Surprisingly complex banned voltage detector

[@kjpmi]

That’s a Texas Instruments chip. That blob on the upper left corner is Texas.

[@damowdotnet]

I feel like it might be a Schmexus Tinstruments tbh. Looks a liiiiitle but knock-offy to me!

[@johnscott4493]

​@@damowdotnetChinesium instruments

[@jimsvideos7201]

Blob left Texas?

[@BritishEngineer]

@@johnscott4493ningbo instruments (silly oil filled capacitor joke, yes, more like taipei instruments because they’re more specialised in semiconductor design and manufacturing- qwq)

[@marcse7en]

I've always thought Texas looked like a blob! 🤣

[@technocardy]

Hey man, I just wanted to say a genuine thank you for sharing your incredible library of knowledge. I know almost nothing about this stuff but I watch you religiously because I enjoy watching people talk about something they’re passionate about. On a bit more of a serious note I’m a paramedic who is off work because of diagnosed PTSD, it really means a lot to have this content on the really rough days. So from an internet stranger in Canada, Thank You ❤️

[@bigclivedotcom]

Thanks. That's very generous of you.

[@nobody8717]

The old circuit looks well made, and has features to combat component degredation and to eliminate false positives. It's just a better circuit than a simple step up amplifier indicator. Made to last, and until you tried to disassemble it, it did its job pretty dang well.

[@dogwalker666]

There never was a problem with the metal case, The paint was extremely thick and were never a problem, The plastic version was rubbish, I still use the "Banned" one.

[@deang5622]

False positives aren't really the issue. It's the false negatives that are.

[@deang5622]

​@@dogwalker666So you think a layer of paint is good enough insulation at 400 volts RMS which has a peak voltage of 565 volts? Hmmm.

[@dogwalker666]

@@deang5622 Even more fun I was installing DC drives so there was also 500VDC armature, 220VDC Field, and 60V/K Tacho, Along with the 415v 3phase, Some of the high speed clutches used 1200vac too. You just didn't touch any live parts, Guess you haven't Done any Industrial control systems.

[@deang5622]

@@dogwalker666 Don't guess.i have a degree in this subject.

[@SebBrosig]

I remember making one of those magic charge detector things with the cmos inverters when I was a boy, from a circuit I found in a book of "fun LED projects". It did not use a transistor, I think it had multiple gates at the last stage as you suggested. The high value resistor was homemade out of a match stick with copper wires wrapped around each end. It was not for detecting mains voltage but for switching the led on with your hand at a distance, like a magic trick

[@robert_g_fbg]

I worked with hybrids back in the ‘80s. The process is silk screening, the resistors are printed first, followed by the metal layer and solder mask. Printed Resistors are far less expensive than attached ones, and can be trimmed (with scribe or laser) to achieve 1% or better.

[@amorphuc]

Wow. I'll bet that was a pricey little probe when it was offered. Sheesh. Thanks Big Clive. That was interesting.

[@bigclivedotcom]

I think it was quite new and expensive at the time.

[@dogwalker666]

They were expensive especially as mine was R.S. Branded I used it for ages before it was stolen, The plastic replacement rubbish.

[@yngndrw.]

I always found the old ones to be far more stable and sensitive (Which is odd as you'd expect those to be mutually exclusive) so I think the added complexity is well justified. I don't think it's over-engineered at all. (Okay maybe the ceramic PCB is, but the actual circuit is fine.)

[@nobody8717]

regarding the ceramic, i wonder if it was at the time of manufacture, actually cheaper to do small components on that. surplus stock, batch sale, something like that. maybe just for insulation. which seems odd considering the metal grounded casement.

[@MikhailVladimirov]

@@nobody8717 I suppose that's for in-circuit insulation due do tiny currents and huge resistances involved.

[@grzegorzdomagala9929]

My first gess was that it was cheaper because they actually printed the resistors on ceramic substrate. But frankly - no idea how the calculation goeas since the circuit contains wide range of resistor values and they probably couldn't print it in single pass. Maybe they had fabrication line for hybrid ics and decided that this curcuit could be added to existing process to fully utilize the line? Anyway - someone produced a lot of high quality testers :)

[@mysock351C]

@@nobody8717The ceramic circuit board could also be needed due to the very low currents involved. I suspect standard PCB materials may have too much leakage due to humidity and other factors. Whenever things get up into the megaohm region and beyond, everything starts looking like a conductor.

