This video almost didn't happen. You see, this is a Aldi FX hot milk glue gun with a built-in uh lithium cell so you can just basically just turn on and use it. and uh, because it's quite easy to turn on. If you press this button, the back hold it for a few seconds it lights up and starts heating up.

and because of that I thought as a safe precaution I won't put it in my hold Luggage in the plane I should take it on as hand luggage and I went through the X-ray machine and they decided was a gun. um I'm not sure if it's because my appearance cuz I'm like 250 6'4 got a big beard. uh I just maybe that's why they thought I was going to weaponize I'm just this is dribbling goo cuz I've just turned on. that's how fast it heats up.

Let me demonstrate it by dribbling goo. There is a nice little bead of Hot Melt glue. There we go. That's the demonstration complete.

I should just turn this off. but anyway. uh, while they were, uh, seizing this, they also seized this Dremel tool type thing I say Dremel it's a a clones type Dremel thing. um, Fex again from Aldi I don't It's one of these things that they get in from time to time and there were no bits.

no pointy bits, nothing, no grinding wheels I it was just this and I thought that's relatively safe and innocuous. It looks a bit like a ladi's toy and it has exactly the same components. but no, Apparently this was a weapon as well. So uh I did plead my innocence and uh, the called the The lady dealing with me called her Superior who turned up in her power suit and announced no I could brandish the Hot Melt glue gun and threaten people.

So um, they took them. But they did offer me an opportunity to get them back by paying a special service which ended up costing 2020 and the two tools did come back. Um, that include a nice healthy cut for the English government in the form of vat for the value they added to the whole experience. But anyway, anyway, let's get on with the video.

You've seen it operate now, it is rechargeable. It charges a USBC Port um I will open this up and I'm actually just realizing this contains hex screws. so I'm going to pause momentarily while I remove them one moment please. the screws are out.

turns out they're Trck type bits. Let's gently euse this apart I Should have mentioned there's another button here that turns a little LED on the front. It also has a slight time delay. Oh, this is not coming apart the way I expected.

Okay, here is the charging area. Is this going to actually car heart I Think it is. Yes, Oh oh it's an 18650. This is not surprising.

Uh, two little dims have fall out the little light guides for the LEDs Well, that's reassuring. It's an 18650. What's its capacity? 1,500 Milah Power There is scope for boosting up on that the the heater section. We I'll take this apart and explore it.

This is where everything will fall apart, won't it? So um, oh, there's a little switch there on the trigger that's interesting, right? Tell you what. I shall remove the circuit board and take this apart and we can explore the circuitry one moment please. Okay, I have to say that was a longer than average one moment pleas. So one day later because I had to like take a break from this design, then come back to it because it's quite odd.

H I Shall show you the main components here and then the schematic and why it kind of tripped me up. Now things worthy of noting this: It looks as though they've solded the Wirs onto the end of the Lithium cell, but in reality they've tacked on metal strips. I don't know if they've sold I think they have soldered afterwards and they've just used that that as a solderable surface. That's a bit odd.

I tried desoldering the positive from this and it didn't come off and I was too worried about heating it too much. Um, so I just disconnected from the circuit board. Uh, so let's take a look at this socker board. I shall Zoom down in this so you can Marvel at it in great detail.

This side is dedicated to power, so we have the charging circuitry and it's not based on I Thought they might have used uh one of the little Lt7 type chips for charging, but they've used their own dedicated circuitry here for the charging and monitoring of the Uh charge status. There is also a big fat mosfet here. It turns out it's switching quite a lot of current potentially and we at the microcontroller, um, all that's on this side. other than that stuff is uh, just fairly chunky tracks.

