This is just technical information. The end user can just buy a kit, board, or complete relay controller from a hardware vendor.
A relay controller is the means to interface from software to the physcial world. From WRRC's software it sends a command to the controller to turn things on or off. Since this is software, can also take a reading from a sensor then decide if a physical action should be taken. Or we can do time events to turn physical objects on or off.
The idea behind a relay controller is to send a low voltage signal to a controller which then triggers a relay that can switch on or off a high voltage device. Such as a pump, lighting, valve, fans, or whatever else you might be running in your reef setup.
In our 1-Wire world, the WRRC sends a command via the 1 Wire network to a 1 Wire Switch. The 1 Wire Switch is a low voltage device (typically 5 volts) and low current. The only way we can make this operate a real AC device is to use a relay.
The design idea for the WRRC relay controller is to use a Maxim/Dallas 1 Wire Digital Switch. Such as the DS2405?, DS2406?, DS2407? and DS2408. The 1 Wire switch will be on a board in a box with a standard relay socket. The purpose of this is that the user can select a relay based on their needs for the intended load. To address 1 Wire Network protection, a Solid State Relay should be considered.
code to turn our switch is as simple as:
echo "1" /var/1wire/<1-wire switch id>/pio.1
This will turn on our target device's Switch 1 in the case of a multiple channel switch.
The following are some of the 1 Wire Relay Controllers I have found. Most can not handle our loads such as pumps, but from the relay outputs it is very easy to add a higher load carrying relay for our needs.
H. Roelle's Scalable 1 Wire Relay Controller. Complete with a Board Layout
AAGelectronica?'s Multi I/O board. 4 inputs, such as floats or contact switches. 4 outputs to turn on or off relays. Very good circuit protection. Based on a DS2408
Embedded Systems has a complete line of I/O boards. From 1 Channel up to 8. They even offer bare pc boards for 1 Channel Relay operation that is very affordable.
1 Wire Dimming
For controlling the level of lights. Such as moon lights.
A way to protect your 1 Wire network from the High Current and Voltages in the event of a failure.
Regular surge protection
A small inline circuit to help protect against lightning spikes
A very good tutorial on various relays with example circuits