[@mysock351C]

As for complexity, I will take this any day of the week since it’s going to work potentially way better. Sometimes a little more goes a long way, and these are nice when you are hunting for the breaker that controls something you want to work on or just as a quick check for power. No replacement for a proper meter to ensure something is truly off, but they are still useful.

[@hob991]

Bought myself one of those last year after seeing one in use during my bathroom revamp.useful for us non tech types.

[@jagmarc]

Just remembered my father had the first one that came out in the 80s. Officially banned by the CEGB but they all had them.

[@penfold7800]

Theres always captan tape to help with situations like that I guess.

[@jagmarc]

@@penfold7800 or heatshrink tubing

[@krashd]

@@jagmarc Or marigolds.

[@okbridges]

I used a newer version of the old all-metal red one with a red plastic case and white plastic cap for several years. The shirt pocket clip was still metal, but painted white. Very good unit, and was much more reliable than most of the designs I had used. They were still available new in 2015.

[@davidcrocker4285]

I remember building one of these devices more than 50 years ago. I used a 2N3823E jfet and I think one PNP transistor. The indicator was a torch bulb, which I later replaced with a red LED when they became widely avaliable.

[@rbmwiv]

I have this pen style meter I bought for about $10. It's pretty neat especially for the price. It has no contact current detection even will pick up power in a USB cable, it will also tell you what phase the leg you are checking is. It has other features also. I have compared the readings with my Fluk and voltage and resistance were bang on. I keep it with my small home repair tool kit. I don't want to have to break out the fluke, it is pretty big comparing but does so much more and I don't need the extra functionality to check batteries and resistance. It only has a ground lead and the point is the positive probe. Very handy for around the house. I gave one to a friend because it also will count frequency. It just gives the number no waveform.

[@chrishartley1210]

Would those ceramic circuits be intrinsically safe with an effective high degree of separation? If so, it's a shame they then compromised the whole thing with a metal case.

[@tonysheerness2427]

Put heat shrink tubing over it.

[@deang5622]

​@@tonysheerness2427As an aftermarket activity? Still can't be sold. It would need the heat shrink fitting during manufacture. And might not be considered robust enough.

[@jamieblatantsparky]

I had the fluke one of these and a T3 Electrical tester back in 1999 , I spent 3 years searching to replace both for the ajar of it and finally managed to get both last year

[@Petertronic]

Maplin used to sell a live wire detector kit, it was the first circuit board I ever assembled, around 1987. It used a HCF4069 hex inverter chip and one BC548 transistor, and a piezo buzzer as well as an LED. It needed a 9V battery. Still have it.

[@hectorpascal]

The first circuit is what I would expect Digital Electronics 201 EE students to come up with. The second is what my Analog Electronics 201 students would probably design! 😄

[@hotmetalslugs]

Thanks for the video I’d never have guessed that shoving a metal object into a mess of live wires with my bare hands might be sketchy

[@roshantv6355]

Ive recently discoverd this channel and i love it. I binge his videos

[@RODALCO2007]

Nice for working out the circuit Clive. I still have one of those simple Neon screwdrivers. No battery required.

[@ralphj4012]

Excellent explanations, as always. If you stuffed the simpler one direct into the mains you may see a brighter light than expected (together with the additional vibration function).

[@MrBradleykeith]

I recall making one of the old type from a article in a magazine way back in the 80s (Before OHSA) came and made things complicated. Every time I walked under overhead HV overhead powerlines it would glow.

[@bigclivedotcom]

Standing on a railway platform or near a neon sign does that too.

[@BRUXXUS]

I've been learning electronics and circuitry for like... maybe the last 15 years now, and I've never seen those embedded carbon PCB resistors before until now. What a cool idea, but probably crazy expensive. This thing seems luxuriously overengineered.

