An ESP8266 in Every Light Switch and Outlet

[Hristo Borisov] shows us his clever home automation project, a nicely packaged WiFi switchable wall socket. The ESP8266 has continuously proven itself to be a home automation panacea. Since the ESP8266 is practically a given at this point, the bragging rights have switched over to the skill with which the solution is implemented. By that metric, [Hristo]’s solution is pretty dang nice.

esp8266-smart-lightswitchIt’s all based around a simple board. An encapsulated power supply converts the 220V offered by the Bulgarian power authorities into two rails of 3.3V and 5V respectively. The 3.3V is used for an ESP8266 whose primary concern is the control of a triac and an RGB LED. The 5V is optional if the user decides to add a shield that needs it. That’s right, your light switches will now have their own shields that decide the complexity of the device.

The core module seen to the right contains the actual board. All it needs is AC on one side and something to switch or control on the other The enclosure is not shown (only the lid with the shield connectors is seen) but can be printed in a form factor that includes a cord to plug into an outlet, or with a metal flange to attach to an electrical box in the wall. The modules that mate with the core are also nicely packaged in a 3D printed shield. For example, to convert a lamp to wireless control, you use a shield with a power socket on it. To convert a light switch, use the control module that has a box flange and then any number of custom switch and display shields can be hot swapped on it.

It’s all controllable from command line, webpage, and even an iOS app; all of it is available on his GitHub. We’d love to hear your take on safety, modularity, and overall system design. We think [Hristo] has built a better light switch!

84 thoughts on “An ESP8266 in Every Light Switch and Outlet

    1. Most EU countries require a ground fault isolator to be installed. This trips if there is more than a 20mA difference between live and neutral wire. Touching a live wire is harmless now days, you don´t even feel a sting.

      1. Trust me, you feel the sting :-( The GFI (30mA nom.) did not trip, when I was tracking down an intermittent fault in an audio mixer and accidentally touched the mains pins of the transformer. It did not harm me, but it hurt. And I took the glue gun and glued 1/4 of a CD cover in front of the offending terminals.

          1. I don’t think so. I think it was just a high enough contact resistance (dry skin, small contact point) that the current was below 30mA. But the level at which you can feel the electricity is way below 30mA, it is less than 10mA.

        1. although it COULD have been 60vDC inside, it could ALSO be the reason why your suppossed to TEST AT LEAST ONCE A MONTH, or, ya know, when ya plug something in.

          PS by test im talking about the test button, i know the electronics can fail but it wont trip anyway if the button is jammed, which i have seen often, if you cant press test (or reset) then treat it as a normal outlet/circuit

      2. A Residual Current Device is in the EU Regs. Im in the UK, and still, at the moment, the EU. Here we have an RCD and Earth connections but you only really need an RCD, it goes like this:

        All Current flowing out of the live must flow back through the neutral. if it ain’t flowing back through the netutral, it must be faulting to earth through something, i.e. a person

        It knows this via electromagnets connected to switches on both the live and neutral primary connections before the consumer unit, or “breaker box”.

        The RCD can trip to as little as 10mA current imbalance, it takes at least 30mA to stop an average heart.

      3. In a perfect world (Australia), 30ma of current will trip the RCD in 40ms but in the real world, the switches take a little persuasion to operate properly after an extended period of not being used. In my testing, I found several that would take more than 1000ms (the maximum recording time of the test unit I was using) to operate. All following tests of the units came up within spec.

        If you were relying on those particular RCDs to save your life, you would not be disappointed. Brief surprise followed by a very short period of confusion, maybe (ask me how I know) but no time for disappointment before you depart this mortal coil.

        To be fair though, many people rely solely on RCDs to save their life, and most of them survive.

          1. @mcnugget: 20% can be “something”. But do you have so many electrocutions in 120V country? I think in USA are also many outlets without ground connection. Here in Europe we have 230V and GFI and or protective earth connection.

          2. Actually sometimes a harder shock can save you, since your heart stops and you can get cpr’d. If the current flowing through you is not enough to stop your heart, it messes up the pumping , burns and destroys your organs. So lower voltage is actually more dangerous at this level

    2. In the Netherlands ,and also in the rest of Europe IIRC, there is only a earth wire in wet rooms ,like kitchen and so.
      Most of all electrical equipment ,used in doors, are double isolated and don’t have a earth connection int their plug.
      For security there is a 30 mA earth leakage breaker in the main box.
      For wet areas they use a 300 mA or even a 500 mA leakage breaker.

