Maybe we should introduce a "BCA" marking on units that are "Big Clive Approved" !

It was interesting to note your comments on these relays. I bought a voltage controlled relay for charging a second battery on my van, supposedly rated at 20A per circuit(2). The cover was just a simple sleeve and despite the attempt to scrape the markings off the relays it was possible to make out that they were only 10A rated and probably cheap ones actually only capable of carrying at most 5A. He was extremely rude when I started an eBay return. Even said most people just contact him and send things back (although he hadn't responded to me contacting him). My bet is that he claims he's never received the item back.

Splendid! I like it when they use those "Switches 10 amps, at least once!" relays. Being able to enjoy the audio/visual indicators that signal their operation, slash demise, is always a treat. Cheers!

C13 also got a hole burned into it from the arcing. Replaced plenty of those little Songle relays from them cooking the contacts, the 10A rating is very optimistic indeed on them. Years ago I needed some snubbers for a contactor, so looked up the price of the manufacturers one, sat down, then looked up the price of generic ones from RS. Also sat down, then went to the one local supplier and got 3 68n 4kV polypropylene flyback capacitors, normally used in TV set flyback use, and some 33R 5W resistors. A little overkill, but guaranteed never to fail, as those capacitors normally run 2A of 15kHz current through them in the TV set, so 50Hz mains would never even bother them. Resistors 5W because they were not much more than the 1W versions, plus had longer leads, as this had to go across the pins of the 11 bin base, so long leads were good. Put some supply filtering in as well, 3 4uF 450VAC motor run capacitors in star, so as to handle the current spikes from the contactor as it was rather rapidly switching, which is why the snubber was there in the first place, wanted plug in relay to last longer than 6 months. Old Brown Boveri took 40 years to fail, but seeing as the new ones were Omron plug in, much better than needing to do wire surgery, just plug in the spare. Old Brown Boveri failed because the steel of the core mushroomed out, jamming the core up in the housing, not from the contacts failing. When they said 16A there, they meant it, not will switch 16A, or will do 100k cycles. Brown Boveri meant that, at 16A inductive load, and 100k cycles, they will not fail, and would still look almost like new. They probably were well over the 50 million cycle count. Not made like that any more.

Many pir's are designed for a couple of 100w lamps at most, but people use these on 300w (or more) halogens, i've seen several that the contacts have simply overheated (or the circuit track) It's much better to use a pir to control an external relay, and let the relay switch the load Incidentally, i just found a similar one that's advertised as 1200w, but zooming into the label it says 300w (on amazon)

It's always very instructive to see failures and sleuth the cause of their demise. Thanks!

This looks to me like a case of over current…. Perhaps a seized pump ? And a 13A nail in the fcu ? These pir things usually power up in the ‘on’ state …….. awesome videos Clive, keep up the good work!!

Once again I watch one of your videos and I'm amazed how interesting you make a subject, that in normal conversation would make people fall asleep.

It's fascinating to me that someone would be able to design an operational circuit without the understanding of mains clearances. I'm just a little hobbyist, and any time I've built something for mains voltage, I lean toward the ridiculously cautious. Sure, why not have 10mm of clearance, and add slots between just in case.

This has brought back some very vague memories of working on an unit that had a plastic housing identical to this including the trim adjustments. I do however remember it having a through-hole multiple opamp, can't remember if dual or quad, but it was a chip I had used in university in the analog labs so I recognized it at the time.

I think the relay contact got hot, burnt up the PCB over time and compomised the isolation properties of the PCB up to the point when the arc jumped the carbonized PCB... The PCB design is dreadful.

On the subject of snubber networks, old rotary dial phones had what we called the spark quench circuit across the impulse contacts. They were also found all over equipment that used relays, which is why it was so rare to find burnt contacts causing faults. Of course, failure was usually in the form of what we called "low insulation" or LI faults, and was never spectacular, just noise (crackling) over speech, or where no speech CCT was involved, strange behaviour of equipment.

I have on of those on my garage light. Installed ages ago. I have this urge to take it apart and compare it to the circuit board design of the 2018 one in your video.

Electric current smells. Since my first AC transformer experiments in the early 196ties I found this wisdom proved a plethora of times.

There's nothing like a good catastrophic failure. The more spectacular, the better. "Sniff... Ah I Love The Smell Of Burnt Circuit Board In The Morning"

In our 5th grade classroom, a kid next to me said "I smell burning raisins!" moments before a florescent fixture above popped and smoked. Every time I smell burning raisins, I recall that kid's face.

So close to a decent product. Interesting teardown and analysis, as always

The vise of knowledge should be paired with the hammer of curiosity for the really tough jobs.

