Laboratory

Welcome to my lab!

This is the latest iteration of an ongoing endeavour to realise a fantastic childhood vision inspired by cartoons, books, comics and daydreams.

Attempts at an accurate rendition of that vision within the mind of you, the reader, will be utterly in vain. The few words that I can spare here will do little justice to this concept, but with the help of the following stereotypes I can give a good piecewise approximation of it: mad scientist’s lab, sorcerer’s chamber, hall of the mountain king (*cue music of the same name composed by Grieg).

Now that your mind is prepared — Behold! The splendour of the Chamber of Labour! Where holes and electrons move in accordance with my will! (And by the blessing of quantum mechanics.)

Mouse-over to get acquainted and click to read more:

Alas! I exaggerate. Surely you do understand that reality is often a much more modest affair than the grand visions of our dreams? Yet dream we all must. The unfantastic appearance of my lab belies great ambition! The best is yet to be, as you shall see!

In addition to a laboratory, I also maintain a great stockpile of junk. The Stockpile (as I have so named it) is an essential complement to my laboratory, and to highlight its role, ‘The Hinterland’ has been suggested as an alternative name. Yet although it is a rather fancier title, it is also rather less accurate, for the whole wide world is the true hinterland of the engineer.

Anyway, let’s get on with a tour of my lab, and please accept my apologies for not showing you around the Stockpile also, for it is an embarassing mess very dear to me and must be kept private.

A short history

In ancient times, which is to say when I was a much younger kid (now I am but a grumpy old man), dreams were bolder, and reality was much closer to fantasy than it is today. Though memories are hazy and truth is hard to separate from legend of those times, this much I can claim to be true: In my childhood home I once had a wet lab (actually, an unused toilet which I claimed for my realm), which was a kind of lab for chemical and biological experiments of the wet and messy kind. Notable experiments include an attempt at re-animating the limb of a dead crab.

I also owned a second facility for ‘scientific’ experimentation, and this was of course my own room. It housed several departments (these days they call such things ‘interdisciplinary cross-pollination’): a chemistry department equipped with a fume chamber I built myself (mainly for the nasty business of liquefying the vile oils of insecticide spray), an electronics laboratory (lots of dead electronics abducted and dissected), a jet propulsion project (I began by making engine blades from drink-can aluminum. Later on, the Internet told me I could build a proper one with a car A/C compressor; may try that someday.), and on two separate occasions, short forays into rocketry (first was the water-propelled sort, which had leakage problems; second was the chemical sort where I tried different fuels – rubbing alcohol from the pharmacy, and hydrogen peroxide with a manganese dioxide catalyst that was hard to obtain in useful quantities!)

So you see, back in those days I was quite the Natural Philosopher. These days, I am merely an Electrical Engineer with a Bachelor’s degree, Honours of the Second Class, Lower Divison, blah blah bleah. Indeed, in my case it seems that ontogeny has recapitulated phylogeny (to borrow out of context that popular phrase of the developmental biologists), and evolution has not been for the better.

Yet all is not lost. For now, the Necromancer Natural Philosopher lies hidden in the shadows, biding his time and building his strength…

Plans for the future
  • To design and build a modular power supply solution. Presently, I use several power adapters from old electrical appliances, and other more proper ones from work as I can get my hands on.
  • A general pneumatic unit — one that can serve as vacuum cleaner, solder sucker, air pump…I will build one by hacking a tyre pump (an approach I learnt from hackaday)
  • Modify desk lamp to accomodate a lens. Maybe I need that; maybe I should just get a stereo microscope?
  • Acquire a long blackboard and modify it so that it can be turned into a whiteboard if my whim so desires.


