Good versus evil socket testers. (with schematics)
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- Опубликовано: 17 янв 2018
- One of these socket testers is great and one has been over-engineered with lots of extra weaknesses as a result. In hindsight I'm wondering if the hot resistors (110C) were masking the transistor or if the transistor itself was getting that hot. If it is dissipating about quarter of a watt then it should be within its capability.
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Наука
The earth fault LED is s really good idea, because if you press the switch and the RCD doesn’t trip, it’s easy to doubt the tester, and assume the RCD is okay (it’s a safety device after all). But having a red LED come on shows you that the tester is responding to the switch push, confirms it’s working and the RCD is bad.
I agree with you.
I think its a nice feature, and also a really simple circuit.
more buttons = goodier
I think that the LED that lights up when you push the button is quite a good idea because if you push the button and the RCD fails to trip then the first thing you are going to think is "does the button work?" Then you're going to risk your life connecting a resistor between the live and earth any way. It would be better still if the current in the LED was the same current that was used to trip the RCD. It would be even cooler if it was a black light that lights up black when you press the black button.
exactly, I've had test buttons work intermittent, unless held down and wiggled about.
And if it successfully trips then you can see how quickly it did so.
I've been LOOKING for DED's for YEARS, no one seems to source them. (Dark Emitting Diodes)
You know what else would be cool? If I could breathe vacuum, I could flap my arms and fly to the moon.
The Duratool was probably designed as an aromatherapy device for dodgy electricians to say, “Oh bloody hell, you’re lucky I arrived in time.. Can you smell that? You need the house re-wired!”
We need a mains tester tester for extra safety.
Okay, who let the OSHA guy in here??? (obUK - H&S guy)
Then we'd need a mains tester tester tester to make sure the mains tester tester was up to the job.
Okay, you put this wrist strap on, which is connected to this Tester Tester Technician Tester, which I will hold in my hand, while you operate the Tester Tester...
Yeah, I think you're exactly right: the button-press indicator is so you won't have any doubt where the fault is if your GFCI outlet doesn't trip. The last thing you'd want is for someone to think it's just a bad tester and to wind up cooking themselves with a hair dryer instead of just fixing the wiring or replacing the outlet.
Please start saying "Computer, enhance image." more often when you zoom in.
Virtua Tom I'm fine with it every so often, but not every time.
Kinda makes me want to see him take a smart-speaker (like the Amazon Echo, for example) to bits and compare it to ebay knockoffs.
Yeah, you should say enhance
It would be like a joke you've heard many times before if said all the time.
Enhance 224 to 176.
Enhance. Stop.
Move in. Stop.
Pull out, track right. Stop.
Center and pull back. Stop.
Track 45 right. Stop. Center and stop.
Enhance 34 to 36.
Pan right or-and pull back. Stop.
Enhance 34 to 46.
Pull back. Wait a minute. Go right. Stop.
Enhance 57 to 19. Track 45 left. Stop.
Enhance 15 to 23.
Gimme a hard copy right there.
Actually, epoxy transistor packages that size are *better* at dissipating heat than, say, a TO5 metal package. Ferranti figured that out a long time ago with their ZTX transistors. Ferranti is long gone, but the semiconductor operation was spun out as Zetex, which is now owned by Diodes Inc.
Quick firtle on google... ZTX753 rated at 1W at ambient 25 C, derate at 5.7mw/deg C for higher ambient. Storage and junction temeperature range -55 to +200 C. Which is a lot more than epoxy packages could handle 30 years ago. It's a higher max junction temperature than was typical (175 C) than 30 years ago, too. Oh, max Vceo is 100V. But there may be others in the ZTX range that are rated for the job.
Anyway, 110 C for that transistor is not scary. Assuming they're using decent epoxy. The circuit is fucking stupid in the first place, but the choice of transistor type may not be.
For some reason I'm really taken with that round print off of the last circuit, it really looks like you have a giant circuit board in front of you. I feel like it should be made into a round cushion...
I would buy one
Matt Tester I hope not on all. It would certainly look "traditional" on christmas lights, but also a bit washed out. And I really enjoy the vivid colors that LEDs can create.
