Rocker switches - imported Chinese rubbbish! (RANT ALERT) - Page 1
Forum section: electronics / general

author: brian_mk
author_rank: Regular Contributor
timestamp: December 12, 2021, 01:20:52 pm
content: I needed a SPDT mains rocker switch for a project.Foolishly, I looked on eBay and found a pack of 5 rated at 6A 250V.When they arrived I tested them using my trusty Fluke DMM.One was intermittent and had an ON resistance of 20 Ohms.The others were also intermittent. The ON resistance varied - sometimes up to 1 or 2 Ohms.2 Ohms at 6A gives a power dissipation of 72W.If a switch gets as hot as a 6OW tungsten light bulb, to me that is worrying.It's a potential fire / safety hazard.I looked up the manufacturer's website. As you might expect, the switches were made in China.The spec stated an ON resistance of 35 milliohms max.Naturally, I have arranged a return & refund. The seller will be receiving negative feedback.I have ordered some from Farnell that will hopefully operate as specified.It seems to me that every time I buy something made in China it turns out to be poor quality rubbish.I had a similar experience with a replacement fan for a NVIDIA 960 GPU card.The existing sleeve bearing fan became noisy after a couple of years.It was impossible to find a replacement in the UK, so I ordered one with the same part number from China.After I fitted it, it lasted just one day before it became as noisy as the original.The fan design and construction is rubbish.I have now ordered an alternative fan that uses two ball bearings - again it had to come from China. I could find no alternatives.I've also had bad experiences with fake ICs from China.I despair that we have to put up with this.What has happened to the electronics industry?

author: brian_mk
author_rank: Regular Contributor
timestamp: December 12, 2021, 01:50:21 pm
content: Maybe we should be thankful that when the inevitable future war between China and the USA begins, chances are that the Chinese 'launch missiles' button doesn't work.

author: Gyro
author_rank: Super Contributor
timestamp: December 12, 2021, 02:16:31 pm
content: No, there's a lot more to it than that with switch contact materials...Contacts rated for mains use will be something like Silver Nickel or Silver Cadmium oxide. These need a significant voltage (and minimum current) across the closing contacts in order to break down surface contaminants and oxide layers and attain low resistance. In exchange, they are resistant to welding and premature contact erosion though arcing (when interrupting an inductive load).All switches / contact material combinations have aminimumvoltage and current spec. A DMM typically won't meet these for unused mains rated contacts. If you want switches for signal level switching then they will typically have Au flashed Ag or Au-Pd contacts - these would be immediately destroyed by switching mains. Some switch and relay contacts these days are 'dual purpose' - they have Au flashed contacts where the Au immediately evaporates when used for high current switching. They are then rendered unsuitable for signal switching. You won't be getting these with a bog standard mains switch though.In all probability, those switches are absolutely fine for their intended mains switching purpose, and so the negative feedback is unwarranted (unless there are other defects).There are entire books written on contact behaviour.P.S. Try not to rant so easily, there's always the possibility that you've missed something, and it's bad for your blood pressure.

author: brian_mk
author_rank: Regular Contributor
timestamp: December 12, 2021, 02:28:47 pm
content: Ok - thanks. That's news to me. I will investigate.

author: brian_mk
author_rank: Regular Contributor
timestamp: December 12, 2021, 02:30:52 pm
content: The manufacturer's spec doesn't give that information - it just states a maximum on resistance.

author: Gyro
author_rank: Super Contributor
timestamp: December 12, 2021, 02:37:07 pm
content: Yes, minimum switching capacity isn't something that you'll typically find for bog standard mains switches - in all probability they don't characterise them, just relying on the contact materials being suitable for mains use, it's probably not something that makes its way through ebay translation anyway. The easiest way to understand the differences between different contact types is go onto somewhere like RS and look at the contact combinations and ratings in the datasheets of different switches and relays.If you've got a bench PSU then you could try setting the voltage to around 20-30V with a 1A current limit, connect the switch across the output and close it - then measure the voltage drop across the switch terminals. That ought to give you a measurable figure.

author: brian_mk
author_rank: Regular Contributor
timestamp: December 12, 2021, 02:41:29 pm
content: Good idea. I will try it.

author: brian_mk
author_rank: Regular Contributor
timestamp: December 12, 2021, 02:49:54 pm
content: I did test a similar SPDT mains switch I bought from Maplin some time ago (remember them?)I used the same Fluke DMM. The switch worked perfectly.This is partly why I thought the Chinese eBay switches were faulty.

