Greetings,
I am hoping to use the Particle Photon to switch 4 control signals (24VAC at less than 1 amp each). This 4-relay unit seems ideal, except my guess is that it would not be appropriate for such a low current. Is this true?
Update: After writing this post, I found this relay unit. Oops. Would this be an appropriate solution?
Any input on the simplest solution for this case would be much appreciated!!
Thank you in advance.
@gareth.rose, either will work. The ratings on the relays are maximums not minimums. The big difference between the two boards is that the ControlEverything board is I2C based meaning you can expand beyond the board with their other boards using the I2C bus. They offer a huger variety of sensor and other boards to expand with. You will need to get a power supply (12V typically) to power either boards. 
@peekay123 – Thanks for your note. I heard from an electrical engineer that the ‘flash’ can wear out quickly (10-20 duty cycles) on a relay that is vastly oversized for the signal it is switching (in terms of current capacity). Thoughts?
The ControlEverything board seems to be a good solution… just checking to see if anyone has any comments on alternate / optimal solutions.
I need whatever I pick to be very reliable (order 10,000 duty cycles), as it will be difficult to access for repair / replacement once it is commissioned.
@gareth.rose, neither board is vastly oversized in this case. What is nice for either boards is that they each have a Photon socket so the entire solution is provided. You can look at the specs of the relays provided for the rated life. (BTW, I am an Electrical Engineer) 
I have a lot of the ControlEverything modules and relays and have been very happy with the quality, prices and support. It seems that they release something new about weekly. One thing that I did learn on the relays etc was to buy the Electron version of the boards, the same board will also work with the Photon. They also have a module that will adapt the Particle module to take just an I2C input and use it with raspberry pi and other platforms.
Chuck
Wouldn’t a SSR deal with any potential ‘flash’ issues, if that’s a concern? In the long term, aren’t they supposed to be more reliable as well?
@Moors7, yes SSRs can work though they do have switching issues at low currents. Also, SSRs tend to cost more. The relays on the ControlEverything board have great durability ratings:
Mechanical 5,000,000 operations min. (at 36,000 operations/hr)
Electrical 100,000 operations min. (under rated load, at 1,800 operations/hr)
These exceed the OP's requirements of 10,000 cycles by an order of magnitude.