Overview

Goal is to use a Raspberry Pi to gather sensor readings from a variety of 1-Wire sensors (mainly DS18B20+ assembled inside RJ45 jacks) embedded around the house. Previously I used ControlByWeb devices which support either 4 or 8 sensors per $150-200 control module. This Rpi based approach scales up to a much larger number of sensors with less hardware and a more convenient 1U rackmount package.

Included in this repo:

• Design for 1U rackmount bracket to mount Raspberry Pi, PiWire+ HAT, and four 1-Wire Breakout Boards.
  • These are simple laser cut designs that can be assembled in a single step with wood glue.
  • Any 3mm thick material of the requisite thickness is fine, mine are 0.112-in/3mm masonite "hardboard" ordered from Ponoko US.
  • Sadly the only Ponoko material size that is wide enough is "P3", which is so large that two brackets can be ganged up in a single order
• Notes (below) on configuration for Raspberry Pi

Thermal sensor is a DS18B20 IC inside RJ45 plug (inspired by aaronpk):

Assembled, sensor hub fits in 1U:

Hardware & Assembly

Do be sure to enable the ROM id chip on the breakout board for each port, which helps:

• Ensure each port is wired properly
• Determine which port a sensor is connect to. OWFS enumerates buses in a strange order, but groups devices by bus, so knowing the ROM id on each port chain will facilitate debugging in the future

I used a bulk pack of 3-pin fan extension cables to wire each port back to the PiWire+, though any sort of jumper cable is possible.

Software configuration

The actual code that gathers data from this system this runs in a Docker instance on a different host, connecting to owserver over the network. Configuration on the Pi is minimal.

Configure Raspbian

• Log in via ssh, user is pi and password is raspberry on default Jessie-Lite image
• sudo raspi-config
• Set boot option to expand filesystem at next startup
• Advanced -> I2C = Yes and Yes
• Make i2c device nodes readable by all users

echo << EOF > /etc/udev/rules.d/99-i2c.rules
SUBSYSTEM=="i2c-dev", MODE="0666"
EOF

• Reload udev rules udevadm trigger

Install Packages

• sudo apt-get update
• sudo apt-get install owhttpd owserver ow-shell owfs i2c-tools
• sudo systemctl enable owserver owhttpd
• sudo systemctl start owserver owhttpd

Configure OWFS

• Edit /etc/owfs.conf

# 1-Wire interfaces for PiWire+/AbioWire HAT (http://www.axiris.eu/en/index.php/1-wire/abiowire)
server: i2c = /dev/i2c-1:0
server: i2c = /dev/i2c-1:1
server: i2c = /dev/i2c-1:2

# Allow owserver access from all IP addresses
#server: port = localhost:4304
server: port = 4304

# Allow owhttpd access from all IP addresses
http: port = 2121
http: port = 80

# 2 minute caching timeout for "stable" (e.g. temperature) values
timeout_stable = 120

# Human-readable aliases, per http://owfs.org/index.php?page=aliases
#alias = /etc/owfs-alias.conf # don't bother if aliases will be maintained on client side

• Restart daemons: sudo systemctl restart owserver owhttpd