The weird one was probably designed by someone who had heard that you should use constant-current drivers with LEDs instead of just a resistor, and then looked up an example driver but didn't bother to determine the power ratings or change any of the component values from the example. I'm willing to bet that exact circuit is in a textbook or on electronics stackexchange or such. It's a very "new grad" (or even still a student) engineering feel.
It does have a student feel to it. Where the lessons of real life have not been learned yet.
That actually makes sense. The circuit was over engineered, something that students do quite often because of the lack of experience.
And it goes in every field i know of. The masters of their trade usually prefer something simple and reliable.
More likely they thought it would be a good idea to keep the LEDs visible even if the supply voltage was low
Yes, that's a big part of why one would use a constant current driver. But that doesn't explain the design of that driver being unsuited to the task at hand. Especially when it's so simple to do it better, and so easy to notice the problem in the simulation and prototyping stages. Even as a student I always ran a test of power dissipation for all components in SPICE as part of my worst-case analyses. The professor gave the class a project to build an audio amplifier that had a circuit specified (including all components) but no layout or other info. We had to analyze it, build it, and demonstrate it working. My group had heat sinks on our PCB, one other group (out of about 8) did. The rest let the magic smoke out. You'd think they'd have figured it out from the analysis graphs and the datasheets, or at least have tested it, but many didn't. It wasn't until the end that they got the lesson.
Most students probably didn't have professors give such a project, and so never really thought about thermal design considerations or simulating & testing everything properly. Learning through failure tends to stick rather well.
Hah. I like your professor.
The rare case where removing components improves the circuit. Normally things are value engineered to the point of insanity.
mozismobile not from China direct
Not in case of Fluke.
I blame Germany.
The 100R resistors are for safety. The axial types that have been used typically "fusible resistors". Once this resistor/fuse combo reached an overload situation it will die open and without causing fire. - somone must have read the EU safety standards when designing that thing ;-)
My thoughts were also that Handyman has fusable resistors as a protection device. It seems a very good design, should have no problem with voltage either unlike the designs with only a couple smd resistors in series. (SMD resistors can have very low voltage rating!)
Great video Clive. Always keeps me coming back for more.
Yay, you saved 3 innocent transistors!
he cut legs off... they die
All they needed was a power resistor in the collector circuit to off-load some power dissipation if they wanted to use that current regulator.
Another very informative video, thanks Big Clive
So... watching bigclivedotcom video on some crappy socket testers with a glass of Bushmills whisky right after watching Ralfy's review of some other whisky - a nice way to spend friday evening ;)
I'm just preparing for my Friday evening, but first I'll make a video.
Cheers then :)
I did not know Ralfy had a channel, still catching up, about at 10% watched so far LOL - What channel?
ralfydotcom :)
+Slawek B. - Aaah TY!
Wow a pic 1208C I havent seen one for years. I used to use a lot of them. Ordered them from Maplin in the days before it became a toy shop. I used them to chip the old PS2 so it would play all games.... Now I feel old :(
My theory as tobwhy the light for the GFI button is there: If you push the button and nothing happens, there are two possibilities; 1. The GFI is faulty or 2. The tester is faulty. The light helps eliminate the second possibility.
I'm eager to see a reverse engineer on the Fluke now, yesterday at work we had a preempted warning from Fluke that they're going to issue a recall on all of the SM series socket testers for some reason, we've been ordered to stop selling them all together for the time being! Thanks again Clive!
I wonder if it's electrical or a failure of the case seal risking them falling apart when bumped about in a toolbag.
Clipping off the transistors at 9:48 reminds me of Earl "Madman" Muntz, who manufactured TVs from the late '40s to '60s.
He often carried a pair of wire clippers, and when he thought that one of his employees was "overengineering" a circuit, he would begin snipping components out until the picture or sound stopped working. At that point, he would tell the engineer "Well, I guess you have to put that last part back in" and walk away.
When I worked in TV repair shops in the '70s I repaired a couple of Muntz TVs.
They were simple, but not cheaply made.