      1. It’s more like 300 mA is acceptable if you have a good link to earth, 30 mA otherwise. And you definitely prefer 30 mA for wet rooms! Remember that this figure basically means how much current can flow through your body before the safety trips; so smaller is safer!

      2. We do have a earth wire in every outlet in Germany. There are only a few without. We still do have earth leakage breakers (30 mA – also in wet rooms). But hey it’s Germany everything is regulated and idiotproof here.

        1. Someone further up said ” Touching a live wire is harmless now days, you don´t even feel a sting.” Is this true for Germany? I know we have a FI-Schalter and such but, is it really that harmless to touch live wires in germany?

          1. The thing is: everyone who survived an electrical shock will report on the Internet that it is harmless, because he survived.
            Everyone who did not survive cant report this on the Internet, because he is dead.

          2. If the house has a working earth leakage breaker you will not feel a thing, or a very small sting, the breaker trips before you have time to react.
            For Sweden the law is 30mA in households, for all rooms, including wet rooms etc.
            For industrial and outdoor installation it’s possible to use higher current levels.
            The ground connection is mandatory in wet rooms if the unit is not double insulated.

            Most people think the ground wire is ment to protect people, and in a way it is, way back in the days.
            A outlet has a fuse of around 10A, depending on country and specifics.
            The fuse has two functions.
            1: To protect the system from overload so the wire,s don´t burn.
            2: To protect people by enclosing the device in a metal case, that connects to ground. If a wire comes loose inside it will touch the metall case and there by trigger the over load, ie the fuse pops.

            Now the #2 there is a bit tricky today. A loose wire touching the metal case does not always trip the fuse, leaving a deadly voltage (current) on the case. Many devices now days have plastic cases, but if they get wet you can still form a conductive path between from inside to outside. And you only need 100mA to kill a person, so the outlet can deliver 100x that current before breaking. And a fuse is Slow! It has to cope with high start currents of motors in all sorts of machines.
            The earth leakage breaker solves this in one go.
            By measuring the difference in current going in and out of the electric box, between live and neutral, it can determine if there is a leak. The ground wire has nothing to do here, it’s left out all together.
            So at any time, if more than 30mA of current goes any other way than via the cable back to the box, it trips.
            By that there is no need for the ground wire, and you get a 100% protection of people.

            There are still accidents, mainly caused by broken leakage breakers, or old units, a leakage breaker should be tested every now and then using the push button on the device. Or by using a testing tool in a power outlet. The test tools simply connects live to earth (not neutral) via a resistor to draw a 30mA current. But as this test cuts power to the whole house, most people skip this. Who wants to wait for the wifi to come back online or the Tivo box to restart..
            Older houses might also be missing the breaker. Your garage or shed might be connected outside the leakage breaker so not to trip the whole house when it rains.

            So before you test with your finger, get a tester from a hardware store, plug in in a socket and push the button. If the breaker trips you have a working system and you should be very safe.

          3. I can’t speak for Germany, but yes, touching a live wire is harmless if you have 30mA ground fault protection. Harmless in that it won’t kill you, maim you, or otherwise wound you for any length of time.
            Does that mean that it doesn’t hurt as hell? I haven’t tried myself, but having heard from friends, you *definitely* feel a sting, and it’s pretty rough. You don’t die, but it’s still painful.

            Adressing a few other comments from other people:
            “In that case, if there is no common ground on the plug, the 30mA breaker is useless as it can’t detect when such current is leaking (how could it detect it if there is no wire to transmit it to the breaker ?).”

            Wrong, it’s still useful. When you touch the live wire you’ll create a path to ground through your body and the RCD will trip. You’re mistaken about how a RCD works (we call it a “differential breaker” in French, which is a bit more telling in my opinion): it measures the difference of currents between live and neutral. It doesn’t use the earth connector at all. The earth connector is only there to ensure that any fault triggers a leak to earth through a path that isn’t dangerous because it doesn’t include your body.

            “This explains why I’ve seen the earth wire to a socket in a bathroom in the Netherlands connected to the water pipe – earth is usually not included in the cables so they just got it from there, right?”

            Not quite. In every modern European household with earth wiring, every exposed metal part of the house will be connected to earth, to guarantee that it can never be live. Imagine a fault in your water heater that connects the copper pipe to live mains — having it connected to earth ensures that it can’t be live.
            So you are technically right: you can “get” earth from the pipe — because it is, by design, connected to earth elsewhere.

