ESP8266 Community Forum

The board referred to in the original post is pretty decent. It has an nice little onboard 5v power supply and a 3.3v regulator. Power input can be up to 28v with TVS and fuse protection.

It also has an opto isolated input connected to gpio 5, so you can use either the onboard 5v supply to trigger it or an external powered input (higher dc voltage with common ground), very versatile. The input also has an led indicator and TVS protection. When you turn on the opto, it brings gpio 5 low.

The relay is connected to gpio 4 (active high) and also has an led indicator. Rx, Tx and boot (gpio 0 to gnd) holes are broken out also, but you will have to solder in some pins. No other I/O is available from the esp, but one input and relay output, not bad for about 8 bucks on ebay.

Thanks for the feedback Robert.

Obviously things like the Sonoffs are ok for switching low current high voltage mains, but it's a bit more difficult finding something to work at low voltage high current Security/CCTV/Vehicle voltages with tolerant inputs ptotected against emf spikes and other abuse, which are capable of switching lower DC voltages.

It's encouraging to hear that this one seems to have had some thought put into its design.