This is a fun little thing. It's uh, I guess children's printer I Don't think it is just children who are buying it, but it's one of our wide range of these available. And it's a thermal printer and it takes a tiny little paper roll and prints whatever you design on the app. So let's tick.

For instance, we'll go for a sticky note and we'll choose a symbol like say, for instance, picking a pork. Then you can add text if you want, then press print and when you're ready, you can choose various options. press print and out comes your printed item via the miracle of Bluetooth and it's not that bad. It produces a fairly good crisp image, albeit that it is pretty little resolution.

Then it's got a little child safe, serrated blade and plastic which is not great if you try and rip off too quickly. It usually shreds of paper, but that space cutter can do I believe there's other things you can do. you can print text and stuff like that, but I really just got it to take to bits. So let's turn it off, open it up, and take it to bits.

It's rechargeable by the way. So let's Zoom down. So you push this button to release this catch and there's a roller inside and the roll of paper that goes in such that as it has driven up, it passes the printhead which is a little ceramic printhead. Well, I'll show you it I'll open it up.

Uh, let me grab a suitable screwdriver for this. Something thin. Just looking for a suitable screwdriver here? There we go. Suitable screwdriver located.

So I'll take these two screws out here and the two screws are located inside down at the base here. and once there's a route, the unit should come apart and we can Marvel at the minimal nature of many of these things. So here is there is a 18650 rated 1 200 milliamp hour. Let's unplug that.

Let's diffuse it. There is a circuit board. There is a ribbon cable going to the print head mechanism. Uh, let's see if we can get the ribbon cable out.

Oh, how does that one come out? All these ribbon cables. they have different mechanisms. This one seems to flip up and it's come out. This is good.

I'll take the circuit board out and we'll take the print mechanism out. Then of course I will take a picture of the circuit board and we can explore what's on it. I Don't think we're going to learn a lot because it's going to be dedicated chips. I Can already see the little Bluetooth antenna next to what I guess is a Bluetooth chip in there.

Another chip here? not sure what that is. anything in the back? No, there's nothing in the back. There's a facility to put other chips in the back. In fact, it's missing quite a lot of components I wonder what other circuitry they can use here? All right, let's get the printer mechanism out.

So it's got two screws holding in to release the print mechanism. Foreign and that is absolutely microscopic. Let's Zoom down this. It has a little step and water with gears going up to the drive here that drives the paper past this ceramic head with all the tiny little heater elements on it that respond very quickly just to actually change the state of the paper.

Because that's how they print in the paper. They basically heat it and where the paper is heated, it goes dark. but that's the nature of thermal paper. It means you don't need a separate sort of ink system.

Another thing that's a rhythm cable here is presumably going up to this little circuit board here, which has a little reflective Optical sensor um, and that is being used to actually detect when the paper is present I Don't know if there's any other switches or anything I don't know if it detects the lid that's been opened in any way I Shall explore that, but in the meantime I shall take a picture of this and then we can take a closer look one moment. please. Reverse engineering is complete. Let's explore and I have to say that reverse engineering this was made quite complex by.

The Fairly Detailed circuit board layout with lots of tracks jumping backs and forwards from the front to back. and usually I go by the uh, the plated through holes to get a reference. but there are tons of plated through holes in this because it connects a ground plane from the front to the back and I had to actually put little index dots to keep track where it was in the circuit. So in the back of the circuit board, it's mostly ground plane, but there is the space for extra Anonymous Circuitry Little Nick Components are identified to these two diodes.

I Reckon it might possibly be step up circuitry. uh for the voltage, but I'm not quite sure because if we look at the other side of the circuit board, it alludes to the circuit board potentially being intended for 7.4 volts even though only uses a single cell. not really sure what the script is there. Let's zoom up in this and take a closer look at the components on board.

So we have the connector for the Lithium cell. We have a button over here. we have the 456 Classic 4056 charge circuit. We've got the USB port and it's worth mentioning that the USB port doesn't just provide data for charging the cell, but it also has data pins going across to the little tiny bluetooth microcontroller.

We've got the ribbon connector for the printhead, which contains a lot of the circuitry. It does a lot of the work. Um, we have a little anti-reverse polarity protection circuit which is nice and we have a very interesting power switch circuitry to make sure that in standby condition, this unit draws virtually no current at all because the processor is completely off in standby. Uh, we have a step on water driver trip a very common one as manufactured by Uh Texas Instruments possible manufacturers.

It's an 88833 and it's a set of dual H-bridge stepper driver and it's got 2.5 ohm Central resistors uh, smooth capacitor or general Reservoir capacitor for stability of the microcontroller and the antenna. There are two LEDs a blue and a red one. The red one is entirely controlled by the charge circuit and the blue one is internally controlled by the Bluetooth chip here. and um, and it's when you plug it into charge, the red LED is the only indication.

It's only going to get syndication from the charge control chip and this remains off during charging. Let's take a look at the schematic which will make more sense of this. I Have to say, the most complex bits to reverse engineer where the power management circuitry and the reverse polarity. So here's the incoming Supply USB Supply comes in.

there is a coupling capacitor I've left most capacitors off the circuit. they're peppered all the way through as they usually are, particularly around the Bluetooth chip and the stepper drivers. various support components for internal and stability of voltage references. So the incoming Supply would go to the charger, but it has to get past this 2301 a P-channel mosfet first and it's a classic arrangement of a gate resistors such that if you apply the reverse polarity to this this, transistor will not turn on and it will protect against reverse polarity damage.

So if the priority is correct, this transistor does turn on. It starts charging the Lithium cell and there's a 1.5 K charge control resistor there, circumventing the large protection slightly. but it's no great deal. There's a 1K resistor and a red LED and that is your entirely your charging status.

