Another one for the mechanics. This is a very simple but useful tool. It's an electric circuit tester for vehicles. Brilliant tool for the Auto Electrician and mechanic I Have to agree it is pretty too handy Tool: It's very, very simple.

It's written. the manual is written in very much Chinglish It's bizarre. It even gives wrong instructions. It's fantastic.

I'll put that out of the way and show you the tool. So this thing is very simple. It lets you connect to the car battery and then you can promote electrical connections. Well, I'll show you let's air power up a very long lead, but that's because it's designed to wander about all over the engine compartment and indeed to the other end of your vehicle.

Social: Connect that black to the negative red, the positive and no when you I'll keep that clip out the way when you take the cover off the tip and you touch it onto positive. If you watch the LED here, it shows that what you're connecting to, it is positive or if it lights green, what you're touching is negative. So it helps with tracing things. But also suppose for instance, that you had a light which was referenced to the chassis like many of the lights and vehicles are, that chassis if you're American chassis if you're British or indeed, uh, French which is where the word comes from.

But now, if you were wanting to trace a problem with the light and you could test it locally by going on to the light or Tesla on the whole circuit, you can put it onto the connection and then you can choose whether tip because negative or positive and as you can see when it goes positive, it's just switching the street to that. Now if you were to put it onto the negative connection and then you're to switch to positive, The power supply is limited current, but what would actually happen in a vehicle with unlimited current from the battery is it would trip internal protection. It would also sound an alarm to let you know that something had tripped Auto reset trip. Okay, that's more or less it.

I Think it's time to open this up. This incidentally is a little portable campaign type light. It's just LEDs and resistors. Nothing fancy.

It's a a 12 volt light. I've never made a video about it I Don't think not really much to make a video about. Should get these clips out of the way now. You might think they're red and green.

LED is going to be super simple. You'd think maybe you could use a resistor and an LED from the positive to the tip and then another one from the negative to the tip. but in that instance, both the LEDs would be lit all the time and it wasn't connected to anything. It's quite clever how they do this.

I'm looking forward to uh, reverse engineer to see how they actually do that. So if I pop the cover off this thanks to Phil for the uh screwdriver it gave me a while ago. It's hand machined, not available commercially custom machined just for me. It's quite neat how we made it.

he, uh, the adapter for the end is actually a little socket and uh, he machined it down and then put it into this so the grub screw to hold it in. Quite neat. Very smart. I Do appreciate it, especially because it is handmade.

It always makes things a bit more special. Does it not Okay. Oh, incidentally, this black lead here. if you want to test something that's actually removed from the vehicle, you can basically put this clip onto and it's connected directly to negative here.

So you definitely don't want this clip to touch the positive because there is no over current potential look of it. Okay, the first surprise is that this probe is actually captive here and that it's going on to these little springy contacts down here. I was expecting that I thought it was just going to be our wire soldered onto. I Can see the Beeper for the overload indication I Also see the switch here I'm going to have to desolder that to get the circuit board out.

Is there much on it? Anyway, there's the there's the LED it's a three connection. LED they're all connected. Does that also have an indication mode? For other things, there's the Uh over current device. It's a PTC Thermistor a PTC Thermistor is basically a thermistor temperature sensitive resistor that is designed to.

initially. it has a low resistance, so it allows current to flow through it without any problem. but as soon as the current reaches a certain level, it causes T-top map when it heats up itself Heats itself and its resistance goes up and it just basically goes into a high resistance state. There's anything else under there, there's not.

There's really not much in here. There's a bridge. react far. There's a transistor.

There's some resistors on the LED. Okay, right, tell you what. I shall pop this out I'll take a picture of it so we can reverse engineer it one moment. Please, Reverse engineering has done its refreshingly simple.

It's almost excitingly simple. So let's zoom in in this and we shall explore this now. the two circuit board sections here. This is the main component side with redirect Fire and the buzzer on it and the components here.

and the side of the LED is the other side. but I've flipped this top image so everything correlates. You know this pad is here. This pad is here and things worth of node.

The buzzer circuit for indicating a fault is just stunningly simple. This Uh is a 7 amp 30 volt over current device. It's a PTC positive temperature coefficient thermistor and when it trips, it goes open circuit. When it goes open circuit.

if you get the probe, say for instance, you've got it switched positive. but you put the Probe on negative. so there's a dead Short Circuit The high current will flow through that will trip, but then you'll have a high voltage across it. That high voltage.

