Monday, March 28, 2016

The fun of buying directly from China

I now buy a lot of stuff directly from China.  It's easy to use Aliexpress, and keep everything under $20 if you want to stay under the arcane Canadian limit.  I have had a 100% success at getting good stuff, but recently I have suffered with the adxl345 accelerometer boards.

The local internet price is $16 for a breakout board that you know will be perfect.  But I can get them direct from China for $2.  What could go wrong?  Everything.  The first batch was all wonky after I tested them.  The second batch, with a different board, from a different seller was all perfect when I tested them using the first i2c address.  Unfortunately, they shorted when I tried the second address.   If you want to put two on a single i2c bus, which I want to do for my production accelerometer, then this is bad.

Fortunately, Google loves us, yes I know.  I found this link.  This was classic board disaster, thousands of those must have sent to the crusher, only to be saved, Sar Wars fashion, by the ingenious Chinese.  This is what you get for $2 -- rejects.  But the fix is dirt simple.  I made a mistake the first time when I thought you shorted out the R4 resistor, but that's stupid, since it is a short anyway.  You melt the solder and scratch it out, and leave an air gap.  A perfect accelerometer with the second address, when you put SDO high.  Yeah!  I'm not buying anything more because I'm in the doghouse with the wife.  And I really want a raspi zero, but you can only buy them right now in expensive kits.

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