Time about people getting electric shocks from online modules for home automation control. So i i got a message from a child called michael. Let me just read this message you uh. I got this curtain controller tested.

My bench. Just live a neutral new earth. All worked added to my home automation system test. The functions and check.

There was 240 volts on the various switched live points. So far so good wired onto the curtain motor and turned on he was holding the earth metal housing of the curtain controller and he brushed against antenna and got a significant electric shock off it so he was wondering is this normal because it is ce marked that's that the ce mark means nothing in this stuff. Caveat. Emptor is the best thing you could describe it as so let's explore it and take a look inside.

But i have already checked and true to what was said if i get the meter in here set to continuity and this is where you know i should strip the end of this wire be a lot easier let's just dab between live uh. There's a diode straight off there's a diode between live and uh. The antenna right that's enough that's going to give you a good wallop. So normally with modules like these they are because they've got exposed terminals.

Here you can't just have them mounted to the wall. You have to mount them in enclosure. So normally the antenna would be an enclosure. But normally you'd have a heat shrink sleeping over the end of this quite often with the largest folded double at the end and then the heat shrink over it just to make sure it doesn't pop off.

And that's kind of important because i'm guessing that michael was there in the controller like this pressing the little programming button. Which is needed to actually program. The various modes turns us out this is quite a competent little module it's got loads of inputs right tell you what i shall pop it over so it's got this clip let's zoom down this so you can actually see what is happening so it comes this little clip here that you can either screw directly onto the back of our well screw to the back to the wall. I think a lot of people will do but into an enclosure or it's got this uh daniel mounting facility.

Which is quite useful and then this clips into it the unit itself. I'm i'm looking for my spudger here. I'm not seeing a spider. There's my spudger.

It was hiding in plain view. If we pop it open if we try to pop it open it reveals the circuit board. I'm going to have to undo that now it just pokes through a hole in the case. It reveals their circuit board with the two relays.

A little stack. It's got a little riser board with two modules on it it's got the inductor for i'm guessing the power supply right tell you what i shall take some pictures of this and then we'll explore it one moment. Please and resume. So here is the top of circuit board you've seen already it's got two five volt coil relays.

The incoming supplier has a smoothing capacitor. It's got an inductor and then another capacitor that's uh just filtering before the switch mode. Buck regulator and it's got a fusible resistor this capacitor here is for the 5 volt. Supply.

Other things are visible just a little peeper. That's about it this little stack of socket boards it turns out that this is a 433 megahertz receiver and underneath it is a wi fi receiver quite interesting also interesting i'll show you in a moment. The circuitry associated with that the switch inputs. It's got the facility that you can control it via a clicky remote control or you can control it via your home automation system or phone via wi fi or you can connect a switch.

Which goes between live switch one switch two and then you can just push the buttons for open curtains closed curtains. Or open blinds close blinds to give you an idea of how this controls. The motors. There are two relays that switch live to live one and live two and you wire your motor between neutral and the two outputs if i bring in a doodle of the motor.

There's the open and close inputs and if you energize open via this limit switch. It powers. This winding of that what i'm guessing is a synchronous motor to neutral. But it also powers the other winding via a capacitor that causes a phase shift.

Which causes specific rotations. So open might turn the motor and say that direction until it finally hits that switch when it will stop if you then power close it will power this winding directly and that winding via the capacitor and it will wind in the opposite direction until it hits this limit switch. That's what that aspect of it is very simple and straightforward. It's used for things like raising and loading screen that sitcom server circuit range.

Let's take a look at the back of this circuit board and see what is on it. This is where it gets more interesting the images flipped simply so it tallied up with the other image. So everything's reversed here that's fine it just means that say for instance. This capacitor is here and this inductor is here just means.

It's much easier to trace for a start. They've started by skimping out on the power supply. And they've got a single diode that's not a full bridge rectifier. They've got a single diode charging this capacitor up with the live coming via that fusible resistor so this capacitor here charges to peak mains voltage.

There's an inductor for filtering and then another capacitor which basically charges peak means voltage. And then there's a little switchboard chip which poses this inductor it's a buck regulator. So it's not isolated from the means. This is where the electric shock came from so when this uh powers up this inductor initially the inductor as the magnetic field builds up it creates a bit of resistance to current flow and that is used effectively to charge the capacitor on the low voltage side of 5 volts.

When this turns off the magnetic field collapses. It goes through this freewheel diode and it still pumps capacitor up so it's just efficiently using the build up and collapse. The magnetic field to charge that capacitor and this thing will have a built in voltage reference of 5 volt. It will be dedicated 5 volt chip things associated with this a diode and capacitor probably for its own power supply and a sent resistor.