The real problem with having such inferior products in the market is they create a demand for cheap goods, which creates pressure on otherwise safe product manufacturers to cut corners. On top of that is the fact that its impossible to tell whether something is safe or unsafe without doing an expert teardown. (Price is a good indicator but insufficient, because nothing stops a disreputable vendor from marking up the unsafe cheap products to the same level as the safe expensive ones.) We are going to have a number tragedies reminiscent of 19th and early 20th century West before this phenomen get fixed. Which is why BigClive's channel is a service to humanity, if you think about it!

You could have a look at some of the Shelly products. Especially the Shelly 1 or the Shelly 1 PM. The actual relays inside seem so miniscule for what they are (aparrently) rated for

Always grateful for someone who suffers that terrible smell and shows us what has happened - thankfully *Smellivision* is still a long way off!!

Those pipe grips are the best nut crackers you can get.

YES! The Vise of Knowledge! We don't get to see that tool often enough.

We Merkins in 120 VAC land have it easier than the rest of the 240 VAC world. Things are not quite as catastrophic and 'fun' in the fireworks sense. We do have failures but with half the voltage, the results are not as spectacular! My torture toy when I was growing up was an old TV transformer not much smaller than a microwave oven transformer. It had a HV winding that put out about 700 VAC - I didn't bother with the center tap. 😂😂 I tortured a lot of 1 watt carbon comp resistors with it. Thanks, Clive for bringing back the memories of the smells.

What an interesting experience. For a moment I thought I got smell-o-vision. Turned out some dump truck next door somehow started burning up a belt or whatever it was, while I had the window open. Have to stop watching the video, have to get some coffee and snacks and watch them try to get the thing back running again. Molten belt seems to have fused quite nicely with a melted pulley and they don´t even get the thing started again.

I love when one of your videos hits on a problem that I've been having with arcing contacts. And I have the components it fix it.

Thank you for another great video. Thanks, especially, for the Snubber Network explanation

I must comment, I was just watching you tear apart this unfortunate PIR unit, and my mind was wandering. I thought "Well, dissecting a HUMAN is called an Autopsy, dissecting an ANIMAL is called a Necropsy, so what do you call dissecting an ELECTRONIC corpse? Why, a Techropsy, of COURSE! lol LOVE your channel, you're always a hoot!

Good explanation of the use and reason for snubber networks. You'll find them across semiconductor switches too (mosfets, bipolar transistors, IGBTs) too with inductive loads to limit the rate of rise of voltage dV/dt from the flyback effect when the load is switched off. Before they were as well understood it was not uncommon just to find a capacitor with no current limiting resistor across switch contacts. I had an amplifier like this with a C across the mains snitch directly and on an occasion I was doing some servicing, found that this capacitor had obviously been subjected to a large current that had blown it into 2 pieces and the foil inside had unwound like some Christmas decoration. It's now in my rouge's gallery along with other remarkable instances of total destruction like the KT88 power output valve that dissipated so much power that the anode melted and fractured its glass envelope due to thermal shock and an Altec compression driver diaphragm that was so overloaded by amplifier clipping that the aluminium dome ended up like confetti. Curiously the driver still made sound since the voice coil hadn't itself burnt out but it was fabulously distorted.

I try to assume that any relays that are not from reputable sellers are going to be no more than 12.5% of the rated value...I used to assume 25% but to my detriment :(

2:15 that's usually my response when somebody asks me if I could open something for them. "Its not a matter of being able to open it but a matter of being able to close it again." 🤭

The leakage current from that snubber circuit is more than enough to drive a solid state relay, but not a mechanical one. Leads to some fun problems when "upgrading" equipment.

Street light collector Mike Barford from streetlightonline gave me a Royce Thompson Monostar 1000 NEMA photocell that had water ingress, this had caused tracking across the Common and NC relay solder joints, in turn burning the PCB under the relay to a crisp and melting the relay, it also burnt a hole in the casing of the cell. I managed to get the thing working just by replacing the relay and bridging one trace, those things are bulletproof!

I raided a couple of PIR modules from my dad's outdoor light assemblies when he bought self contained LEDs. One has a mechanical relay, the other a solid-state relay capable of half brightness. The first one, I'm going to "upgrade" it by having the line output push a relay or contactor. I've got enough of those laying around that I've got options. Maybe that 4PDT, or that NEMA 0 3ph...

I'm always amazed at the amount of development or should I say guess work that goes into Chinese circuitry.

TOS been a long time we last seen the vise of knowledge or X-ray, was beginning to miss them.

And suddenly I vividly remember that foreman during my apprenticeship that would rip screwdrivers out of our hands if the size was like one size off for a screw… also he told us screw drivers aren't prying tools. We really learned a lot.

