As you may judge from the title, today was a bit frustrating. I got home with very good news; my boards had arrived from China! As soon as my son was to bed I started inspecting the boards, and the first thing I wanted to do was to test the Qi receiver; I opened the sample bag and saw this:
Now I know that the Qi receivers are small, but apparently I had ordered the BGA version of the chip, not the TQFP! DOH! OK, so I wasn't able to test the Qi receiver. A bit dissapointed I started soldering the other components. Recently I bought a hot air soldering station, and I'm really happy with it; look at these pictures to see the components lying in the paste, and then the soldered board:
Wow, that looked like something!
Now I had to start testing; quite soon I found some errors in my thinking process; to protect the output of the BQ2002, I had placed a resistor divider from the gates of the power switching FETs it was controlling. This pulldown DID protect the BQ2002, but also disabled the functionality; the FETs were always on. Also, some other parts of the design needed attention:
Conclusion so far:
- It's too late, I need to go to bed
- The switch mode converter is working, but quite noisy. Changing the output cap changed a lot, not for better.
- I managed to get the charge controller working with parts I had lying around. YEAH!
- Some uggly, some less uggly patches need to be made, but in general, the design IS working; I charged some cells, and at ~9V the charger switched from full current charging to trickle charge. Another great purpose of the hot air soldering gun is the possibility to change the value of NTC's. When I made the NTC hot, charging was terminated. Great, exactly what the bq2002 is supposed to do!
- After a bit frustrating evening I'm glad I can show you this picture of a LEGO battery box charging from my power supply. Next post it'll be wireless......
Green light on the battery box ('on') and small red LED on charger board. Operation in progress!