Seattle: The Tiny Desk Aquarium

On one of my many trips to Seattle, I began contract work with the University of Washington, and decided to start a new aquarium in my hotel room.  For $2.99, found an 8″ cubical vase with thin, fairly even side, and stocked it with plants and mud from the U of W lakeside grounds and in ditches around Koll Business Park.


Anyone who has been around marshes knows that oily films on the surface are very common, and result not from pollution, but from substances released from decaying organic matter. Examining these quickly shows that they are a rich and possibly poorly explored environment.

The tiny hotel desk aquarium is doing well, but has developed a film of this type as the leaves, organic debris, and mud stirred up during collection undergo natural processes of degradation; the film can be best appreciated by comparing it to the clear avenue in this image (see image where you can see a clear avenue in the film):

Aquarium with Surface Oily Slick
Aquarium with Surface Oily Slick

Passing a slide through this film brought up a layer of mucky brown substance:SURFACE SLICK ON SLIDEYet the microscope revealed an area of almost unbelievable richness of bacteria, flora and fauna, as shown in the two videos, one of the film of degenerating plant material, and one of the water between islands of decaying fibers. Resolution is not perfect, but best I can manage in the field, and you are looking through a fair anount of guck on many of the levels. I count long strands of acinetobacter, gliding algae, cyanobacteria, ciliates, sessile algae, a rotifer, a small water flea (not shown), Synura or a similar species, several Vorticella, and many flagellates, a few of which I think are euglenoids:

Many questions come up regarding the function of these surface films and their role in the marsh in terms of gas exchange, absorption of sunlight, breakdown and recycling of organic material, possibly aided by solar energy, etc, etc. Fascinating – like having a webcam into a stretch of Amazon rain forest!

Seattle: The Tiny Desk Aquarium

How Bright is Your Light? Part I: Rebuilding the Nikon S Light Intensity Control with a $4.95 Dimmer Switch

Nikon S-Kt illumination system, base removed.  Note old-style “toroidal” transformer at bottom and voltage adjusting potentiometer at upper left.  The toroidal design is actually highly efficient and shows less power loss than square designs.  The thyristor (Triac) is the pillbox-sized rectangular structure at upper right.  Someone has improperly rewired the potentiometer at upper left – note bare wires!


Restoring my beautiful old Nikon S proved to be a continuing saga – and a remarkable learning experience.  In my last article, I described the procedure for replacing a broken nylon fine focus spur gear, a problem that has sidelined many of these finely-crafted old scopes.

I originally bought the Model S-Kt with lenses (in lovely shape from 20 years on a shelf) for only $75.oo because the light would not turn on.  Getting the light working took only ten minutes with a soldering iron to re-secure a loose flange on the light bulb, after which the bulb connected properly.  However, deeper problems lurked within.  After repairing the focus gear and bulb, using the newly-restored scope revealed that the bulb voltage could not be raised over two volts and the transformer was overheating and smelling hot. It was unclear whether the transformer was shorted or the electronics were not working.

This question was solved when, after half an hour of operation, the light suddenly flared to its full brightness and the intensity control stopped working.  Clearly, the transformer was producing full voltage, but the 45 year old electronics had blown.  Removing the baseplate revealed homemade circuits on the intensity control potentiometer; these may have contributed to the overheating and failure of the old circuits.

I knew nothing of light control circuits, but online research informed me that the core of a light dimmer system was something called a thyristor.  So what is a thyristor, and what are those mysterious little thingamagummies on the printed circuits inside the base of any but the oldest microscope power supplies?  I had to educate myself in the history of microscope illumination, and it turned out to be a fascinating journey.

(With thanks to Mark Morris for suggesting this fix)

In the 1950s and 1960s, microscopes typically had external power supplies for the illumination system. These usually had no electronic components, and relied on an autotransformer, or variable transformer, to control light intensity.  The latter is a simple device, with a single winding on a circular core, and a moving contact to take off a variable secondary voltage for the bulb.  Autotransformers are primitive, heavy,

Old Nikon Autotransformer Illumination Control

clunky, and much too large to fit into a microscope base – but they are also simple, sturdy, and almost indestructible under normal conditions.  And when one did (rarely) short out, you tossed it into the trash, bought a new one, plugged it into the scope, and went on with your day.  The insides of the microscope contained a bulb, a mirror and sometimes a few lenses, but little else.  With the exception of dirty contacts or broken cables, these simple systems could be expected to function reliably fifty years after they were first turned on.

As microscopes became more streamlined, power supplies moved into the base of the scope and incorporated newer, more compact electronic control systems made possible by the advent of solid-state electronic devices.

