Hi welcome to another Tear Down! Tuesday where I tear stuff down so you don't have to but I know you still want to cuz it's cool. It's fun. So what do we got? We've got one of these voltage detection sticks. Let's check them out, see how they work, see what's inside, and you know what we say here on the EV blog.

don't turn it on, take it apart but H I don't see any screws. Could require a little bit of persuasion H Let's go. and of course, these things come in many different brands, but uh, they're all generally this uh stick type thing. They've all got a pocket clip up here for your uh, average nerd who wants to stick it in their pocket.

and this is the Fluka Vault alert here, but we're not going to look at that one today. What we're going to tear down is is this ideal uh brand? Vault aware and this Vault aware one is a basic uh Twist on Twist Off type. It's Cat 4 rated. Uh, it claims to have a detection range of 40 to 1,000 volts Ac.

There's a button here which uh, turns the uh beeper on and off and it comes with all sorts of standard goodness as well. Ulc rated and stuff like that. Let's see if we can take this thing apart. Now this is the Twist on Twist Off type.

you just. it's not really obvious how to take the thing apart, you just pull it like that and it's got these guide channels down in there and a mating little bump down in there which sort of uh, slides the two halves and of course it's powered from two AAA batteries don't need those and there won't be anything in there. so all of our Electronics is down in there and there won't be much I can sort of see through the transparent uh end there. You can see that there's a little tiny bortle, probably have one chip on it, couple of passive components, and uh, there's the uh, there's the uh sensor probe out the front there.

it's just a flat bit of metal there and uh, well, we'll have to apply some Force to get this sucker open I think and you can see that the battery, uh, contact there when it slides in to there. it actually makes. When you twist it, it makes contacts with one of those internal pads down in there, so that's a rather neat little solution. I Don't mind that at all.

First thing we're going to try is I See these little holes around here like this? Maybe we can get a screwdriver in there and pry it off? Perhaps that would be one of my first guesses? Well, I'm not having much luck prizing this thing open I'm not sure how they've assembled it, whether they've um, this is sort of. uh, this plastic end is sort of really snapped on first. Then they insert the PCB and it locks in place. I've tried to pull the board out, but, uh, with a pair of long nose pliers, but that's rather tricky.

so I'd probably ordinarily get the Dremel out and drill right around there, just grind it around and cut it off. but uh, that's the Dremel's not in the lab at the moment. so uh, just get some side. Cutters and uh, try and compensate a this is ugly.

Excuse me? Wow. Well, that was really thick plastic around that thing and it's was quite messy. but there you go. There's two chips.

So going to wiggle that board out, which is the official technical term for it. double-sided load. Look at that. It's rather interesting.

H I Like this one. see if we can get the board out? Well, that was wedged in there really well. Let me tell you. I had to cut away the plastic, but it looks like it's going to pop out like that.

Hey, that's a rather neat solution. I Really like the design of that so I Suspect these ones are a little bit more advanced than just a basic, uh, electrostatic, uh, digital uh detector that just detects the electrostatic field. It's still detecting the electro static field around a wire with the probe tip and a high impedance input, but uh, there's probably some uh, smart filtering or something going on in there, and uh, maybe even a custom device to actually do it. Why else would you rub the numbers off? I Don't know.

Maybe it is incredibly simple. um, but they just want you to think it's complex H Who knows. And here's the board under the microscope. I'll attempt to, uh, do this.

sorry I'm actually handholding my uh, little compact camera at the moment against the uh stereo microscope so this is really hard. It could fade in and out. But look at that. They've gouged out that chip that, uh, obviously connects to the antenna there.

it's got the date code 1009c I'm presuming that's a date code the 9th week 10, but they've gouged out that I see the bastards so we can't tell what that is and maybe we can get a closer view of the LED there. There we go. That's one of those uh, four pin uh Square packages. It's a red, green, uh combined uh Jewel color LED And of course they've got one uh top and bottom, which of course will allows the light to show out both sides of the module itself.

so that's really rather nice. There's a tactile switch there. there's another IC there, and that one is unbranded. It's got regardless of the angle.

I Cannot see any branding on that chip at all. And check out that bodge resistor with the 302 on it there. That's nice little bodge. that one.

