Sequent Microsystems’ “Raspberry Pi 8-Relay Card” provides 8x relays and can be stacked to enable 64 relays per Raspberry Pi for home automation applications such as smart sprinklers.
Sequent Microsystems has gone to Kickstarter to launch a “Raspberry Pi 8-Relay Card,” a more-focused version of last fall’s successfully Kickstarted Raspberry Pi Mega-IO Expansion Card. The new version is 40 percent more affordable because it strips out all the general-purpose I/O and focuses only on the relays. Like the Mega-IO, the boards are stackable, so you can stack up to 8x boards for a total of 64 relays per Raspberry Pi.
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Kickstarter prices, which are available through July 2, are $17 (early bird) or $20 apiece for delivery in September. If you pay $22 you get an early July delivery. Volume discounts are available for 2x boards ($35) or 4x boards, which go for $70, or $85 for July delivery.
The Raspberry Pi 8-Relay Card is aimed at home automation tasks that require multiple relays. The company provides a tutorial on using boards to build a smart, web-based sprinkler controller for as little as $3 per zone with “no programming needed.” The device is “smart” in that it can make watering decisions based on weather forecasts.
The problem with 16-relay boards for the Raspberry Pi is that they use up most of the I/O pins, which prohibits you from using the same Raspberry Pi for other home automation tasks, says Sequent. If you need more than 16 relays and there’s no stacking capability, you are faced with the complexity of using multiple SBCs. Assuming you’re setting up a sprinkler system, you could buy a “smart,” web-connected commercial product, but it would cost $10 to $30 per zone, says Sequent.Requirements include a Raspberry Pi 2, 3, or Zero. In the case of the Zero or Zero W, you would need to purchase and solder a 40-pin header. Or you could buy the new Raspberry Pi Zero WH with pre-soldered header. You will also need an 8GB microSD card, a 5V power supply, and 24V transformer. Further information