Yep, you can do that, external lights should have the power at the switch not the light like most internal lights depending on where you live.
Sorry to jump on this thread but I have been looking at a few ideas for this. One idea I have been toying with is to use a sonoff pow in the ceiling rose as a sensor that would tell when light is drawing power. Does anyone think that could work?? I have an rf switch for remote control but it gets out of sync when manually switched on and off.
However on further investigation I think I have neutrals at the switch in which case would I be better off with a sonoff t1 with tasmota? I cant find many you tube videos that show the flashing process. One video shows you have to solder (that aint happening) but reading another thread you can flash OTA. Has anyone done this successfully? I would need a 3 gang
Any tips gratefully received
I have just taken delivery of a Sonoff Touch and didn’t realise I had to solder to a pin on a chip to make it work… my soldering is shocking, but I think that is the only way to flash it. OTA is after you have flashed… I think
He’s talking about SonOTA which is a wireless flash from stock.
Are you implying your inept at soldering as all the ‘simple’ and cheap solutions would involve that at some point.
I’m sure a quick search will reveal if the T1 can be flashed with SonOTA.
I have never really tried soldering before. Had a go once and just got the solder glued to the end of the tip 
so gave up.
I managed to flash the sonoff basic without soldering. I thought I might have a go at the soldering required to get that to work at the switch as its only cheap, so if I mess it up i’ve only wasted a couple of quid.
What other way is there to do this? I have a 3 gang switch so definately no room for 3 sonoffs anyway!
The other way I was looking at was sonOTA. I think it can be done but again not sure how easy the process is. Wondered if others had tried it. Most instructions are for the basic and not much else.
Did you manage to solder the pin and successfully flash? Or have you not tried it yet?
I will try this tonight
Not yet as it only arrived the other day, but will see how the above goes 1st! 
Soldering can be a bit of a mare until you get the technique sussed, if you get the circuit board from a broken/unwanted device you can get some practice in before committing to something you want.
You can put the Sonoffs in the ceiling rather than at the switch and then connect the switch wires to the Sonoff GPIO at that end. Probably easiest if you can get to the light fitting from above.
Ok I see what you mean with sonoff basic in the ceiling. Similar to my first thought of using sonoff pow to act as sensor in the circuit. Anyone think that might work? If I can’t nail the soldering that might be my only option.
Good tip re the use of old pcb for practice. Think I will definitely need to try that.
Just one more thought will I have any issues using the sonoff switch in a metal back box? Just wondering if that affects the WiFi signal?
@EGO01 I did exactly that. Connected the sonoff to the fixture so that when the light was on the sonoff would power, connect to the WiFi and then using a binary sensor would confirm the sate in HA. The wall switch was RF. There was of course a bit of a lag in reporting the state as the sonoff needs to connect to the WiFi. Maybe 5 seconds between turning the light and getting the sensor feedback. That was ok
Until I started using motion sensors
It just doesn’t work
So I ended up changing all switches to WiFi, especifically sonoff touch
I flashed 18 switches without any soldering
Needs a bit of dexterity, but sure beats soldering
Ahh so not using the SonOTA version?, which I just tried and the touch doesn’t advertise its wifi at which point I gave up… Soldering tomorrow or a bit of dexterity as you said
sonOta does not work on the latest ewelink software. The only way is hardwired
Thanks for the tips. I think I may take a punt and have a go if there’s no soldering involved.
what a disaster… I tried to solder pin 2 on the sonoff… 90 minutes later, I gave up but have a flashed sonoff touch. Dexterity and took about 10 minutes. I did solder GND on the FTDI for pin 2 which was easy
So I have been trying all morning to flash but no success. The board manager had an update from the last time I flashed my basic. I tried that successfully compiled but it failed to upload due to memory.
Eventually installed the older board manager version and used same settings as last successful attempt (on sonoff basic) but just got stuck uploading.
Any ideas?
these are my settings that worked
Thanks. I eventually got it to work. The main problem turned out to be my laptop - either not enough power or not fast enough. Not sure which, but as a final desperate attempt I thought I would try my desktop computer. Worked brilliantly first time and was so fast.
I am having quite a few issues with the switch today. Loosing access the web management page after a while. I think this is still a memory issue, so I will reflash with some of the features removed to see if that helps.
I am supposed to be saving money with this project but its costing me a fortune in wine!
and this is a problem why?