• Inside Eric's Toolbox: An Electrical Engineering Kit

    Thursday, November 21, 2013

    11/21/2013— Eric Kolker

    In engineering we talk a lot about tools. Some people have a favorite collection of software, some a metaphorical belt filled with tips, tricks, and techniques, and others a literal box or lab bench filled with instruments. In my experience, a good engineer not only maintains all three, but seeks to expand his or her collection and share it with peers on a daily basis.

    Today I’d like to share what I keep in my literal toolbox and provide some commentary and backstory for the tools I carry with me. Expect some tangents and links to more Wikipedia pages, too.

    Figure 1: The box. Starts closed, gets opened, returns to closed configuration for transport.

    Boxception


    Unpacking from the top down, the first thing out is a smaller box.

    Figure 2: box of hand tools, closed

    The box contains the things I use most often: a plethora of small hand tools. In it I somehow manage to stash:

    • Wire strippers
    • Needle-nose pliers
    • Hemostats
    • A spool of 30-gauge wire
    • A spool of solder wick
    • A spool of solder
    • A loupe
    • Three sets of tweezers (yes, I use them all)
    • Four dental picks (ditto)
    • An assortment of connectors in various states of dismemberment
    • Some small plastic bags
    • A few scraps of wire, heat shrink, and other miscellaneous parts

    Figure 3: box of hand tools, open

    Big things with two handles


    Figure 4: Left to right: wire strippers, needle nose pliers, and hemostats

    The wire strippers I use for, well, stripping the insulation off of copper wire. I use them only and exclusively on copper because otherwise I would risk plastically deforming the tool and ruining it. Side note: I used the word “maintain” earlier not only imply that you should keep a kit of tools, but also to hint that good tools warrant, and often require, good care. But I digress: never use wire cutters or wire strippers on anything other than hookup wire. Headers, nails (tack, finger, or toe, it makes no difference), small steel shafts, etc. are not to be cut with my tools.

    Needle-nose pliers are great for pretty much everything. I like these in particular because they have good grips (compliant but not too soft and not the kind that dry your hands out or cause blisters), close evenly, and are lightly textured at the ends. They’re also a good size.

    Hemostats (point of interest: they’re supposed to be used to clamp arteries during open heart surgery) are a new addition to the box, and are useful because they ratchet shut and don’t let go. I often use them to hold things in place or grab onto tiny wire when I strip it.

    Things directly related to soldering


    Figure 5: Left to right: 30 gauge wire, solder wick, solder, and a loupe

    This tiny spool of tinier wire is what lets me hack boards with surface mount (SMT) parts. Thirty gauge (technically 30 AWG) is small enough that I can attach it to a tiny pad, but big enough that it can actually be manipulated without a microscope. This particular spool is insulated with plastic (as opposed to enamel-coated magnet wire which is a royal pain to strip), so I can run it all over the board without worrying about shorting things out, but strip off the insulation easily (with heat, even, if need be).

    Solder wick, sometimes called solder/copper braid, is used to desolder (mop up solder) by following these easy steps:

    1. Place wick on affected area
    2. Place soldering iron on wick (on affected area)
    3. Wait until solder in affected area becomes molten (you’ll see smoke rise when the wick’s rosin flux melts)
    4. Mop up molten metal
    5. Remove tools from affected area
    6. Feel like a boss because your ugly solder job is gone

    Up close, this stuff is a flat, woven strap made of tiny copper wires. It comes in different thicknesses, but I generally like think stuff so I can be precise with my solder removal.

    Not all solder is created equal. There are a myriad of different blends of tin and lead (and others), flux and no flux, fat and skinny, etc. My preferred blend is 63/37 (%tin, %lead by weight, which is the eutectic ratio for the metals, and corresponds to the lowest melting temperature for the alloy), rosin core, and super thin. It’s one step below good solder paste for precise SMT work.

    The loupe is effectively a magnifying glass that sits in your eye socket. I first ran into these guys when I took a photography class (we used ‘em to look at negatives before making prints). If you don’t have a microscope and need to make sure a board looks good (all the solder joints are nicely connected, components are properly seated, etc.), you’ll want one of these and a good flashlight to see what’s up.

    Tweezers

    (aka “small things with a debatable number of handles”)


    Figure 6: Tweezers!

