Advertisements

Arduino Knockoff: Cold Solder Joints!

The knockoff Arduino Pro Mini I used for the strobe photography controller ran the default Blink sketch perfectly, but didn’t respond to its own Reset pushbutton. Probing the Reset line at pin 29 on the microcontroller showed that the pushbutton didn’t pull the +5 V line to ground, so the switch was broken, a trace was broken, or …

Touching the soldering iron to a switch pin caused the whole thing to pop loose. One glance at the pads tells you something’s badly wrong:

Arduino Pro Mini Knockoff - cold solder joints

Arduino Pro Mini Knockoff – cold solder joints

A closeup, rotated a quarter-turn clockwise:

Arduino Pro Mini Knockoff - cold solder joint - detail

Arduino Pro Mini Knockoff – cold solder joint – detail

That’s the nicest picture of cold solder joints you’ve seen in a while, isn’t it?

Resoldering the switch solved the problem and, while the iron was hot, I touched all the microcontroller pins, too, just in case

Advertisements

  1. #1 by smellsofbikes on 2014-04-18 - 01:44

    My coworkers keep buying arduino clones off ebay and the clones keep not working. I’m collecting quite a pile of repair parts.

    • #2 by madbodger on 2014-04-18 - 08:12

      What are you going to, wait until you accumulate a reasonable batch (or need one), and repair ’em a bunch at a time?

      • #3 by Ed on 2014-04-18 - 13:27

        Nah, I fix ’em as I find ’em. That loser didn’t even make it off the breadboard…

      • #4 by smellsofbikes on 2014-04-18 - 20:21

        I build a lot of embedded boards, so I can always use the 328 and the crystal, on a custom-design milled board. One’s linear regulator went on in place of an import atmega that showed up with a burnt-out regulator. It’s a little like having cars up on blocks in the front yard.

    • #5 by Ed on 2014-04-18 - 13:25

      Hmmm… another precinct heard from. I may have to adjust my predilection for buying from the cheapest possible vendor; maybe I must split the difference between the most and least expensive. Of course, you can’t tell what you’re getting from the picture: they’re all the same.

      • #6 by smellsofbikes on 2014-04-18 - 20:17

        I can tell you this: make sure the usb chip is an ftdi with the right number of pins. One board had a 14 pin chip labeled ftdi232, which they don’t make, and windows drivers wouldn’t talk to it. Linux would, though. That was labeled ‘uno’ although obviously it wasn’t. Another, labeled ‘uno’ and with a qfn that is labeled as an avr usb-capable chip, also doesn’t talk, even though I can successfully reflash the chip’s firmware through avr studio. No idea. A third, also labeled uno, but with a real (?) ftdi chip, works as a diecemila once I replaced the avr8 it came with, with an avr328.

        • #7 by Ed on 2014-04-18 - 22:38

          replaced the avr8 it came with, with an avr328

          Ouch!

          As nearly as I can tell, eBay offers a nearly endless variety of pure unadulterated crap, purchased under conditions of no recourse. I use it to keep my toy budget under control, but only for stuff that really doesn’t matter…

      • #8 by smellsofbikes on 2014-04-18 - 20:24

        In contrast, the ones I’ve purchased through adafruit or sparkfun are all still working, including the one I jigged up as a geiger tube counter and managed to put -740V on one of the digital pins. AVR’s esd structures must be pretty burly.

        • #9 by Ed on 2014-04-18 - 22:42

          There’s that Sparkfun sage of counterfeit chips showing even they get suckered, but they’re definitely operating a lot higher on the yield curve and dealing with reputable suppliers. Their stuff costs more, but if you can’t afford to do some (well, OK, a lot) of test-and-repair, it’s well worth the expense…

          On the other hand, watching eBay crap fall apart does have a certain amusement value, doesn’t it? [grin]