Controlling electric current electronically is not a new idea.  In 1906, Lee De Forest invented the “Audion”, the first functional vacuum tube; this design and its basic theory was later improved by Fleming.  Electrons boiled off a hot filament flowed to a positively-charged second electrode (the “plate”).  A small negative voltage applied to a thin mesh (the “grid”) inserted between the filament and the plate could control this relatively large current, thus allowing the tube to be used as an amplifier and heralding the beginning of electronic communications and controls (see De Forest’s original Scientific American article:  However, vacuum tubes were fragile and wasted large amounts of power to heat filaments.

1915-20 ad for the De Forest Audion Vacuum tube

The transistor, invented at Bell Laboratories in 1947, uses three layers of semiconductor material to accomplish this function much more efficiently, with a small current applied to the “base” layer controlling a much larger current traveling from

Transistor -courtesy Sparkfun

the “emitter” layer to the “collector” layer.  In solid-state devices, current can travel either as electrons or as “holes” – vacancies in atomic outer electron layers that act as

Transistor - courtesy Corollary Theorms
Transistor – courtesy Corollary Theorms


Current amplification by Transistor (Courtesy Sparkfun)
Current Amplification by Transistor – courtesy Sparkfun

mobile positive charges.  In this way, the transistor, employing the base current like the grid of a vacuum tube, can perform the same functions as the vacuum tube, but with less weight, much less power consumption, lower voltages, and much smaller size.  With choice of physical configuration and semiconductor material, as well as “doping” (addition of trace elements to the semiconductor material), an almost infinite variety of functions can be designed into semiconductors.

Model S microscopes were manufactured just as electronic controls were becoming available.  Depending on the amount of space in the base, these microscopes employed either in-base, electronically-controlled power supplies (Model S-Kt) or older-style, transformer-based external supplies (Models S-Ke and L-Ke) if supplementary lenses and levers in the base left insufficient space for transformers and electronics.  The electronic illumination control system in the Model S-Kt was simple – essentially the most basic of light dimmer circuits – but in the 1970s was considered to be very advanced:

“Modern, advanced semi-conductor technology has provided a facility for changing the flow time of electric means. A so-called thyristor of extremely small size has been developed to enable regulation of the brightness of the lamp. The Microscope Model S-Kt has adopted this type of light adjuster built in the microscope base.”  (S-Kt Manual, Page 9)

The heart of the S-Kt system, wall dimmers, motor controllers and many other electric power control devices is the thyristor, a solid state device very similar to the transistor but with one critical difference:  while the current allowed to pass through the transistor is roughly proportional to the tiny current applied to the base, or control electrode, the thyristor (with leads designated anode, cathode, and gate) is completely non-conducting until a small current is applied to the gate, after which the thyristor flips fully to the conducting state. Thyristors therefore function as fast-acting electronic switches and, unlike the transistor, can easily control hundreds of volts and considerable current, even in high-power electrical transmission systems:

Thyristor valve hall at New Zealand power transmission station

Like the transistor, a thyristor is basically a direct current device.  However, if one connects two thyristors in parallel but oriented opposite to each other with the gate connections wired together, one has a very functional, solid-state electronic AC switch:  the Triac, or bidirectional triode thyristor.  Furthermore, many triacs are not fussy about the polarity of the gating voltage, and can be switched on by either direct or alternating current, thus making the control circuitry simple: a small control voltage can be pulled off the main power supply, applied to the gate, and control a much larger current travelling between the cathode and anode.  Although the theory and structure of triacs are complex, if one is not concerned about the niceties of symmetrical AC triggering, harmonics or very fine control (for example, with an incandescent bulb dimmer) the circuitry can be very simple:

Simple Triac Dimmer. Capacitor helps control phase of gating current.
Simple Triac Dimmer. Capacitor helps control phase of gating current.

This circuit also demonstrates the simple concept of the basic incandescent dimmer, with the AC supply, the light bulb, and the triac dimmer wired in a simple series circuit.  For a low voltage bulb, the primary of the bulb transformer can be placed where the bulb is in the circuit.  Essentially, the triac acts as a switch, cutting out increasingly large chunks of the AC supply’s sine wave as the gating current and phase are altered by the resistor/capacitor combination.  Chopping out pieces of the alternating current reduces the effective supplied power:ThyristorwaveformdiagramsThis system works well for incandescent lights, where the filament stays hot between pulses, effectively smoothing out any flicker in the illumination.


