Sunday, January 1, 2017

The combination of aging eyes...

The combination of aging eyes ... and modern electronics is not necessarily a good thing, as I'm discovering.  I'm working on a project for our mud room, to turn the lights on and off with a touch of a cabinet handle.  Thankfully most of the parts are available in (now) old-fashioned DIP packages.  Some of the parts, however, are only available in packages intended for surface-mounting.  The part at right is one such; it's the capacitive proximity sensor at the heart of this little project.  It's available only in a SOT-6 package, which is tiny!  I've glued it to a piece of vector board (the green stuff with holes in it).  Those holes are a mere tenth-inch apart, which gives you some idea just how small this part is.  The wires that you see there, with black and red insulation, are 30 gauge wires – not much bigger than a fine hair.  Somehow I've managed to solder them onto their pins, after much trial-and-error.  I could only do this because I have a tip for my soldering iron that ends in a sharp point that you could hurt yourself with.  Also, I'm using a 5x magnifying glass and a nice, bright light.

I'm stopping for the day, as my eyes hurt and I can't hold my hands steady enough to do this any more.  Four more of those wires and I'm done with this one.  But I have another of these surface mount parts to do, too – yikes!  I'm beginning to see why so many guides I've read advise people not to do this.  I'm not sure it would really be any easier even if I had a circuit board, though.  This is the first time I've ever attempted to use a part this small; hopefully it will get easier with some practice.

I hope...

1 comment:

  1. I've done a couple of projects with surface mount parts and I agree that it is a bear. The ones I did had appropriate pads on the PCB, which makes it a lot easier. If you find yourself doing this much, you might consider some of the available surface mount breakout boards. You can use these to adapt a surface mount part to a DIP footprint. For example: