pins for either 2 contact sensors or more I/O via I2C I/O expanders.
  • Up to ten DS18B20’s via a 1-wire interface.
  • This leaves one spare pin – for a status LED or to monitor the voltage.

Am still looking for alternatives for the SHT11 sensor – it’s more expensive than the rest of the components combined! Maybe I’ll fall back to a 1-wire DS18B20 sensor for just temperature and skip the humidity measurements in some rooms.

The software for the Pulse is mostly a matter of cobbling together existing bits and pieces. But first, the hub needs to be extended to better deal with packets coming from different nodes. Right now, I’m not logging the name and type of the originating node – whoops!

As for constructing actual nodes, I’m exploring some ideas for a daughterboard PCB that snaps onto a JeeNode. It should accommodate a few types of sensors, any of which can be omitted. But the tricky part is not the electrical aspect but the physical one: how is the end result mounted? what type of enclosure should I aim for? what sort of power brick / hookup to use? Lots of loose ends…