Practical Electronics: Components and Techniques (2015)

Appendix D. Resources

This appendix contains a collection of URLs for electronics distributors, sources for mechanical components, and vendors of surplus components of various types. It also includes a brief discussion of buying electronics components and other items from vendors on eBay, with some guidance and caveats.

This is not a comprehensive list, just the companies I am familiar with. This is not an endorsement for any particular company or product line.

Note that many of the sources listed here carry more than just what the list heading might imply, and some sources appear in more than one category to reflect the diversity of things they offer. Major distributors, for example, carry everything from passive components to hand tools and test equipment. Other companies, such as Adafruit and SparkFun, are more focused on the maker and hobbyist markets, but they too carry a wide range of products.

Software

Open Source Schematic Capture Tools

CAE Software Tools

PCB Layout Tools

Hardware, Components, and Tools

Electronic Component Manufacturers

Electronics Distributors (USA)

Discount and Surplus Electronics

Mechanical Parts and Hardware (Screws, Nuts, Bolts)

Microcontrollers, Kits, Parts, and Supplies

Electronic Enclosures and Chassis

Tools

Test Equipment

Printed Circuit Board Supplies and Fabricators

Most major electronics distributors sell things like etchant and single- and double-side clad PCB blanks with photo-resist applied. If you aren’t comfortable with the chemicals and the procedures, consider using a commercial prototype PCB house.

Prototype and Fast-Turnaround Fabricators

PCB Kit Sources

eBay

It is possible to find some amazing deals on eBay, but it pays to be careful about what you buy and from whom you buy it. Overall, eBay does a pretty good job of making sure that sellers aren’t scammers in disguise, and PayPal makes payments safe and painless. I have also had good results purchasing items from various vendors in China through both eBay and Amazon. I’ve been able to find amazingly cheap things and I’ve never had any hassle with a Chinese seller. In fact, they go out of their way to make sure you get what you ordered and you like what you received. As a bonus, the shipping is usually free for small items (although it can take a while to get to you).

Shipping cost is probably the main drawback to buying anything on eBay. Most sellers are honest about the shipping, but there have been a few times when someone tacked on a “shipping and handling” charge that far exceeded what the shipping label stated for the cost. After experiencing this a few times, I started to pay close attention to the shipping costs stated in the item posting, and now I simply look elsewhere if it seems to be out of line. But sometimes the cost is just what it is. For heavy or bulky items, the shipping can be steep, particularly if the seller decides to use a pricey service rather than the cheapest method. If what you are bidding on or buying is something you just have to have, then that is what it will cost unless you can convince the seller to use the standard service instead of the express delivery option. It pays sometimes to look around locally before jumping on what seems like a good deal only to be shocked when the total with shipping comes due.

Lastly, beware of sellers who state “all sales final, no returns” in the item listing. This is a big red flag. If sellers aren’t willing to stand behind what they’re selling, you should probably think twice about giving them your hard-earned money.

Other Sources

If you have a local electronics supply outlet, I suggest visiting it to see what it has. In addition to parts and supplies, some have a section set aside for surplus test equipment. Occasionally, you can get a good deal or even haggle to get a better price. In the retail realm, there is Radio Shack, and most stores have a fairly decent selection of components, kits, and tools.

If there is a used tool store in your area, it might be worth your time to go and check it out. Where I live, we have several, and I’ve found some really great deals on interesting stuff, most of which only needed some cleaning and adjustment to make it work like new (it doesn’t look like new, but that’s not really important, at least not to me).

Some large manufacturing companies and universities have surplus property sales from time to time. These can be great places to find everything from old computer gear to office furniture. The downside is that they are sometimes overrun with people thinking they are going to get a great deal on something good, and willing to pay far more than what it is really worth. The truth is that the stuff at these sales is usually there because it is too worn out, too broken down, or too obsolete to be of any practical use any more. You can get great deals if you’re looking for parts to salvage, or if you have the time and skills necessary to fix broken things, but otherwise, it might not be worth the effort.

