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?

Trying out Itead Studios’s PCB prototyping service

I’m working on building a breakout board for the high-performance AK5388 audio ADC. In my last post, I revised the schematic to help with the PCB layout and test-fit the key components on a printout of the board.

The next step was to order the board. Laen’s PCB order is taking a hiatus this month. Feeling impatient, I decided to try one of the Chinese options: Seeed Studio’s or Itead Studio’s PCB fab services. They offer prices as low as $9.95 for 10 copies of a 5 cm x 5 cm board. Unfortunately, the ADC board is 4.9 cm x 6 cm. That extra centimeter nearly doubled the cost of the board, because I had to buy a 5 cm x 10 cm package. At least one dimension was still below 5 cm!

My son wandered in while I was comparing prices. He asked, “Is your circuit board going to be purple?”  I told him that no, it was probably going to be green.  “I think it should be red!” he said.  “What the heck,” I thought, and clicked on the button for Itead’s color PCB service. The deal was $23 for 8 boards. That compares with $18 for 10 boards if they are green. Since both 8 and 10 boards are more than I need, it’s basically $5 extra for the custom color. I went for it.

For what it’s worth, one difference between Itead and Seeed is that Seeed only offers 50% electrical testing for their base prices, with 100% testing costing more. Itead has 100% e-test with their base prices. Itead and Seeed are having a bit of a price war over these PCB services, so their offers may well have changed by the time you read this.

Itead is offering an interesting bonus deal with their PCB services: PCB sharing. For a token 10 cents above the cost of the PCB service, they will send me two random boards from other designers. In exchange, they will send two additional copies of my board to other sharing participants. There is no guarantee the boards will be remotely useful to the recipient, but for 10 cents, how could I resist?

(By the way, if you’re reading this because you saw the skywired.net URL on a board Itead sent you, please drop me a note! I’d love to hear who you are and what you’re working on.)

I expected roughly a five day turnaround from Itead, and was disappointed when after five days, I received an e-mail that the fab had rejected my Gerber files. Itead wants the board outline on at least one Gerber layer. Now, both Laen and Sparkfun’s BatchPCB accepted the groundplanes on my boards as the outline, so I didn’t expect trouble from Itead. However, they were certainly within their rights to ask me for a correction. It was quick to add it, and a few hours later they told me my new Gerbers had been sent to the fab.

I’m still waiting for the PCBs, which were shipped Wednesday. Now I have to wait for them to come by airmail from Hong Kong. It’s hard to be patient!

A Trip to Electronic Surplus in Cleveland

Yesterday my son and I took a trip to Electronic Surplus, Cleveland Ohio’s candy store for electronics hobbyists and professionals. From a warehouse building in Mentor, ESI operates both a brick-and-mortar store and the website electronicsurplus.com. This is my home-town surplus dealer, which has been a good source for parts for me. Read on to have a look around.

The welcoming sign tells me I’m in the right place. Their location is near a busy intersection, but out of sight of the main roads. An earlier incarnation of the business was known as “Electronic Surplus Inc.”, hence “ESI”. Today the “I” is vestigial — the company is an LLC — but the abbreviation stuck.

The retail store fills about a quarter of the warehouse-style space, with the rest used for storage and web order fulfillment. The store has an odd C-shaped floorplan. This is the view from just inside the front door. The grey drawers contain a variety of parts. The shelves behind them have some of the test equipment that is for sale.

Not far from the counter is a selection of odd circuit boards and modules. This one is a sound and light board from a toy, and next to it is a high voltage supply board. Out of sight to the right was an LM317 power supply board. I was tempted by that, but decided it would be a better idea to use up the ones I already have in my parts collection. Continue reading A Trip to Electronic Surplus in Cleveland

Farewell, Digi-Key catalog

The May 2011 High Frequency Electronics arrived with the sad news that the most recent Digi-Key catalog is the last, replaced by the www.digikey.com web site.  Digi-Key are also cancelling their TechZone magazine.

I suppose it was inevitable. The warning signs were certainly there, as Digi-Key sent thinner and less frequent catalogs to hobbyists than to professionals, then cut back  to annual issues. Nevertheless, I will miss the giant catalog that has always had a prominent place in my office and home lab.

I received my first Digi-Key catalog in 1983. Back then, it was thin, only 32 or 64 pages long. They had a good optoelectronics section, which remains one of their strengths. The only US semiconductor manufacturer they carried was National Semiconductor, though they distributed several lines of Japanese semiconductors.  (At one point, I wondered if National was Japanese, too!) Continue reading Farewell, Digi-Key catalog

Exploring ABC Electronics in Minneapolis

Exciting stuff is going on at work, but as often happens, excitement involves a bit of overtime. I spent last week in the Twin Cities, working with two test engineers to evaluate an ASIC during the day, and working on patent paperwork at night. I did manage to get away long enough to visit ABC Electronics, a surplus dealer in Minneapolis. (The Twin Cities are also served by the Ax-Man Surplus Stores, about which I will write another time.) I left ABC assuring myself that I am not jealous of the Twin Cities’ surplus options, but I’m not sure I believe myself.

Continue reading Exploring ABC Electronics in Minneapolis

The FPGA boards are here… and they’re purple!

Despite my last post mentioning the lateness of the breakout boards, it turns out they had already arrived.  The mailer was stuck between two magazines in the mail, so my wife and I missed seeing it.  I had hoped to get the PCBs by February 26.  They were here the 22nd.  Oops!

They came out quite nicely, with no obvious defects, and they look quite regal with gold plating and Laen’s signature purple solder mask. How often do you see purple circuit boards?  The gold is nice, too. Laen’s standard boards are have a solder finish, but sometimes some of his customers pay the extra for gold, in which case all the boards on that order come back with gold.

The FPGA board, gleaming and ready for some solder.

I’m looking forward to building up these boards and writing some Verilog to bring them to life.