A Source of Encouragement

Working alone on a project has its ups and downs. Sometimes it feels awesome, other times I get disheartened and worry about how the work will be received by others. But Richard Feynman always looks interested, his unconditionally encouraging face an eternal source of motivation.

feynman-postcard

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Anti-ESD Atmospheric Environment

Taking electrostatic-discharge (ESD) precautions to the extreme, the lab is housed in an anti-ESD atmospheric environment. This is achieved by locating near the equator (where summer lasts all year round and the air is always humid), opening the windows, and keeping the air conditioning turned off.

thermometer

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Benchtop Multimeter

A Fluke 8808A bench multimeter provides great precision for many sorts of measurements (current, voltage, resistance, frequency, and continuity and diode testing). So much precision is available, that one now has to worry about meter calibration, and other things that fall under the theme of measurement accuracy, in order to exploit the full power of such instruments.

bench-multimeter

Besides the front panel, the multimeter can also be controlled ‘remotely’ from a computer via an RS-232 interface, which makes it useful for data logging and other sorts of automated measurement applications.

In a more general sense, the bench multimeter fills a niche as a highly accurate and precise digitiser of analog signals coming from an instrumentation frontend, which saves the trouble of having to build one from scratch when it is not worth the trouble.

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LCR Meter

This is an Agilent 1733C LCR meter which measures inductance, capacitance, and resistance, as well as other related figures of merit which quantify certain inevitable non-idealities present in real LCR components. An extremely useful piece of equipment not only for engineering purposes (particularly RF work), but educational ones as well; it is regrettable that LCR meters are not commonly available, because aimless play with an LCR meter and some conductors can help one develop an intuition about how inductances and capacitances arise, particularly the stray/parasitic ones that are easily forgotten until physics rears its ugly head.

lcr-meter

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Oscilloscopes

The oscilloscope is an absolutely indispensible instrument for electrical work, being effectively the eyes of the electrical engineer. I presently have three analog scopes in my possession, none of which are completely operational. Nonetheless, all are very interesting for various reasons.

oscilloscopes-all

scope-leader

Leader LS-1020

The Leader LS1020 is the very first scope I’ve ever owned, and it was my Mum who bought it for me. After I found a suitable model online that wasn’t too expensive, she drove me down to collect it from the dealer. Over at the office, I was shown into a room full of equipment and electronic parts, where approximately two elderly men worked. While Mum waited outside, one of them proceeded to demonstrate that the scope was in working condition. We went through various settings on the control panel, and cross-checked its display with another piece of test equipment to which it was connected. This was a huge, white, and impressive-looking machine made by Fluke, with many knobs and buttons and a blue-on-white backlit LCD display; it exuded an aura of superiority from its perch upon a wheeled instrument trolley, and I reckoned it was some special oscilloscope/function generator used for calibrations.

I was barely able to keep up with the demonstration, as I hadn’t had much prior experience with scopes, but was as satisfied as I could be at that time that the goods were in working order. Being but 17 years of age, I was trying hard to impress upon others that I could be taken seriously as a real engineer, and took great care not to show any signs of ‘weakness’. At the end of it, the old man told me (in Cantonese-accented English no less): “Some day you can make your own equipment too” (or something to that effect); I felt like a kid visiting a kungfu master, and it was awesome.

Even at the beginning, the trigger was always tough to use, and getting a stable display was like trying to grab an eel in muddy waters – you fish around blindly for awhile, and then after getting it, it eventually slips out of your grip. It was many years later, upon using a fully operational scope, did I realise that the trigger was faulty (and not my understanding of scope triggers). After all these years, one channel no longer works, and everything has likely gone out of calibration, yet it remains the only scope that I can still depend on at home. It recently featured in the video of a friend’s marriage proposal.

scope-tek-tas250

Tektronix TAS-250

This TAS 250 is a scope from the early 90s, and it comes with cursors and readouts. Such analog scopes are, in my opinion, a perfect union between the high contrast display and high waveform update rate characteristic of analog scopes, and the measurement capabilities that a microprocessor and good software can provide. Even today, on lower end digital scopes with their LCD displays, the waveforms are uglier and sometimes laggy, so the analog scope with readout still has its place.

