Cheap electronic modules

[artag]

There are lots of cheap modules on ebay and aliexpress, but it's hard to know much about their quality.
In many cases there have been reviews, mod suggestions, schematics etc. posted but these can be hard to find.

Does anyone know of a good resource for such documentation ?

Some such are https://www.electroschematics.com and https://www.codrey.com/learn/lm2596s-module-a-trivial-tale/

Unless anyone does, I'm going to suggest we create one here. We can post links and I (or a helper) will update the thread start to keep an index. If it works out, perhaps we can get the thread pinned. This thread will do for functional modules such as power supplies but other devices such as test equipment can have their own thread (and I've made a similar post in test equipment to do that).

It may be that areas such as RF modules and audio deserve their own threads : I encourage that but don't like excessive topic splitting so I'm not suggesting it to start with.

Note that this is an index, not a review site. It will link to other people's information wherever that is, it won't steal or copy it.

[RoGeorge]

Those are typical Aliexpress modules.
Usually they are OK, but quality can vary wildly.

They often look the same, yet the manufacturer may differ.  Therefore any review/testimony about quality is almost useless.  Best tip is to look at the product feedback page on each shop, and at the seller's feedback on Aliexpress/Ebay.

[5U4GB]

They often look the same, yet the manufacturer may differ.  Therefore any review/testimony about quality is almost useless.  Best tip is to look at the product feedback page on each shop, and at the seller's feedback on Aliexpress/Ebay.

And as an extra comment, to assume that by default every imaginable corner will have been cut in order to save costs, including not designing your own but creating a poor copy of someone else's, which in turn may be a poor copy of another one, so with say 10% random corruption of component values, types, and ratings.  I occasionally buy some cheaper ones with a particular function just to see how bad they are, and you can get quite different items even from the same vendor over time as they switch suppliers or someone figures out how to replace a ten-cent component with an eight-cent component that at least looks mostly the same.

A lot of the feedback, at least on Ali, is also pretty useless, it's more "item arrived very quickly" or "looks nice, haven't tried it yet".  For things like woodworking tools you can find, mixed in there, comments about the quality of construction and usability, but for electronics there's typically very little useful feedback.

Having said that, perhaps comments on which Ali sellers people have had good luck with?  Certainly you'd expect more consistency from "Uni-T Official Store" than "Garden Fun Dropshipping", particularly because the dropshippers often get scammed by their suppliers and then you've got little recourse.

[RoGeorge]

Another tip would be to avoid the absolute cheapest place.  For the sake of a few cents shaved out, you might get a shoddy module.  My usual way of shopping from Aliexpress is to search for low price, but with hundreds of items sold.

There was a time, some years ago, when I was ordering almost weekly from Aliexpress.  Only once I've got something so bad I had to redo the soldering myself, but it was clear that would be the case from the feedback, only baught that because it was very, very cheap (it was a kit of 37 sensors for Arduino).  Other than that, I've received good enough products.  For example, the DC-DC converter linked in the OP, bought a pack of 5 in 2014 or so.  Used a couple of them and they still work fine today.  Of course they can not give 3A without a radiator, I think it was written on the sellers webpage too, that the datasheet maximum possible current.  For DC-DC, buy the ones that can stabilize for either lower or bigger input voltage than the needed output.

The usual things to look for when buying:
- search for the needed item, don't go to the first popped listing
- look for small price, but with many items sold
- read the negative feedback first for the item you want to buy
- also browse the shop by products, sometimes the same shop have the same item listed twice, at different price 
- sometimes you may find generic non-electronic shops selling an electronic module at high discounts, that's a gambling, often a wrong listed price or product (they won't ship and return the money)
- pay attention to how many items you will get (often the picture shows 2-3 items, but you'll get only one for the price)
- pay attention to shipping fees, some are listing very cheap item price, but they charge extra for shipping
- pay attention to "color" aka "model" when ordering, sometimes the top of the line is in the main picture, but the default model ordered is the cheapest
- again, read careful the item description and title, don't assume you'll get the biggest pack and the best featured items by default, and when in doubt ask the seller
- watch your shopping account around the expiration date, and contact the seller a couple of days before buyer protection expires (seller can extend the buyer protection time), or else the seller will assume you received the package, and you won't be able to open a dispute for no package received

In my experience (ordering from EU/Romania), the arrival was usually slow.  Assume the maximum listed time.  A few times the seller have had to extend the time, and eventually the package arrived.  Other than that, I have had a good shopping experience, never been scammed, and got products with very good value for the money. 

[5U4GB]

In my experience (ordering from EU/Romania), the arrival was usually slow.  Assume the maximum listed time.  A few times the seller have had to extend the time, and eventually the package arrived. 

Speaking of this sort of thing, be aware of common Aliexpress scams around shipping and refunds.  In terms of which shipping to choose, avoid Sunyou and Yanwen which are about as effective for shipping as using carrier mackerel across the Sahara.  I've found the pseudo-shipper "Aliexpress Standard Shipping", which is almost always Cainiao, Ali's in-house shipping operator, to be best, they'll get stuff to you in a week or so while almost anything that isn't them can take months, even ones you'd think would be better like Singapore Post.