            “How can you power this module installed in the place of a light switch?
            In most european countries the switch only breaks the live wire going to the lamp socket.”

            Yes, a very common and annoying problem. Sometimes the neutral wire is still present next to the switch, just not connected, but often it is not. I’ve seen some Chinese devices that claimed to work without a neutral wire, but never got them to actually work. I think the idea was that when the lamp is off, you do have 230V AC between live and the lamp wire — very little if any current, but enough to charge a capacitor and power the electronics from there. The real problem is when the lamp is on – unless you put a power resistor large enough to cause a ~1V voltage drop, you can no longer “steal” power from the live wire.

          4. No it is not harmless to touch live wire in germany. These breakers minimize the possibility to get a shock when an appliance gets broken, like the heaters in the washing machine or anything else. When you disconnect the ground wire on your toaster because it always “flips” the RSD-switch and then use it without that there is a real chance you get a shock with max 30mA through your body. That is not very harmless but you should have a high chance to survive it.

          5. “The thing is: everyone who survived an electrical shock will report on the Internet that it is harmless, because he survived.
            Everyone who did not survive cant report this on the Internet, because he is dead.”

            Likewise, everyone that suffered instant death immediately after pressing the E key on their computer keyboard isn’t around to testify either.

          6. @sven337:
            Powering the module without a return wire is an increasing problem with modern energy saving lamps. The old fashioned light bulb has a very low cold resistance, most TRIAC light dimmers work in the 2 wire configuration in series with the bulb. But compact fluoro or LED bulb can start to flicker instead of being off already with a very small current. The internal cap charges, the PSU starts, the LED/tube flashes with this energy and the cycle repeats.
            I had this one time at an LED lamp with an unconnected return wire: It was connected to the live wire and the return was just capacitively coupled to neighboring return or earth wires. The lamp flashed like a small disco strobe :-)

        2. Similar story here in Australia, it’s illegal to do your own work (even if you do it better than the contractors, on account of you’d rather not have your house burn down) every plug hole has an earth pin, on top of the leakage breaker, most appliances have an earth pin… and from experience… you do get a nice buzz out of touching live… but not half the buzz I got from touching a rail in my solar inverter (why you’d put that right next to the telemetry pins, no idea)

      3. In that case, if there is no common ground on the plug, the 30mA breaker is useless as it can’t detect when such current is leaking (how could it detect it if there is no wire to transmit it to the breaker ?). So if any of your appliance is broken, it can only burn down (30mA is 6.6W, so that’s a lot of power to dissipate at AC voltage), and not leak to the ground. I had so many appliance that broke in the previous year, and I was glad to have the a ground wire on them (the breaker caught them immediately and I was able to track down what appliance caused it in few tries by unplugging them one at a time). Most of the time, one of the wire was “somehow” connected to the metal chassis (I had once a complete cup of not-evacuated dirty water in the dishwasher doing the contact!). Clean the contact, make sure it’s safe, and your appliance is working again for years. If I did not had a ground wire, the electrical component on one side of the connection would have to dissipated 6W and probably burnt. Then the appliance would be dead.
        In all case, it’s not a good idea to let your body do the fuse part of the safety system even if the breaker is a second security here. Because the breaker itself has a lifespan, it can be not functional anymore and you don’t know (yes I know about the “test” button on it, but really, how often do you press it ?).

        1. No ground wire at the receptacle is needed for the GroundFault breaker to detect leakage to ground; since there is no garuntee that it would be the source of ground. For example, your fridge is incorrectly wired and you touch it and the kitchen sink at the same time. GroundFault breakers and receptacles work on sensing the difference in current between the hot wire and the neutral wire. If there is more than 10mA (in Canada) difference then it trips. We do have 30mA rated breakers but those are intended for equipment only.

      4. This explains why I’ve seen the earth wire to a socket in a bathroom in the Netherlands connected to the water pipe – earth is usually not included in the cables so they just got it from there, right?

        In Germany, there are connectors with earth contact on all outlets since at least the 1950s (I know buildings from that time and their original electrical installation) – https://en.wikipedia.org/wiki/Schuko (there is a map showing different connector standards there) ; First these earth pins were just connected to neutral, to trigger the fuse if the metal chassis of a device was connected to phase by internal fault. Later they were connected to actual earth to make RCDs work. AFAIK, If you now expand such an old installation you are required to retrofit the earth wire (=redo most of the whole installation).