[@Nono-hk3is]

Take apart a trim potentiometer (variable resistor) and you'll see a carbon resistor. Most pots have three leads (contacts). The middle lead is on a swing arm that moves across the carbon resistor. This is why the sum of the resistance between the first and second contact plus that of the second and third contact equals the resistance between the first and third contact, which is that of the carbon resistor. Embedded carbon patches are also used as very low profile contact points, used in some older calculators.

[@emmettturner9452]

One of the first things I ever took apart as a kid was a Nintendo Entertainment System controller which used printed film resistors. As the other guy said, it’s the same thing you find in potentiometers. Keeping with the NES controller theme, I’ve also seen a lot of PCB contacts for carbon-impregnated rubber membrane buttons which look like they are coated with the same stuff as printed film resistors… perhaps as a way to protect against contact oxidation.

[@emmettturner9452]

I’ve also seen them used as flexible jumpers on Mylar flex circuits (Atari 5200 controllers). I’ve seen the same for the Turbo Express / PC Engine GT. Some devices do this in order to get away with a single-sided PCB.

[@johndododoe1411]

They were originally invented as a cost saving technology that created approximate resistor values when making the bare PCB . But the extra production steps turned out too expensive for current production lines thanks to cheap SMD resistors .

[@BRUXXUS]

@@johndododoe1411 Ah, that's interesting! Makes sense how things changed with SMD parts and how PCBs are fabbed.

[@tomsworkshop5856]

I just love your videos... KZbin keeps me seeing them all, and until now, I had no idea I wasn't subscribed.

[@Tim_3100]

Seen one like this someone i know took one to bits like you always amazes how small pcb's can get

[@pauls5745]

a whole computer can be so small now its crazy

[@nobody8717]

@@pauls5745 i have one in my pocket, and another on my wrist.

[@aurthorthing7403]

I had one very close to this but mine had a plastic housing. It was very reliable and even worked around other live wires.... it was not overly sensitive.

[@jessenic]

I had one as well, but I put the batteries the wrong way around once, just for a few seconds until realizing it and that killed it 😢

[@aurthorthing7403]

@@jessenic mine died from leaking batteries. I tried to repair the traces but it never worked again.

[@tomsmith3045]

I thought for sure after the PCB board broke that it would be the end of the investigation. But! You did a large size pictorial of the circuit board, and then a completely reverse engineered schematic. That was beautiful... If I had to sell them, I understand why the second design is more popular. If I'm working around potentially live circuits? I want the first one. My take on the use of the ceramic circuit board is this - that they discovered that a ceramic board was either cheaper or more reliable than conformal coating, and that the 100M input impedance of the circuit meant it was otherwise prone to damage from a soggy circuit board. Now I want to make myself one of the old style, minus the metal case. Thank you for the breakdown!

[@KeritechElectronics]

Interesting and nice. I like them both. One for the sophistication and technology used in computing, military applications, whatnot - and the other for the utter simplicity of the design. C'mon, just a bunch of semiconductors and that's all? Nice :).

[@confusedofhinckley5294]

I suggest that "dual diode" package is, indeed, a transistor! they've just used the BE junction as a cheap diode.

[@bigclivedotcom]

That did go through my mind.

[@somedutchguy7582]

A7 *is* in fact the marking for a BAV99 dual diode.

[@mysock351C]

Seeing this brings back memories of fixing the oscillator in my Metal RF solder station. They used a similar arrangement of gates to make a crystal controlled oscillator to provide the needed 13 MHz for heating the tips, which used the curie point of ferrite slugs inside to control the heat. Once it hits the curie point, the driver circuit detects the impedance mismatch and throttles back. Bitch of a repair, but I do like those solder stations a lot.

[@hullinstruments]

Would be awesome to have a super-sensitive version of this. Still hoping someone will reverse engineer the HP "current tracer" probes. And introduce a somewhat straightforward DIY approach. They now sell for hundreds and hundreds of dollars. Because they are so useful. Was lucky enough to get some before they went up. but we need someone to reverse engineer it because it is one of the most useful tools in my entire lab when tracking down issues on a board

[@martinahlqvist4560]

That looks like the one I had around 1989 it was named Phasen and they are still being made, originally it was made by a Swedish company but today probably not. I think i still have mine, I just have to find it.

