So basically, it’s a 8-channel I2C GPIO expander, with 4 of the ports connected to relays, and 4 of them broken out for general usage. Costs 34.95, also bought a power supply for 8$, with shipping and insurance of 10.25 and 1.64, the total came out to be 54.84. The board shown on the website is Rev B., while I got a Rev C. board. Main changes seem to be some shrinking of the board around the relay outputs.
The board came nicely packed, and includes a Photon with it. Also a really nice looking ~6ft long usb cable. Simple to unwrap, plugin the Photon, connect the power supply to the board, and claim the photon. Just to try it out, I used the provided library on the Web IDE (NCD4 Relay), and was easily able to switch the relays on and off, and view the status of the GPIO. It doesn’t seem like it’s possible to switch the extra pins from Inputs to Outputs using the NCD4Relay lib, but using the 8Relay lib, then you can, and I was easily able to switch the extra pins on and off using that one.
The board itself seems well designed and manufactured. The header for the Photon uses the Swiss style (round) female header, which is nice. In addition, there is an extra row of pins on either side of the Photon for implementing a shield on top if you wanted. There are three jumpers (included) for switching the address of the GPIO expander chip, if necessary. Some minor nitpicky things about the board:
- The text for the extra GPIO screw terminals is basically covered up by the screw terminals, which makes it somewhat inconvenient to figure out which is which, especially because there are only two grounds for the four pins (at positions 2 and 5 out of 6)
- The expander chip that’s used has the capability to provide an interrupt to the MCU, but it’s not connected. I realize that they don’t want to take up more pins on the Photon then necessary, but a solder jumper pad would be nice to have if I did want to take advantage of the interrupt.
- The text under the relay LEDs is super small, esp. considering that there is a fair bit of room there to print bigger text.
Other than those things though, I really like this board! Considering that it includes a Photon, you’re basically getting a 4-relay board, and 4 extra GPIOs for only 15$. I’d quite recommend it. Here are some pictures of the board