They've got, uh, a transistor or something there in that So 23 package. And there's the uh buzzer there, which is rather nice. It's round and it's sunken into the board like that. They've put a cut out and they've got two pads.

um, on the end here, where it where it connects in. That's a nice bit of, uh, nice bit of mechanical design engineering that they've got a couple of more passives up near the antenna up there. Don't know, um, the topology of this thing, but it's obviously detecting the electro static field and uh, there's a couple of diodes I'm presuming that there are dodes there, those black ones and uh, that's it. There's some passive devices and ah, very disappointing.

I Was hoping to trace out this board I really was I was hoping that we'd uh, it would be like a um, you know, a really easy doublesided. We'd be able to trace it out. It would have the part numbers on it. It would use some identifiable Um Ic's and those passives around the front end there.

No surprise at all you'd expect cuz this is an electrostatic detector. You'd expect, uh, some very high value resistances there. And that's exactly what we see. see the T226 up there.

that's a 22 Meg resistor 395, you know, 3.9 Meg and uh, there's another 4 point couple of another 4.7 Meg and a 470k. So um, no, no surprises there at all. the Uh 226 up there. the 22 Meg that'll most likely be in series with the probe tip there going into the detection.

I see on the bottom of it this gouged out thing here and um, yep, what? that one is I don't know your guess is as good as mine and my guess for this input chip with the numbers rubbed off was going to be a Uh Smith trigger just a Smith trigger logic gate uh device like a 7414 or something like that or a 4,000 Seos equivalent device. Uh, because this is a very common Uh technique for um using um, electrostatic, uh, sensitive, uh, touch switches and things like that, you can do it with just a a Smid trigger. So I did a bit of a patent search here and I came up with this: uh United States Payton number 5 million 10 3,165 from the April 7th 1992 and it's from a Uh James M Saratz. um uh from Rayy North Carolina and uh I presume he worked for uh static control components Inc um and they um, it was filed in 1990 and was granted in 1992 and uh, let's take a look at it.

it is, well the uh name of it is insulated handheld non-contacting voltage detection probe and bingo That's pretty much exactly what we've got here. and uh, it's the pen style probe. It's even got the Uh pocket clip on it. but uh, most importantly, if we go down Bingo we've got a schematic.

Let's take a look at it and what we've got down here. If you decode all the patent is, you eventually find the Uh part number for the IC and it's an mm um MN uh 14 584 which is a Uh standard uh, seos uh Schmid trigger. So um, you could uh, use like a 74 Hc14 or another 4,000 series equivalent or something like that. It's probably not um, that fussy.

although you might have to, uh, tweak tweak the values for uh, the individual device. um, actually use the the the particular brand and uh model number but it's basically just that. It's it's a it's a Hex Schmid trigger And here's the waveforms here and it's got another uh uh schematic there. But here's the main schematic.

So um, basically and it's a 14 pin chip and if you remember the uh, look at the photo for the our board. it's also a 14 pin chip. uhuh I Don't think it's a coincidence. They're probably most likely uh, using this.

uh, same circuit here and they've probably got a a a resistor on the input shows the antenna connects directly to pin one, which which is the input on one of the uh hex um Schmid inverter Gates but uh I'd say they probably got a resistor in series. They got another resistor going the ground and the output goes through the cap. so we might need to uh, redraw this thing a little bit just to make it a little bit clearer. but I think we might have the basic operation of the front end here.

and here's this same circuit but redrawn in Tada Dave Cad and uh, what we've got here is up in the top left. we've got our antenna input. It's exactly the same Uh circuit as before except uh I've redrawn it with the Uh Schmid inverters in there to instead of just the big just the block chip which you know doesn't make it very descriptive at all. You got to sort of fill in the blanks there.