[@jorgealzate4124]

I knew that kind of circuit because of Don Lancaster when I was a kid, and his explanation shows the real simplicity. You can make the same device without any Schmidt Trigger, a 4069 will suffice. The reason? A CMOS inverter is just a complementary pair MOSFETS, and given the right conditions, they behave as a very good inverting amplifier, there is no mistery 😊

[@jimballantine4408]

My thoughts regards the 'simple' circuit is that it could trigger in the presence of strong radio frequency pulsed fields causing an false or anomalace indication. The one using scmitt triggers looks way 😊 more robust

[@waldolemmer]

Anomalous?

[@jimballantine4408]

@@waldolemmer yes indeed just could not remember the correct spelling

[@waldolemmer]

@@jimballantine4408 Anomaly + ous :)

[@jimballantine4408]

@@waldolemmer tbf I wish I could rewrite it totally, there is a lot of anomalous grammar in there 🤣

[@Steelplayer59]

As an industrial electrical instructor back in the days when these became popular, I always stressed that these were for the exclusive use to prove the actions of a switch or circuit breaker, and never for use to touch exposed conductors. As handy as these are in a shirt pocket (yeah, I’m from the pocket protector days😄), proper direct-contact volt meter, either a multimeter or the solenoid-style, previously tested on a known live circuit, is how you test for a “live” wire, and continue to “live”. Nicely done “break”-down, Clive. Full disclosure- I, too got curious, and broke my original one much in the same way. I’m using the tube to build a home-brew detector of another type!😁.

[@davidcook99]

Good post and thank you for the breath of sanity. These things, along with neon screwdrivers, are not considered to be approved voltage indicators and don't really have a place in an electricians tool kit. Phew; rant over🙂

[@Scrogan]

I think that high-pass cap is necessary for only coupling to mains frequency (or higher). Without it you’d get it to trigger off stray electric potentials, like those hacky electroscopes with an open-gate FET. While the low-pass filter in the next stage removes the problem of getting short pulses that are too far apart, it doesn’t remove the problem of getting one long positive pulse, which would charge up the low-pass cap and activate the output transistor. Also I think I’d call that a “diode detector” circuit, rather than a “charge pump”. Charge pumps have series caps and parallel diodes, not the other way around. Wait is that a CMOS output directly sourcing current into a BJT’s b-e junction? You’re sure that’s not a MOSFET?

[@mrfrog8502]

06:25 More like an integrator than a charge pump. Integrator's role is to average out all incoming pulses into slower changing voltage of more decicive value. Charge pumps are used where higher or offset voltage is needed to drive the switching circuitry. Presented schematic is basically an AC field detector.

[@will_doherty]

Years ago when I used to do a lot of hands on electrical work, I used to fairly regularly meet a guy I knew locally on site, as he worked for the MEB. He always used one of these detectors, as did I, though they were plastic bodied. The MEB, having originally supplied and mandated the use of these things, eventually banned them. I asked him one day when he was without his whhy he wasn't using it - he said they were banned by the MEB, and anyone seen using them was up for instant dismissal. I asked him why, he said it was because they'd had some instances of their guys having accidents, as they weren't pre-testing the devices before use, as they were mandated to do. I always tested mine, as I liked the way I looked, and a brisk rub on my jacket sleeve produced enough static to trigger it, proving it was working. Nowaday most of them seem to have a pilot lamp to confirm the unit is working, so they are failsafe...

[@chrispomphrett4283]

I have a couple of the original black aluminium volt-stiks which are very old and still work perfectly...pricey they were too.

[@jimsvideos7201]

What a bizarrely elaborate gizmo.

[@flowerpt]

That spring is a pretty clever idea! There's a special place in heaven for the EE who can reduce product cost by 10x. Literally the reason Apple exists today (Woz's floppy and NTSC circuits). I like my current detector that also beeps - would not downgrade for merely visible because not every spot of concern is easy to see in old work.