R3003. Ohms uh and that is it so. Here's the five volt supply with our little goblin capacitor for. Noise.

Reasons and then that goes over to. This which is a 33. Volt. Regulator with another decoupling capacitor for that and uh that generates the 33.

Volts for the circuitry. The 5 volts is used for the two relays. Which are under here these pins. Here are the coils for those relays the stack uh at the top circuit board here is a 433 megahertz receiver.

I can tell that because it's using a generic chip when a search for it is said equivalent to blah blah blah. Which. Means it's a clone. Uh and it's got a crystal of 1352127 megahertz and that equates to a 433 megahertz receiver.

And it has a small chip here which is probably just decoding that information and storing code. I'm guessing because this can be programmed for you press the button various combinations of pulses or hold it for a long press and stuff like that to interference modes. One is to program. The open uh switch and one is to program the closed switch underneath that with its little screening can is the wi fi receiver with an antenna on its circuit board and if you want it i suppose.

If you weren't going to use the 433 megahertz option you could just chop this off. But i mean i'd leave it on because well there's no point doing that you're not going to have this outside enclosure anyway. It's going to be enclosed hopefully. But that wi fi unit.

The only other thing here is this mysterious chip um. It's odd because this chip. The only thing it obviously drives is a little buzzer. It's that buzzer is it uh actually driving it as a coil or is it an active buzzer.

I don't know if i'd be able to power it from my meter. Sometimes uh. If it's really low current it may make it beep. I think that might just be i don't think that is anything fancy not sure i don't know if that's an active one or not that certainly didn't approve anything it could either be a self contained paper or this little chip here may actually be mainly just providing a stream of pulses to buzz that that would be odd.

But certainly the transistors are switching the relays are actually coming from the stack. The riser that goes up to the other uh units. I'm guessing that a lot of this stuff will be done by the circuit board here the wi fi circuit board because it usually contains uh decent microcontroller the esp type maker controllers very strange okay uh moving on each of the relays when the circuit decides to turn on has a transistor and a back emf protection dialed across the coil. The reason for the back emf protection.

Diodes and these things is that when you turn a relay coil on the relay clicks in uh when you turn it back off again with the transistor. The coil de energizes. The magnetic field collapses and because there's no load it can create a high voltage spec. So they put a diode across it for that reason so the transistor switches.

It's got the diode for the back emf spike. It's got a resistor here to limit the current to the base because it's an npm transistor and also a pull down resistor to the negative reel just to actually keep it turned off and that is repeated over here for the other relay uh. The other two bits of circuitry here that are notable are the switch inputs and they're interesting. I have doodled the schematic out for you because they're interesting slightly over the top.

It's kind of like maybe a river over complicated. But here is the switch input keep in mind. This is going directly to live. So the switch inputs for open and close.

If you've connected external switches. Noting. They are at phil means voltage. It goes from live via this diode via this current limiting resistor.

Very high value uh 422k and then there's a little bit of a circuitry here before it hits the base of a transistor. The circuitry is a four point symbol zener kind of not needed because. Ultimately the transistor is going to clamp that down to about 06. Volts because when you drive the base or transistor.

It acts. It looks to all intense properties like a diode so they could just have had this capacitor here and they could have used this resistor up there. But they've used it as a kind of divider. It's all a bit strange maybe.

That's just to discharge that capacitor for uh to provide a decisive switching and input. Which could have been filled in the maker controller but they didn't but that this is what they have uh. But that provides effectively uh dc current into the base of the transistor that turns on the transistor has a resistor here that is tied up to 33. Volts.

So that when the transistor turns on when you push that external button. It pulls this input to the microcontroller low. And that is what uh signals. It and tells you that you've pushed a button is there anything else worthy of note on this.

There is not really anything worthy of. Note. Um crude rectification. Power.

Supply. 5. Volt uh. Section.

33. Volt. Section. Riser to the mega controllers.

This bizarre. Little chip. That must have broken an accountant's heart because it just doesn't seem to be terribly functional. Um.

And then the uh drive for the coils and the button inputs that's it just basically pairs of identical circuitry uh. So the answer here is when you're dealing with stuff like this treat everything is effectively. It means voltage. It should be an enclosure preferably.

A enclosure made of fire resistant plastic just because well you know it's just generic. It's an internet of fire. Yes. That's what it is so much electronic stuff and uh disregard.

These little wires that are dangling out if they've not got a bit of sleeve in the end at the very least put a bit of sticky tape over there. And it's not going to affect its ability to receive signals. But it will affect your ability to avoid getting a shock off the end of the wire. So that is it it's a fairly typical little unit moose go wi fi curtain module it probably works fine accepts input from your standard.

I'd guess 433 megahertz. Remote your wi fi and button inputs. Quite an interesting little device.