I work with security systems and a lot of access control equipment comes with something similar to the encapsulated resistor and capacitor which you showed (or it's recommended that they are fitted). Most of our kit is 12 or 24 volts DC and those the snubber devices are fitted across the relay terminals and across positve and negati0ve near to the lock, which tends to be an inductive load like a solenoid bolt or a maglock (electromagnetic lock).

Always promising when Big Clive has to bring out the Clamp Of Persuasion!

Love your videos Clive. Haven't watched is a little while, not your fault of course. Thanks for all you do. Your one of my top 5 youtubers.

The "vice of knowledge" - if I heard that right. I love it.

Nice teardown Clive !

I'm curious if this PIR matched the power of the pump that ran that "water feature" and whether its inrush current ablated the relay contacts, since those things can be triggered repeatedly by birds and falling leaves etc..?

This is almost exactly the same PIR module that i used to revive an old halogen motion detecting lamp - and due to the magic of having bought two, i have one open here. Mine has a date code of 2019-12-29 and is thusly slightly newer than the burnt up one here, but yes the non-existent spacing between the relay output and neutral is still here in this one. (Now feeling that if i ever use this spare module, it will be with some extra safety mods... like cut the neutral near output, use a seperate snubber, add a fuse..) The relay model in mine claims to be a DAOHENG DHT78-A-24D-SS, rated (or "rated") 5A/250VAC, 7A/125VAC, 20A/14VDC. (Hopefully it is better built than that burnt up one lol). Looking at the PCBs, the differences between the one in the video (2018) and mine (2019) are mostly PCB component options, mine has one extra hole for different length resistors for R1, and the removal of the through-hole option for C9 (that one is a bit odd, why remove unused pads? just to drill less holes? hm). Also my CDS light sensor has been mounted up way higher (next to the PIR, not down low) than the one in the video.

"a resistor of unknown value because it's cremated"

Idk why I laughed so hard at “A resistor of unknown value because it’s cremated”

Thanks Clive.... I've been filling up the comments sections of my favourite electronics channels with "can you explain snubber networks please" for ages.... :)

Thanks for another great video Clive 🙂

Very interesting and odorous item! Do you think that the relay's demise could have been hastened by having to switch on the locked-rotor current of the "water feature" pump motor; as opposed to a light which this was surely designed for? Or; at turn-off; the inductive nature of that same motor might have overwhelmed the voltage rating of the snubber network capacitor?

The relay could probably switch 10 amps... ONCE!

The cause was probably the water feature (likely pump, inductive load) overloading the relay. Such mains automation things usually have two figures: for resistive loads and for inductive.

Love the vice opening technique....

The first thing I would check for is a short or overload in the water feature. Excessive amperage could easily start the failure cascade you see on the board. Of course, an underrated relay would produce the same effect.

Head on the nail there. That relay wasn't up to the task (under dimensioned). It started to arc, and the rest was just a slow chain reaction. I've seen these very exact devices myself, and they've failed the very same way.

For a minute there I assumed you branched off into modern art appreciation.

The "Pipe Grips Of Knowledge" seen at its finest!

Hurrah! The Vise of Knowledge. Perhaps the next one should be the Saw of Wisdom ;-)

03:15 WOW, you could sell that close up photo as art.

Those relays don't like capacitive or inductive loads. That's why finding a PIR that allows more than 100 W LED or 5-8 light sources is hard to find. You will need a contactor to take up the load. I don't know if the astro clock I put in will survive since it controls a lot more light than I like. But the customer is always right.

I love that fried electronics smell in the morning. Aaaaahhhhh

Very interesting - I hadn't realised that about snubber networks and LEDs (explains a lot!). Basically I guess just ends up a capacitive-dropper. Interesting too that if you confidently put a label that says 240v on the outside, they might hope to get away with under-rated components on the inside.....and I guess for a while at least, they do get away with it. Kinda sad really.

A resistor of unknown value because it's cremated. Gold!

Nice forensics for that poor relay 👍🙂

Water feature--inductive load perhaps? That could be part of it. With resistive loads, these things usually last quite some time.

I love the smell of hot plastic in the morning...its smells like victory.

its so fun investigating burned stuff like this. i feel like a CSIS agent.

the funniest thing is that as you kept mentioning the smell... I could almost smell it myself. I know this smell so well. :D

The picture at 3:16 looks like a piece of modern art :D)

A very good Thursday morning to you sir

Interesting internal construction. I'm using a bunch of eBay 12V PIRs to control external LV LED lighting. Ours use two PCBs, the IR module and the 12V PS and relay PCB. So far none of ours have let out the magic smoke but we have had a couple of dead ones over the years.