Things worthy of note: this 100 ohm resistor had me perplexed. It says 1,000 but that's 100 with a zero decimal multiplier and this 200 Ohm kind of solved that. Um, there is a mosfet for charging and there is a Uh Npn transistor for the controlling the mosfet. Um, It's also worth mentioning that the actual the charger circuit board itself has a04 Ohm resistor on it, a little sort of shun resistor, and then two programming resistors that just basically tell Smart Chargers that they can put Power out to.

this on the other side of the circuit board is Oh, One thing I want to mention about that one, there's two voltage dividers giving an indication of the charge voltage. I'm not sure why I I Guess one's trigger the a the Uh to let the processor know it is charging, but I'm not sure what the other ones for. Um, on the other side, we've got various bits of circuitry including uh, this switch is the LED on this transistor. uh, and these two transistors which I drew a blank on the number NJ 717 that showed up the closest I could get online was an Npn transistor they're not, they're mosfets n kind mosfets.

so NJ 717 not sure And we got a couple of bolor LEDs red and blue and a couple of buttons. And we've got the little switch in here to detect when you actually pull the trigger. that's quite interesting. that does that.

I'm guessing it just uh goes into a sort of standby Cur and then boosts it up when you pull the trigger right. Let's take a look at the schematic. Anything else worth mentioning here? Oh, these, uh. Incidentally, these uh enable things like voltage dividers for monitoring voltage cross the mosfet and also the thermister.

There is a second thermister position here that is populated with the components required and a common enable circuit, but there's no thermister in there. It's also quite an odd value of thermister on the heated head itself, right? Let's go to the schematic and then I'll show you how the uh actual the heater tip is constructed because it's quite interesting. So here's the USB charge socket. It's got the Uh plus and minus, but it's also got those two voltage uh in those pins that enable the smart Chargers to actually put output in the first place.

and there are two 5.1k resistors in those pulled down to the Z volt rail. There's the4 Ohm resistor, which I think is mainly to do with limiting current into the Lithium cell. There's a little shunt resistor here just to keep make sure that when the thing is unplugged, it shuns it down quite quickly. I'm guessing because there are two voltage dividers and I'm guessing that one is for just telling the processor that it's being charged and also maybe to monitor voltage on the charging side which is a bit odd.

Not sure. maybe it detects an over voltage situation and uh, turns off the mosfet I don't really know, then it can't because there 100 oh resistor across that. So when the processor wants to turn on charging, it turns on this little Npn transistor which pulls the Gate of this mosfet down to the Zer volt. Rail and that turns on and current can flow from the charging circuit into the Lithium cell via this shy diode.

There is a 100 ohm bypass resistor. Initially, I was thinking that's odd because it means when the mosfet's turned off. Technically speaking, it could keep charging current into the Lithium cell and could overcharge it. But it turns out there's a 200 ohm resistor here and they form a basic potential divider.

and uh, what that does? It means that if the processor, if the voltage drops so low that the processor is actually shut down completely, it can still bypass that charge circuit. Um, but this will cap the voltage from going too high and it means it can put enough into the Lithium cell that the processor can boot. We also saw that I'm pretty sure on the Guinness Serger circuit. Quite interesting.

Um, and the reason for this transistor down here? controling the mosfet I'm guessing is just because it means that the processor has to do something decisive. it it has to actually turn on, uh, fairly High current input to this transistor I say high current. It's 30k resistor, but it has to uh, actively put out a KNN output High state to actually get that moset to turn on. Let's take a look on.

it's a 1,500 milliamp 18650 cell which is going to have to deliver potentially 10 amps based on my computations. Here's the battery supply Rail and it starts off providing power to the microcontroller via 20 Ohm resistor and a little decoupling capacitor that decoupled Supply is also used for the two clicky push buttons. The clicky push buttons here and they um are basically pulling down Uh 51k resistors 1 each and then that signal then goes to the processor. so it sees the when the button pressed, it sees that input goo.

The little switch down here for the trigger is normally closed when the trigger's relaxed. um, and it's only opens when you pull it if I Remember correctly. Um, but it's bridging to the zero volt Rail and I'm guessing the reason for that is that when the processor is put to sleep, if it turns off its internal pull-ups then that switch by default is pulling to the Zer volt rail. that's a stable input.

