Having already explored the mechanical aspect of the FedEx Fortivo angle grinder from Aldi in the UK that probably sold in other countries as well under different brands I Thought it would be good to explore the circuit board that actually controls emotion that because it seems to have the battery monitoring, it has the ability to shut the power off to the tool if the battery is getting low. Now it's worth mentioning: the battery has five terminal positions here marked B1 plus B2 minus B1 minus B1 plus should say and B2 Plus And then in the middle, it's got two stack terminals marked ID and T for temperature presumably and a little battery level indicator. So internally, this is effectively two 20 volt batteries or 18 volts most other power tool companies would call them that can either be connected, presumably in parallel for the 24 20 volt tools or in this case series for the 40 volt tools. I'm going to put this down on the ground because these are the interesting bits you want to take a look at.

So the battery contact block that sits in the tool has the circuit board in the back of it sitting on roughly like that. very hard to remove. The terminals are held in, they're slotted in like this and then a little dovetail strip is pushed in like that that locks them in position and presumably then because you can't really pre-solder this and then slide it in. This must have then been put in and pushed down those Terminals and then soldered and the anchor screw put in there for the robustness of the connection.

The mounting uh very hard to get out because I was hoping to just slide it out but there's little uh tangs in the side that go into indents and circuit board that stopped it coming out. very annoying. Other things that were in the tool was a changeover switch there's a reason for that, although the wires are all the same size, one of them's not really taking much current because it is just an indication War but the other ones are taking the full current of the tool but not controlling it completely and this is a very loud clicky switch which Uh is rated 25 amps, 84 volts. It's quite stiff for a micro switch.

There was also a common mood style suppression inductor or choke whatever you want to call it inside right? Let's take a look at the circuit board. I Have a picture I've taken of the socket board. Here is the back of it for a start. the circuit board is going to look messy because it had a conformal coating on it that was extremely hard to remove.

Very messy on the other side. Overall, the sort of important circuitry here to give it well outdoor to resilience, but that made extremely hard reverse engineer because it was this gooey sticky silicone but with a plasticy layer on top of it. Very strange, very hard to remove. Now things are worthy of no, they have just connected to the batteries directly in series here and they're only using one of the two middle connections.

they're using the one marked NDC But I think there's more to it than just the NTC temperature sensing I think this is basically the batteries I am okay pin and it can either tell the tool yes, you can run or it can say batteries low or overheating. No, you can't run. Um, it's strange that the markings are different on the battery, but it doesn't really matter. it's just the basically these ones round back to front I think another one on the battery itself, but it doesn't really matter.

Uh, things are already wrote in the back. these odd tapereds are solder joints. I Guess are they just for spreading current? It's quite strange. um, but not much in the way of the control circuitry.

just really. uh. tracks. just mainly big chunky reinforcement of tracks on the other side.

Okay, let's take a look at the other side. The circuit board is upside down, but that's just the way I Reverse engineered it. Things worth of note here is the mosfet standing up here. It is a K-i-a hold on I'm gonna have to read this with a magnifying glass Kia 2906a and that's a third.

about 120 volts I think but a fairly High current mounted very close, but literally mounted hard onto the circuit board with the leads physically cropped right up to the base, the end itself and we've got the motor load which is a go. It's got a shortcut across it for the back EMF suppression and also a capacitor across it for filtering both. These are to protect the Uh, the transistor from damage when the motor is turned off, sweeping stuff off yours covered in little bits of this horrible conformal coating that was over it. Very annoying.

Uh. Two wires going up to the motor, three wires going out to the switch One the common of the switch switches to the yellow wire. When you basically pull the trigger when you turn it on and that activates the circuitry. it tells the processor This Little Light pin processor here that it's been powered up and the process will then use positive modulation to ramp it up.

It doesn't doesn't just slam it on. Although this, uh, the switch is actually enabling power to the motor, the bulk of the work is actually in. The initial current is going through the mosfet because the mosfet doesn't turn on initially, but it ramps the speed up to give it a soft start. Uh, when you let go of the switch, it does something interesting.

