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Stackable 8-relay add-on supports up to 64 relays per Raspberry Pi

Jun 4, 2018 — by Eric Brown 7,719 views

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.

Raspberry Pi 8-Relay Card with Raspberry Pi (left) and dual stacked with Pi
(click images to enlarge)

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.

Raspberry Pi 8-Relay Card block diagrams
(click images to enlarge)

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

The Raspberry Pi 8-Relay Card is available through July 2 starting at $17. More information may be found on the Raspberry Pi 8-Relay Card Kickstarter page and the Sequent Microsystems website.

(advertise here)

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7 responses to “Stackable 8-relay add-on supports up to 64 relays per Raspberry Pi”

  1. Cathy Garrett says:

    The relay labels claim they can each switch 10A @ 250VAC. Does this mean I can pass upwards of 80 A @ 250VAC through this board perfectly safely?

  2. grubernd says:

    changing wires on the lower boards is going to be quite cumbersome when you have to disassemble the whole stack..

  3. Norm says:

    @Cathy Garrett

    No, each individual relay will only take up to 10 amps

  4. Cathy Garrett says:

    The question was not relating to individual relays, but to the board as a whole. So, I restate it here. Does this mean I can pass upwards of 80 A @ 250VAC through this board AS A WHOLE perfectly safely?

  5. Cathy Garrett says:

    I guess you’d have to invest in some right-angle mini screwdrivers.

  6. grubernd says:

    well, that’s the mindset of the usual banana politics where the customer has to fix the flaws. i’d prefer the manufacturer invest in a better design. they sure spent more time testing and developing their product than the 5 minutes it took me to see this major usability flaw.

  7. fillfreakin says:

    @grubernd: That’s not really a usability flaw. You’re unlikely to have to remove the wires once set up. Even if you do have to, it’s not terribly hard to un-stack the boards to access the terminal screws. If you are building an application that requires frequent re-arranging of wires, you simply wire everything to a proper terminal strip (which would allow for labeling as well). The idea here is to create something compact. There are lots of other options if you’d rather have everything laid out for easier access.

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