New Blank PCBs & Cheap Asian Modules Experiences?

[Chris56000]

Hi!

I've submitted this post as EPE Magazine is doing a long series on using cheap Asian ready–built modules – what are Members' experiences with these?

I'd like to read about:–

1) Whether any supporting documents were received;

2) Reverse–engineering these cheap devices;

c) Examples of uses other than what they were primarily sold as;

I'd also like to read Members' experiences of buying very cheap blank designed PCBs – assembly, documentation, typical uses, etc., etc!

Finally has anyone actually built a complete cased product for use on the bench with these very cheap modules or blank boards? Please post 'em!

Chris Williams

[Nusa]

1) Whether any supporting documents were received;

Generally not. Depending on the product, some sellers might point you at on-line resources, or include some details in the listing itself, but most of the time you're on your own. You must be able to use search tools.

2) Reverse–engineering these cheap devices;

Depends on your skills. Most of them are not that complicated. Example: I consider an Arduino UNO trivial to reverse-engineer (without looking up the open-source schematic). Do you?

[Gregg]

I like cheap Asian electronics modules; I have learned a lot testing, troubleshooting and even sometimes repairing them.  I always buy them two or more at a time to raise the odds and have a ready comparison board if I do run into a problem and replacement components may cost much more than the whole module.  If both are bad, they sometimes are bad in different places.   My rules of thumb are:
•   Never expect to get instructions unless the listing specifically states it is included. If you do get an instruction sheet then deciphering it could be another challenge.
•   Any reverse engineering is usually only in relation to fixing or upgrading a module
•   Buy modules with at least double the rated maximum power I expect them to ever see
•   I skip over items with listed specs that are obviously exaggerated way beyond what I can tell is bogus by looking at the pictures of the boards.    I look for heat sink area, number of filter caps, etc. and will pay a little more for something similar that looks to be higher quality (but it is sometimes hard to tell).
•   I have found that fleaBay is often faster and more reliable than Ali Express especially if it is shipped from Hong Kong --- Malaysia and Singapore usually are slower. 
•   I also search for the same item from many sellers and copy pictures, instructions and any connection schematics to a file for future reference.  Sometimes a module will no longer be listed by the time it arrives and making a reference sheet at the time of ordering saves headaches later.  Many of the better sellers have found out that including some diagrams with the listing helps sell their modules; I’ll pay a bit more because of the listing quality.  Another advantage of making up these reference sheets is that it is easy to add my own notes as to failure mode; how much I tested the module and for how long etc.

[Mechatrommer]

on using cheap Asian ready–built modules

which asian?

[Nusa]

Good point, since the OP is tagged UK where Asian usually doesn't mean Oriental like it does in the US.
But the rest of the context would seem to hint that is what he meant.

[james_s]

I've bought loads of cheap models from China, almost none came with any documentation at all though for many of them I was able to find example projects using them. I've had a few duds but for the most part the quality has been fine, astonishingly good if you factor in the price. You're generally more or less on your own, but there's a lot of really cool stuff available for very little money if you don't mind tinkering.

[LukeW]

A lot of the "Cheap AliExpress Modules" are ripoffs of products of companies that will provide good documentation - Sparkfun, Adafruit, or Arduino knockoffs etc - so *sometimes* going back to the real product will give you documentation that can be used - if they have faithfully cloned it without changing anything.

But buying the cheap clone and relying on Adafruit or whoever to give you free documentation (even though you don't buy their product because you want the cheap one) is kind of unethical and unsustainable.

If the module is just based around one IC you can pretty much nut it out if you have the datasheet.

You mainly just need to search online and see what other people have done - "crowdsourced" documentation is common, although sometimes the online pages where you buy the stuff do have minimal documentation.

Here's an AD9850 module example - one example of such a module from EBay/AliExpress etc.
http://www.vwlowen.co.uk/arduino/AD9850-waveform-generator/AD9850-waveform-generator.htm

It's always a bit of an experiment, a risk, an adventure buying this stuff - if you want no risk, design the board yourself and buy the silicon and components which are exactly the ones you specify for your design, from a reputable distributor.