It does kill the power to that circuitry, but it also sends a signal via this wire over to the processor to tell it that uh, it has a been turned off so even if there's a residual charge in the capacitor here, it will uh still node, it has to do a reset if the trigger gets pulled. Again, quite odd. Anything else worth mentioning? Yes, this is a standard transistor being used as a first stage voltage regulator. This is a standard 7805.

I'll show you them the schematic. There are quite a lot of transistors. again. I'll show them the schematic.

it's probably the best thing and a programming Port Over here. Okay, let's go straight to the schematic actually the schematics since there are three of them because it is quite complicated. let's get in just a little bit closer. Focus down onto there.

So here are the two batteries wired in the series: Excuse any huskiness in the voice: I Have a bug I'm under the moon. That's fine. There's another connection coming off the battery and it's the NTC which is that enabling thing. There's a switch that switches between the off signal to the processor, the on signaled processor, but in the on position it also Powers the motor circuit which is then enabled by the mosfet which is also controlled from the processor, but it also provides power via this diode to this capacitor and to this circuitry here, which has a couple of resistors to help remove some of the dissipation because it is 40 volts, but it's got a discrete transistor.

NP Engines that start with a Zener diode on its base and a current feed over to to act as a basic voltage regulator and let's just correct this drawing. right now. let's get rid of that and actually put it down to the right. but that would be much better wouldn't it? How unprofessional? Hold on? Where's my We? uh, where's my Wii Error Eraser Here it is.

Tip X Error Eraser The the error has been erased. Good enough, so that provides a base voltage of 12 volts and that is used mainly for driving the mosfet because the higher the gate voltage, the most fat, you can turn them on quite hard. Yeah, it means you can use a more rugged mosfet because the logic level ones, the ones that operate super low voltage just tend to maybe not have such a low on state resistant or tend to be aimed at sort of lower power tasks. But after that, the 12 volt we've got the 12 volt Supply and that also takes a lot of strain off.

The seven, eight or five regulator produces a 5 volt supply for the microcontroller and the 7805 typically has a voltage rating up to about 35 volts I think which means that the 40 volts would have been well exceeding that. So by using a standard transistor, roughly regulating down to 12 volts and then to some the 5 volts spreads of dissipation, as do these resistors. Here, they're all taking a bit of a share of that. Okay, so what have we got? We got the two signals going out to the processor, off and on and we've also got? the mosfet feedback and the NTC thermistor signal.

So here's the most effect: Gate Control and more Tip: X too Because just before making this video I thought I'll just write in the numbers of the transistors. I Mix those two up. Oh bollocks, not to worry. So there's the 40 volts.

There's the motor. There's the mosfet. It's interesting how it's being driven. The microcontroller switches this transistor on when it wants to actually power the mosfet.

Now, normally. before even things even started up, there is a 10 key resistor from the gate to the mosfet, down to the zero volt rail to make sure the mosfet is off and in a stable. State Uh. Otherwise, they're so sensitive that if you just turned it on before the process or the chance to stabilize, the mosfet could have actually caused motor rotation or just sat there and dissipated some heat.

so the 10K resistor brings it into a stable State That's also useful if other parts the circuitry go wrong. but when it wants to turn it on because it's going to actually take it positive to the 12 volt reel, there is this P channel uh P Channel this PNP transistor which pulls the gate up positive via this 39 Ohm resistor. That transistor is normally turned off because it's a PNP you have to pull it negative the base negative with respect to the positive real as opposed to Npn which is the opposite. So when you turn this transistor on, it does.

it pulls that uh, base negative uh via this resistor. It also does another thing. It turns this little tiny mosfet off and this is just a signal mosfet somewhere to N7002 just marked 702. But it turns out much well.

if it turns this one on and that takes the gate positive. When the processor turns off, it turns off, it removes the signal from this transistor. This transistor turns off that transistor, then gets pulled up to positive. It turns off.