[@zyeborm]

Aside from the ceramic I'd wager the first is cheaper to fabricate. Untouched by human hands until it goes into the device. The second one will need a lot more hand work. The components basically don't cost anything.

[@petehiggins33]

I remember that when CMOS first became available it seemed such a magical technology that we tried to use it for everything.

[@MRooodddvvv]

XD

[@jagmarc]

9:06 Ordinarily, the transistor junctions would theorectically blow up with the way they're arranged in series directly across the battery. There'll be cries of "can't do that". But in practice the first transistor isn't normally fully turned on enough to hurt it. Plus there's not enough current *FROM* zinc carbon batteries anyway. Plus it's only on for half-cycles.

[@deang5622]

Not enough current in zinc carbon batteries....last time I looked, there was no current.

[@jagmarc]

@@deang5622 :) I was speaking at metaphorical level to use less words. But I guess there'll always be some who get distracted by a literal interpretation and then only see a carbon rod, electrolyte, a zinc casing, ions, polarisation, pH.....

[@deang5622]

@@jagmarc I am being precise. The fact you weren't may suggest you are not that knowledgeable in the subject. You should be precise in what you say, if you are qualified in the subject.

[@davelowets]

I had an El cheapo one similar to this years ago. If I held it in an outstretched hand outside during a thunder storm, the led would flicker and flash whenever there was a fairly close lightning bolt in the clouds or hitting the ground. It was time to head inside when the LED flashes got fairly bright. I had totally forgotten about that hidden feature til now. A newer design one that I have did not do this during a storm, just that old one did.

[@jagmarc]

Another thing about these, is it you rub them on any nylon or wooly jumper you're wearing, it lights up with no mains electricity.

[@fatblokes_ferguson]

Was curious about this one. Thanks Clive 👍

[@theantipope4354]

Back in Y2K, I was given a Fluke version of this probe that just used a single cell. Sadly, I lost it many years later, but I pulled it apart at the time, & it used a very similar circuit to this one.

[@misterhat5823]

The pull down resistor on the input is because floating inputs tend to make CMOS gates draw excessive current because both the upper and lower transistors will be on. I assume that series capacitor is so it won't respond to DC. Although I'm also not so sure it was needed. While the 74HC14 looks like overkill, the amount of gain and extra filtering it allows for makes for a more sensitive tester. The IC is cost effective when compared to a few transistors. I think the ceramic PCB allows for that very high resistance. Otherwise it'd need a series string of resistors to achieve 100M and not be affected by leakage.

[@misterhat5823]

They probably used the transistor because CMOS gates' ability to supply current varies with supply voltage. At 3V it'd be pretty puny.Probably only 1mA or so. Without pulling the datasheet, I don't know if using the extra gates would help enough.

[@deang5622]

​@@misterhat5823No. Data sheet for 74HC14 shows continuous output current of 25 mA. And it's not CMOS. It may be CMOS design but technically it is not CMOS, it's High Speed CMOS and the supply voltage range is limited to 7 volts, considerably reduced from the CMOS equivalent part, CDP4014 which has a maximum supply voltage of 18 volts.

[@misterhat5823]

@@deang5622 No. It is indeed CMOS, just not the same process as the old 4000 series CMOS. That 25mA number is an absolute max. The typical operating section states 2.4mA for 3V. Regardless, that is better than 4000 series and the three gates in parallel should easily drive an LED without a transistor.

[@acmefixer1]

The probe with the 3 transistors is a 'marginal' circuit. The 2 AA supply is only 3.1 or 3.2V at most. The red LED requires 2V, so that leaves about 1.1 or 1.2V across the transistors with fresh AA cells. The base of the first transistor requires not, 1, not 2, but 3 full B to E diodes' forward voltage to overcome in order to turn on the transistors (explanation below). If the B-E diode requires 0.6V, then that's a total of 1.8V, which is why the LED lights up so dimly. Note: the collector of the first darlington transistor, call it Q2, must have at least 0.6V, so when Q2 is turned fully on, it can supply enough current to the Q3 base to turn it on. But when Q3 turns on, it causes the Q2 collector to drop to below 0.6V, which then causes Q2 to no longer have enough current to turn the base of Q3 on. The above means that the base of Q2 can never drop below the 0.6V B-E forward voltage of Q2 plus the 0.6V B-E forward voltage of Q3. This total is about 1 volt or more. Then the the 0.6V B-E forward voltage of Q1 must be added to the 1V, so the total is more than 1.5V. But the LED takes 2V of the 3V, so it's a really very marginal circuit. And the B-E forward voltage is dependent on the temperature. It could stop working when cold, or get much brighter when hot. And as the battery voltage drops, the LED quickly gets dim. At 2.8V or less, it's likely the LED would not be visible. My conclusion is the circuit is a poor design.