Lastly, if you are fortunate enough to live in an area with an electronics surplus outlet, then by all means, go and check it out. These places can be a fascinating experience, and generally they are willing to negotiate the price, particularly for older items. When I was a teen, one of my first surplus acquisitions was an almost complete set of 19-inch rack-mount chassis for a sounding rocket launch control system. I never launched any rockets with it, but it was awesome anyway, and I learned an immense amount just taking it all apart and figuring out some of the circuits by following the traces on the PCBs. After all these years, I think I still have the red Launch button around somewhere in a box.

Datasheets, Application Notes, and Manuals

Almost every electronic component has a datasheet available for it. These are essential documents that describe the functional, electrical, and physical characteristis of a device. Even resistors have datasheets.

Application notes are intended to provide inspiration and guidance, and also to illuminate dark corners that a datasheet might not cover explicitly. Many successful product designs started from circuits described in an application note.

User manuals, sometimes running upward of 500 pages, are readily available for complex parts like microcontrollers and microprocessors, and manufacturers usually make them available for free. With a little effort, you can also find manuals for old test equipment and service manuals for consumer electronics. There are individuals and companies that specialize in locating and selling manuals for all types of electronic devices.

Never pay for a component datasheet or application note, if you can avoid it. The only time you might encounter a situation where you can’t get the technical information any other way is when dealing with an old part that has been out of production for many years. Otherwise, you are paying for something you can get for free by downloading it yourself.

Datasheets

The history of datasheets goes way back to the dawn of the electronic age, when manufacturers realized that, if they wanted people to use their parts in a new design, they needed to be able to communicate essential characteristics to engineers so they could use the part correctly. As electronic components have become more complex, this has become an essential activity in the electronics component industry, and whole divisions of a large semiconductor company might be dedicated to doing nothing but testing, characterizing, and generally experimenting with the component products. For those with an inclination to poke and tinker, and a good background in math and semiconductor theory, this could be a dream job.

It’s always a good idea to have the datasheets for the parts you are working with. There’s no need to guess; the information is readily available in PDF form from the websites of companies like Atmel, Fairchild, Maxim, NXP, Silicon Labs, Texas Instruments, and many more. See Chapter 9for a walk-through example of deciphering a datasheet.

Application Notes

Semiconductor manufacturers have a long history of providing documents called application notes (or app notes) that describe how their products work, how they can be used in various applications, and how to interpret datasheet parameters. In the past, before the Internet and PDF files, it was common to see a row of bookshelves in an electronics engineering lab filled with printed paperback volumes of datasheets and application notes. The application notes were particularly popular, and it wasn’t unusual to see books with some heavy wear and tear.

Today, you can download and print these documents for yourself as you need them. Personally, I like to keep printed app notes in three-ring binders so I can quickly find them when I need them, tag the pages, or even write in my own notes (using a pencil, of course!).

Manuals

User manuals (also called user’s guides) for components such as microcontrollers and microprocessors are readily available for free as PDF downloads from the manufacturer. These documents are typically written in a terse, cut-to-the-chase style, and they focus on the specific functional and operational characteristics of a particular device or family of devices. They aren’t tutorials, by any stretch (although some manufacturers do have tutorials available for download as well). Still, when you need to know what a special function register does, or how to use the PWM (pulse width modulation) function of a device, the technical data in a user manual is invaluable.

If you need a manual for something like an old signal generator, or a consumer device like a video camera or a radio, you will need to do some hunting. If a user or service manual for something once existed, chances are, someone has a copy of it that she will sell for the right price. You have to decide if it’s the right price, of course, but most of the time the cost isn’t unreasonable. eBay is a good place to start, as many vendors offer copies of old technical documents, either as originals or as duplicates.

Caveat emptor: if you are buying a copy of an old manual, the odds are good that it is an unauthorized copy. In most cases, the original manufacturer might not really care, since the product has long been out of production and it gives them some free market exposure. That’s assuming that they are still in business. But then again, they might care, and you might be in violation of their copyright. If in doubt, drop the manufacturer a quick note and ask how they feel about it.

You should also be prepared to inspect the document the minute it arrives, because some of the people who sell old manuals aren’t always as careful when copying things as they should be. If you get something that isn’t readable or is missing pages, return it, and check the listing on eBay before bidding or buying to make sure you can return it. As noted earlier, don’t deal with someone who flatly states “all sales are final, no returns.”