But now because, uh, this transistor is off. The current is flowing through these resistors and it actually goes to the base of this mosfet and it turns on. And that makes sure that the uh, the gate gets pulled to the zero volt rail via this 20 ohm resistor. So it's pretty much pushing and pulling and that's purely for the reason that it has been posted modulated to make sure it's done efficiently.

It uses high current via this 39 Ohm resistor to charge the capacitor and the the Gate of this mosfet. and then it uses this 21 to discharge it. And that just means it turns on a lot faster and turns off a lot faster than if you're just driving it directly from the processor, which would make it so much simpler if it was. Next comes the inputs.

Oh, God It's so easy to describe this when I've drawn it all out, it was. not easy to reverse engineer. It took quite some time, largely because of the effort required to actually get that coating off things like transistors just to be able to read them and probe about on it. The probes I also had to pierce that gelatinous gooey stuff which was quite tough.

So when you squeeze the trigger to the on position, there's a 3K peel down resistor in the input to my controller and inline 30k resistor and that just sends the pretty much the full 40 volts here. But it gets divided down by these resistors to a tenth, which is about 4 volts which is enough for the processor and this capacitor just uh, filters. That just makes sure that glitches and transients don't affect it when you release the trigger and it goes off. You can't really do the same thing because otherwise there'd be a fairly High current flow.

What would the current flow at 40 volts be so we can work the current flow out? Uh, that's 33k. So 40 volts divided by 33 k equals its 1.2 milliamps. That might not sound a lot, but if the tool sits in your toolbox or in your workshop for a long time, the battery in that is significant. It will gradually trickle discharge, and if you've used the tool until it cuts out and then put it into storage without charging again, that's worse because it can actually trickle it down below the point it can recover.

So in this instance, the user mosfet to get a much higher in input impedance. So the processor presumably has a pull-up resistor in there and it's got this little love signal mosfet to pull it to the zero volt reel. But this time they've got a two Meg Ohm resistor from the off position, a zener to clamp the voltage to protect that mosfet, which isn't really rated for a high gate voltage. But they've also got a 10 mega Ohm resistor here um, and a capacitor for filtering.

and now if we calculate that again, 40. volts divided by the 12 megams 12 million ohms that comes out at Um about three microamps, which is a lot better than a milliamps. Yeah, interesting. So the other thing the processor has, there's output to the main mosfet.

It looks like more mosfet, but it is the main mosfet. It also has this uh capacitive resistor Network here which I It's not connect to anything else. it's just basically a 1K resistor and capacitor I Wondered if that was a partial reset circuit, but it may actually be part of an oscillator I'm not sure. undo another part of the circuitry is this: 10K cooldown resistor with a capacitor in parallel and then the NTC signal from the battery pack which I think isn't just a temperature thing I think it is temperature and battery status I think it's probably just a logic level that's being sent to the processor to tell it when it can and can't run.

presumably because this is a pulling to the zero volt rail. Maybe the processor pills? No, it wouldn't. It's probably gonna have to take it positive to actually basically enable it. perhaps.

And then when you unplug it. Uh, the battery. Well, nothing would really have to unplug the battery. But when it actually signals, the battery is low.

Maybe it just lets go over that line and it drops to zero. I'm not really sure. Um, we shall explore the battery a little point and see what's in that. so that is more or less it.

Most of the circuitry in this board is well to half the transistors are for driving the mosfet and the rest is, uh, just discrete sort of level shifting and basically impedance changing to allow for long storage times. The tool that is it. So quite interesting. Slightly different to what I was expecting.

Let's Zoom back out here. Um I Thought there might be more a thought. There might be data I Mean there could be data coming from that uh pin on the battery, but um, there's only one way to find out that's to look at the battery itself and see what sort of uh signals are coming out of that. if it's just from discrete components, or if it's from a process or something because that will have to indicate that.

we'll have to monitor both separate sections of battery with a common signal, so that's going to be quite interesting. but that is it. that is the circuit board inside a typical 40 volt tool. Well, certainly the angle grinder from the Aldi Ferex range.