[@Milkex]

boy howdy i sure am enjoying these voltage detector pen vids!

[@maxrobe]

The thing I like about electronics is that you can do the 'job',. but there can be a way for someone to do it differently. You can get paid for the sub optimal, but can appreciate the economy of a different design.

[@jamesfirth7795]

I remember these, I bought one maybe around 20 years ago? Got it from Maplin if memory serves. Thought it'd be robust, what with the metal body, but turns out that the guts break if you even hint at dropping it. Wasn't too worried about shocks from the metal body as the probe is a pretty long plastic insulator.

[@davidbandler]

Would be curious to know how old that tester is since it has a Texas Instruments IC in it? I don't think I see chips by TI so much anymore, and they usually are more expensive than the generic mass-produced available now days.

[@joelmurphy9369]

i love the 7414 hex inverters. The hysteresis is critical for charge pumps and for building stable oscillators. Yea, the ceramic circuit is way over done, but the printed resistors!? That is really cool. I wonder if my board house will print resistors on my boards...

[@srenkoch6127]

Yea, those 74HC14's are just so useful - low power consumption, ease of use and guaranteed sharp output transitions combined with low cost and you have a winner.. No matter what project I'm working on I usually end up using a 74HC14 somewhere (be it a capacitance meter, a sonar or a full blown CPU, I have used a 74HC14 on all of them :-). Even if the hysteresis is not strictly needed the 74HC14's ability to make sharp transitions is a nice feature if you want to be sure that your digital transitions are sharp enough.

[@vsvnrg3263]

there are quite a few commenters who approve of the complexity and sensitivity of the first voltage detector. building a device with a metal housing that is used for poking around in dangerous places is unacceptable. the blunt end of my e-z scan is a hindrance for poking around inside a switchboard but i would never do that. but it is great for running along a wall trying to find out where the wire is hidden. that is the sort of sensitivity i appreciate.

[@patriotmu4741]

The SOT23 marked "A7" is a BAV99, Small Signal Switching Diode (Dual in Series) used to be a very common component but you dont see them very often these days. gone the same way as the BAS16 I guess

[@bigclivedotcom]

They do still appear in some very odd applications.

[@eCitizen1]

Thanks for that explanation. I appreciate your insights and knowledge share.

[@sparkykevboss]

I've just had to bin one of these as the batteries leaked and ate into the aluminium and i couldn't get the cap off. I was gutted as it's been part of my tool kit for around 30 years at a guess, used regularly and often commented on by younger sparks. It was MK branded and always reliable, i did wrap insulation tape around most of it for safety though. I was hoping for it to see me out to retirement as we'd clocked up a few miles together and seen a few sites and it had become my 9th finger. RIP voltstick.

[@TechStuff365]

Hey Clive, you got a mention on technology connections latest vid on light bulbs, re the dubii light.

[@raymitchell9736]

I've seen this kind of voltage detector before... It used a 4049 CMOS Hex Inverter, I think the one you had, emphasis on HAD, on ceramic is probably the better one... although I have to admit the 3 transistor works too... Now I recall your "Ghost Detector" that was basically the same circuit. They use EMF on those programs with a K2 being the preferred "gold standard" I guess I should call it the "Ghost Standard" LOL... but why not have both the E-field and the B-Field (magnetic flux) Sell them as Clive's Ghost Detector and make a million bucks... if you actually make a million bucks, send me a few free detectors LOL

[@dsracoon]

I rememeber some older models where it was only a Neon lamp and a resistor. One went into the outlet, the other you could put it on neutral or just hold it. Not sure if those were banned. And I think the diode pack might have really been a transistor (maybe just w/ a different marking by the manufacturer) but going by the principle of 'cheaper and it works here '

[@bigclivedotcom]

The neon screwdrivers are still sold here.

