Thursday, October 30, 2008

The return of a hobby

The year 2000.

In early 2000, I was shopping for a new hobby and remembered how much I enjoyed electronics when I was younger. I figured I could afford to do it right as an adult. I was mostly correct. Electronics as a hobby can get pretty expensive.

I started by spending time in my local library looking at various books on Electronics to get ideas. One of the most useful was Build your own home lab / by Clement S. Pepper.

I got a Jameco catalog (downloaded it actually - couldn't do that when I was in middle school) and ordered some merchandise to build up a startup stock of components and a prototyping bench of my own. One of the things that was way to expensive for me back in the day was a solderless breadboard, so that was the basis of the workbench. That was my first project, I'll detail it in another post.

My initial stock was based on what I used to use in the past and many of the books I read in my research. Much of it has been useful, some of it not so useful. Here is what I started with:
  • An assortment of commonly used 1/4 W 5% tolerance through hole resistors. I bought these from Jameco in packs of 100 pieces for .99 each. I won't go into the specific values, because if I was going to do it over I would buy an E24 assortment from one of the many vendors selling on EBay at incredible prices. These assortments have all of the values within a specific tolerance such that the range of usable resistance covers all resistance values. For the record, get lots of 1k resistors if you're going to work with digital circuits.
  • Discrete IR LED and Phototransistor detectors (still haven't used them)
  • A grab bag assortment of trimmer pots and capacitors
  • A grab bag assortment of switches
  • A grab bag assortment of linear ICs
  • 2 pcs of 6N139 (Darlington Opto-Isolator)
  • 4 pcs of 4N35 (Phototransistor Opto-Isolator) (not enough)
  • Common Cathode and Common Anode LED Displays
  • A Grab bag of assorted LEDs
  • 10 pcs of 2N3906 and 2N3904 signal transistors
  • 10 pcs of 2N4401 and 2N4403 signal transistors (More of these than 2N390x would be better)
  • 20 pcs of 1N914 switching diodes (more would be good)
  • 20 pcs of 1N4004 1A Silicon recitifier diodes (buy more)
  • Grab bag of assorted transistors (signal and power) - waste of money - most are still in the cabinet
  • Grab bag of TTL ICs (waste of money - these are mostly obsolete with the advent of cheap microcontrollers)
  • Alligator clip test leads (can never have enough of these!)
  • Mini-grabber test leads
  • 7.25" X 7.25" 3220 point solderless breadboard.
  • Solder Wick
  • Desoldering Pump
  • Third Hand tool
  • Solder and a real soldering iron
  • PCB Etching kit
  • Specific parts: LM555CN, LM301, LM324, LM317, LM337, LM386, LM308, LM567, LM348 (most of these are handy to learn with, but probably will never end up in any circuits that I design -- there are much better alternatives available now with better performance all around)
  • A cheap digital VOM.
The goal of these purchases was to have a basic stock to experiment with rather than build specific projects. For the most part that goal was achieved, but I wouldn't recommend a beginner go buy the stuff I did. Instead, I'll go through my current stock and post the "Ultimate beginners list" of items that are must haves some time soon.

Some basic thoughts for folks at this stage:
  • Buy the basics to have a stock, especially a good assortment of resistors.
  • Capacitors are not as important for a stock. Get at least 20 1uf and 10uf caps in a 25 or 35v. If you're going to do digital circuits, get a lot of .1uf caps (say 100) for power bypass - you'll need lots of them. If you're going to build power supplies (of course you will) - get some bigger caps for filtering - 470uf and 1000uf (not many of these - and keep the working voltage reasonable or they are going to be really big).
  • Beginners use lots of trimmer pots - don't do it. Fact is, resistance is usually not that precise a factor in most circuits (if it was you'd be using .1% tolerance instead of 5% or 10%).
  • If you are going to do digital, buy at least 5-10 7805 voltage regulators - you will end up using them. I tend to buy more of the 78L05's that are good for up to 100ma - because you will find 100ma is really plenty of current for most circuits. (unless you are using realys or lots of leds)
  • Switches and connectors are expensive. They (and big caps) are about the only thing worth salvaging off broken electronic devices. Most other parts are not worth the time to desolder. If you can get switches and connectors cheap from surplus sites (BGMicro / AllElectronics, etc) buy them.
  • Cases are expensive - be creative instead. Buy them on sale, or use Altoids boxes or cases salvaged from discarded electronic devices.
  • Buy cheap (real cheap) Digital Volt-Ohmeters (VOM). Personally I tend to buy the little red VOMs from the local Harbor Freight tool store when they are on sale for $3.99 each. Buy several and you have the option to measure several different voltages simultaneously, which can really help you figure out what is going on in a circuit. You also have spares when you smoke them by measuring a high voltage on the ohms setting or blow the fuse when measuring a current.
  • A hotter soldering iron used for a short time is safer than a cool iron used for a long time. Soldering technique is a fairly simple skill learned easily from many good internet videos now. The most important thing to remember early is melt the solder on the part, not the iron.
  • Organize your parts! You can't built anything unless you can find the parts, and you definitely can't design anything unless you know what you have available to build with. Little 2x3 plastic bags in a pull out drawer box works nicely, and both can be purchased cheaply. (try US Plastics for the bags - 1000 for 5.77 at the time I wrote this). You can also get anti-static bags, but I didn't and have yet to lose a part to static).
  • EBAY! You can get a lot of parts on Ebay, including some very good assortments, at incredible prices.
  • Keep a list of parts you want or need and only buy online when you have more than the minimum purchase amounts and the S&H is reasonable.

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