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Update:- There IS a very minimalist wiring guide in the setup instructions that clearly shows two brown wires going to both the live and the earth terminals. If wired like that, the case of an earthed appliance plugged into the socket would become live at full mains voltage.
Note that while there is a metal mounting plate, it has a painted surface, so it does not make a good connection to the earth/ground tabs at the sides.
This is a smart socket that is sold under different brands. As it's been recalled I thought I'd take a look at it to see if we could work out why.
I didn't test it under heavy load, so I don't know if the recall is purely down to the obvious grounding oddity, wiring diagram error or other aspects too. But the circuitry actually looks well designed, notably the use of a synchronous rectifier, basic filtering and good electrical separation.
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It's a high-tech internet connected smart socket, but not just any old smart socket, but a product recalled smart, socket. I'd like to thank civilized muffin for mentioning this was happening, and i have to say once you see the back of this. I've got deja vu. I think i've looked a very similar socket, maybe an early version of this tcp smart, wi-fi two gang socket white uk high risk of electrical shock.

Tcp we'd like to make customers aware that the above product has a high risk of electrical shock associated to incorrect electrical wiring instructions and design flaws, and this has been put out by companies like wilco's amazon argus and they basically save this pro. If you've purchased this product from us, please stop using it immediately. Unplug all devices and contact tcp. Okay, let's open it up.

I've had we looked inside. I was wanting to see these exciting uh misleading instructions. So it comes with some screws. Pointy screws.

It comes with a leaflet. I shall slide it out, so you can actually see what it looks like and the leaflet basically just tells you how to connect it to the internet. It does not give you any wiring information with it at all, so normally that would be very straightforward. Here's a typical british socket, let's compare so typical british socket, has a live connection, a neutral connection, an earth connection.

The earth connection is bridged from one end to the other and connects both the earth pins and also the outer lugs that go onto the socket. This one has two earth pins. This is why i'm getting slight deja vu and it's got the neutral, pin and the live pin, and it turns out that these two are not connected. Let me just grab a meter and show you that i shall put those screws out the way.

I don't think i need them metal continuity, so normally i'd expect just one earth connection, but uh we've got two here and they're not connected. If i go into this one and i go into this, pin there's continuity to that earth pin, but not to this one and if i go into the one at the other end, it is connection to that pin, but not this one. So the correct way to wire this - and i have to say that if i was given something like this to install - and i saw those two earth terminals, i would check for continuity between them and once i realized there was not continuity. I would bring one of the wires into this one, one of the other earth wires into this.

One then put a link across between them two, so there was continuity through either a radial or a ring. I think the risk here if this is the main fault with it. I think the risk here is that, if you were to say put it in a radial circuit, where there's lots of sockets in a row - and you were to put an earth wire in here and an earth wire in here, it would effectively disconnect the earth to All the other sockets beyond this one, if it was a ring, as we have in the uk where it comes from the the live neutral earth, come from the distribution board. They come round all the sockets go through this one and then return back, and you did the same if you connected one uh earth to here one to here, it would break the the ring at that point which isn't an issue well, it is an issue from An electrical test perspective, but uh the ring is fed from both ends anyway.

However, if you then put another one in another position in the ring, then it would effect leave all the sockets in between with their earth, disconnected as it is. Most people are likely to, as i saw another youtuber installing a similar one to this. They put both the earth wires in here, and what that would mean is that this socket here would not have an earth connection in it. It's odd that the this is this way up, and then that is kind of like that way up right, tell you what let's pop this open and see if there's anything more to see inside, so it's usually one of these little hidden metal frames.

Let's see if we can get this off, oh, i don't like these uh clip-on plastic fronts. The idea is that uh they're very neat, because there are no screw holes. It's worth mentioning that uh those little logs do connect the earth connections do connect to these. So if you put into a metal back box, it would theoretically bridge them together, but it wouldn't be as compliant as it should normally be uh.

Is that a screw down there? That would be so annoying if there was a recess screw or is this just gon na unclip? I think it's gon na unclip. I might be wrong. How is this clipped together because we are going to take it apart? Uh? Let me just shine a light down here. I see what could be.

Is that an led or a rivet? I think it's an led. I tell you what let's try getting this apart then, so i shall use brute force to try. Oh this. This might not be going to go to plan.

This looks as though it's clipped in tightly. I will take a look at the circuitry inside and we'll see if there's anything else that might have caused this recall other than this uh strange wiring arrangement. Oh, this is not designed to come out. Is it this is not designed to come out, i'm just going to pause momentarily while i play about with this and see if i can get it out, the module has been liberated from the metal frame.