The scope was once used in an educational institution, and was originally destined for scrap before ending up in my possession (which is always a good fate for junk, I daresay). Unfortunately one day, the trace disappeared from the display, after no more than 6 months of delightful use. I tried to take it apart to fix it, but quickly hit a dead end because I couldn’t figure out how to remove parts of the front-panel assembly. Without the service manual, repair seemed impossible. And so it sits in my room till this day, a reminder of my happiest analog scope days.

scope-tek-2235

Tektronix 2235

The Tektronix 2235 scope was purchased from a shop that sold lots of wonderful industrial and automation equipment: oscilloscopes, function generators, power supplies, a spectrum analyser, a ‘Regeltransformator’, microscopes, solder pots, solenoids, linear actuators…mechanical seismograph! I was then looking for a good analog scope that could be repaired, which meant that the service manual also had to be available from the Internet. Fortunately this was the case with the 2235, but I was also torn between it and another even older, analog storage oscilloscope (I think it is a Tektronix 434, which comes from the early 70s).

An analog storage oscilloscope has a CRT with a special kind of phosphor coating that persists in glowing, even after the electron beam no longer impinges upon it. The old waveform can be erased of course, at the press of a button. This sort of feature is very useful for tracing out waveforms on a very slow timebase, and especially for capturing infrequent transient events. The ability to do the latter would not be found in digital scopes until the ‘digital phosphor oscilloscopes’ were invented, and even today such scopes are pretty expensive to own, whereas I could get the old analog one at a price tag with fewer digits in it.

However, the manual for the analog strorage oscilloscope remained elusive, and having only succeeded at finding the manual of a related model (with no storage function), I decided that it was perhaps safer to get the 2235. Soon after making that purchase, the shop went out of business, and the wonderfully exotic analog storage oscilloscope that I came so close to owning is now lost.

The 2235 service manual is a great example of excellent documentation that can scarcely be found these days, particularly when ‘repair’ really means exchanging the old unit for a new one. I haven’t yet found time to repair the oscilloscope, and will likely not try to do so until a suitable isolation transformer can be found.

Tektronix-2235-service-manual

A page in the Tektronix 2235 service manual, showing the very impressive block diagram of the oscilloscope.

At work I’ve used a cheap Uni-T digital scope, which has served my purposes far better than any analog scope has. On several occasions I was able to abduct it to serve in my lab for a few days. Yet I have grown sufficiently intimate with it to see its many shortcomings (e.g. aliasing, inferior waveform appearance, slow waveform update rate especially at certain time bases), which are fairly representative of the age-old challenges faced in digital oscilloscope design.

Some day I will save up enough money for a good Agilent scope from the Infiniium series, which I’ve heard features waveform update rates high enough to finally convince me to put away my analog scopes.

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Electronic Parts Cabinet

Overview of drawer allocation for storage of electronic components.

A great portion of the assortment of magic dust electronic components that I currently find necessary to keep in stock is stored in these two cabinets — a total of 50 drawers to sort stuff with.

Generally speaking, the parts fall into one of the following three categories:

  • Passive discretes
  • Semiconductor discretes
  • Integrated circuits
Passive discretes

The passive discrete components are the inductors, capacitors and resistors. Having ready access to a wide selection of component values (of inductance, capacitance and resistance) is crucial for work on analog circuits, so some effort and money has gone towards maintaining a ‘standardised inventory’ of passive discretes for general prototyping purposes.

The first thing to consider is how to organise these parts properly. The passive components are usually manufactured with certain standard values that are repeated across every decade, and those values are standardised by the IEC. In fact, there are several possible sets of standard values to choose from, and a sensible choice depends on the tolerances of the manufacturing/sorting process.

For the purposes of this lab, I have decided to stock and organise all passive components according to the IEC’s E24 series of standard values. As the name might suggest, there are 24 standard values per decade. Roughly speaking, the commonly useful range of values for all three passive component types spans approximately 6 decades. Altogether that means a rather long list of items, and not nearly enough drawers in the cabinet.

