Rack Mount Home Automation With A RPi

February 6, 2013 by Eric Evenchick 19 Comments

[Patrick] wanted to have centralized sensing and control over various parts of his house. His Raspberry Pi Home Automation System integrates a bunch of functionality in one rack mount package, salvaged from an old network switch.

The automation system is based on a Raspberry Pi running Arch Linux, which talks to an ATmega over SPI. We’ve seen this setup used many times before to add additional ports to the Raspberry Pi, but what makes [Patrick]’s build unique is the amount of control he’s built into the system.

The box controls outdoor lighting at sunset and sunrise, generates wakeup calls, controls IR cameras, and plays sounds based on events. It’s capable of monitoring sump pump water level, the state of a house alarm, and more. A custom REST API is used to interact with the device. This allows for programs on any platform to interface with his home, and acts as an API for his house.

[Patrick] provides a lot of details in his build log, which should be helpful to anyone looking to roll their own home automation system. The source is also provided.

Re:load, An Open Source Dummy Load

February 6, 2013 by Eric Evenchick 14 Comments

When testing power supplies or LEDs, a constant current dummy load is needed. These devices will draw a constant amount of current, regardless of the voltage at the input terminals.

[Nick] was looking for a load to test out a power supply, and found commercial offerings to be too large, too powerful, and most importantly, too expensive. This lead to the design of the Re:load, his open source alternative.

Like other constant current sources, the Re:load uses an opamp to control a pass element. While most constant current loads will just use a transistor, [Nick] opted for a BTS117 smart low side switch IC. This device has a built in current limiter, over-voltage protection, over-temperature protection, and short circuit protection, which makes it much safer. The project write up goes into detail on how the device works.

If you need a constant current load, [Nick] is selling kits on Tindie. All the design files are available on Github so that you can build your own.