After that, the Lithium cell provides power up to here and then this I should write just plus volts. It will vary as the Lithium cell drains down, the voltage will drop, but this seems to have its own internal references. I Don't know how that will affect the print density. It might be blacker when it's air when it's fully charged and at that slate, the higher voltage I Don't know if the Bluetooth processor changes the timing to give a control down DOT density.

However, there is this mosfet and that mosfet there, um is normally held off by 100K resistor. It's a peach and a mosfet to turn it on. There's two things you can do to turn on. You can push the button and when you push the button, that basically turns this whole section of circuitry on and the processor starts booting up.

That's that thing that you can't just go click and expect it to turn on. You're gonna have to click and hold that button until the processor boots up and once it's booted up, it turns this standard Npn transistor on which bypasses the switch and turns on the mosfet. And that means that the process can now keep itself powered. Likewise, when you push the button to turn it off at that point, there is a dual diode package here that is this little Jewel diode package here and when you push the button, it also it keeps it separate from the transistor here via the diode.

but it also lets the Bluetooth chip read the state of that switch. So even when it's just holding the switch on and bypassing it, you can still see the switch being pressed. and that's how you can press and hold, then release. and as soon as you release it, the Bluetooth if you've held it long enough for the Bluetooth to actually time out and detect you want to turn it off, it will then have turned that transistor off and as soon as you let go the button, it just Powers the whole circuitry down.

Very neat. Here's a Bluetooth chip. There is its little 500 ohm, the blue LED that it uses as a status indicator, and there's the USB coming in at the data command. so presumably it can be plugged into USB port.

I've not tested that I should put it back together and plug it into the Chromebook and see if it even recognizes it. Not sure what would happen there. And there's a stepper driver with four control lines from the Bluetooth processor and it's got its 0.50 ohm sent resistors so that no matter how fast what sort of impedance the motor is putting back, it always gets the same constant current. You set the current to the motor with these resistors and then it's data going up to the printhead.

So let's take a look at the printhead. Now, the Bluetooth chip is a GL chip. It's a GL BP or zero s plus five I think it's an S 342-56 C4 a GL Bpos342-564 I Didn't immediately find data on that, but I didn't look too much I Have to say, but it looks like a very standard part used in many products. It's very cable.

I Mean there's little little circuitry around it at all. just some. It's got a crystal, it's got the support components like a smatter of capacitors for internal voltage references and some pool Opera pull down resistors. That is it.

Very it. Very basic. Let's take a look at the print head. This is where I may have to zoom out a little bit so we can fit it all in.

and no, I will not need to zoom out that much to fit it all in. I'll just hold it right there. So here's the ribbon cable and the ribbon cable goes on to a ceramic substrate on a metal sort of pressure and heat sink plate. Um, a lot of the work is done on that ceramic circuit board, but there are also two section Urban cable that just peel off to the side.

One goes to the stepper motor and takes the four connections up to that because it's got two windings and the other goes uh, to a sensor on the front of the printhead. Let me show you that it's it is right there and it's a tiny little infrared emitter under detector and that uses that to indicate to the control system if the paper is in place because it's important not to run these print heads without paper in place. and that is literally on this little ribbon cable. It's sticking out the top here and then you can see the white plastic clip that's just pushed in and clips that in place.

That's so there's no fancy multiple PCB assemblies. Everything is in the ribbon cable and then they're just clipped and clicked into place. Very, very neat. Construction You can actually see the blob this Blobby material here that curves at the end.

That is a trip on board. and we've got the ceramic sucker board here. We've got the blob with all the decoders and the drivers. and then if you see these V shapes, those are just Fanning out connections.

Uh, to the thermal printhead itself, which is just basically a series of tiny little resistors. And uh, that's one of the reasons that there is a coat in front of it for protection, probably against abrasion. It's important to make sure you do put the paper in the right way around with the thermal printer. Don't let it run with the paper the wrong way around because some of them have a coarser back.

the surface should be glossy, and uh, the thermally changeable surfaces. stuff that goes black when you heat it up. That should be that nice smooth surface pressing against that, and it definitely doesn't want to press directly against the roller. So that's why it detects when the paper has run out or been removed or the lid's been opened.

It's interesting to note that ruler here is actually part of the print head and when you close the lid, what actually happens is it clicks in like that and then it's captive. So almost like the the cover of this is well aligned. but it's really just designed to present the roller because ultimately the printer itself wants to take control of that roller and get it into the right position. And when you press the eject button, which is just literally a wedge, uh, all it does is just release it from the spring clips at the side, Let me see if I can show you those those little spring clips there.

But that is it. It's a very minimalist thing, it just it's ridiculous that you know, uh, children's Toy Effect of late or even adults toy, uh, can be made so cheaply when it's basically a full-blown printer. and the fact That uh, the units are used in almost every single point of sale terminal you know, basically cash register and stuff like that means there are millions of these. It's all over the world.

It's just an industry standard thing. There was a paper I used to get. Even if you find you can't get uh, there'll be mini rolls, which is unlikely you should be able to get them off. eBay It's worth mentioning that you can just get a big huge roll of the stuff the same width uh, usually about 58 millimeters I Got a measuring tape here to measure that, but you can just basically pull some off another Rule and you can wind it round, but it has to be in the right direction so that the ruler can pull it up past the printhead with this thermally sensitive side the Crag bit around.

If it doesn't print, then roll it up the other direction. But that is it. The incredibly. It's simple looking, but actually quite complex.

Uh, mini bluetooth printer. It's pretty neat little device. Very clever indeed.