That cut out enlargement was brilliant.
It wasn't a cutout.
He used his Wambo beam to enlarge the actual circuit board.
I recognize that current limiting circuit. I first learned that one in my freshman year in college during a digital design lab (current source for an autotrading DVM). Used it frequently ever since.
It looks like a complicated way of covering all voltages from 100 to 240, but they could have sized the resistors for 240v and allowed it to be dim at 100v and 120v and no one would care.
Clive, after seeing your illuminated loupe in several episodes I decided to go ahead an buy a 40x loupe. OMG, what a difference it makes! I can actually read values on surface mount parts and spot my many solder bridges.
What happened to the vice of knowledge? Not seen it for ages.
mintyfreshpenguin on holiday with the screwdriver of certain empailment
I like the hammer of knowledge myself.
It ran away with the explosion-containment pie dish :D
Buddy Clem the hammer of knowledge made a come back in the latest video.
The constant current circuit has been designed by someone with a basic electronic knowledge but no common sense, probably someone fresh from college. As is normal practice the zener diode current has been set at 5mA because that's the current at which the zener voltage is specified. If you were to operate it at say 1mA then you wouldn't get any clue from the data sheet as to what the voltage would be.
17:20 , this is gold right here
love you big clive
Please keep "enhancing" when you zoom in. It's fantastic.
Excellent máster!!!! v.g.👍
It is meant to double as a kettle element?
Solder Joe I don’t think so 😂
Oh, you don't want to know what I think, mostly because my mind is just filthy... :P
That last picture though of the cut-out picture of the PCB, that should be mounted in a round frame and hung on the wall, it looks perfect as some electronic art... :D
"Zoom in on that reflection!" "..enhance!"
Nerds understand why that is funny.
And the shows that take it too far to the point they can identify a suspect from one pixel.
The TV shows got it from Blade Runner. Please do feel free to take script cues from this scene: ruclips.net/video/qHepKd38pr0/видео.html
The LED for the RCD Test is not bad at all. When you see the LED lighting up, you know that your test device is working fine, but your RCD is not.
Meiestrix Also note that some modern RCDs (they have an extra P in their name in some markets) are certified to trip even if the leak is true a diode. Ideally, those would need two test buttons connected through two different LED+Diode circuits (press both to simulate an AC leak).
the "enhance" works for me :P
4:21 - also reminds me of Star Trek, where the captain's order "On Screen." was invariably followed by "Magnify."...
Another great vid. On a slightly different note could you do a video on building your own bench power supply?
I think Julian Ilett has a few videos on that maybe? Though a Clive-designed power supply, hmmm, what evil could be put in there :p
The reason for the constant current drivers is simply because that circuit will work with same LED brightness at both 220V and 110V. So basically its the same PCB sold all over the world and just put in different housing.
Yes, its overkill to limit current that way unless you wanted it to work on several different voltages (perhaps the same circuit is used in a US tester?). 110 degrees is not a problem for a tester like this, its going to be used for seconds at a time in each socket is practice, and long term reliability isn't a design factor like it is for 24/7 equipment I reckon.
I'd be interested to see you compare the accuracy (and insides, of course) of a Kill-A-Watt meter to a HOPI.
The reason is, I bought a Kill-A-Watt a few months ago and some of the readings it gives me just seem right out. Like when stress testing my computer (Ryzen 5 3600x, GTX 1060TI, 16gb DDR4 etc) which has a 700W PSU, the Kill-A-Watt says it's only drawing about 120W. And my 3A USB charger quick charging a cell phone only draws 80mA according to it, while one of those USB Volt/Ammeters says it's a more realistic 1.5A.
I would have loved to get a HOPI just because you use them so much and you've always had such good experiences with them. And I love what I've seen of them. But from what I could gather from the pictures, it looked like it was for European plugs only.
Or hell, maybe I could even mail you my Kill-A-Watt and you could have a look at it. Just not sure where to get your mailing address. Lord knows it's not doing me much good here. I think my final test will be to hook it up to a 1200 watt microwave and see what it says.