Happy Thursday and I hope all is good with you.

"Squeezing the base." Ooh Matron. 😁

I don't think these devices were ever designed to be used with an inductive load (water feature pump as mentioned). Have used many of these with a great deal of success but only with low powered lighting. Yes the tracking dose look a bit skimpy but I don't think that's it. Remember these things are built to budget and once in a while a defective component will show its head. Great video by the way 👏

very likely, whizz poor contact materials within the relay failed, overheating and melting the solder at the board, then the board starts charring and ZAP arc over. this happens on tons of appliances, (fridge, freezer, washer, dryer, dishwasher, oven, microwave, hvac boards, thermostats, garage door openers) yeah I could go on and on, but that's plenty to get the point across. alternate ways, thunderstorms and lighting arced across leaving a carbon track. it got water inside and fizzled away.

So fun to see the pir sensor I used to use on the channel

This picture of the relay looks like art! You could sell prints of it, I guess 🙂

@2:04 I actually expected you to use the X-ray ;)

And this is why you "never just replace the fuse" 😂

Thanks from Texas Clive

quite informative. wonderful as always

I bought the 12v variety of this PIR sensor and found it massively unreliable on my off grid 12v outdoor set up. Watching this has made me think otherwise on messing around with it further

On mention of it controlling a water feature my first thought is it's beig used to switch an inductive load.

Good quality relays that are properly designed and manufactured can run continuously for many, many years at full load. The problem is that cost cutting and the grey market has and is continuing to undermine safety and reliability. If it’s cheap, they have had to cut costs somewhere. Why pay for a qualified experienced engineer when you can get someone on a significantly lower wage to copy another design? Why use quality parts when you can use cheaper parts? Why include parts that don’t affect its basic operation (never mind the safety benefits they provide)? Everyone loves a ‘bargain’. Until it goes wrong… And it’s very difficult, without having the knowledge, to always work out if an electrical item is cheap crap inside… If you go to a British, or European well known electrical/electronic supplier, such as RS, Farrnell or any of the others, if you search for and find a suitable good quality relay (24V DC coil, 240V 5A contacts), the price of this will be a significant proportion of the cost of a complete grey import PIR unit… For example, a reasonable relay may cost between £1.15 and £2, but on eBay a complete PIR unit from China costs £7 to £9.

Oh, a Barbequed and crispy PCB and components, looovely, LOL. I wonder if it was down to inferior parts and should have been recalled.

Regarding *copying* a design. I ALWAYS warn against this since you'll include any original design iffy's without knowing they are indeed dodgy and likely add some new errors yourself ! Especially true of PCB layouts. It's highly important to explicitly point out layout specifics like clearances and components that dissipate POWER. I had a board laid out including a 1,3 W zener diode where it needed some heatsinking using large pads/copper land. The layout guy couldn't find the space and made them vias. After some days of use that diode was effectively *welded* into the board although it didn't fail !

I can smell the burnt electronics from here in the USA. Sheesh Clive, put that lid back on ;)

oooh, I can smell it without having it closed, I was actually just this week replacing a PCB at my job that had a catastrophic fuse failure making the PCB burn in flames which stink sooooo bad too

Hahaha from fried electronics to zapping sausages "smellevision" would suit this channel 😜

I truly miss the ale sipping breaks.....

20 years ago one of those relays stuck closed in a bread machine, had the heating element on for some time and smoked out the apartment pretty bad. The bread machine never caught fire but it turned the bread into a small cube of carbon carbon. Since then little tiny 10 + amp budget (or now even grey market) relays always scare me when they switch any actual current (over 2 amps). If I could I'd like to rig up a good test setup with lots of amps and try a few.

There's a security light that pops and fizzes on the wall outside my unit.

Clive, you might find interesting a video I just put up on the Dollar store "$1.25 these days" LED lamps in the USA.

A new episode of CSI (Clive scene investigation) with an impressive forensic analysis of the murderously destructive current levels.🤣👍🕵

I think the clue is in the original covering letter "Water feature" to me indicates bl00dy big inductive pump, I suspect the relay contacts draw an arc when switching off creating so much heat the PCB turned into a resistor. If I was Toni Peters I would be checking that the new PIR is rated correctly for the water feature Load.

"the vice of knowledge"?? God I nearly choked on my vodka! rofl.

I repaired a PIR light a month or so ago, the fuse wasn’t soldered in properly (inline) and the wire had fallen off!

Near the beginning the live connection in the choc block looks like it might have gotten rather hot, and the insulation on the live wire going into it looks as if the cable has gotten hot as well

soooooo it had a live-neutral spark gap. nice.

Excellent video thank you

we need to get a stink counter