*WARNING* SONOFF MINI DANGER !

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M*I*B
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*WARNING* SONOFF MINI DANGER !

#1 Post by M*I*B » 01 Nov 2019, 15:36

... the past few days I have built a court and garden lighting for a friend. There were also a total of 5 SONOFF MINI used.

I preferred the SONOFF to the SHELLY due to the outgoing antenna and the already for WLAN considerable distances. For many lamps, the SONOFF is housed in the lamp housing, with the antenna projecting upwards into the plastic lampshade and thus not being shielded from the stainless steel housing.

When mounting a SONOFF, it happened then that I had damaged the insulation of the antenna (the edges are very sharp inside) and this damaged area came into contact with the grounded housing ....

* BUMM *

After examining the now-dead SONOFF, I found that the developers somehow have one on the waffle (germany topic for an Idiot)!
How can one only come up with the idea, to place the connection for "phase" (over the bridge rectifier) ​​on the internal equipment mass and to attach the "neutral" via condenser (not potential-free RC power supply)?
Had it been done the other way round, nothing would have happened, except maybe a burning of the protective resistor due to overload ...


So here's a haunting warning:
The lead-out antenna is directly at the potential of the connection "L in", ie directly to "phase" !!!!
Also the connection "S1" is also on internal ground and on "phase" potential


If I have the next week some time, I'll see if the circuit can be rebuilt without much stress, so that the internal mass is at "neutral" potential ...
DLzG
Micha

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M*I*B
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Re: *WARNING* SONOFF MINI DANGER !

#2 Post by M*I*B » 01 Nov 2019, 16:06

... sorry, I'm partly wrong ...

The bridge rectifier is connected directly to L and P via a series resistor with 39R and directly fires a 3μ3 / 400 electrolytic capacitor. From there it goes via a throttle on a 6μ8 / 400 and from there to the actual switching power supply.

In this way, it really does not matter at what potential the antenna or the internal ground lies; which is practically every second half wave at "P"

So you should make sure when using the MINI's that the antenna is not touchable!

The CE mark on the case is therefore definitely a fake
DLzG
Micha

kimot
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Re: *WARNING* SONOFF MINI DANGER !

#3 Post by kimot » 15 Nov 2019, 21:17

Yes, it is good to know.
But with this type of powering (without transformer ) is widely known not parts of circuit is touchable...

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