Make any smart relay no-neutral?. Explanation

Something like this from Chinese sellers:
https://pl.aliexpress.com/item/10050033370875....0.0.24f8452cnVM6zT&mp=1&gatewayAdapt=glo2pol
I bought 2 of them myself and they work great.

Thanks for the link. I did not know that.

@kaczmarj
I’ve bought it before as well, what’s great is you can flash tasmota/esphome since ewelink diy mode works and it’s small enough to fit behind the switch.

Not ideal for 2 way switches unless you already have those extra cables in your existing 2 way wiring though. That’s where this no neutral hack comes in for the tuya module.

Added after 8 [hours] 46 [minutes]:

@spin55
Finally got it installed on my 2 way light switch for the bathroom and it’s working nicely

We already knew it worked.
If it works with one wall switch, it works with two or three.
Enjoy it!!
This:

And this is the same:

@spin55 my wife just called and complained the ac’s 20a switch is not turning on and asked me to check on it.
Oddly enough this happened after i did the modification for the 2 way switches and both (light switch & ac) are on different breakers.
Could this be somehow related? Just asking since it’s gonna be a while till i get back home

I think the same as you, that they are different circuits, but you never know.
There is only one way to clear up doubts: disconnect the assembly and see what happens.

@spin55 looks like it’s not related
Gonna need to call someone to check it since replacing 20a switch doesn’t fix it

By the way i have a 5 Gang switch, could i just use 1 diode and loop from live to other gangs or just use 5 diodes

ferbulous wrote:

By the way i have a 5 Gang switch, could i just use 1 diode and loop from live to other gangs or just use 5 diodes

I don't understand what you want to do. If you do a freehand sketch I could try to give you a coherent answer.

Hello, is there any difference between using a single capacitor? Also, does the capacitance matter? Some have a 0.4 uF and anothers user 2 uF or 4.4 uF.
I have seen some devices that includes only a single capacitor but others come as a built in module incluiding a resistor and a thermistor like this:


Basically, these are two 2.2 uF in parallel connected to the resistors which appear to be in series with each connection.

Hello. If you really want to understand why capacitors are used instead of resistors in alternating current (AC) electric circuits, it's best to familiarize yourself with the basics. This link will help you understand it better than I would if I tried to explain it.

https://www.youtube.com/watch?v=J8lNkVzukSM

Roughly speaking, capacitors are used instead of resistors in AC circuits because they are much more efficient. NTC-type resistors are often used to limit the maximum current peaks that can appear at the time of connection to the network, and the resistors that go in parallel with the capacitors are so that they discharge quickly after disconnection and avoid a shock by touching them. They are protective elements.

The capacitance values ​​of the capacitor/capacitors are related to the current that the circuit has to supply, and the voltage values ​​to the maximum peak voltage value that it has to withstand. Keep in mind that although the effective value of the mains voltage is 230V/50Hz (in my country, for example), the maximum value it will reach will be 230x1'44 (square root of 2) = 325V.

Grettings

Thanks for the reply and the video, it explains very well the reasons of the resistor in parallel.

One could easily just use a capacitor without the resistance in parallel, but it will imply safety risk of discharge. This is what I've seen in cheaper no-neutral smart switches, they just ship a capacitor.

Best regards.

EDIT: I came across to this video for a full no-neutral use with sonoff minr2.
https://www.youtube.com/watch?v=oBR5O391m_c

Hello.

Interesting link, but if you want to put it into practice it is highly recommended that you follow the author's instructions regarding security measures. I am referring to the test with an incandescent lamp connected in series with the circuit to prevent the circuit breaker of the electrical installation from tripping in the event of a short circuit caused by an error in the placement of the components.

The use of the 10 ohm resistor should not be optional because if we take a look at the datasheet of the 1N4007 diode we see that the maximum peak current it can withstand is 30 amps for a maximum of 8.3 milliseconds.



In my humble opinion, resistance should be an obligation, not an option as it seems to be interpreted from the video display.

For a network voltage of 230V/50Hz we know that the maximum value is about 325V and that this maximum occurs in half the duration of a half cycle, which is 10 milliseconds. Therefore, that maximum peak will never last more than 8.3 milliseconds. To calculate the minimum value of resistance, divide the (325-1) = 324V by the 30A that the datasheet says that it is capable of withstanding and we have an approximate theoretical value of 10.8 ohms.

This maximum current spike only occurs when the capacitor is fully discharged. Once it has been uploaded, the datasheet says that the current that the diode can withstand is 1A.

If for any reason the diode were short-circuited, during the negative half cycle of the wave the polarity applied to the electrolytic capacitor would be reversed and it would explode. Therefore, it is very important not to exceed the limits set by the manufacturer.

You have to know that the mains voltage has the form of a sine wave and its value is continuously varying between a maximum value of 325V and a minimum value of -325V. At the moment you plug into the network or the relay is closed, you will not be able to know what instantaneous value the voltage is. In this case, the dangerous moment is the maximum positive value of +325V because it is when the diode conducts and has to withstand a voltage at the ends of 324V (325 of the maximum wave minus 1V that falls on the diode when it conducts). That's why the resistor is put in, to limit the maximum instantaneous current specified in the datasheet. If you don't put resistance, the maximum theoretical value that this current peak could reach would be determined by the value in ohms of the resistance of the copper traces, cables and contacts of the relay, which would be a very low value. Assuming it was 1 ohm, the peak current could reach 324A (325-1/1)(Ohm's Law: V=I*R).

Greetings

I do completely agree.

Looking at the Sonoff zbmini l2, it does not come with a capacitor and it does not induce flickering to the lights, do you know why?

If that Sonoff was designed to be powered with a single phase without neutral, it is assumed that the internal electrical design is different. It probably doesn't blink because internally it's designed not to. It would be interesting to get the electrical schematic and try to analyze it.

If you could fit those external components inside the box it wouldn't make a difference visually. Surely there would be internally, without a doubt, but that is another story.

The assemblies described in the videos are adaptations that are made to adapt a generic device of any brand that needs Phase and Neutral to work, but since only Phase reaches the wall switch, you have to add extra external components to get it to do so .