It's worth mentioning. I was trying to price out the wrong direction. It's got these little uh ratchety type clips that it pushes and it clicks in and once you've released those it actually just releases everything here. Here's what we've got two very, very tiny relays: they don't bestow a lot of confidence for the current being switched um other things worth mentioning before i go into this in more detail.

Um i got this since it had been recalled. It wasn't being just stopped by the distributor, so i got this from an ebay seller. It made me think that someone could buy one of these and they could effectively um load new firmware into it and then uh then sell on ebay and you might already be getting a compromised device, i'm very cynical about um internet of things stuff. I think most of the older youtubers are in this regard, because i, i always think, there's a bit of a weakness.

These are that's. I wonder if the reason they've left the earth strap off is because it was effectively going to make it harder for it to actually communicate. It was going to screen it, but anyway, here we have it. Let's see we can get this out now.

I think it may be screwed or latched in in some way. So live is going down there, it's being switched in neutral, the neutral is going to the correct terminals. That's reassuring right! Let's see, if i can get this out, is it just being held in by friction? Is there something else here? Let's grab a suitable, screwdriver i'll grab this screwdriver? This appears to be the live connection onto the pcb i'm looking for screws. I am not seeing screws, but then again i have been mistaken the past and have used unreasonable force in circuit boards in the past when in reality they should have come out easily.

Oh, i see a screw. I see a sneaky little screw. Where is a smaller screwdriver? Can i get this one in there? I think i can so that's one screw. Are there any more hidden screws? Yes, there are see.

I was gon na start, ripping apart and using unreasonable four, so i've just spotted an antenna. It's a very, very simple basic antenna how's. This is this better nope nope still not coming out, there's another screw over here somewhere. This is where this is where i'm gon na have to shine some extra light in here.

Oh there, it is it's hiding behind an led, so i shall hike this circuit board out and then we shall explore the circuitry on it here it comes. This is what we want. We want access to its technical innards, it's almost coming out there. It is there.

We go well, that's another! Oh of course it's got a neutral connection on as well. Is this going to unplug or is it soldered? Oh, it's soldered! On okay. Let's take this out scrunchy scrunchy! No, i'm kind of losing patience. Now, i'm not going to use this anyway, just uh, destroy it um howardly, it looks like it's got really good separation.

The transformer does look as though it may be wound with appropriate separation here as well. That's pretty good right. Tell you what i'm going to take. Some pictures of this, so we can get a closer look at it and we can see what it's a other aspects of design are.

One moment please: okay, it has been reverse engineered to a degree, it's quite complex when it gets over to the esp wi-fi bit, but i can summarize what's on the circuit board, so i'm going to zoom down this and we'll take a closer look. The live supply comes on here, and it goes to one contact in each of these relays. It also goes via this 3.3 ohm resistor to a metal oxide barrister and a class-wise suppressor capacitor and then on the other side of the circuit board and i've not flipped. These uh i've not mirrored them.

Another side is a bridge rectifier the bridge right fire converts it from ac to dc. It goes over to these capacitors and inductor here, which are on this side in this area, and we've got a 10 micro, farad, 400 volt capacitor. We've got a 560 micro, henry inductor and then a 15 megafire capacitor. That then goes to the spiritual power supply, which is a fairly classic switchboard power supply complete this little bootstrap capacitor here and uh.

That's all mounted in the back over at this side, so notable things. It's just stereotypical. It's got the current sense. Resistors, it's got a feedback resistor, it's got a bootstrap circuit, so it can actually provide its own power and it's got a snubber network across the primary.

Just to actually remove any sort of sharp switching transients when the little mosfet inside here switches, then it gets quite interesting because it jumps over from the transformer the secondary side. The low voltage side comes over with these two wires here and they go to this area. Here and this chip is a pn806m, it's a synchronous rectifier. What that means is that, instead of having a diode, you have a bit of sensing circuitry in a mosfet and the mosfet when it detects the output from the transformer starting to rise.

It will actually turn on at something low like 40 millivolts or something like that, and it means that there's very little heat dissipated from that. It's just efficient way from converting to ac to dc once it has converted from ac to dc. It's got two smoothing capacitors in parallel. It's got the usb port.

The usb port is set as a standard charging port uh. It has the two middle pins just bridged together. Here, then, the supply goes over to this hidden chip here, which is little 3.3 volt regulator. For the uh esp microcontroller that deals all the wi-fi things worthy of note, this little antenna, just basically a plastic standoff with that coil of wire on top okay, let me just grab the notepad and we'll explore the schematic to a degree.