Well, the 12 volts gets rectified so that no matter which polarity, whether you had it switched positive or negative, it gets rectified and it goes to buzzer. That's it. So that as long as the probe is held on and there was a short circuit and that was open circuit, then it the buzzer will sound to show it. You know there's a short circuit and a protection trip.

The LED is actually an RGB LED with the six pins. kind of like a video. While LED I suppose it's just the cheapest way to do it and their Arrangement the resistors is quite odd. Uh, there's not really much to show in this.

Let's cut straight to the schematic and there is an anomaly. I'll let you chime in in this. Tell me what you think. So zooming up here's a crocodile Clips or alligator clips that go onto the vehicle battery.

Oh something. I should mention. One thing you shouldn't do. this probe is probe.

low voltage stuff like centers that are expecting 5 volts. Back to the engine management system. you definitely don't want to stick 12 volts on that. I Just thought I'd Mention that.

Be careful what you're proving. It's mainly for the sort of 12 volt side of the vehicle. Um, so here's a 12 volt rail coming. in.

those clips, there's a little auxiliary clip. This little clip which is designed to allow you to test things when they're out the vehicle. Things that would normally be grounded to the chassis or the chassis as you might see in America Um, so that's just connected straight to the negative. There's a switch that can toggle between off and either positive or negative for the probe.

and there is the PTC Thermistor 30 Volt, 7 amp PTC and the bridge rectifier and the buzzer across that so that if that goes open circuit while you, you're proving, it, will simply make this buzzer sound an inner priority. It's incredibly simple. Now, the LEDs There's a resistor Bridge across from the positive to the negative two 1K resistors. Meaning, there's going to be a current flow probably about five milliamps roughly typically.

Is that about right? Yeah, it's going to be about six milliamps actually continually flowing. But if you connect the probe to see, for instance, the chassis which is negative current will flow from the positive through this resistor, through the green LED shows negative and then through this resistor and this diode that's the resistorant diodes I get to feel these aren't needed. Likewise, if you're to connect to the positive, current will flow from the positive into the probe, through this diode, through this resistor through the red LED to show that you've touched the positive and then find its way to the negative rail via this one key current limiting resistor. I Don't think these are needed.

In fact, they actually pose a slight problem. Uh, if the LEDs were just bridged in parallel, then the voltage across them can't the reverse voltage can exceed the forward voltage of the other LEDs so it's going to protect the other. LED It's a bit like those bipolar bi-color LEDs with just two leads, but by adding an extra resistor here, it means that if you were to touch the probe onto something with a very high inductance like say, for instance, you touched it to the starter coil um, and the starter relay and then you click the switch to energize that. but then you release the switch, you could get quite a high voltage spike in that probe and normally that would be clamped across.

it would go through the LEDs and their appropriate resistor and it would result in a sudden current Spike but it should. the LED would clamp that. However, if the current spec was high enough, it could create a high enough voltage across these that it would pose a slight risk of overvolting the other LED with the leakage through the diode. I Do think it's a huge thing, but it just makes me think they've over complicated this by adding these two diodes and these two resistors.

They literally could have just bridged those like that and just run them straight over there. am I right in seeing this: I think um I Don't know why they've put those in. There must be a reason, but um I don't know. Let me know what you think in the comments down below, but that's refreshingly simple, isn't it? There's really not much to go wrong.

Um, the LED could fill the PTC is rated to break fairly High currents, and there's a certain element of resistance in these cables that's going to limit the the current sort of sensible level before it breaks it. And that's nice. It's a very simple design, a very simple and functional tool that is extremely useful for Diagnostics on vehicles. Nice enough case as well.

That does surprise me that the I thought there's going to be a wire sorted under here, but instead this proves it's kind of oh, you know, it's pushed in and then it's actually clamped in place. It hits an end stop there, and then it's clamped in place by this little um, spacer here. That's quite neat. Um, and I Suppose that makes sense that they've just got these little spring-loaded good plated contact, so just touch up against that to make contact with it.

It just keeps things simple from Manufacturing but that's it. A very neat little device. A very functional device. It's uh, perfect for diagnosing many problems in vehicles.

It's got a relatively long cable I don't know how long the cable is and I'll just measure it one moment, please. It has been measured. It is roughly 4 meters or 13 feet, so that's a good distance. It may struggle to get to the back of the vehicle if you've got that in the battery.

depends the vehicle. There's a length of it and the accessibility of the battery, but that is it. A nice, chunky, robust case. I Like this fairly solid switch.

the nice simple: LED Buzzer circuit tuner protection It's actually a really nice, well-designed device.