As the deadline approaches, the project is getting more and more stressful which was expected. With that being said, it was quite the relief to test the board and see that there were no problems with the board that would require me to order another batch. I am still on schedule and should be able to finish the complete prototype by this upcoming Friday.
- What did you do this week?
This week, I continued to test the functionality of the board with the code that I wrote. Of course, testing comes with a lot of debugging so a good portion of my time was spent on solving problems involving my code and just ironing out the kinks of the program.
I also spent time over the weekend fabricating the mounts for attaching the watch band to the heatsink. I was very pleased with the results.
- Describe the problems you encountered
I encountered a number of problems this week, but luckily I was able to solve them quickly.
1) When I first powered my board, I noticed ‘magic smoke’ and disconnected the power supply. I then realized that I had soldered my diode backwards, which had fried my boost converter chip
2) I noticed when testing the populated board with my multimeter that there was a short somewhere. However, when I tested the unpopulated board, there was no short. I first thought that I may have accidentally bridged some pads during the surface mount soldering operation. I inspected every component and ruled that cause out. I further deduced that this short was a result of soldering my diode backwards. It turns out there was an internal short within the boost converter chip so I removed the component and there was no short!
3) I forgot to place a power switch on the board when designing the PCB. To solve this, I had to solder the header sockets on the board and now to turn on the board, you just insert the microcontroller and that initializes the program. When it is removed the board, no current is drawn. However, because I had to solder these headers, that adds 1/4″ to the height of the unit
4) When testing my LEDs, they were not illuminating. I took another look at the schematic and realized I mixed up the anode and cathode. To solve this problem, I cut the common anode trace to negative and placed a jumper to the positive line and then I had to account for this in my code by pulling the pin LOW instead of HIGH to turn on the LED.
5) Next problem I had was with my code. When testing the if the LEDs responded to the push buttons, I noticed only one button was working. Well, this turned out to be a bracketing issue.
6) The last problem was also with my code. Finding an alternative day of performing a digitalWrite in the loop without using the ‘delay’ function. If I used ‘delay’, the program ran very slow and often didn’t function. To solve this, I made use of the millis() function. You can see the code in the following link
https://docs.google.com/document/d/1rI2vCf5E__gzYc5JgFOSnOJRUpK55umKUBSVFD3ubfk/edit?usp=sharing
- Are you on schedule?
Yes I am! I should be able to finish the complete prototype by Friday
- Describe the successes you had
Like I said above, I was very pleased to find that there were no problems with my board that would require me to print another board.
I also was able to fabricate the physical device without any issues.
And also, after many hours of debugging, I wrote a program that works very well.
- What do you plan to do next week?
Next week, I plan to wrap up the prototype and test if it actually gives you the perception of your body heating or cooling down. i will have to test many pulse frequencies to find the optimal one that is most effective.