So how does one replace a 45-year old thyristor that belongs in a museum???  Excellent older microscopes (and many expensive and not-so-old models) are often sidelined because of failing electronic components and unavailable parts.  This was becoming a thorny problem until Amateur Microscopy friends contributed ideas, and Mark Morris, who has been fixing these microscopes since I was in elementary school, gave me the key idea.

For $4.95, my local Home Depot gave me a cheap Leviton wall dimmer switch.  Filing off the rivets and removing the case revealed the  simple guts of the controller: a potentiometer, a small inductive load, two mica capacitors, and the tiny, all-important chip of a Triac thyristor:


Dimmer switch, front and with back removed. Note barely-visible, 1 cm square, black thyristor behind mica capacitor (small brown object)

Tracing the dimmer’s circuit shows it to be similar to the basic circuit shown above:

Circuit for the Leviton dimmer. The potentiomer, thyristor, and capacitor comprise the basic control circuit.
Circuit for the Leviton dimmer. The potentiomer, thyristor, and capacitor comprise the basic control circuit.

The potentiometer, thyristor, and small mica capacitor on the right comprise the control circuit, while the small coil and capacitor on the left limit interference from the switching process.  As much as possible, these components were unsoldered from the dimmer potentiometer as a unit and reconnected to the intensity control potentiometer on the scope, thus maintaining the physical appearance and controls of this classic scope  – the electrical equivalent of a heart-lung transplant.  The original circuitry of the Nikon light

Components of the Dimmer - thyristor, small ferrite core inductor, and resistor
Some components of the Dimmer – thyristor, small ferrite core inductor (coil), and capacitor.

controller was very similar and equally basic, but the 1970 thyristor’s volume was around 100 times greater than that of the tiny chip removed from the modern dimmer.

Cutting out the old thyristor
Cutting out the old thyristor

After the components of the dimmer were isolated, the wires to the old pillbox-sized Nikon thyristor were cut, and the hay-wired electronic components added to the Nikon light control system (trim potentiometer, capacitor, resistor, and connecting wires) were stripped out, leaving the Nikon potentiometer in place:

Nikon Inensity control potentiometer, all other components removed.
Nikon Intensity control potentiometer, all other components removed.

The tiny thyristor from the dimmer, which had a metal flange riveted to the dimmer’s front plate as a heat sink, was secured to one of the potentiometer mounting screws inside the microscope base, and the dimmer’s circuit was recreated using the Nikon’s potentiometer:

Dimmer components installed on Nikon potentiometer. Heat sink on the thyristor, the barely-visible black chip, is secured under one potentiometer mounting screw.
Dimmer components installed on Nikon potentiometer. Heat sink on the thyristor, the barely-visible black chip, is secured under one potentiometer mounting screw.

One of the problems with this “transplant” was that the Nikon potentiometer had a resistance value of 100K ohms stamped on one side, but the resistance of the Leviton dimmer potentiometer and the trim pot were unknown;  this introduced a degree of guesswork into matching the two systems.  When this configuration was tested, the Nikon bulb would only dim partially.  Clearly, the amount of resistance provided by the Nikon potentiometer was less than the dimmer circuit was designed for.

With a considerable amount of hope and finger-crossing, the small trim potentiometer was soldered in series with the Nikon intensity controlling potentiometer.  When it was turned on, the system worked perfectly!  The trimmer’s resistance set the dimming range of the original built-in Nikon potentiometer; at one extreme, the bulb would not light at all, while at the other end of the trimmer’s range, the Nikon potentiometer could not dim the bulb fully.  Using the trimmer near midrange, it was possible to set the range of the Nikon potentiometer to ideally cover the full dimming range needed for the bulb.  This is the completed illumination control system:

Completed control system. Range-setting trimmer pot soldered to left of main illumination potentiometer
Completed control system. Range-setting trimmer pot soldered to left of main illumination potentiometer.  Tiny modern thyristor barely visible below the trim potentiometer.

The completed Model S illumination control circuit with the new dimmer components is thus:

Final Nikon S illumination control circuit. Dotted line surround components transplanted from the dimmer switch.
Final Nikon S illumination control circuit. Dotted line surrounds components transplanted from the dimmer switch.

This simple fix should work with older, 60Hz illumination control systems based around a simple power control circuit and a transformer.  It could also be used to replace a missing or non-functioning external transformer system:  a dimmer switch and a 6 volt doorbell transformer in a small electronic case, with appropriate cords and plugs, could form a cheap and simple microscope light power supply.  One could add a voltmeter and a little panel light to make it fancy.

Next:  Part II with some thoughts on repairing more modern systems as well as LED conversions, plus references.