[@davidparkins1808]

It feels uncomfortable connecting the LEDs directly through the transistor to the supply. Nothing to limit the current through the LED. Isn't that a waste of battery powered driving the LEDs harder than needed?

[@billjuaire3316]

I am going to try making a NCV tester , I ordered TA7642 AM radio chips from Amazon . Theyr are 3 terminal, TO-92, with multiple stages of amplification.

[@norfolkngood8960]

Hi Clive I've got a complete Libre 2 wearable glucose monitor if you want it for disassembly, uses NFC and Bluetooth to send your readings to your phone.

[@SteveWhiteDallas]

The Darlington setup makes sense. The other one was just to prove someone could complicate what should be a simple ckt.

[@kareno8634]

Sorry tester's ceramic board 'crumbled', .. crunched to bits. Older style testers are neat to see, especially those "Banned", adding a comical edge to one like me that has learned enough to know why they're banned. .. I think. Again, you Pick up all the bits to pointing out each little piece I will one day understand. Thanks Clive!

[@sparkyprojects]

The simple circuit is what i have in one of my detectors, which i still have many years later

[@ks-hg5vo]

The original "volt stick" still got mine must be 25 years old. Replaced it with a martindale with gradiated 5 led scale . Can now tell difference between actual and induced voltages

[@d.t.4523]

Thank you. Keep working, good luck.

[@GothGuy885]

came for the electronics tear down and reverse engineering, stayed to watch Clive pull on his tip with a pair of pliers ;' -)

[@chrisswindell7517]

I had one of these exactly the same, I'm sure it was MK branded. I never used it to poke around a live panel as there is always too many cables in close proximity, and certainly never for checking for dead!

[@adoughertycontracting7243]

It was defo MK, i had one in 97 lol

[@CrimeVid]

I have two Fluke volt sticks, The older has no audible signal, when they get a bit erratic on live test, they need a new battery ! (at ridiculously long intervals !) These and the much maligned Martindale plug will do most of what I need.

[@railgap]

Oh this takes me back, yes, I too remember when it was possible for a product to be "banned". 😜

[@Steve-GM0HUU]

Thanks for video. I suspect you may be right about the LED driver transistor not being required. I am sure I have seen RF circuits with paralled 74HC14s driving power transistors. Quick look at 74HC14 data sheet suggests total max. input current is 50mA for all x6 inverters. The first x3 will be using very little current, maybe plenty left to drive an LED with the x3 remaining? I will stick with my trusty old neon screwdriver 😂.

[@felixokeefe]

A7 is a dual series diode. BAV99. Which is two BAW92 diodes in series. Pin 3 is the centre tap. HC14 is most likely an SN74HC14DR

[@t1d100]

Thumbs up! Would an inductor, of some value, make a good antenna for the probe tip. Yes, or no, please explain why. Is the C3199 a common NPN transistor? I have not heard of that model number... Comparable to 2222, or 3904? Please and thank you.

[@TheAzuratis]

3.14 That works because transistors are constructed very similar to dual diodes. They are just very very close together and with different dotation. So a fault in the dual diode could case it to read as a transistor.

[@MsLancer99]

I have the second one you showed with the metal tube that I bought way back in the 1970's and it still in working order. The only problem is it will light up on the leads from a 12 volt battery charger where the AC is leaking pass the receiver

[@bigclivedotcom]

All modern ungrounded switching power supplies like USB chargers will trigger it.

[@railgap]

The resistor at the tip sent me down a rabit hole of thinking about fields. (I normally avoid thinking about fields, that's what computers and masochistic interns are for)

[@broderperdurabo]

On the Transistor variant we used BC337 an BC517 on the last version.

[@kevin30b90]

I wonder how the two probes would cope with static electricity? Would the simple one be biased either on or off? The complicated version has a differentiator to filter out dc followed by an integrator to filter out false positives. Maybe the designer was trying to address some of the inaccuracies that this type of device is prone to.