A sample row of labels for passive components. Each label is marked with 3 numerical values and 3 unit symbols (Henries, Farads and Ohms) accompanied by the appropriate prefixes (e.g. capacitances start from picoFarads but resistances start from a couple of Ohms). Labels are striped in a shade of grey that reflects the decade to which the component values belong, so the columns are visually differentiated from each other.

The present solution (besides getting even more drawer cabinets, which I may have to do in the future) is to have one drawer hold 3 values of all 3 passive component types. The drawers are labelled such that one decade of component values occupies a column of 8 drawers, and altogether the cabinets can accomodate 5 columns/decades; that’s 40 drawers. One more drawer is used to keep components with large values i.e. a sixth decade and beyond:

Label for large component values i.e. the sixth decade.

Of course, such a sorting system is not perfect. Items that fall through the cracks in the labelling system are just stuffed into the closest matching drawer.

The second issue to consider is the selection of appropriate parts for the ‘standard inventory’. This is such a tedious task that I have only had time to assemble a nearly complete collection of resistors (capacitors are still obtained ad-hoc from sources that provide uncharacterised parts and sorted by decade in zip-loc bags, while the inductor collection is a complete mess). The ‘standard prototyping resistors’ have the following characteristics:

  • 1% tolerance
  • Metal film
  • Through-hole axial lead package
  • 1/8W power dissipation rating

The first 2 requirements are important characteristics for analog circuit prototyping; they ensure good accuracy, low resistance variation with temperature, and low noise, compared to the cheaper carbon composition ones. Next, through-hole components are desirable for most prototyping purposes, being really easy to handle. The last requirement concerns power dissipation, and in this case my choice is less than optimal. I think a 1/4W resistor would have been ideal, and besides the 1/8W resistors are too small to read the colour code properly! But I had little money when this collection was acquired (still in junior college), and the 1/8W ones were cheaper; I have been living with the consequences ever since!

By the way, I have stuck to using the E24 series of component values even though the E48 series makes more sense with 1% tolerance components. The reason is that I have found E24 parts easier to find — manufacturers make E24 parts even when they’re 1%. Just as important, working with E24 values means retaining the flexibility of substituting 1% parts for 5% parts, if that is called for.

Label for drawer containing all other discrete passive components.

Finally, one drawer is reserved for special discrete passive components, and these include light-dependent resistors (LDRs), thermistors, and power resistors. Potentiometers and other variable passives are currently found here too, until I can find a sensible way of organising them with the drawers containing the fixed-value passive components.

Semiconductor discretes

Discrete semiconductor components are stored in drawers labelled like so:

Diodes include both LEDs and small signal ones. Schottky diodes are indispensible! Transistors include BJTs, MOSFETs and JFETs. Everything else (e.g. UJTs) is considered exotic and dumped in the “Special” third drawer.

Integrated circuits

Integrated circuits from analog to digital and everything in between are kept in these five drawers, labelled as such:

  • Amplifiers, Comparators and Power — Op amps, comparators and power regular ICs.
  • Analog (Special) — A bin for all other analog chips.
  • Mixed-Signal & Misc ICs — For everything that lies in the middle of the analog-digital spectrum, such as ADCs, DACs, digital potentiometers and V/F converters.
  • Digital (Standard) — Standard digital logic ICs go in here (e.g. chips from the 74XX series)
  • Digital (Special) — All other digital ICs are kept here, including microcontrollers and 555 timers.

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Power Strip

The power strip is a most essential lab facility. A high quality one should be purchased, and no expense should be spared.

I have taken care to ensure that every individual socket has its own power switch and for extra safety, a power indicator lamp. Ideally, the strip should withstand the rigours of lab use, which means that the sockets maintain good electrical contact in spite of the repeated insertion and removal of plugs, and that the indicator lamps always glow when the respective power switch is turned on. Unfortunately, from personal experience, many power strips (even the one I currently use) fail in this requirement somewhat. Doubly unfortunately, such things are hard to ascertain before purchase.