      1. +1 “Earth pin” is protective earthing conductor and is bonded to exposed metal appliance cases, pipes, bench tops etc to prevent their potential rising far above the “ground” which you are standing on. This not only prevents you getting a shock in the case a live conductor touches an exposed metal part (or similar fault eg motor insulation breakdown), but should also overload the circuit and trip the breaker/fuse.

        The OTHER type of protection is an Residual Current Device AKA Ground Fault Interrupter. This monitors the current flowing in and out of a circuit and trips if there is an imbalance of more than 30ma/10ma (depends on specification).

        Where I live (New Zealand) ALL sockets are earthed but not all appliances will use it. New wiring installed in the last 10 years should be protected by RCDs, but this is poorly enforced and is often not done on renovations.

      2. No, not just plastic.

        Dunno why I keep posting cause many of my comments get delete by overly sensitive moderators.

        Not just plastic…
        Try 5VA or 94V-0, also double insulated (note the concentric squares symbol on your hair dryer or blender)

        Also, TRIAC switching, unless done at zero-crossing, means very noisy switching and failing conducted emissions. Big LC filter needed at higher currents or inductive loads.

        Also, TRIACs have a Vt parameter most of the time around 1.1V. Compute the power dissipation of controlling a 15 AMP load and you’ll quickly move to a different approach.

        A much better approach is to use a TRIAC and relay in parallel. TRIAC to turn on / off load and relay to conduct. You get no arcing from triad switching and low resistance (little heat) of relay while conducting.

        UL498…

        Have fun.

        1. Zero-volt switching is something triac circuits usually have. It’s a well-known problem.

          As far as dissipation, maybe just use a relay instead? Triacs are more for fast switching, dimmers, disco lights, etc. If something’s only switching once every few hours, a relay is probably better. My remote-controlled sockets have relays, you can tell from the click.

    3. There is ground but only in newer buildings, the old ones (from decades ago) don’t have it. It’s the same with the GFCI. There have been a few lethal cases actually. I think it’s crazy not to add a gfci, it’s just a few bucks but can save you.

  1. Love it, but yes it would need some grounding, am wondering if you have a lot of esp8266 devices on your wifi, plus the normal wifi load (phone’s, tablets, laptops) isn’t a normal accespoint going to get smashed

    and 2.4GHz is already so full. isn’t a radio module on 866 of 443 MHz more stable

  2. Devices that are ment to be plugged in these outlets (lamps) don’t have earth connection at all, so it is not dangerous for that use scenario. However, if outlet leaves possibility to plug fridge, angle grinder or some other device that requires earth connection it’s a bad design. Since outlets are 3D printed I suppose it wouldn’t be a problem to make some kind of notches that will get in the way with earth-enabled plugs while allowing those that has no earth.
    Otherwise, those are pretty nice internet-enabled plugs, I like that AC/DC adapter that makes whole thing very compact.

  3. “Every Light Switch and Outlet”?
    ——-

    So, like 50? With ESP8266?

    Power consumption? Why promoting the wasting of energy (and money)?
    Delay until the light actually turns on after pushing the button?

  4. How can you power this module installed in the place of a light switch?
    In most european countries the switch only breaks the live wire going to the lamp socket.
    So if you switch that off with this module you kill your own power supply. If you switch it on you (the ESP power supply) will be in series with the light bulb which makes most of the light bulbs unusable (I know, i tried)
    Do they have an additional (3 cables total) neutral or protecting earth in their light socket holes?

    1. @pusher The lack of neutral in UK switches is why I’d go with battery power and a TI CC1310. Probably a latching relay rather than a triac too.

      #1 Rule of any home automation system is that my wife has to be able to turn the light on or off with a switch regardless of flat batteries or bugs in my code.

    2. And yet dimmers work.

      Draw the circuit out and include the load and wiring back to the mains panel.

      The light switch doesn’t have to be totally off, it just has to provide a low enough power to the load that it doesn’t operate.

          1. Yes they do draw power.

            Lutron has special pull-out programming tabs for some electronic dimmers for use with CFL or LED bulbs.

            They set the minimum TRIAC on time to be low enough to keep the light off but high enough to keep the dimmer powered on.

