Sonoff dry contact

In this short tutorial we see how to make a Sonoff dry contact which will be useful for other applications.
What is a dry contact?
It took me a while to figure it out, but it’s a simple switch. In fact, there is no potential difference on the two poles of this contact. The same thing happens on the wire of any light switch in the house or of a lampshade. Whether this is the phase or the neutral, the wire will be “interrupted” by our apparatus (diverter, button, switch).
Typically the sonoff does not have a dry contact as it will have both neutral and phase wires at the input and output. However, it is possible to physically modify it (and quite simply) to make it a drycontact. In short, the result will be that from the input we will have neutral and phase, but they will not communicate with the output, where we will instead have the two cables to “interrupt”.
Many household appliances work with this type of contact, the first of which is the boiler. It can be a normally open (NO - Normally open) or normally closed (NC - Normally closed) contact. In the first case the circuit will be energized only when the two contacts are short-circuited, in the second case when they are disconnected.
Let’s make a Sonoff dry contact
There are many guides on how to make this modification and I leave you this website (Indomus, Vincenzo Caputo, LaMiaCasaElettrica) with very detailed articles.
There are only two steps to do, the first is to disconnect (in my case I cut it cleanly with the dremel) the phase from the output.
The second is to solder (or bridge) the neutral (N) on the contact we have just separated, in this way we will have created a “common” contact.
I recommend checking that there is no potential difference between the two output poles (i.e. 0 volts), or you can use the “buzzer” function on your multimeter to check continuity.
Final considerations
Carrying out this small modification allowed me to learn new knowledge regarding my electrical system and the functioning of the boiler. Furthermore, I was able to connect the heating system to my Home Assistant so that I could control it even when I was away from home.
Sonoff base - amzn.to/47AzC5s
Sonoff R3 - amzn.to/48LaXfu
Sonoff mini - amzn.to/48SW8Yj
Dremel - amzn.to/3vyCYJ8
#sonoff #circuit #drycontact