Peter Fearey

Electronics Production

Assignment

Make the FabISP in-circuit programmer. FabISP is what you use to communicate between the circuit boards you build to the computer. It’s the equivalent of the USB port on the Arduino.

Ideas and Approach Taken

I knew this one was going to be a stretch to me.  I had never soldered such small components and when I've done big components the solder job wasn't great.  Doing this project, while it was painful and frustrating in the moment, increased my confidence that I can do things close to this.  As for my "approach take"...I just jumped in.

Steps Taken

I did two boards.  The second board seemed to work (at least it was successfully programmed). Here were the two iterations and what I learned (or the mistakes I made).

Files

Board #1:

I thought I had this one made.  We missed it.  That seemed to go well.  I started soldering and I was moving right along...until the last piece.  I started to put in the six-pronged part where the cable would attach.  It was a little off (aka it had a small tilt to it).  To get around that, I tried to melt the solder and turn it.  Bad idea!  The solder wasn't melted enough and it pulled the trace right off the board.  It hadn't occurred to me that the trace might come off.  I tried to recover it and tried re-soldering, but to no avail.  So as far as I know, that was the only mistake. 

Board #2:

Again, I was moving along after milling the second board and I messed it up at the last step. 

1. First, I soldered the  pin (left/bottom) pin and that solder hit the small excess ground trace that is between the second and third pin.  I wish I had noticed that and scrapped the excess away ahead of time.  We found this out because the 3rd and 6th traces set off the voltmeter when touched and they shouldn't have been related at all.  
   
2. Second, To recover from that, we thought it would be ok to cut the ground at the top right between the 4th and 5th traces...BAD IDEA!  This cut the whole pin header from the ground.  We didn't look closely enough.  To recover from that, we ran a small jumper cable from the big ground trace by the 6th pin and ground on the bottom right ground.  THIS WORKED!  Yeah! 
   

Final Board...

Learnings

Here are my key learnings...

• Boards are sensitive:  I didn't occur to me that the slightest bit of pressure would pull the traces.  I figured they were attached quite well. 
  
• Equipment matters:  I have soldered before.  Generally it is with breadboards and large circuits.  When I saw the size of the resistors and the circuit boards I thought there was no way I could do such small parts.  Then I learned about the fact that the right equipment makes it possible.  Flux, Wick, a magnifying glass and bright lights all make it DRAMATICALLY easier. 
  
• Test as you go:  One incredibly useful thing I learned in this was how to use the basics of the voltmeter.  I had tried to use it before, but nobody has explained how so I was a bit in the dark.  Once I learned how, I started using it to test my traces as I went.  This helped me make sure I had things right as I went.  It also gave me more and more confidence.
  
• You can recover: I made MANY mistakes with my board. I pulled traces off.  I cut a trace in half because I thought it would solve a different problem.  I burned the heck out of one area.  On yeah...and this was all on Board #2, which is the one that eventually worked.  But with a jumper cable I made out of a small piece of wire and a glue gun, it is now sturdy and in locked in place.
  
• Give yourself space: So I love the fact that these are small and compact.  I don't understand why they had to be SOOO tight and compact.  I supposed I wouldn't care if I were great at soldering, but as a starter board I would separate things a big more.  If/When I build my own boards I plan to add a bunch more space.  Additionally, I plan to scrape additional traces out when I am sure I don't need them.