    Each pair of tweezers is so important that it deserves its own paragraph. Left to right:

    These babies are my go-to. They have a long pointed tip, are acid resistant and anti-magnetic, are lightweight, and have a very abrupt taper at the end. The last two characteristics are especially important when I use them under a microscope because they help me know exactly where my fingers are on the tool at all times.

    These next guys are called “reverse action tweezers” because when you pinch they open up, rather than close down. These aren’t super useful for surface mount work because they’re so big, but are great for holding “normal” size wire (~24 AWG) or through-hole components in place when I solder.

    The last pair of tweezers is probably the most expensive tool in my box that doesn’t use electricity. They’re made of stainless steel, are corrosion resistant, anti-magnetic, and are designed specifically for SMT soldering (and surely give +5 Dexterity). The shape of the tines lets me apply pressure to chips evenly along the sides (crucial for precise placement) without hitting other components on the board (essential for densely-packed boards). When you turn them sideways (so the tines are vertical), you can grab the chip perpendicularly to the board and still see everything in the microscope.

    Dental picks


    Figure 7: Dental picks

    Unlike the tweezers, these dental picks are all pretty much the same (sorry to disappoint). Some have pointier ends or are better shaped for some specific task, but all are used for some combination of scraping, pushing, or cleaning boards or chips. Because they have all come into contact with lead, I can no longer recommend that they be used to clean teeth.

    Miscellaneous smallbox-dwellers


    Figure 8: Miscellaneous occupants of my meta-toolbox

    This is an odd assortment of stuff. Left to right, top to bottom we have a (probably broken) RFID IC, the cover for one of my super swank multimeter probes (read on!), SMA connectors, two small plastic bags, heat shrink, and some black wires (for ground, should I need ‘em).

    SMA connectors are industry standard RF (radio frequency) connectors. They belong to a family of connectors called “coaxial”, whose name comes from the arrangement of the inner and outer conductors (the latter, a ring in cross-section, should always be used for ground). I keep these particular connectors around because 1) connectors in general are expensive (these were maybe $3 each, but some are truly pricey) and 2) because they have been modified (read: I broke off some pieces off of each one) so they’re easy to attach to boards quickly for the purpose of testing something.

    Scopes and meters


    A tiny oscilloscope


    Figure 9: DSO Nano with probes plugged in and the box it comes in

    One holds a DSO Nano, which is a pocket-sized oscilloscope/function generator made by Seeed Studio. As far as scopes go it’s certainly a budget model, but when you need a scope you need a scope, regardless of how small. I use it when I’m in a pinch, am too lazy to walk to the lab, or have simply run out of channels on a larger and less portable scope. It’s also nice to have on hand because it’s battery powered, and therefore it floats (in the electrical sense, that is: it has no connection to Earth ground, which could get you into nasty trouble when dealing with things that plug into the wall).

    ##Multimeters and probes

    Figure 10: multimeters and probes.

    My old, crappy multimeter and the thoroughly destroyed probes it came with, the probes for a new multimeter, and the new multimeter with my fancy probes. The old meter still mostly works, so I keep it around. The new one is honestly untested, as are the probes it came with, but the probes installed in it are the best. Their tips are spring loaded (called “pogo pins” in the art), interchangeable, stupid sharp, and gold-plated, which make them good for getting a reliable connection on tiny surface mount parts. They even have their own datasheet! The downside is that, as probes go, they have a super high resistance (maybe 0.6 Ohms or so).

    Tape


    Figure 11: Tape!

    I carry Kapton, Crapton, and electrical tapes.

    Kapton is great: it’s corrosion-resistant, has excellent thermal properties, is a fantastic insulator, stays sticky even when abused, and is rated by its thickness, so even mechanical engineers appreciate it. It’s a little pricey, though. I use it to cover up wire hacks (when I use that blue wire) and strain-relieve wires I’ve soldered onto a board temporarily for testing.

    Crapton is fake kapton. It’s still an insulator (read: when something has been taped up, it can no longer be poked), but I don’t trust it on the other counts. Buyer beware: a lot of the cheap kapton on Amazon is really crapton, which is how I wound up with this roll.

    Electrical tape is, well, nonconductive. More often than not, I use the stuff to secure boards to the lab bench when I’m soldering them. Electrical tape is good for that because it ‘s a little stretchy, so I can keep the tape under tension to make sure the board doesn’t slide around.

