Tubes and Boxes

October 10, 2012 9:55:57 PM CDT

This is one of my recent mixed-success projects.

One of the electronics hobbyist's eternal questions is, "what do I do with all these small parts?"

Take resistors for example: I use two different kinds for most of my breadboarding and "let's build it and see what happens" work: 5% carbon film and 1% metal film. I stick to values in the E6 series (10, 15, 22, 33, 47, 68) because that's cheapest and I can generally cobble together any value or ratio I need. Still, I keep seven decades of values on hand (1, 10, 100, 1,000, 10,000, 100,000, 1,000,000) which gives me 84 different type/value combinations to wrangle.

To make matters worse, I reuse parts from one breadboard project to the next, so I end up with tiny piles of resistors bent to span various distances: .1", .2", .3", etc. Mixing them all together makes it hard to find the specific part I want, so I prefer to keep them separate if possible. Doing that requires even more storage.

After much searching and head scratching, I finally decided that the author of this article has the right idea: use test tubes.

In hindsight it makes sense. Chemists are smart people who've been moving and storing large numbers of small items for centuries. There's a lot of operational wisdom baked into the field, and there's a whole industry dedicated to providing chemists with supplies at competitive prices.

A little digging around turned up Lake Charles Manufacturing, a lab supply firm that sells tubes in the size I wanted at a bulk price of 2-1/2 cents per tube (lids are another 1-1/2 cents each).

Of course, that led to a new problem: organizing the test tubes:

how not to 
do it

That's an easier problem to solve though. The tubes I have are all the same size, so grouping them is fairly simple.

I divide storage into two different categories that have different jobs:

  • long term bulk storage
  • easy-access prototyping supplies

Probably 90% of my parts live in bulk storage because, when you're prototyping, 90% of the parts in a pile don't do anything but fill space. What I actually need for prototyping is a small set of parts that are already trimmed and bent to the sizes and shapes I normally use, plus a dozen unmodified parts for situations where the standard shapes won't do. Then when I run low on unmodified parts, I refill that tube from bulk storage.

Since I only pull parts out of bulk storage a couple times per week, I don't have to optimize that system for easy access. I buy through-hole resistors in bulk rather than in pick-and-place machine tapes, so I toss all the bags for a decade into a parts bin and forget them until I need a particular value.

I don't have a good organization scheme for the prototyping supplies tubes yet, but that's mostly a matter of fussiness on my part. I've gotten it into my head that the tubes should live in a series of book-like containers, with the part type and value printed on the spine. My prototyping inventory, then, would be more or less like a bookshelf.

There are some subtle differences between books and boxes though, and when you deal with designs that represent centuries of continuous experimentation and improvement, it pays to be humble. Every detail is there for a reason, and 999 times out of 1000, ignoring those reasons just means you'll spend time and effort rediscovering them for yourself.

Instead of following that (admittedly interesting) philosophical path, I opted for practicality, choosing a box design that opens more or less like a book but has been optimized for low cost and ease of construction.. the cigar box:

Unfortunately, I tried to be clever and build the bulk storage into the same box that would hold the prototyping tubes. My idea was to put a false bottom in the box, store the bulk parts under that, and keep the prototyping tubes on top.

Bad idea.

Fortunately it was bad enough that I was able to see how much of a stinker it was in the first five minutes of playing with a sample box.

Among the more objectionable features of the design were the facts that:

  • It more than doubled the thickness of the box.
  • To get the false bottom out, I'd have to tip all the prototyping tubes out, then replace them after getting the parts I wanted.
  • I'd also need to build some kind of handle into the false bottom so it could be lifted out, rather than being dumped out beneath a pile of fast-moving components.
  • Ultimately, it was a solution to a problem that already had a better solution.

Building the sample box did give me a chance to refresh my memory regarding cigar box construction though, and to spot some details that will let me make a better version next time.

Random brain cookies:

If all the world's economists were laid end to end, we wouldn't reach a conclusion. -- William Baumol