author: brian_mk
author_rank: Regular Contributor
timestamp: December 12, 2021, 02:55:41 pm
content: I have a bunch of vintage, ugly looking, Bulgin mains switches. I will test those as well.I am willing to bet that those old switches are perfect and far better than the chinese made ones.

author: Gyro
author_rank: Super Contributor
timestamp: December 12, 2021, 03:05:17 pm
content: If you compare to something like Bulgin then yes, they are going to be a lot better. They probably have better mechanical wiping action and contact pressure (which can offset contact contamination and oxide layers). Like for like there is probably no comparison, but neither is the price. I'm not excusing the lower quality of the Chinese ones but they would probably be fine in a consumer appliance or bedside light. They probably won't make the 100k operations of the Bulgin though, due to mechanical wear, faster degredation etc.EDIT: If they do fail to switch reliably with a bit more voltage and current, then they are of course total crap and worthy of destruction.

author: brian_mk
author_rank: Regular Contributor
timestamp: December 12, 2021, 03:19:11 pm
content: The Bulgin (Arcolectric) switches from Farnell/CPC are no more expensive - they can work out cheaper.You need to order a miniumum quantity to make it economical because of the small handling and delivery charge.

author: Siwastaja
author_rank: Super Contributor
timestamp: December 12, 2021, 03:26:48 pm
content: Gyro has the right answer.The lack of understanding how the switches work, i.e., PEBKAC is the root issue. The Chinese switches in question may or may not be fine. OTOH, you may be able to find high quality expensive Western switches which show exactly the same "problem" on multimeter ohms range. Your calculation of 70W dissipation when running rated load sounds alarming, but it's easy to prove in a simple experiment. Try it and see what happens.I have a Chinese heatpump keeping my house warm and I like the fact it does work unlike many of the overengineered "Western" counterparts which require constant servicing. This seems to be the general trend. Chinese quality has gone up, from crap to high-tech, while keeping overengineering and all kinds of "we don't want to actually sell you our products" BS games down.Obviously, if you go to the Aliexpress crap markets, buy crap knowingly, and expect it to be crap, then is this a surprise?Many if not most of the components you buy from Farnell have China as country-of-origin.The story of not being able to buy a fan locallyat allis very descriptive. So even the crappy fan from China was working better than the non-existing fan. Go back to the Good Old Times and you weren't able to buy the fan anyway. The whole affordable GPU thing (and hence, need for the fan) is enabled by China, like it or not.Regarding the question to what has happened to electronics industry, the answer is, the products are cheaper than ever, last longer, require less maintenance, consume less energy, offer more bang for buck than ever.You may have fond memories of childhood, but they do not represent the reality. And if you find a "built like a tank" electronic product from 1960 or 1970's which still works, it's only because of selection bias, the one that survived is not a representative sample. In reality, electronics in the past required constant servicing. They were so expensive to buy that youhadto repair them. There were actual repair shops everywhere and repairmen made home calls to fix TVs and radios. Nowadays the expectation is a product lasts at least 3-4 years without repair, usually for much longer, and then you can just easily afford a new one.But yeah, avoid Aliexpress components. They are not even cheaper. Buy from proper distributors and try to combine a few projects on single order to hit the minimum free shipping.

author: brian_mk
author_rank: Regular Contributor
timestamp: December 12, 2021, 03:34:54 pm
content: Well, maybe I am biased because I used to work for GEC Marconi.I admit I am an old fart and at the risk of sounding like Victor Meldrew, products were tested to destruction and designed and built to last.

author: brian_mk
author_rank: Regular Contributor
timestamp: December 12, 2021, 03:47:15 pm
content: The overwhelming response seems to be that China will rule the world.I'm just glad that I am 66 years old and won't live to see the day.

author: Siwastaja
author_rank: Super Contributor
timestamp: December 12, 2021, 03:50:49 pm
content: That's a complete strawman, no one said that. But you seem to like oversimplifications.When it comes to producing affordable consumer electronics, China already pretty much rules the world, this is just an observation of reality. This has been obvious for at least two decades now, so you have seen it already in your late 40's.That doesn't need to be a bad thing, and we have a lot of brain resources here in the "West" still able to come up with important electronic things.