I think I like the old ones with the neon bulbs better. I'm sure I still have one in a tool box somewhere.
The next updated socket tester will have a sign lighting up on it saying,
"Button Pressed".
I can see one possible feature of the constant current driver ... it would be quite sensitive to a N-E voltage differential
12:01 -- I suspect that the current sources ensue that the LEDs receive a constant minimum current throughout the half cycle during which they're active. Probably causes the LEDs to appear a bit brighter and probably also reduces flicker.
Loved the snip, snip, snip......no more transistors!
I was just looking at these on eBay and there is a new one, a smart and fancy Aneng AC11, with a colour display.
I bought one. They advertised it as a UK version and it came with a different plug and UK death-daptor with sleeved earth connection that means that when used together they show an earth/ground fault.
@@bigclivedotcom I am afraid I got enchanted by the beautiful display and bought one just a couple of minutes ago. Just as an afterthought, I checked the reviews on BangGood and exactly the thing you have mentioned got me worried - people had pictures of it with an adapter stuck on. The eBay auction had an option where I could choose UK/EU version, so I wonder what end will it arrive with. Ehh...an impulse buy, we'll see.
I hoped that you would leave at least one transistor on and wait for it to go bang.
The regulator should make it work from 20 volts or so. Even if there is a low voltage the LEDs should still be adequately bright.
And on 240 volts they are nicely bright, without any component dissipating too much. Otherwise they could have used 220K resistors and increased the transistor current a bit - but now the dissipation is nicely distributed.
Oh Clive - don't go for gadgetry like shouting 'enhance' - you are so nicely understated and calm... keep it so please!
Never before seen a white LED used in a colored package.
I wonder if the next generation of colored LED's will be warm white LED + phosphor, under a colored package.
It might allow for a more incandescent look to things again.
Some LED Christmas lights used white LEDs in coloured cases so the LED voltages all matched. Latterly they used all blue LEDs with the red, greens and yellows using coloured phosphors on blue chips.
I'm thinking that maybe they just wanted the indicator lights to be as bright as possible to be seen from across the room just in case. They may also have wanted to use LEDs with higher voltages to better fit their circuit. That's really the only reason I could think of for using the GaN LEDs. Possibly just sheer cost reduction.
Big Clive should do the tide pod challenge
I can't. I've eaten them all.
i really laughed at the idea of just getting rid of transistors if control circuit takes more current
I’m guessing they intended to limit the current through the LEDs (to make it work at both 100 and 230 V) but didn’t realise where to put the LED in the current limiter circuit.
Aussie50 mentioned you in a vid related to these device Clive.
Haha, I just found Aussie50's channel, awesome
Hopefully he can gain traction now he has a decent internet connection, he was on a very very poor connection last year and it was painful for him to upload. He now has better means to upload stuff etc, so I'm hoping to see more from him.
His extruder videos were very interesting, and the "just doing stuff because I can" attitude is great. Nice guy too.
Interesting, that's great. He's quite a character!
That blow up (circuit board not the doll) well done. I had taken my contacts out earlier I was squinting watching the video them, bam I could see. Then i realise 2 Big Clive videos awesome.
Is it possible that the current regulation circuit is used in the case that the voltages across them are not full voltage?
Hey Clive, in my opinion you do a great Job reverse-engineering al kinds of circuits. Then you present the Schematic which is a great deal in understanding the circuitry, at least for me. Maybe you could show us some recently opened Circuitry simulated in LTSpice. Also the whole "how do I get 10V peak to peak out of a 5V circuit" discussion (eevblog) might puff into pink smoke as you are clearly measuring "from here to there" (on screen) or the other way round, just to have a hands on explanation for what sh*t is about. Everyone could replicate a simple LED Capacitor Dropper for ecample...
My equivalent testers are all simply resistors and neon bulbs (plus a switch and resistor for GFCI test) in a really stout case. As a "Grey Beard Engineer" I abhor the seemingly excessive parts count in these units: More potential failure points.