I say to a degree because i'm not going to go into it in too much detail, because i i'm going to treat certain sections as blocks, because otherwise it would end up a very big schematic. Indeed, so the liver neutral come on and uh the live goes to these relay contacts. It also goes to that 3.3 ohm resistor, the metal oxide resistor for clipping transient voltage, spikes and a little 447 nano farad, x2 suppressed capacitor goes through the bridge rectifier. The dc comes out, goes to the first capacitor 10 microfarad 400 volt through the 560 micro henry inductor and then to the side capacitor, which is oddly higher 50 megford at 400 volts, and that then feeds a pn8370 which is a switchboard power supply chip and i've.

Just abbreviated that just into a box here, the output of that uh drives the primary. Then the secondary at one end is the plus five volt rail. The other end is via the synchronous rectifier down here, which just has three connections and then there's a couple of capacitors in parallel on our side of the usb connector. So that's the 5 volt supply being generated from the mains.

The 5 volt supply is used for the usb port, which just has a two middle pins bridged, which indicates it's just a charging point port. It will depend on the device plugged in what it will draw, but it is perfectly capable of supplying over two amps uh. This is the relay coil for the the first relay coil and that's the second relay coil. They have a snubber diode across them that for the back emf spike you get when the car turns off and the calls are turned on by a mosfet little 7002 mosfet uh, with a 1k resistor and a 10k pull down resistor, so 1k and 10k pull down And they're, driven from the uh esp8285, the five volt supply also goes that little 3.3 volt regulator provides the rail there's the esp a couple of buttons and a few leds as well, and it also drives those relays via the mosfets, and that is fundamentally it so That just asks the question: everything looks okay, but what about this transformer? So what i'm going to do now, i'm going to do so to this transformer and i'm going to bridge the primary side and bridge the secondary side and then we'll do a high voltage test on it.

One moment please: okay, let's do a flash test. So here's a little transformer that's being tested, i've connected the primary side, all together and the sector side all together. So it's going to be an insulation test. I've got it connected up to a unit.

I've set it to burn mode, which means it'll just keep burning. Once it starts arcing it will the trip level uh shouldn't trip, because the trip would normally be in that mode. So it doesn't really matter the voltage i'm going to take it all the way to 4 000 volts. I would expect to fail at 4000 volts, but a flash test.

I'd expect to be okay up to about two or three thousand volts. Let's start the test, so the voltage is currently at 500 volts. 600 volts. 800.

900. It's at 1000 volts no significant leakage. Current one point: five thousand volts one point: six, seven, eight nine two thousand volts go all the way to see if we can get it to arc. It's passed by now, 2.5 3000 volts still doing very well.

I can hear a bit of corona discharge. 3.5. 000. Volts 4.

000 volts. It's just tripped, i think hold on. Let's uh see if we can wind that back up again, so that uh 3000 volts looking at leakage current here in milliamps, it's only about 40 microamps, but that could be ac. Coupling 3.5 2.7.

4. 000. Volts 60 microamp leakage. No, it's just.

I think it's just cutting out because it's uh because it's reached the top of the test. Okay, i shall power that down so that kind of suggests that uh well, i'm just going to put this out the way. One moment please and going a little bit further into the transformer. Let me just focus down on that: uh i've taken the transformer part.

The final winding on the outside is uh two layers of double insulated wire, which is wound, on top of all the other windings and kept well clear, the bottom. So that is, you know, that's an absolute pass that transformer is absolutely fine, so that just leaves the conclusion for this is that the reason for the recall notice is that uh, it's just that earth issue the fact there are two separate earth connections in that yeah, Where is that plate and here's the thing they've probably had to play safe, because if your average diyer has put this socket in themselves, they won't know that you know, i think a seasoned electrician would uh say there were two earth terminals. They might intuitively. Do a check between them uh.

I certainly would myself but do-it-yourselfers, wouldn't necessarily know that or how to make the modification to actually put the link across and actually the two wires terminated or three wires into one side and a link going across. And that means that uh they couldn't be trusted to actually modify this because the instead of recalling the socket they could say, put that link in there for the earth. The other thing, the other type of people that like to have affected by that are the house. Bashers, the people just bang these sockets in not really giving a toss about anything, really they're, just doing it to a price and throwing stuff in so they wouldn't necessarily have the knowledge or the desire to bother testing something like that.

