I’m using a 12v relay module from SainSmart ( https://www.sainsmart.com/collections/relays/products/16-channel-12v-relay-module ) with a pin expander MCP23007 and my Particle Photon.
The MCP23007 is powered thanks to the VIN from the Photon.
So you have : RELAY <—> MCP23007 <—> Particle Photon
I have discovered that I don’t need to power my Photon with the USB when the relay is powered by a 12v arrival. And everything is surprisingly working well…
Why ? Is it ok for the Photon on the long term ?
By the way, do you know any other relay module with 16 channels ?