    Soldering paraphernalia


    Figure 12: An itty-bitty soldering iron and some syringe tips/needles.

    At 12 Watts, this iron is truly puny (even the inexpensive industrial grade ones are usually 60 W, and they do as high as 240 W before you start to get to plumbing gear); you can’t beat the portability. The needles go on the ends of syringes of solder paste, which are stored in a refrigerator (we probably confused some people at Highland this summer…).

    The needles allow you to apply paste super precisely to the tiny pads of obnoxious SMT chips, but they often clog, so it’s good to keep extras on hand.

    Miscellaneous debugging tools


    Figure 13: Assorted jumper wires, a big electrolytic capacitor, a bag of grippy things, a binder clip, a ruler, and a Bus Pirate.

    • Jumper wires are just generally good to have around when debugging
    • Same goes for a decently sized capacitor. This particular capacitor (220 microfarads, 50V, aluminum electrolytic) helped me debug Tessel’s power input circuitry.
    • The grippy things are like small versions of those robot hands they sell at science museums, but for circuits; they’re used to grab onto unsuspecting wires, pins, or leads so that you can measure the voltage there. Lots of different tools come with these kinds of things, but these particular ones are made by Tektronix (one of the big test equipment manufacturers, and a company known for its analog oscilloscopes) and are designed to be used on SMT parts. In short, they’re the best grippy things I’ve come across with their long, skinny necks and super strong grip. There’s a reason I have so many of them.
    • Binder clips hold stuff, keep bags closed to keep moisture-sensitive parts dry, etc.
    • This ruler is open source! No, really. It also happens to have metric/imperial conversion charts, PCB spacing guidelines, hole sizes, and a whole slew of other useful information.
    • The Bus Pirate (and cable assembly) is a piece of OSHW that’s essentially the Rosetta Stone for communication with embedded devices. You tell it what you want to say and what protocol to use and it translates. Works with OSX and Linux and is available from Dangerous Prototypes (the creators) through Seeed Studio and SparkFun.

    Knife


    Figure 14: Cardsharp, aka TSA bait

    This knife usually lives in my pocket, but bears mention because I truly bring it almost everywhere. The blade is good (medical-grade stainless which I keep sharp), but the handle is a little weird when you unfold it.

    Cables and boards


    USB Cables


    Figure 15: USB cables

    I have a bunch of USB cables. The ones in this picture are A to B and A to micro, and I use them to talk to an Arduino Uno and Tessels, respectively. The two in the little box are the same kind that our Beta backers get (whoo colors!).

    Arduinos and Tessel modules


    Figure 16: a handful of modules and an esoteric Arduino

    Tessel modules (RFID, Ambient, and GPS), an Arduino Pro Mini, and an FTDI USB to serial adapter + mini USB cable. This particular Arduino is great because, unlike the Uno and the Mega (which I have but don’t always carry with me), it’s a 3.3V device (so’s the Tessel). I use it to test and debug modules without worrying about breaking the module with a 5V signal. The downside to the device is that it needs the external USB to serial adapter in order to be programmed.

    Tessel (of course)


    Figure 17: my Tessel

    Last but not least, my Tessel (and yet another micro USB cable). This particular board has been hacked so that it uses an external antenna, and I’ve been using it to test the range at which Tessels can connect to WiFi. Perhaps “hacked” is a strong word: the current version of the board has the footprint for an MMCX connector (the smallest, most robust RF connector I know of) on it so that it’s easy to swap to a more sensitive antenna. Here I’ve attached an MMCX to SMA adapter from SparkFun to connect to a 2.4 GHz WiFi antenna.

    …And that just about does it. The old school EE in me feels compelled to also mention the concept of a good lab notebook (there are actually some interesting legal reasons here) in which you date every page and write only in pen…and that I almost always use a fountain pen. The rest of me would like to remind our readers that I am not, in fact, an old man.

    ~e
    e@technical.io

    P.S. Even though studies overwhelmingly show that learning by doing is the best way to retain information, good whitepapers and lectures still have their place. Here’s a link to my personal stash of application notes and reference guides from a few of the big players in the electrical engineering space. The trove grows with time, and grows fastest when I’m building exciting new things. Enjoy!

    #tessel #technical machine #eric kolker #electrical engineering #hardware #hardware hacking #toolbox #tools

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