Chinese relay module - reliability??? - Page 1
Forum section: electronics / beginners

author: Tantalum
author_rank: Regular Contributor
timestamp: July 15, 2019, 09:40:58 am
content: HelloAre those cheap relays module available on ebay, reliable, or at least won't put my house in flames if they fail?I only need them to power pumps and fans (2-3A @230V)Are there alternatives available with better components?Thank you

author: jaromir
author_rank: Unknown
timestamp: July 15, 2019, 04:28:11 pm
content: The problem is that nobody knows. You may be lucky or perhaps not.Anecdotal success (or lack thereof) expressed by any member here has limited value as long as those suppliers are using parts that were the cheapest that week, often reused ones; with unknown history and uncontrolled factors during hardware harvesting, desoldering and cleaning.

author: Connecteur
author_rank: Frequent Contributor
timestamp: July 15, 2019, 04:40:59 pm
content: The myth that all Chinese products are inferior is just that, a myth. The factories build to the requested specifications of a product, but they do it cheaper than anyone else. Greedy contractors often specify "cheap as possible, as long as it works," so that's what you get when you shop for the cheapest price. Regardless of the quality level, you are almost always getting spectacular value.

author: kjr18
author_rank: Regular Contributor
timestamp: July 15, 2019, 05:31:19 pm
content: I installed one of those in my shed, to control 4 independent mains led lamps. I put in in electrical junction box, with controller and small power supply. I did it around 2016 I think. One day about 4 months ago I went to grab something and noticed that one of lamps is turned on no matter if it's turned on or not. After some digging inside I found that bcb decided to burn right between two tracksAfter some desoldering I made a slot to prevent further board carbonisation.

author: Domagoj T
author_rank: Frequent Contributor
timestamp: July 15, 2019, 06:27:43 pm
content: I tried using them to switch mains to turn on some 200-ish watt SMPSs, but the contacts would weld together.I suppose the inrush current on SMPS was too much for them. They lasted about a week before I replaced them with something with same declared rating, but physically much bigger (about four times as big).

author: floobydust
author_rank: Super Contributor
timestamp: July 15, 2019, 06:28:48 pm
content: Quote from: Connecteur on July 15, 2019, 04:40:59 pmGreat value as your product burns upThere's no cost hit by moving the terminal block over 1 or 2 mm. It's simply a lack of knowledge that makes this kind of mistake.The terminal blocks are too close together so spacings between those two end channels is less. Per relay, the spacings seem reasonable.The spacings violation is likely happening at the underside of the terminal blocks. Nobody looks there. The metal from the wire clamp/pin is wide and the two terminal blocks butted up against each other can be a problem.

author: Connecteur
author_rank: Frequent Contributor
timestamp: July 15, 2019, 07:38:47 pm
content: Even the good ones are built in China to the proper spec. They simply build within the parameters of quality and cost they are given, and they happen to do it better than anyone else. The cheap garbage is not their fault, they are simply producing the garbage the way that their client specifies.

author: tautech
author_rank: Super Contributor
timestamp: July 16, 2019, 12:28:36 am
content: I prefer not to expose cheap modules to mains switching and instead just use them as the control interface to a better industrial DIN rail relay and let them do therealwork.Examples:

author: Psi
author_rank: Super Contributor
timestamp: July 16, 2019, 01:09:40 am
content: Look at all the prices for a particular item you want, they will be in groups.As long as youdon'tpick the lowest price group you should get totally reasonable quality 95% of the time.If you pick the lowest price group its 50/50 what you will get.

author: rstofer
author_rank: Super Contributor
timestamp: July 16, 2019, 02:28:05 pm
content: Quote from: blueskull on July 15, 2019, 05:57:18 pmThe most you can say without researching the actual UL files is that they have the logo stamped on the housing. Whether UL has actually evaluated them is a second question. There should be a UL file number on the relay or at least in the documentation.The CE mark is a self-certification and only a consideration when things turn south. Everybody marks their stuff with CE.More important to the OP: Are the relays HP rated? Simple contact ampacity is not sufficient when there are motor loads involved since the inrush current will be at least 6 times full load and the high current lasts, at some level, until the motor gets up to speed.Next up: Is there sufficient creep distance between traces for the voltages involved (and the environment)? Note the post above about PCB failure.If I were connecting to mains, I would buy something of quality for controlling the load and use the little interface board at much lower voltages to drive the control relays.

author: Connecteur
author_rank: Frequent Contributor
timestamp: July 16, 2019, 02:32:26 pm
content: There's usually a tier of ridiculously low prices. These are likely a scam to collect your money and ship you nothing. But there is intense competition for sales, and you can often get good quality for very low prices.

author: Geoff-AU
author_rank: Frequent Contributor
timestamp: July 17, 2019, 04:32:30 am
content: 80% of the product for 20% of the price.Just gotta ask yourself which 20% they've left out.Personally, I'll buy from a proper channel like Element14 or Digikey if it NEEDS to work.