I tried with a small charger, (16V 1.5A) it was working properly, I was able to pair it with wifi etc. Then I connected it to the Eagwell 12V 30A transformer. Nothing happened, the device did not turn on. Maybe I connected the wrong way the + and - and provided -12V to the Sonoff from the transformer. Would that matter? or the transformer provides a constant 30A current which is way too high for the Sonoff?
The device smells a little bit (typical burned electric smell) but not soo bad. I measured the transformer output and it provides 12V exactly.
Honestly, I have no idea what did I do wrong, the Sonoff is totally bricked cannot turn on anymore, no matter what power supply I use. Any help would be highly appreciated to understand what should I do, not to burn the next Sonoff I am about to order :).
I know it is a very noob question, thank you so much for any explanation to understand the problem.
With the next one, Double check your connections. Measure the voltage out of the psu and note the polarity before you connect it.
Did you connect the Device and then power up the supply? Some cheap power supplies have a transient spike at switch on that could take out the regulator.
Yes, I connected the Sonoff to the transformer first and then plugged in the transformer to the wall.
It does not matter if the PSU (transformer) rated to 30A/360W, until I only have like 100W of LED lights connected the Sonoff, it should be OK with the 10A max, since the load will never be even close to 30A, am I right?
First up, it’s a power supply, not a transformer. A transformer only works with AC. You have a switchmode power supply.
The power supply is rated to supply 30A at 12 V or 360W. The load will take what it needs. If it only needs 1W, that’s all it will consume. You only need to worry if the Voltage of the supply is higher than what the load requires.
I would turn on the power supply, then connect the Sonoff, put a switch in the 12V DC line if you wish. That way you know you won’t get a transient when the supply switches on.
Most likely I “just” connected the wrong way the + and - and provided -12V to the Sonoff which killed it.
@bukurat - Thanks a lot for explaining, confirming what I thought! I am afraid that the switch is not a good solution between the PSU and Sonoff, since e.g. I cannot always turn it off once we have a power outage etc. Any other idea what could avoid this? Like a fuse or something? Also the Sonoff can handle 24V and 10A, so I do not think the 12V PSU spike would be higher than this. Maybe I am wrong.
@namadori - Unfortunately I have multiple zones which I am willing to control separately. That’s why I bought the 4CH Sonoff. So it is not an option to place the Sonoff switch front of the PSU…
The 10A rating on the Sonoff refers to the relay. The relay is rated to switch up to 10A AC but its DC rating is a lot less, probably 2A or so.
When the contacts open an Arc will form across the gap. An AC arc is self quenching whereas a DC arc isn’t. The greater the current the hotter and longer the arc, leading to burnt contacts and in some cases welding the contacts together. If you want to switch a substantial DC current you should think about a special high current DC relay or a power mosfet driven by the Sonoff relay.
Sorry if I wasn’t clear in my advice. The Sonoff 4CH Pro has independent power and switching. You can power it with AC mains and still use it to switch 24V, the relays are only contacts and are not influenced from the power source that makes the sonoff work.
Thanks for the idea! I have no clue why did not I try this, totally makes sense. I connected quickly the device I bricked to AC and it works Now I am sure that unfortunately, I mismatched the + - DC cables, but luckily did not kill the Sonoff only the DC input
This is how I am planning to do the wiring. THANK YOU ALL!!!
Now I am sure that unfortunately, I mismatched the + - DC cables, but luckily did not kill the Sonoff only the DC input 