  5. Two more problems:
    The used BT136 is rated for only 4A. Where i live, a typical mains outlet delivers 16A. So to avoid burning down the house, a fuse is needed.
    The switching on of the BT136 seems not to happen near voltage zero crossing. At least the utility companies where i live do not like this because of EMI / missing PFC.

    1. 4A at 230V, that’s more then 900Watt, I would say that is more then sufficient for any lightbulb!
      If you are worried about burning down the house, well that can happen at any current.
      But, let’s assume he’s using a component that can handle 16A, well then you let must have a device capable of drawing/handling 230×16=3680W NOW that would be a possible fire hazard! The device by itself, the wiring in the house, etc. And then we haven’t spoken about contact resistance in the power outlet pins, these could/would be very hot, melt the plastic of the 3D printed case eventually leading to all sorts of problems. 16A is a lot for a simple power outlet!
      So in short, when used for connecting simple lightbulbs or devices… I think he’s safe on the BT136 regarding it’s current capabilities.

      1. From memory, all devices connected to mains must be able to handle the current rating of the main breaker for that circuit. In Australia this is 10A for light circuits and 16A for power outlet circuits (usually – some outlets can be higher). If your device is intended for connection to a light circuit, it must be capable of handling 10A, so 4A will not cut it. This remains true even if you expect to use less – and for LED bulbs, perhaps a lot less.

        1. You can use the 4A TRIAC, but you need an extra fuse (5*20mm part is sufficient). This is mostly to protect the TRIAC from a failed bulb. Otherwise the TRIAC would act as a fuse, which is normally not desirable.

      2. Ehm, you must count with everyday use. Leave device like this with someone who does not care and your house is on fire. People still trying to put AC air heater on 25meter (>80ft.) power strip and wondering why they catch a fire. So that is why good electrician must be smarter and anytime trying to fight against risks of using electricity.

    2. A fuse is *required* for safety. The idea is to make sure than none of the components and wiring has to handle more than their rated current in case of a *fault*. It doesn’t matter how much nominal current is.

      Not sure about flammability rating for printed plastic. :P

  6. The AC wiring is just too close to the digita part of the circuit, this could lead to arcs that could potentially destroy the device in case of power spikes.

    The AC part of the circuit probably does not meet certification requirements for applications that have AC outlets exposed, for example it does not have a fuse rated at the max current that can be handled.

  7. I swore when I saw this.
    I’ve had a ton of time sitting on my butt lately, thinking about how to do something (instead of being able to do something).
    I decided it was time to improve the humble light switch with a simple wifi connection (especially of 802.11s actually has any acceptance). The ESP8266 modules have become insanely inexpensive.

    The tripping point I’ve had is how to present some of the basic “smarts” behind the switch plate to the user. In essence, when a “non-connected user” (person in the house, but not on the network/not trusted with the access) wants to turn on the light, they need to be able to turn on the light. If they want to dim the light, they should be able to dim the light. Nine times out of ten, the local, manual user should be able to override the remote user.

    I got stuck on this. The whole light switch should be cheaper than the nice light switch at the hardware store down the street (~$50-~$70). I think it could be done much cheaper than that. The goal being to get one of these in each room, along with a temperature sensor, maybe a motion sensor or light sensor.

    How do you keep it inexpensive, but allow a user to walk in and see the status of the switch? Ideally, they should be able to look at the switch and see that it is off versus on (up versus down position). Servo mounted switch? Powered linear slide? Not cheap.
    The switch itself should consume a very small amount of power. As an ecology, smart equipped plugs could ultimately reduce power consumption, even as they sip small amounts of power through the day. All of the parasitic power losses due to chargers and standby systems could be solved by a smart home grid, a sensor at every power dispenser. Want to watch TV, pull out your phone and power up those outlets involved. I shudder to think how much parasitic power is involved right there. But there is no way that one of my house denizens is going to flip the switch every time she wants to watch TV. But she will pick up the remote, or even her cellphone (frequently she turns on the TV and pulls out her cellphone anyway….)

    I love this project. Keep pushing at it. Small, incremental changes are going to make it awesome.

    1. I have been looking for 3 position latching rocker switches for exactly this reason.

      Position 1 – on, manual override.
      Position 2 – retain the setting from which you entered position 2, allow remote control.
      Position 3, off, manual override.

      So far, I have been unable to find anything that matches the above requirements.