Over here in Singapore, we use the UK-type three pin sockets. Very often, plugs with only two pins are encountered, so power strips which allow their insertion without additional hassle are very desirable (a compromise in safety, perhaps, but I am no toddler!). For the more exotic plugs (of course that is relative), a good adapter or two is a very useful accessory to have.

power-strip-apower-strip-mount

Proper positioning of the power strip is essential for good fengshui! Many fine points concern the mounting of the power strip. First of all, it should be placed above the table where it is most unsightly (novices to the art take note!). Second, it should face the person seated at the table. Third, it should be located within arm’s length, so that the plugs can be reached at without the slightest stretch. Fourth, the power strip must be mounted at a suitable height from the table surface, to ensure that the cable from the plug does not impede the latter’s insertion into the socket. These considerations are necessary to ensure great convenience in both the application and the withdrawal of power to anything, the latter being especially important in the event something threatens to melt down or blow up.

The power strip is hung (not permanently fastened) from L-shaped wood supports (actually, hacked shelf supports from Ikea), which are fastened to the underside of the tabletop shelf. This means that the empty space behind it can be easily accessed for storage of items needed only on occasion. Care has been taken to ensure that the mounting screws on the wood supports fit snugly into the mounting holes at the rear of the power strip, so that it does not move when a plug is yanked out of its socket.

An apparently common affliction of electronics labs is the lack of power sockets! To avoid such problems, a separate power strip was purchased for plugging in electronic equipment of a more permanent nature, and they’re turned on or off all at once with the switch at wall socket to which the strip is plugged in.

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Soldering Station

A soldering station was acquired for its ability to regulate the soldering temperature (fried chips are more useless than their edible counterparts!), though the particular choice of a Weller with digital temperature readout is admittedly a little frivolous. It is an extremely useful feature that the soldering iron’s stand is separate from the power unit of the soldering station, which allows the iron to be brought close to where all the action is.

soldering station

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Table and Extension

A part of my study table serves as the lab bench, but alone it is not deep enough to accomodate work in front and supporting instruments and supplies at the rear. The remedy for this shortcoming is a plank of wood (originally meant for an Ikea shelf) halved along its length, and attached to the table by the inappropriate use of a television mounting frame and some bad carpentry.

The originally rough surface of the plank of wood was sanded down by an improvised rotary sander (hint: involves a drill), and then given multiple coats of urethane laquer to yield a smooth finish. Discrepancies in appearance between the surfaces of the original table and its extension, while slightly glaring at first, gradually disappear through the neurological process of adaptation.

table-ext-top

table-ext-underside

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Theoretical Workspace

lab-notebookA horrible mess of a table is an inescapable by-product of practical work. This tangible mess, as I have found, constantly seeks a chance to invade the poorly defended mind, and it is easy to let one’s guard down when experiencing the frustration of things not working. When one’s wits are breached, enlightened practice will quickly degenerate into blind randomised trials that lead to nowhere, and in the worst case one may end up forswearing electronics (especially of the ‘analog’ variety), accusing it of being a discipline of the dark arts (nope, that will never be me).

I believe that the best defence against such insidiousness is to dedicate a separate space for theoretical work, one exclusively reserved for clearing the mind and strategising the campaign. Additionally, at the boundary between theory and practice, it is good practice to lay down some pen and paper, to facilitate the timely documentation of practical and experimental investigations. Paper should come in the form of a notebook, because loose un-numbered sheets are hard to put in order later.

Altogether, these measures ought to help keep one’s wits together and maintain sanity. Alternatively, just grab a hammer and ‘Widlarize’ the offending circuit, then take a walk outside.