author: brian_mk
author_rank: Regular Contributor
timestamp: December 12, 2021, 03:52:16 pm
content: That's a politician's response.

author: Siwastaja
author_rank: Super Contributor
timestamp: December 12, 2021, 03:54:10 pm
content: No, it's a response of a scientist. Observe the reality, report the facts.You are the one who's making it political. This was obvious from the opening post already. That's fine, I'm not a huge fan of China myself either, but I don't like mental dishonesty.And if you complain about switches being dangerous, first learn how to measure their performance properly.

author: brian_mk
author_rank: Regular Contributor
timestamp: December 12, 2021, 03:55:41 pm
content: I so love a good argument :-)

author: brian_mk
author_rank: Regular Contributor
timestamp: December 12, 2021, 03:56:46 pm
content: I've had a few beers so you have no chance :-)

author: Siwastaja
author_rank: Super Contributor
timestamp: December 12, 2021, 03:58:26 pm
content: Not interested. Goodbye.

author: amyk
author_rank: Super Contributor
timestamp: December 12, 2021, 08:44:21 pm
content: Did you buy from the manufacturer directly? If not, you could be getting the rejects. But as others here have mentioned, contacts for mains use may look high-resistance if they haven't been used already.

author: brian_mk
author_rank: Regular Contributor
timestamp: December 14, 2021, 08:04:13 pm
content: OK I was a bit annoyed at the time, so my humble appologies to Siwastaja and Gyro for being stupid after their informative replies.I carried out some tests and found that a wettting current of 2/3 Amps did indeed reduce the contact resistance.I stand corrected. It's always good to learn.

author: Neomys Sapiens
author_rank: Super Contributor
timestamp: December 14, 2021, 10:02:09 pm
content: Quote from: brian_mk on December 12, 2021, 01:50:21 pmTHAT will be an American or European switch!

author: Bud
author_rank: Super Contributor
timestamp: December 14, 2021, 10:20:58 pm
content: Quote from: Siwastaja"Affordable" does not mean "quality". My observation of reality.

author: johnboxall
author_rank: Unknown
timestamp: December 14, 2021, 10:25:52 pm
content: Quote from: brian_mk on December 12, 2021, 01:20:52 pmEvery time you order cheap shit from China it turns out to be shit.You can buy good parts from China, but you have to pay more. Consider LCSC etc.Otherwise... Farnell, newark, digikey, mouser, element14, RS, arrow, etc., all exist for a reason.

author: G7PSK
author_rank: Super Contributor
timestamp: December 18, 2021, 04:36:03 pm
content: China is getting expensive now, India and Africa is the next countries to be exploited for cheap labour. I recently purchased a Remington battery shaver to keep in the car it said made in China on the outside I took it apart to oil the motor (they don't seem to put much oil in the bushes these days) and inside is said Made in India.

author: DrG
author_rank: Super Contributor
timestamp: December 18, 2021, 04:54:00 pm
content: Quote from: johnboxall on December 14, 2021, 10:25:52 pmI certainly agree with that, but I note that if you take a broader view, you could replace the word China with a number of other words, depending upon time and place.I am old enough to remember when 'made in Japan' was treated as a synonym for 'junk'.There was a time when California wines were garbage compared to French wines....and so on. It's a moving target.We maintain a market for these because of the desire to see, as the *good advert sent to me just a few days ago says "Not Expensive But Good Enough". Experience teaches us to discriminate, but the desire is still there. Also, if one simply does not have the $$, the choice has already been made or at least it has become binary (either get the cheapest or don't get anything).One fear that I have is that manufacturing has become so heterogeneous and branding so dynamic (who makes what is sold under a particular brand), it becomes more and more difficult to have an accurate perception of reputation before purchase. We seem to be left to the mercy of a plethora of reviews, cooked, ignorant and otherwise.

author: rstofer
author_rank: Super Contributor
timestamp: December 18, 2021, 06:58:29 pm
content: It's been known for 1000 years or so that you can't use power switches as inputs to logic circuits, In fact, if you want reliable inputs, you buy a switch with bifurcated (forked) gold plated contacts and these won't survive in a 'mains' application. Different applications, different switches.Quality switches, like those from DigiKey, have a datasheet that will discuss things like minimum current and minimum voltage as well as maximum stuff. Note that the DC voltage limit will be significantly lower than the AC voltage rating. The problem is arcing when the contacts open a DC circuit.Precision switches are a bit pricey.