I decided to tear down a UL approved “smart switch” and compare it to the Sonoff Basic so I could create a modified Sonoff with all the UL-approvable parts included.
I called my new creation the Zzonoff!
Sonoff Basic: https://www.itead.cc/sonoff-wifi-wireless-switch.html
Or, for not much more and faster shipping: http://amzn.to/2GJnd4b
Capacitive Touch Module: https://www.aliexpress.com/item/10PCS-Blue-HTTM-SCB-2-7V-6V-Capacitive-Touch-Switch-Module-Strong-anti-interference/32837535126.html?spm=a2g0s.9042311.0.0.aLxG0f
Again for faster shipping: http://amzn.to/2E0pdmC
Fuses and Fuse Holders: http://amzn.to/2EECkeB
Electronics Kit: http://amzn.to/2E23JFW
(this isn’t a kit I’ve bought, but looks like it’ll work. Use the 100k resistors and the 104 capacitors)
Some people have brought up concerns about using a Sonoff Basic as a light switch. These have been the basic concerns:
- Not UL listed
- Not fused
- Not grounded
- Mains voltage connecting screws are weak
- Minimal separation between HV and LV components
Since we’re back on the subject of Sonoff’s as light switches I want to address a couple concerns that people have raised.
- These devices are not UL listed: True
- Most importantly, insurance companies use UL listing as a standard. So if a non-UL listed device causes a fire or some other damage or harm, the insurance company could, and probably would, deny your claim.
- UL stands for Underwriters Laboratories. An underwriter is someone who assesses risk for a fee. In other words, there is no way to get UL listed without paying a fee. So not having the UL stamp doesn’t mean the device is going to blow up in your face. It means the manufacturer hasn’t paid UL to test and certify the device. Interestingly, in 2012 UL changed from a Non-Profit organization (after over 100 years) to For-Profit, meaning it is now answering to investors. Investors want to maximize profit, and UL has no competition. Just food for thought.
- The Sonoffs ARE CE certified: True
- CE certification is used in a similar way as the UL, to verify the safety of devices in Europe. One big difference is to get CE certification the manufacturer has to attest to compliance with certain standards. A company could lie about meeting the standards, and some have. But those who do are not in business very long.
- So, ultimately you have to decide for yourself if you feel comfortable with the risk that if a sonoff explodes, your insurance company likely won’t pay for you loses. That would suck.
- Sonoff Relays are “Recognized Components”: True
- There is another mark you might find on a device that should make you feel more confident about using a Sonoff. That is the Recognized Component Mark. It is placed on components which are intended to be part of a UL listed product, but which cannot bear the full UL logo themselves. So if the most vital parts have that symbol, (in this case that’s the relay) then you can feel safer about using that device. And yes. The Sonoff Relay is a Recognized Component.
- The Sonoff is rated for 10 amps: True
- Most circuit breakers powering lights and outlets (in the US at least) will be 15 or 20 amp. So the Sonoff could become the point of failure in the circuit and burn before the breaker is tripped. That’s bad.
- So make sure the load you put on the sonoff is less than 10 amps!
- This is how you calculate the load. W = VxA (P=VxI). So, a 60w bulb at 110v is about 0.5 amp. Connecting (20) 60w light bulbs would really be pushing the limit. Hopefully you’re using LED bulbs. An LED bulb with the same brightness (measured in Lumens) draws only 10 watts. Rounding a little, lets say 0.1 amps. So you could put (100) 60w equivalent LED bulbs on one Sonoff. Maybe I’ll have to test that someday.
- Alternatively you can measure the load on a circuit directly using either a clamp amp meter or your multimeter, if your model supports that function. Direct measurement of current flow requires the circuit to be live, so if you’re going to attempt it make sure you know what you’re doing and follow the directions on you meter exactly.
- The Sonoffs are not fused: True.
- Other UL approved smart switches sold in the US are fused. Fortunately adding a 10 amp fuse is cheap and easy.
- Of all the possible concerns one might have about the Sonoff, this is the one that actually does concern me too. So I’ll be adding fuses to all my Sonoffs from now on.
- They aren’t grounded: True
- Well, they don’t need to be. If you’re using a plastic button, a plastic face plate and a plastic box, there’s nothing that could become a conductor to shock you. If you use a metal box, or faceplate, or button, then you can ground those things.
- This method for protecting people from shock was made in a time when there was the very real possibility that someone could touch a switch and come in contact with a charged metal component. With these Sonoffs, that is just not possible.
- The screws that hold the mains voltage aren’t sufficient: Maybe
- Sonoffs provide 2 means for securing the mains wires. One is the metal screws that hold the bare conductor to the board. These are not as robust as you will find in most standard mains voltage light switches. As an alternative you can solder the wires directly to the board, or solder the wires to the screw clamps.
- Second form of securing the wires are the plastic enclosure ends. These screw down and clamp the insulated portion of the wires in place. The screws are small and it has been pointed out that longer screws would fit and give more strength to the clamp. There is also a third hole on the bottom of the enclosure that could be used to add a 3rd screw.
I decided I wanted to address each of these concerns and create a Sonoff Basic conversion that would match those smart switches that sell for $30.
I called my new creation the Zzonoff! Here’s how I made it:
- I added a 10 amp fuse. You can either use an in-line fuse holder or make your own by soldering wire to both ends of the fuse.
- I soldered the 110v wires to the Sonoff board
- I used a capacitive touch button. This way there are no parts that are at all close to mains voltage that could come in contact with someone touching the switch plate. Ok, honestly I just used that because it’s really cool.
- I couldn’t really separate the 110v parts from the 3v parts. Sorry.
Unfortunately, to use the capacitive touch switch I had to remove the resistor I just added for the Low Pass Filter. I’m hoping the capacitor will still function to collect any stray EMI and prevent ghost switching.
Time will tell.
- The End