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Tools and Consumables Cabinet

The most commonly used tools and consumables are stored in this drawer cabinet. For now, it is the best solution that I can think of for keeping those things in order and within arm’s reach (a recurring theme in the design of this lab!), given the space constraints that I currently face. Here’s a breakdown of what goes into each drawer from top to bottom (i.e. from easiest to reach to the most infrequently opened drawer):

  • Pliers — A good selection of pliers and cutters, of which 3 are indispensible: a good quality cutter with flush cutting edges for trimming wires and solder joints, a cheap cutter for everything else including stripping insulation, and a pair of blunt-nosed flat pliers for working single-strand wires when using solderless breadboards.
  • Miscellaneous Small Hand Tools — Includes a selection of tweezers and penknives, small solder sucker that needs only one hand to use (a convenience bought with the expense of sucking power), a brush (even better if it had come with a rubber squeeze blower thing), small mirror on a telescopic stick (good for seeing around tight spots, better if I could add an LED light to it perhaps?).
  • Electronic Connectors and Housings — A good selection that should include housings, crimps and terminal blocks.
  • Adhesives — All manner of tapes, glues, epoxies, and cable tie! I also keep a box of surgical gloves, but it doesn’t fit in the drawer, although it should…
  • Mechanical bits — Screws, nuts, spacers…
  • Screwdrivers — Test pens (one is subject to mechanical abuse, the other is reserved for its original purpose!!), sets of small screwdrivers with regular and torx heads, a box of 100 different screwdriver bits for undoing every possible screw, and a big screwdriver with a magnetic receptacle for putting those bits to work.
  • Miscellaneous Large Hand Tools — Some odd tools, including a handsaw and a crimper.
  • Hot stuff — ~40W soldering pens with no temperature regulation (many are spoilt, the rest will be used to melt holes in plastic on occasion), a hot air gun (on long term loan to some good friends ;), a hot glue gun, a lighter with a blowtorch-like flame, and a real blowtorch (good for brazing, bending stuff, temperature stress testing, and destructive ‘testing’).

The present method of storage may not work well in the future, when I should learn more of wood and metalworking and try to accomodate these arts in my lab. We shall see.

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Vise

While this lab is nominally an electronics laboratory, mechanical work is inevitable. Moreover, it was never my intention to stop at electronics.

vise

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Wire Reels and Rack

Wire and solder reels are kept on a rack for easy access and replacement. This is just a metal tube that sits on a pair of hooks fastened to the underside of the table shelf. The rack is really short ehough (only ~20cm), so in order to keep a good selection of wire diameters and colours at hand, only small reels can be used.

Many improvements can be made to such rudimentary design, though they require more effort than I currently have the time for. For example, I would really like to add a second deck to the rack by shortening the hooks and fastening another pair to them below. Then the single-strand and multi-strand wires can be hung on separate racks. Another thing is that, although the tube isn’t prone to sliding off the rack sideways when wires are drawn from the reels, it might be better to take an extra precaution. I’m still trying to decide between a mechanical solution or one that relies on friction (it’s my excuse for not sealing off the open ends of the metal tube yet!).

I also wonder about solving these other minor hindrances: 1) How to stow the wire at the end of the reel so it can be quickly located? 2) How to easily wind up excess wire that has been drawn from the reel?

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Work Surface

A PVC cutting mat, suitably ‘augmented’, serves as more than a table-preserving work surface, for it contains a removable ground plane.

work-surface

A sheet of metal serving as the ground plane may be inserted into a hard plastic document holder attached to the underside of the PVC cutting mat. The document holder and metal sheet are suitably sized, so that they are partly exposed along one edge of the cutting mat, and holes are cut into the plastic of the document holder, to allow connection of the ground plane to a suitable grounding point on the circuit being worked on.

Sensitive circuits can thus be shielded against elctromagnetic interference, yet the ground plane may be removed to evaluate a circuit’s susceptibility to interference, or if its presence is not desirable to the circuit at hand.

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