Um, it's not as easy. this one's a bit easier. Anyway, we got our antenna input here. We've got our Uh voltage, uh detection.

well, antenna Pro whatever you want to call it. Uh, we've got a just simple voltage divider. here. the value of that voltage divider will be um set dependent upon uh, the input voltage range you require and the uh threshold voltage of your Schmid inverter here.

and uh, then it's uh AC coupled and pulled High um and then that's for basically when there's no Um input uh voltage there, so it's pulled high and then um, the input uh to this Schmid inverter goes into this diode and resistor and cap Arrangement here, which sort of uh Smooths out, um, the Ac voltage and then puts it through another couple of uh Schmid inverters and turns on the transistor. So basically the output transistor and this Led uh turns on when the input Uh voltage from the antenna is above a certain threshold there and that's all there is to it. It's pretty done basic, and if we take a look at the waveforms here from the patent, we can translate those to the Dave CAD schematic and I've labeled them exactly the same as the Uh points on the wave form. So point A is our AC Um input and that's the Um and that's a reduced voltage input depending upon the voltage divider there.

and B is uh, Of course, the squared up in input uh because that's what a Schmid trigger does. A very slow changing, varying Uh input signal as it transitions through the Schmid trigger threshold levels. Um squares up the input so you sine wave in and you get a square wave out assuming it meets the Uh threshold voltages. So what's Uh Point C here doing? Why have this resistor and capit? All it doesn't seem to make much sense because if you look at signal D here, this output D is just an inverted Uh signal of point B here.

and if you are talking about the 50 HZ signal and these values are set um at a specific Uh design value, then that's exactly what you're going to get B and C. You can actually do without those components. Assuming that the input is Uh is, you know exactly on frequency and exactly doing the right thing that you want to actually detect. and it probably doesn't make much sense at the moment, but it might when we start looking at further on with uh, what's happening with Point E here because uh, if let's say we've got a very low frequency Um input, then uh, a low frequency input lower than our detection frequency, then not see if you look at this Uh Cur discharge curve here.

it won't instantly go back there. It'll go through both thresholds and that'll change the output waveform D to be different from just the Um an inverted Uh version of input signal B here and that will start to Uh affect the the Uh smoothing value that we'll look at in part E here. So we get our output signal D which is a square wave once again based on our Um input 50/60 Htz waveform and it just Smooths it out uh, between the Uh threshold voltages of the of this Uh Schmid inverter down here based on the value of these two resistors need to be set. um just to put it, uh, smack in the middle of the threshold voltage.

So once the input Uh goes above a uh, a certain level and that's to um, get rid of any uh, Any issues with uh, like a dudy cycle. If noise does get uh through and it's not the correct Uh duty cycle, then it's probably may not uh, actually, uh, reach the threshold voltages or something like that. So that's just another mechanism to uh, sort of filter things out a little bit and then it uh, invert and then it double inverts that or buffers it to drive the output transistor which drives the LED And that's pretty much all there is to it. And that is the basic operation of one of these voltage detection sticks.

A check out this. you're going to love it next to Uh 10. Here here is what it says: Figure 8 may use circuit parameters as follows: The Diode is a 1 in 4148 fair enough. Transistor is a BC 847 fair enough.

L is a whatever. but look at the resistor Val values R1 18.5 Milli 65 Mli 265 10 Milli for R6 Got to be me. This thing's going to have a hell of a hard time working with Uh resistor values in the order of million. So clearly what's happened here is the Um Pton attorney who uh, wrote this, uh translated the good circuit description into Uh patent ease.

You know, garbage like this has thought that uh Megs means milliohms. The Meg symbol must equal milliohms. So oh, I'm going to write milliohms in there and well, it's not going to work at all. And uh, clearly the uh, the guy who actually designed this thing hasn't checked it cuz that's a glaring mistake.

It's ridiculous. So what's with the second chip on the board? Well, that one is, uh, probably just uh to drive like a pulse uh, stretcher latch kind of thing to uh Drive the buzzer and the L LEDs in the intended uh way for this particular product. but I think it's probably using this basic uh front end or you know, maybe a slight variation of it. Uh, because it matches up I haven't actually traced out the uh PCB uh yet and I probably don't bother because I think it's probably going to use this circuit or a variation of it and there you go.

That's the Uh deal Volt alert voltage stick and I think probably most Uh voltage sticks are going to work in a very similar way with a similar front end like this. So um, if you have any better um, information on exactly, um, how these things work or maybe even some alternative Uh chipsets, some specialized chipsets on the market that might be able to do it, or some other Uh patents, jump on the Uh forum and share them with everyone and we can all discuss it on there. So there you have it, if you like, tear down ch Tuesday give the video a thumbs up. That helps a lot.

Don't know what we've got in store for next week, but waiting's half the fun. Catch you next time.