Uh, there are the LEDs the two LEDs red and blue chip in each, one common resistor for both. so they're either red or blue and um, they're controlled directly by the microcontroller and I've just shown one LED here just like I showed one button there. Uh, the LED in the front that points where you're working. the white LED has a 100 ohm resistor and a little standard NP resistor and a 10K resistor to that.

Then we get to the heater. The heater I ran out from my bench power supply at 1 volt and it passed 2.5 amps which suggests a resistance of4 ohms. It was just the easy easiest way to measure it. That means at round about 4 volts, it's going to pass 10 amps which is about 40 Watts That's quite high, but it does seem to control it.

It looks like it puls modulates it possibly or just basically Cycles on off to hover at specific temperatures. Um, the battery voltage itself is monitored by a potential divider, but so the potential divider doesn't risk draining the battery when the unit is not in use. There is a moss F effect that switches that on and that's controlled by a common out put that not only turns that mosfet on, but also turns on effectively. The temperature sensors: the NDC thermister at Bridge cuz uh, both the NTC positions have a 10K resistor a little decoupling capacitor across the therm and I actually measured the thermister at 187 degre uh, 187 sorry Kilms at 10 C which is quite odd.

That makes me wonder if it's a 150k. Um NTC Thermister I'm guessing the reason they've used that one if it the for that reason is it's going to mean that at the high temperatures it runs at for melting the Hot Melt glue, it's going to bring it down to a fairly low resistance and it's going to bring it into the sweet spot of the processor. Um, the microcontroller can turn on the mosfet. The mosfet is also monitored by another separately controlled mosfet that can put a potential divider across it and that looks at the voltage drop.

AC cross the Mosat. Technically speaking, you could tell if the heater had gone open circuit by seeing the voltage going up to the or by not seeing the voltage being pulled up to the positive rail when this is off. But I think it's to measure the voltage across the mosfet because you can get something called thermal runaway with mosfets. When a mosfet gets too hot, its resistance goes up and then because its resistance has gone up, it gets hotter and then its resistance goes up higher and then it gets hotter and the resistance gets higher and it goes out of control.

And it can actually cause faor of the mosat by having a potential divider across that 1K and 20K It can look for a voltage rise across that possibly. and uh, then that signals back to the microcontroller that the uh, the mosfet's probably unstable and that it should actually turn off right. Let's take a look at the glue head now cuz it's quite interesting. The heater is this little brown disc Brown disc this little white disc and uh, it's got a brass nozzle section.

The brass nozzle is a a fairly solid section here, then uh, the nozzle coming out, but it's got a tapered section here or a narrower section which the Silicon sleeve is put over and then a spiral spring is put around to grip it on. There is a thermister literally just taped onto the side of the brass Barrel here with a captain tape and then the heater. this little tiny disc that can put theoretically out 40 Watts up which is quite high. This gets put on the end of that and it gets sandwiched against the End by this disc of sort of rubbery, fibrous stuff as best.

probably not. uh, but I think it's fiberglass reinforced um Rubber and it gets pushed against that. uh when you put the cover on, it's got a this end Clips on and it pushes it against it. oh it is.

It's got little uh ribs in there to basically for thermal isolation that does two things. it pushes that against the brass block and it also provides a bit of thermal insulation from the plastic. Um, it's very interesting. Quite an unusual construction and very much dedicated to this specific task.

I Wasn't expecting I Thought it might just use a standard um PTC type self-regulating the. It's odd that it uses the Uh separate thermost and this little heating disc I'm guessing that means that in standby when you're not pulling the trigger, when you turn it on, it will come up to a certain temperature and then it'll cut back. but as soon as it detects you squeezing the trigger, it will just boost the temperature up again up to the higher level. that will help save the battery.

and uh, cooking the glue and uh, other things like that. But there we have it. Um, glad that I got it back from the airport authorities. It was quite interesting take apart, but did take quite some time to uh, reverse engineer because it's actually quite a complex design.

It's very much in the keeping with uh, many of the other Aldian little tools that I reverse engineered. A lot of the circuitry was purely so that when the processor shuts down, it can turn all the auxiliary stuff off and it has a very low standby current. Very interesting. Quite a nice little thing.