[@bigclivedotcom]

The static would be capacitively coupled and show as a brief flash.

[@DirtyPlumbus]

Well I guess we know what the crack noise was. Lol

[@rogeratygc7895]

Donkeys' years ago - 1960s! - I had a mains sensor which just had a high value resistor and a neon bulb, connected to a metal stud on the handle end. It worked, and I never got a shock from it, but I can understand it being regarded with horror by anyone with a responsibility for safety. The device double as a screwdriver.

[@robert_g_fbg]

I did not expect to see a hybrid microcircuit. That’s an alumina substrate with thick film circuits printed upon it. Those resistors will all be using the same resistivity ink. So at the same width at metal ends, resistance is proportional to length. Broken one is a ratio from one measured at same width.

[@bigclivedotcom]

In this case there was a wide resistance to area variation.

[@gadgetman36]

The Kewtech Kewstick Duo is a good, audio visual, and fairly inexpensive NCV tester.

[@gownerjones]

I have a screwdriver with an led in it and a plastic body with a metal end. You can plug it into any outlet, and test for live current by putting your finger on the metal pad at the end. No joke, that's how it works. The LED lights up when you touch the pad and the driver has no batteries or anything like that. It's totally passive. Would be fascinating to see that circuit.

[@bigclivedotcom]

If it lights when you touch both ends it may have a tiny stack of button cells.

[@waynesharp1690]

I recently purchased a CK volt stick and didn't realise it didn't have a buzzer. My fault for not reading the description

[@joshuahymel9750]

I want to get into making custom lighting solutions. Decorative for now, maybe technical later. Can you recommend a good way to dip my toes into your pool? I'm technical enough to not be interested in super simple stuff like led strips. But I'm still quite the layman. Notes?

[@JasonHalversonjaydog]

in my technical school our instructor told us those are good preliminary testing tools but not to trust them with you rsafety and to test with your meter as a backup method. esp if you're working with higher voltages

[@ETORERIGO]

I expect that in a couple weeks china will release an new voltage detector that's disposable, if the outlet turns into black and magic smoke comes out, there is voltage

[@agungpriambodo1674]

You dont need china Just use some wire and black powder

[@williamjohansson691]

I opened one of those before and the EXACT SAME THING HAPPENED! The circuit board, wich also was ceramic broke off, like in the exact same spot! And the sense tip was actually a resistor almost cut in half, and the other long leg connected to the circuit board. And it was also a pain in the butt to get the plastic out of the housing, and i might make a new one out of the old pen.

[@broderperdurabo]

I acctually built an help with the design of those (Hi from Sweden).

[@betterbackwards2701]

Great vid mate. RIP probe😞😞😞

[@daniellassander]

If someone cant figure out that metal conducts electricity, you really cant help them anymore, they will just find another way of dying. So you end up with warning labels saying "caution sharp dont put against any body part" on knives. Or stones with a warning label "very heavy do not put on chest." So they end up not watching both ways before crossing a road. Edit: and the old once was a lot better.

[@PeetHobby]

Those probes started as a high-end product, and later other companies made low-end variations of them.

[@absurdengineering]

That final gate stage could have used three gates in parallel and no need for the transistor then.

[@daveschmarder-1950]

When the schmidt hits the fan, it is taken to bits.

[@MH-wz1rb]

A double diode, huh? Your tester decided "this is technically a transistor, the best kind of transistor"

[@Graham_Langley]

6:25 Sorry Clive but that's a simple rectifier, not a charge pump. A charge pump is coupled by a capacitor with a clamp diode or a transistor if you want to get fancy.

[@TradieTrev]

I don't like the idea of a ceramic PCB for a volt stick! Surprised it was still working prior to the tear down lol ;) These days we are so spoilt when it comes to modern DMMs! My uni-t 210 has a kick arse 5 step NCV but I'm still yet to find a design that can play chip tunes or mp3s :P

[@sntsander]

Even if it was an insulted body, I would not use it. These devices need to differentiate between a defective state and idle state, like the fluke tester does. The fluke tester flashes in idle state.