Polarshield v2.4 compared

I got a pile of boards back from the maker recently: Polarshield v2.4 (https://github.com/euphy/polarshield_hardware). Here it is alongside the 2.2 version (on the left)  to show the progress.

Polarshield v2.4 (compared to 2.2)

Not much right? There’s no revolution, indeed, but a couple of minor changes that makes it easier to build.

  1. More surface mount parts. The tactile switch in the top-left is now surface mount. SMT parts are just quicker to work with.
  2. Moved the microstepping jumper solder pads to the back of the board, and freed up a load of space.
  3. Squished four of the 1k resistors into another 4-row resistor network. This is the smallest part I’ve ever used, 2x1mm, you can barely see them on the picture. There’s one between the two motor driver sockets, and there’s another below the stack of LEDs on the top-left. This makes pick-and-place much faster. I’m not convinced the super-high density was a good idea though – it is far less tolerant of sloppy placing / solder paste application. We’ll see.
  4. Better designed for soldering with hot air, and iron. Some of the traces on the board were sometimes difficult to heat effectively, without also over-heating the component. The electrolytic capacitors were particularly problematic. I’ve routed the traces less efficiently in some cases, so that they have more copper that I can heat with the hot air pencil.
  5. LEDs are all orientated in the same direction. The old board has them pointing everywhere, so I was always spinning the board around. v2.4 has the anode to the right-hand side in every case. It’s to reduce the chance for placing errors.
  6. The holes for the DC power jack are placed off-centre, so the solder tabs are a friction fit. It makes the part self-aligning. Nice work sparkfun!

And the great thing is, it works, ha!

I’ve been taking some time off the Polargraph shop lately, because of work pressures and a couple of other things. It’s been really nice not to have to rush to the workshop every hour of the day to keep on top of things, and I’ve been able to do a little development here and there.

I think I’ll be back eventually, but maybe in a couple of weeks, and I might try a different manufacturing pattern.

Labelling evolution

My manufacturing process is always sometimes evolving. It’s not a complicated one, but there’s enough steps and nuance that I benefit from reminding myself what I’m supposed to be doing.

A run of bad Polarshields last year prompted me to start being a lot more careful about how I assembled and recorded the assembly of them. I started putting little journals on each one, which were just a strip of sticky tape with any story on them. Anybody who bought a Polarshield will have found such a thing.

Quality control labelling on Polargraph gear

I recently kicked myself a couple of times in a row when I thought I’d forgotten to test a certain aspect of the board, and had to open up a pile of sealed parcels to find out. Fortunately in that case, there was no problem, but I made up some new labels to help me not make a mess in the future.

The evolution is in the pic. The QR takes you to Building a Polargraph from a vitamin kit on the wiki. The final version is less handsome, but more useful, and there’s a beauty in that trade-off.

I like seeing these kinds of “work in progress” pics on other makers’ blogs.