Us picky old cranky guys are like that. LEDs are nice for some things tho :)
The square one, although I have I newer model that is different inside and shows the trip current on the display when you press the RCD 30mA or GFCI 5mA depending on the model says on the manual to no let it on the plug for more than 5 minutes, so the heating problem seems to be still there. But the 230V model draws only 18mA in 117V then you test the RCD that is not enough to trigger the RCD for testing. I saw some other that trigger the RCD in 117V so I suppose there is a 230V model and a 117V model although the model code is the same.
the ENHANCE was the best part
Well, we all know what you need to do next:
Design your own PCB for the shitty one that uses just resistors and diodes
That has been going through my mind.
the resistors will fail open-circuit ?
I'd say the reason for the sketchy design might be planned obsolescence. Funny that they even called it "Dura"tool, as if they wanted to stress how durable it is.
About the test button on the first one - If you push the button and the LED stays ON ... well, I guess maybe with a dedicated outlet, there might not be a sudden influx of dark to tell you a bad thing just happened. O:-) (Although, the rest of the LEDs WOULD go dark - if they weren't already.)
Try using manual focus for your videos, or center auto focus. I think that'd help.
A 2N2222 in a TO-92 case (which admittedly is not the same transistor you have, but is the datasheet I have in front of me) is good for 625mW. Theta J-A is 200C per watt, So at 460mW the rise would be around 92C. Add in about 15C for your room temp and you get 107C. Not too far off from what you are seeing. So it would probably work, as long as ambient wasn't too high.
But since the zener is drawing 5.5ma @ 220V and the emitter is drawing a constant 2.1ma, the LED is actually running at 7.6ma, not the calculated value. Brilliant engineering.
The LED on the RCD tester is probably stupidity, since in addition to the 3.3ma for the 68K resistor they have 7.6ma for the light. So the real RCD fault current they are running is almost 11ma, which is probably far above the fault current that some spec says should be the mandatory trip current.
I'm wondering what that transistors' base current was, pre-snip by Clive :p
...... Four things Scotland should be proud of,
Robert the Bruce, Colin Hay, Big Clive, and squeezing the Octopus !
6 years since a very handyman took a handyman apart:) Looked up your video again because i had a discussion about relying on a socket tester. Which that argument i doubt, and even could be very dangerous, but many do by the name alone.
Thing is, and correct me if i am wrong, the 3 light socket testers will / can not test a reversed Earth and Neutral but show the lights show as OK.
My reasoning: If you have a socket with a reversed Neutral and Earth. A toaster would work fine. But if there is a Line to metal case fault, current flows through ones PE wire but reversed in the socket back to the Neutral. A RCD would not be able to detect the fault, but the case is still live. which can in my opinion be potentially dangerous.
Is that correct?
And last, just a fun fact, MacGyver is out. BigClive is in. Heard in a recent sailing video when something was broken: "Well, looks looks i have to BigClive this..." :)))
Since new testers have a test button that puts a resistor between live and earth. If the earth and neutral are swapped the RCD doesn't trip.
BUZZERS! Electrician TV's video titled "Electrician tools Socket tester review Fluke, Di log, Kewtech, socket & see many more" explains why electricians like him only use the ones with buzzers.
Fair warning, his video style is quite......erm.....contrasting compared to Big Clive :P
IT IS SO COOL ...
iOS YooCh00B app is borked. Big Clive’s pleasant voice now sounds like a chipmunk on helium.
I bet they had some other feature that needed that crap and then removed it, but didn't simplify the circuitry afterwards.
When you push the RCD button, the circuit should trip, resulting in the LED *not* lighting. The LED is red because, like the red LED used in the line tester, if you see it, the RCD test has failed.
Can you do Mr. Heli on the next One Credit Champ?
Any chance of looking inside the socket and see one you had in a previous video..?
I'd like to see inside it, but it's quite an expensive one and is my tool-box unit. I get a feeling that it will be a microcontroller surrounded by lots of surface mount stuff making it hard to reverse engineer.
I've got the same one myself. Just wondered about the build and design quality inside.
In the fine tradition of Mad Man Muntz! Chop out components until it stops working.
I suspect the large resistors are some type of in rush limiter.
I have the Tacklife tester. The Chinese to English instructions leave a lot to be desired. There looks like another small indicator next to the ground fault test button. It is labeled "I delta n" with a "greater than" symbol -- what does it do? Is it supposed to light if something is wrong, or not light if nothing is wrong? (Someone could make a good living in China offering their services to rewrite badly written technical instructions for company's products.)
someone should send him a flat calculator, so he doesn't need to hold with one hand and time with the other
he has one and its GIANT
The real problem is that calculators' buttons, SO darn often, miss 1/3 of the keypresses you do on them - Makes using them for math at all distracting and risky in terms of bad results.
Never seen these testers before. Got nothing but the standard neon ones here in the USA, kinda prefer the GFCI ones Not entirely sure I wan't them to get confusing with more circuitry .. More likely they'll fail. imho
Could have been boring AF, but not with Big Clive at the helm; was interestingAF!
Can't wait for you to get to the Fluke. Many people like their products but after two Fluke meters I had died I am not a fan. Both had absolutely poor case design with no webbing on screw mounting "poles". The plastic on these poles just crumbled causing the contacts to come off the rotary dial to not make contact. Actually that meter is electrically fine but mechanically failed so useless.
The Brymen BM235 has been really good for me CAT 4 UL listed got all the other things fluke has and is a bit smaller.
Inductor back EMF I googled it and the first thing that came us is EEVblog. Dave is good at his stuff so I am sure its fine. If I didn't have a decent meter that works for me now I would have considered supporting him.
Right now I am using an Extech set with a clamp on and typical multimeter set. It exactly replaces my Fluke 112 typical multimeter and Fluke 322 clamp on.
I do not do extreme testing so any decent meter will suit me. What pissed me off with Fluke is they charge high prices but the meters failed due to poor design. I have the pictures to prove it. One day I will do a video on it just to ease my mind. Right now I don't have enough views on my videos to affect their sales by even one meter.
meanwhile my 1993 dated 87 has yet to go wrong
"extech" "extreme testing"
I always liked Square-D, but they are expensive.
Designers making a statement or getting more money for including more circuitry?
i got the duratool plug tester it seems fine
How can these devices tell if live and neutral are reversed? I always thought both was exactly the same since its AC. It will power a device regardless of how its wired. I remember when I got my smart meter fitted, he had to take the unit apart again because he'd reversed the mains live and neutral.
+micheals1992 Normally the light connected between neutral and earth will not light because they should be at the same potential. If live and neutral are swapped that light will illuminate because there is a voltage difference.
Why was the handyman made using a double-sided board? It looks to me as if it could be easily done on a single side.
I see a lot of products that do that. I guess that they consider double sided standard.
Hmm, anyone else not seeing Bigclive, AvE and EEVblog in their subscription uploads?
Might be more, but I noticed these weren't in there.
RUclips has been doing lots of weird things including unsubscribing people at the rate of over 1000 a month and turning off peoples notifications. If you go to the homepages of these channels and are still subscribed, then click the bell symbol and you can possibly re-enable notifications there.
I checked and saw I was still subscribed. But the bell didn't do it for me. I unsubbed and then resubbed. Now they are back.
Coincidentally, only tech and engineering channels' videos disappeared...
Happening to me too. It started months ago and is gradually getting more frequent...
Not happened to me yet but I imagine with us knowing about it we can watch for it!
And Cody's Lab can't upload anything...again
Thanks for the explanation on the green LEDs, I got a bunch of them in a ebay pack and well, I thought they we're just shit. well, they are... you know what I mean :P
The old gallium phosphide LEDs are a dull apple green. Not very efficient, but super-rugged and will totally outlast a modern gallium nitride green.
I use one of the Fluke CM100 socket testers as shown in this video and just had an interesting product recall, asking me to stop using and return to the supplier immediately for a refund. Apparently there is a risk of any metallic parts of a socket becoming live during testing. Any thoughts on this based on the design?
Sneak preview of an upcoming video....
ruclips.net/video/_KOYt-0WZxg/видео.html
Great explanation, thanks for the sneak preview!