So it's a shame. I was right in thinking: i'd had deja vu, my deja vu was from 2016 when i looked at a similar socket and once again it had the two separate earth terminals. I wonder if it's from the same base manufacturer that's been sent these out other than that um, the relays, don't look mega bad. Where is the circuit board wherever fit up there? Is i'm not sure how much i'd trust them what's actually selling them for um? What's it say on them for a current rating? Does it give much? Oh it says: 16 amps at 277, volts ac.

So that's i mean if they're rated, that that's okay, but i never trust these little relays for switching really heavy loads uh, but the circuitry. Otherwise, just looks all it just looks: fine um. It's got good electrical separation, the circuit board. It's got anti-tracking slots um.

I like the fact they've used the synchronous rectifier. It means that that uh port can probably supply, probably the full 2.4 amps. If desire, but still leave a little bit spare for powering the esp and the relays when they're active um, so it's a shame. It does seem to be just purely down to the fact that, for some strange reason a manufacturer in china has just decided that uh.

Instead of having the link going across they're going to have two separate air terminals, which is strange, not sure why they'd do that, but there we go uh, the tcp recall um, just down to that silly little thing, just those uh unlinked earth timers appears to be The only problem i can find this socket.

12 thoughts on “Safety recall smart socket”
  1. Avataaar/Circle Created with python_avatars Brian Leeper says:

    In the USA, duplex outlets never have more than one ground terminal. I think the reason why is that they don't want the ground to be interrupted if the outlet is removed or damaged. You have to splice all the grounds in the box together with a wire nut, crimp sleeve or a WAGO.

  2. Avataaar/Circle Created with python_avatars Plasmaburndeath says:

    Why so many people want to put a spying device in their walls on their own free will I will never understand. I don't even use the phone versions of these devices, heck just with what Edward Snowden let us know about and that is the tip of the iceberg on all the Metadata gathering "Filter Bubbles" that surround us.

  3. Avataaar/Circle Created with python_avatars FarmerSteve says:

    Two earth terminals is quite common – mostly on double pole switched sockets, but almost always with a very clear obvious commoning bar between the two. Definitely uncomfortable with the size of those relays & even more uncomfortable with it being a "smart" internet connected thing – very much a solution looking for a problem….

  4. Avataaar/Circle Created with python_avatars Peter Kay says:

    Send them all to me, I'll use them. Tha ESP8266 is ripe for flashing to Tasmota or ESPHome. Like you said Clive, if on a ring, both earths to one terminal with a link to the second terminal…

  5. Avataaar/Circle Created with python_avatars g0hjq says:

    I wonder how many people have plugged their wifi router into the socket to save power when they're not using t'internet? All would be fine until they switched it off, then no way to turn it back on again

  6. Avataaar/Circle Created with python_avatars masteryoda394 says:

    The weaknesses with IoT products is that they are dependent on a server and app, which will disappear when the company ceases to exist or decides they don't want to support that product anymore. There is nothing better than directly controlled circuits.

  7. Avataaar/Circle Created with python_avatars Steve Perry says:

    On a normal double 13A socket the earth link is visible, to the screw holes etc. Not being able to see the whole earth link imediatly rings alarm bells !
    The point about no earth link between the two terminals being possibly to avoid blocking the wifi signal is not valid as it would make no difference with the socket fitted to a normal metal pattress box !

  8. Avataaar/Circle Created with python_avatars DC Allan says:

    We do like a good recall product. So many jokes about the missing link. I
    t is odd not to have the earths tied, randonJoe would just wire this the same way as "normal" sockets and have 1 side un-earthed. ⚡⚡We could put it down to Natural Selection.
    Interesting video 2x👍

  9. Avataaar/Circle Created with python_avatars John Reding says:

    Just wondering if you were to connect both "earth" connections would the lug or terminal where the jumper is added be rated for two wires under one lug or screw? I suppose you could tail it out.
    I guess just need to do what you needto do to make it safe.

  10. Avataaar/Circle Created with python_avatars kiefac. says:

    Well, it's got the other problem of being an internet-connected wall socket, but that doesn't appear to be a design flaw in their eyes

  11. Avataaar/Circle Created with python_avatars Civilised Muffin says:

    It's a shame really because it seems in many other ways that it's a good socket (tho I don't like the screwless façade). Especially considering the Rx, Tx and Rst pins are visible on the reverse so this could easily be loaded with a custom firmware from eg ESPHome as I have done with other TCP products in the past.

  12. Avataaar/Circle Created with python_avatars Iain Grant says:

    Could the flaw in the design be the metal was painted? If it wasn’t painted wouldn’t the two grounds conduct? Is the USB ground common to either of those other two grounds though?

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