Waterproofing marine equipment - 14 - Final Review

Yesterday I did spend some time troubleshooting my transmitter design board. At first I checked all my power supply rails. Both the 3.3V and the 5.0V input rails have the right voltages. After that I checked the bq500212A pins for these voltages, and as far as I could probe the ICs footprint the voltages seemed to be right and present at the IC. After that I started looking at different lines of the board. Almost all of them showed no voltage, nor pulses or other indication of activity. Only the COMM+ line had a constant voltage of 1.4V.

The first step was to follow Hendrik Lipkas advise and check the board for unrouted connection. As he suggested, I turned off every layer but the “Unrouted” one. No unrouted connections. I then also checked my schematic, comparing it with the one of the reference design. I wasn’t successful there either, but I’m very bad at caching these kinds of errors, so maybe it’s worth a second look.

After this first inspection I started suspecting a bad solder joint on the main IC. So I took the hot air gun and unsoldered it to take a look beneath. Although a short between two pins might disappear while unsoldering the IC, the footprint looked nice, with solder evenly distributed along the pads and thermal pad.

“Ok, so let’s solder the IC back in place” I thought. Plug in the power supply, cross the fingers, turn it on and… still nothing. Again, I’m not able to tell if the bq500212 is perfectly soldered, but as far as I can tell it looked good. After that I turned to the CSD97376. I unsoldered them and, this time, the footprint didn’t look that great, and was kind of grey.  So maybe there was some kind of problem with these ICs. I cleaned the footprint, checked that there were no shorts between the different pads and turned the board on, without both CSD97376. If the board was ok, the bq500212 should start working and try to drive the PWM lines to the CSD’s.  But again, no luck.

And there is where my ideas for things to look up started to disappear. If any of you has any suggestion please leave a comment! The only thing left I can think of is that I might have fried the IC while soldering it in the oven. If I get the time I will try to assemble another board next week and hope that it works, like it happed with the receiver board!

But today is also the last day of this Wireless Power competition and probably also my last post, and I would like to write a little bit about the good and not-so-good experiences of these last three months.

Good things:

• I really learned a lot. I had never “designed” such a complex board, nor used smd components. It all looked very daunting at first, but at the end nothing is too complex if you split it up in small enough problems
• The other bloggers. It has really been a pleasure to read the posts created by the other participants. It’s really amazing what some of them have done with the wireless power kit and how nicely it has been integrated into different applications.
• The pleasure of seeing your design finished and working. I don’t know about the rest of you, but I start a lot of projects and do not finish all of them. And my receiver board, with the battery and buck-boost regulator attached really looks (and works!) great.
• My first open source project!
• The organizers:  My Evaluation module arrived early, when I had a question or send an email I got a response within hours…that is how it should always be!

Not-so-good things:

• I really wanted not only to design the receiver board, but also to at least prepare a prototype for a waterproof enclosure. Sadly I had not enough time to prepare a proper enclosure I could show. So, at the end, my series of blog post have dealt about something different that what I promised in my application. Not good.
• Forgetting to order samples. This has been my biggest problem during this competition. I did loose more or less two weeks waiting for the samples of the bq500212A because I forgot to order them with the rest of the components. This introduced a big delay. Lesson learned: A single mistake can destroy all your nice project planning.

Thank you to Würth, TI and Element14 for providing us with this great roadtest. evaluation module and coils! You certainly gained a fan here!

For good or bad, everything has to come to an end at some point, but I’m already looking for the next Road Test to apply.

Best regards,

Eduardo Iscar