Getting parts organized for the Dayton Hamvention

The Dayton Hamvention is coming fast, and for me this year, that means it’s time to get organized.  As anyone who works or plays with electronics soon learns, parts organization is a problem. In addition to not always remembering what I had, finding things that I know I have can be hard. This has especially been a problem in the last year, as I got back into the hobby after a few years away. I have a good memory (at least sometimes!), but no one can remember hundreds of part numbers, values, and locations for years on end.

This caused me some concern as I look forward to my first Hamvention trip in several years. Hamvention has a giant flea market, full of wonderful junk (junque?) to buy. Without knowing what I have, how will I know what to buy?

On top of that, as I’ve worked on projects recently, my frustration has grown with not being able to find parts that I know I have… somewhere.

Disorganized bin of resistors
This is one of the more organized bins in my workshop...

Though I’ve tried at least four different ways to organize my parts over the years, none has worked particularly well. This time, though, I have an edge on the chaos: My dear wife, Lyn, who has spent years in inventory management and running warehouses. With plenty of her help, I think I’ve finally hit on an effective system.

The first step is little bags. Each baggie holds one unique kind of part. Sometimes it’s a single part number, but for commodity components, I will group parts with different manufacturers or part numbers as long as the specifications are identical. In other words, all of my 100 nF 50 V X7R monolithic ceramic capacitors can go in a single bag, but 100 V versions go into their own bag, the Z5U version gets its own bag, and the ceramic disc version gets its own.

Each bag gets a unique number. I started at 0001 and worked my way up. I used four digits because I suspect I might hit 1000 bags by the time I’m done.

Capacitors in numbered bags

The cheapest place for good-quality 3×5″ poly bags that I’ve found, once shipping costs are taken into account, is my local Michael’s store. (Shopping there for bags was another one of Lyn’s suggestions.)

For the semiconductors, I splurged and bought a pack of static-shielding bags from Mouser. Rather than judge the relative static sensitivity of different components, I decided to put all of the transistors, chips, and diodes in static-shield bags, even if robust parts like 2N2222‘s probably would survive fine without them.

Transistors in anti-static bags

Next, the small baggies are stored in 1-gallon bags. Several 1-gallon bags go in a bin.

Gallon bags in a bin

The bin is numbered, and the 1-gallon bags within the bin are lettered. That means every baggie can be identified and found by combining the bin and bag codes and the baggie number. “1-B-0067″, for example, would send me to “bin 1, bag B, baggie 0067″.

Since baggies have unique numbers in the whole system, I can move them around from bag to bag or bin to bin as needed, and I can reuse baggies for different kinds of components as my stocks are depleted.

Tracking these numbers in my head would be no better than where I was, so the final piece of the system is a spreadsheet. With columns for the number and location, I can find things fast. Additional columns have the type and subtype of component (such as transistor/n-JFET, or capacitor/tantalum), the component’s package, manufacturer, part number, and value, and a description field.

Screenshot of inventory spreadsheet

I try to be as specific as I can, and I try to be consistent with nomenclature, to make searching easier later on. For example, I use units of μF, nF, and pF for capacitors, and I do not use decimal μF for capacitances below 1 μF. In other words, all of my 0.1 μF capacitors are listed as 100 nF, and the 0.01 μF capacitors are listed as 10 nF.

I thought about using one of the web-based inventory programs that are available, such as PartKeepr, but there is something to be said for keeping it simple, and besides, migrating a spreadsheet to newer software over the years will be easier than migrating a database.

The big success for this system may also be its biggest failing. As I work through my existing parts collection, I’m finding less and less that I want to buy at Hamvention. I already have all the common capacitor values I am likely to need for several years, and I found PN2907 PNP transistors cached in three different places, together amounting to what will probably be a lifetime supply. The oddball project-specific stuff I’ll just buy from Digi-Key or Mouser when I need it.

The cool part will be putting the spreadsheet on my phone, so I can check my inventory on the spot in the flea market. That should keep me from buying another 100 PN2907’s!

How have you organized your parts? Do you have any tricks to share?

Ouch! Watch out for power supply memory buttons

What is it about power supplies?  They are so very boring, until suddenly they bring excitement. It’s always the wrong kind of excitement, too…

It was a quiet day at work. I was using a GW Instek PST-3201 bench power supply, a nice unit with three 30 volt/1 amp outputs. It was purring along at 12V and a couple dozen milliamps, powering a rare and expensive prototype while I did firmware development. Then, when I reached over to grab something, I bumped the “RECALL ↑” button. Bang! The supply’s relays clacked, and suddenly all three outputs were configured for maximum output. The supply pushed a full 30 V, with a 1 A limit, into my circuit.

Needless to say, I switched the output off as fast as I realized what happened. Thank heavens for the clatter of those relays, which told me something unexpected had happened. With the output off, it was time to check for damage.

To my surprise, there was none. The power supply wasn’t plugged directly into the prototype — instead it went through a test board that interfaced a PC to the device under test. By very fortunate coincidence, the wimpiest chips on that board were rated for a hefty 36V, and some were rated for as high as 42V. (Those “wimpy” chips weren’t wimpy in any real sense — they were some LT1970 high-power op amps, more than capable of hefty output of their own.)  The interface board was undamaged. Better yet, none of the high voltage made it to that precious prototype.

As I breathed a sigh of relief, I looked for the cause of the accident. It turns out this supply came from the box with half of its memories set for 30 V / 1 A and the other half set for 0 V / 0 A. Hitting “RECALL ↑” took it to one of the 30 V memories.

This could have been much worse. It was sheer luck that all of the parts I picked for that interface board had maximum ratings higher than 30 V.

Needless to say, if you happen to use GW Instek PST-3201 supplies or the closely related PST-3202, it would be wise to check the memories and set them all to zero volts. That’s what I did as soon as I realized I was not going to have to tell my boss I had blown the prototype.

Updated 3/24/12: Corrected the name of the button at fault. It is “RECALL ↑”, not “MEMORY ↑”.