CM100 sent back, T90 on the way - Better than the £18.76 refund Screwfix were offering. Thanks for the tip!
Clive I just bought the Handyman TEK989 on the bottom of the unit it says “THIS UNIT WILL NOT DETECT EARTH NEUTRAL REVERSE” why is this? Can this be checked with a multimeter?
Earth and Neutral are connected at the local supply transformer and often connected at the point they enter your home. It's only possible to tell if they have been swapped by looking at the wiring. If they are swapped then things will work as normal unless there's an RCD fitted, which will trip repeatedly. It's not recommended to use the earth wire as a return conductor though, because a fault could result in attached appliances cases becoming live.
That's pretty wild. Mine just has three neon lamps and nothing else, and I have to believe it's more reliable than this complex silliness. :D Violates the K.I.S.S. principle. ^_^
IMNSHO, Fluke shouldn't be making trivial shit like outlet testers, but maybe they can't make profit on good test instruments any more.
Oh Fluke, how you disappoint me...
"If it works, it's a Fluke..."
You seem to assume there are viewers that have an inkling of what kind of apparatus this is in this here video
And he would be right ;-)
+adriaan van harrick - These tell you if your electrical socket is wired correctly, or miswired so that using it could electrocute you / cause a shock. There are 3 wires - Hot, Neutral, and Earth or Ground - Hot is "Hot", it's the live wire - Neutral is the return wire to the electrical panel, and Earth is for safety (so if you have an old metal cased power drill, for example, and the Hot brush breaks, shorting to the case, you don't end up dead, instead you see sparks flying then the breaker pops or fuse blows.) Anyone serious in Electrical matters knows - And now you know as well :)
I'm surprised that would cause the transistors to get so hot. Most TO-92 package transistors are rated for maybe 0.5W, so 0.22W wouldn't have seemed totally unreasonable. That said, I think most 0603 or 0805-package surface mount resistors are rated about 0.1-.125W, so I think they would be the more likely candidate at 0.275W... Either way, that's some majorly sloppy engineering by the designer.
transistors* fixed.
The extra circuitry is just to make it cost more.
It was designed by the bloke who will go on to found the Sirius Cybernetics Corporation. Share and enjoy!
You did it Clive! "Enhance" ahh now I may die happy.
I came for the schematics
Maybe the 100 ohm resistors are removed for 120V ?
It would make a tiny difference. I really don't know why they are there.
bigclivedotcom They are fuses. Ideally they should be dimensioned to reach their trip/blow power dissipation at an appropriate current using the I²R formula and the data sheet. I would estimate that a 100ohm would be set to blow somewhere between 50mA and 250mA, but the Vishay data sheet I used specified their model NFR25 might only increase to 10kohm if blown.
My colleague has designed a fair few socket testers including the one Clive didn't open up. (I don't blame him, it would be scrap as it's ultrasonically welded.)
The great advantage of having a processor in there is the ability to present more advanced diagnostics - for example swapped leads, missing leads, polarity reversal (if you have a touchpad). Processor-based measurements can be more precise allowing a design to be optimized for phantom voltage rejection (if for example you're testing a socket on a long feed with a fault at the far end).
It's actually the LEDs that consume most of the current, particularly when the chinese factory won't pay a few more pence for a high efficiency green. The limit is you don't want to trip an RCD when you have an open Neutral, and also how much heat the box can handle. Capacitive droppers cost too much so it's resistors all the way.
The one I've not opened up yet (because it's my main work one) is now actually a standard recommended unit in the broadcast industry for quick tests on small lighting and sound rigs. I notice it's also widely used by utility companies as a fast test of the basics after a meter change. There's also a suspicious clone of it being sold on eBay.....
Ooh do share the eBay link. I expect it's crap, but you never know ...
I'm looking for a particular video featuring Ipad zoom feature (box under recorded object). Which video was this?
I believe it's the uranium glass and thorium mantels video that has the super zoom feature. I remember it having the Geiger counter.
+kjur18 Geiger counter.
Thanks. This computer enhance thing reminded me of this.
Only half of the 220v is available through the diode into the 40k