One might think that one of the typical uses for a smart wireless switch (like Sonoff devices) is to be embedded behind a normal wall switch so it becomes a “smart” wall switch. It may seem obvious but it’s not that straight forward. There are several things that get in the middle.
Most (all?) the boards have momentary push buttons while wall switches are (normally) toggle switches
Most of the available boards in the market are SPST, even those with SPDT relays often only provide terminals for COM and NO, not NC. I only have one one-throw switch at home, all the others are one-way-two-throw and are being used as part of a multi-way switch.
First problem can be easily solved in code. Instead of detecting one edge of the button signal (usually the rising edge since most push buttons are configured with pull-ups) you can detect both edges.
November was a busy month and the Sonoff Dual that IteadStudio kindly sent me to review was bored in a box waiting for some free time. But it was just fair that another board that has been waiting in the boards-to-review box for longer had it’s chance to have some fresh air too. So here we have the Itead Studio Sonoff Dual and the Electrodragon ESP Relay Board face to face.