Week 8: Input Devices

Assignment: Design, make and program an input device

This week, we had to create an input device. I wanted to integrate capacitive touch to turn on LEDs in my final project, so I thought I would start with Neil’s capacitive touch board. I’d also been feeling a little overwhelmed by all the electronics stuff in general, so thought I’d try to be less ambitious and focus on understanding the basics again.

The nice thing is that milling and stuffing a board has become a lot easier now. Thinking back to when this took an entire week to do right and looking at some of my soldering from the week where we made the Fab ISP, this definitely made me feel good about how far I’ve come. I thought I would start with Neil’s capacitive touch board and make his demo board, but also my own version of it so I could get more comfortable with Eagle. I started reading up on some basic electronics stuff and also used the board diagram to rebuild the board in Eagle. I’m still not super comfortable with routing the traces — I always run into issues. But I think I’m getting marginally better. I learned a few random tricks this time around which was helpful.

My final board traces looked like those below. I milled and stuffed both boards. On my own board, I think I managed to burn off one of the traces by the ISP which stopped it from working. I checked everything with a multimeter and it seemed ok except that spot. However, I did manage to get Neil’s board stuffed without ruining anything.

Then came the annoying part. When I tried to program the board with the avrisp mkII programmer, I kept having it fail. I sent an email to the CBA section and Brian and Pedro helped me troubleshoot a bit. After some hunting online, I found that the avrisp mkII and Macs sometimes don’t get along very well. I thought I would try one of the Fab ISPs so I borrowed Pedro’s. That worked like a charm and I was able to get the board programmed and working! I first tested it with a single copper pad and it worked well. I saw some people last year had made a touch pad with 4 copper pads. I wanted to try and understand how this would work so I made one of the touchpads. I’m still a bit confused about this aspect of it so will try and figure it out in the next couple days.

I decided to be a bit more ambitious and mill and stuff the $4 touchpad board as well. Even though I got it all stuffed and ready, I didn’t have enough time to actually program it. Overall, it was a long week since I had to teach myself a bunch of electronics but it will come in handy later! I’m slowly starting to get the hang of things.