      To explain “position 2” a little better:

      Position 1 and 3 provide explicit on and off capabilities, which addresses Rule 1 of home automation mentioned above (the wife must always be able to turn the light on or off). These could potentially be hard wired to mains, entirely bypassing the automation (and any failures thereof).

      Position 2 is used to allow remote operation. The RF and microcontroller is powered up. If the switch was previously in Position 1 (i.e. on), the output should remain on. If the switch was previously in Position 3 (off), the output should remain off.

  8. Applications notes of AC-DC converter modules almost always demand a fuse and a varistor, often also mains filters. And using a triac without a fast acting fuse means asking for trouble.

    No one stops you from plugging a 3000W heater into that socket. Good luck with the 2*0.75mm mains wire.
    Hopefully the triac will protect the wire by blowing up without starting a fire.

    Don’t try this at home, kids.

    1. And in Mexico too. I saw them run a red wire and a green wire to the socket, then they wired the green to the ground AND neutral socket pins. He told me all those black wires were a waste of money!

      I believe this is TN-C earthing

  9. Yeah but in most countries the light switches do not have neutral or earth connections just a single phase broken in two pieces (hence the two cables) joined by the switch. The “real” neutral is at one end of the light bulb.

  10. There seem to be more and more projects of this type in the literature, and I thought it might
    be time to temper the well-intentioned enthusiasm with some real-world practicality, and legality.
    First, a fact or two (please be advised that I have no knowledge of regulations outside of the USA).
    Most jurisdictions in the USA will issue you a ‘Right to Kill Yourself’ electrical permit, also known as a “Homeowner’s Electrical Permit”. An example of such a permit, taken directly
    from the internet, is shown at the end.
    Notice the particularly pesky phrase which somehow seems to worm its way into all documents of this type: “…the work must meet…the National Electric Code…”.
    Now, the NEC boys and girls, being absolutely humorless, insist that work conforming to the
    NEC’s rules and regulations extend to all wire and devices employed.
    Did you find the ‘gotcha’?–all DEVICES must conform to the NEC’s high standards, which means UL approval. The NEC doesn’t care whether the DEVICE you employ is a light switch, a toaster, or a 25 KW emergency power generator; they’re ALL ‘devices’.
    Two last items of which you should be aware–(a) Any time you bring any electrical ‘device’ into your house and plug it in, you are considered to be under the contractual influence of the Homeowner’s Electrical Permit; (b) The second item involves a much more chilling consequence; if your insurance carrier can trace a fire in your house to a non-UL-listed device, they will not honor any claim for damages.

    HOMEOWNER’S ELECTRICAL PERMIT (USA, typical)

    “…I also understand that the work must meet the Building Code and the National Electrical Code and I am required to obtain the inspection(s) from to ensure the above requirements have been met. This includes a final inspection.
    If I am found to have falsified this application in any way, I will face legal action including a fine and/or imprisonment.”

  11. Can we also use this one as an example of naive and hopeful ignorance? You want to hope that their insurer or whatever passes for a national electrical regulatory agency in their country never sees this.

    UL exists for a reason, and this is so very far from UL compliance (isolation, creepage/clearance, flammability… everything) that it’s frankly terrifying.

    I’m all for DIYing things but you need to know what you’re doing. The downside to this whole “maker” craze is that people make seriously dangerous stuff with no clue as to why it’s dangerous, and it’s not just the builder who is at risk from it all.

    1. I agree but the problem runs deeper:
      Don’t build yourself a smart phone if you can’t ensure its safety and that it doesn’t start burning.
      Don’t build a car if you can’t build reliable electronics
      Don’t build a car if you can’t guarantee environmental standards
      Don’t build a wireless module if you can’t ensure FCC compliance (The one from China with kilometers of range is just fine. It even has the FCC stamp).
      Don’t build an iphone charger if you can’t do it according to safety standards.

      Oh and don’t build your own smart plug. But you can buy and use anything from China. That’s alright. No questions asked. Just don’t look inside.

  12. I have looked for an esp8266 based module that is UL listed, and I don’t think they exist. If you put this in your wall and your house burns down for ANY reason (not related to your project), your insurance company will probably not pay, because you have a non UL listed device. Be smart … Is it worth several hundred thousand dollars?

    1. In the US, maybe you’re right, although I suspect you haven’t double checked that it’s true even there.
      Outside of the US, things are different. Insurers in France would not refuse claims because of that — it’s not in the contract or in law that they can. I believe it will be the same elsewhere in Europe.

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