Hi Sefi Ninio,
There are two ways you can do it, Either change relay to SPDT Relay which is two way relay. this option is not feasible with this pcb. But if you are not using same PCB you can try SPDT relays.

Second option which can work with this setup is ,
Your light switch has two pins, connect them with gpio and 3.3 power .
when switch turn on/off gpio pin input goes high(when on) and low (when off).
You have to write a code to monitor this gpio and if its state changes, you have to toggle the relay state.

This is my idea, I havent tried it yet. and I am newbie too, Please comment.

I hope I am clear enough

Regards,
Abhishek

@HenryWhite why do we need D1 Diode (if i am write) in that circuit? do this circuit will not work without diode?
(sorry dont know much about electronics)

@Yveaux Still no idea about it. Check link if you get something from it. what I know is it can bear up to 10A current and can be controlled using 3v .... my order still in shipping so don't know more then that.

Sorry I didnt get your questions .. do you mean dimensions of 220-3.3v converter. Here they are.
output 2.5W 3.3V/0.8A +-0.2V size: 30x20x18mm

I am not from electronics background so didn't get what holding resistance means?

@GertSanders thanks for this link.
So do you have working prototype? what board are you using? I am in middle of finalising components and trying to finalise design. With little knowledge of electronics my progress is slow.
Also for 220 to 3.3v there is another converter from Olimex https://www.olimex.com/Products/Power/PWR-90-240V-3.3V0.8A/
overall its abit smaller then Hi-Link... Hi-Link abit better because all covered and less dangerous.

Please share if you have any design finalised.

oops..

here is the link

http://www.ebay.com/itm/401045943120

2PCS Mini 3V DC Power Relay Delay SRD-3VDC-SL-C PCB Type General Use

$1.67

Sold out

But 3.3v relay will not match the board. If we use 5.5v relay do we need to add something to circuit?

Nice find GertSanders ... I am planning to use esp8266 which runs on 3.3 volt... best fit ..

If we use this we may have to drop few things from 5.5 board right?
Like no need of 5v - 3.3 converter
change relay to match 3.3v like this http://vod.ebay.com/vod/FetchOrderDetails?qu=1&itemid=401045943120&transid=522355020027&viewpaymentstatus=

Anyexpert around? do we need to remove anythingelse (any capacitor?)

cool .. Any idea how long it last on battery?

Hey Guys,
I am working on ESP8266 as well. But I am newbie to electronic designs. But in my view it should be silmple and we can replace Arduino nano with ESP8266 and remove NRF module.

One diagram and circuit is explained here http://iot-playground.com/blog/2-uncategorised/77-esp8266-internet-controlled-switch-easyiot-cloud-mqtt-api#materials

@csa02221862 you can use this cercuit with SPST buttons. But Switch will notbe connected to mains. It will be conneted to ESP8266 GPIO of (or arduino). And in Sketch (i.e code ) you have to write code based on GPIO when ever it goes 0 to 1 or 1 to 0 Relay state shoud be toggled.

I hope I make sense

@aproxx you did great job here.

I am looking to reduce its size more if possible and wish to use ESP8266. Also looking to add more then one relays to the board. In some rooms there are 3 buttons on one panel. So thinking to use 3 relays. Will it be a good Idea? I think should not matter as long as I have enough GPIO to control relays and Electric wire connectors can bear the load.