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SONOFF. WiFi wall switch. NO NEUTRAL WIRE

Hello from cold Russia.


1)Don't use the grounding wire to connect N pin on your wall switch. If you don't want to win Darwin award. 

Look at the first picture.


2)Use capasitors to connect the switch and the bulb. 

Look at the second picture.


C1 - Capacity. Metal-film capacitor for 400 volts.

It works as a "quenching capacitor" or "resistance". In order for the "part of the current" to remain on the switch and feed it, in the switched on position of the key.

C2 - Capacity. Metal-film capacitor for 400 volts. 

Works as a "bypass" resistor. Serves to ensure that energy-saving gas-discharge or LED lamps do not blink (from the current passing through them supplying the switch) in the off position of the key.

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2 people have this question

Ok, I will do that. I wasn't aware that there are DC and AC capacitors.

Thank you!

Repeat:


This whole scheme using capacitors is not a good or safe idea.  Run a neutral wire and do it right.

Pull a neutral wire and do the job the right way.  I am surprised ITEAD allows this thread to remain in the forum.  This is NOT an approved installation method.

I cannot pull a neutral wire without tearing down the walls in my new house. Maybe in a few years when I will probably renovate, I will do that.

What's so wrong about this way of installing?


1 person likes this

(1.) Series capacitors in AC lines at 100% duty cycle is not something I want stuck in the walls of my home without  them being properly enclosed, selected, and engineered for the purpose.  I have seen too many caps ( of all types) explode and burn over the years.  That is why you will not find this scheme in any manufacturer's documentation.  (2.) You are also forced to size the cap for a fixed load however any darn fool can change a light bulb in the future to a different size and type. (3.) This causes a voltage drop to the load which may or may not present a problem.  Basically this is a "kludge" way to install a WiFi switch which would likely not be approved by any country's electrical code.


One can usually drop a new wire from the attic space inside a wall down to a  light switch box.  I suppose your house may be different.  If it is then personally I would stick with a normal switch.

http://www.vishay.com/docs/28153/anaccaps.pdf


Even with the right kind of caps this scheme still has problems.  I'll repeat my opinion for anyone considering this....Pull a neutral wire and do the job the right way.

To EW. 

In russian language we call it "Capitan - mr. Obvieosely". :) 

That solution is for those who DO NOT have the neutral wire, DO NOT have any chance to drop a new wire in walls(cause walls are concrete in condominiun), and they are going to use GROUNDING wire instead NEUTRAL - that solution in realy dangerous. 


Use only METAL-FILM capacitors. They are reliable. They do not  explode. Place capacitors in special mount-boxes in walls. Use special connetors to make all wiring. (To Marius Herta - pay attention) Remove all that stuff after... If you decided to change the type of bulb. Use you brain and skills.




That's exactly my case, my new house is an apartment  in an apartment building with concrete walls. Pulling a neutral wire is possible but it's very difficult and as I mentioned before it messing with the masonry which is difficult and expensive.


@sshRage what do you mean by "special mount-boxes"?

@sshRage what do you mean by special mount-boxes?

@sshRage what are those "special mount-boxes"?

Well maybe if his walls are concrete they will survive the fire.  Yes folks, use your brains.


I do a bit of radio/tv work and have encountered a lot of failed caps over the years.  Some were pretty spectacular.  I think I will either use a neutral wire or stick with a regular switch when I don't have the proper wiring available.  To each his own.

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Unfortunately, their superior electrical properties and stability come at a price. Film capacitors are bulkier than their electrolytic equivalents, which means that limited SMT (Surface – Mount Technology) packages are available. They can also burst into flames if overloaded, but this characteristic is somewhat common among different capacitor types.

Read more http://www.capacitorguide.com/film-capacitor/


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Concrete walls might be good since they don't  burn easily...

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Characteristics

Film capacitors are widely used because of their superior characteristics. This capacitor type is not polarized, which makes them suitable for AC signal and power use.  Film capacitors can be made with very high precision capacitance values, and they retain that value longer than other capacitor types. This means that the aging process is generally slower than in other capacitor types, such as the electrolytic capacitor. Film capacitors have a long shelf and service life, and are very reliable, with a very low average failure rate. They have low ESR (Equivalent Series Resistance), low self-inductance (ESL), and as a result very low dissipation factors. They can be made to withstand voltages in the kilovolt range and can provide very high surge current pulses. A special class of film capacitors, which is called power film capacitors is available, and this class of film capacitors can withstand reactive power in excess of 200 volt-amperes. These capacitors may have special screw-type terminals which can withstand high currents. Screw-type terminals replace soldered joints because power film capacitors sometimes need to be changed in the field. Unfortunately, their superior electrical properties and stability come at a price. Film capacitors are bulkier than their electrolytic equivalents, which means that limited SMT (Surface – Mount Technology) packages are available. They can also burst into flames if overloaded, but this characteristic is somewhat common among different capacitor types.

Source: Capacitorguide dot com

Hi sshRage,


May I know what will happen if I use the wrong uF?

E.g1 If I put a 4.7uF for a group of 60W LEDs??

E.g2 If I put a 10uF for a 10W LED?


Besides that, I assume this solution can also apply for other smart switch that require Neutral wire right? Example: Z-Wave smart switch??

Hello. 


If you use too small capacity your bulbs will burn less, or will not burn at all.

If you use too large capacity your WiFi switch will turn off in on-position-of-the-key.

In both cases nothing will burn or blow up.

That solution is for any kind of switches.

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