How Bright is Your Light? Part I: Rebuilding the Nikon S Light Intensity Control with a $4.95 Dimmer Switch

The Literary Leech



This has not been a good week. Most days, I lurk innocently near the bottom of my lake waiting for the next meal to come by.  Really, I’m not a fussy eater.  Warm or cold-blooded is fine, just as long as it’s blood.  Though even a leech has its standards.  You hear humanoids say “You are what you eat.”  Well guess what – I am what YOU eat!  Have you ever put a sucker on a pink, luscious humanoid, expecting a warm flood of organically-nourished red stuff, and gotten a snoutful of the big McD?  Chemicals, artifically-digested chicken leftovers, and just plain sludge dressed up as food in a paper box – I’d rather eat fertilizer!  Most people don’t think leeches can barf, but we can – right back into your bloodstream where it belongs.

Enough to make a healthy leech throw up

Here I was, clinging to my usual stem of grass just above the mud, enjoying the warm sun filtering down through the duckweed and waiting for an unsuspecting set of toes and a nice, juicy ankle.  Without warning, the water exploded around me, mud and slime churning up as my favorite stem was jerked rudely upward into hot, dry air and biting, unfiltered sunlight.  Next instant, I was buried under mud in a smelly container with a bunch of other creatures who were just minding their own business.  And the company!  Now, I’m not a snob, but we are members of the ancient family of Hirudinea, and we are NOT bottom dwellers.  We may be may be annelids, but we are NOT worms and, despite what they say about us, you will only find us sliming around in the mud when we ABSOLUTELY have to!  They are down there, and we are up here – we’re blood-suckers, not mud-suckers.

Anyway, I endured this ignomius treatment and absolutely LOW company with as much grace as possible, then was rudely squashed between two enormous, absolutely FILTHY fingers and roughly dropped into a glass box.  As I plummeted through a thick layer of duckweed (really, some people just do NOT care about housekeeping), I could see20150829_170211 an incredibly ugly humanoid staring at me through the glass. I wish I could have sucked him dry when he pulled me out of that smelly plastic container and dropped me into his tank, but he was hiding like the coward and bully that he was, safe behind that glass20150918_104830(1) wall.  So I took myself off to a quiet corner to think (no, I was NOT sulking!  Leeches do not sulk.  We are just quiet, contemplative creatures that find our own company quite sufficient at times, thank you.)


After some thought and exploration, I may not have landed so badly.  Been talking with the locals – not a bad lot for having been raised in ditches and puddles, though no literary or cultural giants.  Bunch of Brachiura worms spend all day in the mud, waving their their gills.  Pretty, sinuous and graceful creatures.  I know they’re exotic, but I get tired of hearing how their great-great-grandfathers rode over from Australia in a shipment of guppies. Really, invasive species should know their PLACE and not be giving themselves airs as if they belonged here and had any class.

The hydras tell me about a lovely cloud of hay water that descends and how the whole world blooms with schools of bacteria and juicy fat copepods, but it sounds like a bunch of religious claptrap to me.  I work for my living – do you think it’s easy hanging by your suckers all day in the hot, sunny water, waiting for the moment when dinner splashes by?  Besides, they’re a bit weird and not too bright.  What do you expect from a creature with a neural net about as complicated as the spark plug on a Sopwith Camel???  And there’s one of them that spends his time getting high on every oxygen bubble that floats by.  Says he’s “In Recovery”, whatever THAT means.  When I saw him, he was sprawled all over his latest bubble and couldn’t even keep his stalk straight.HYDRA AND AIR BUBBLE MAG 20150826_123901

And that other one!  Just because she got “discovered” and spent an hour being photographed and got her image on the internet is no reason to put in airs! Spending your day squashed under a microscope slide and having every tentacle laid out for everyone to gawk at is nothing to be proud of, and it’s not as if she did anything to earn it.  Just happening to be lolling about of the right duckweed root when the tweezers come down doesn’t mean you did anything to DESERVE all that attention!child-crooss-eyed-with-snailsSpeaking of food, a nasty realization just percolated through my ganglia:  there’s nothing with BLOOD in this tank!  Hemolymph doesn’t cut it – thin, nasty stuff, and even though you’re a simple critter, you can’t do everything properly with ONE bodily fluid!  And you think I’m going to running after some scrap of protoplasm  or eat half-dead organic junk like some rotifer?  It’s undignified!  Even though they make those weirdohippie hydras fat and happy, I can’t eat copepods!  I have a problem!


Heads Up in Hostile Territory

Things are looking up a bit.  When that big, ugly biped (dubbed him The Proprietor, though I could run things better with one sucker tied behind my back) wasn’t looking, I went out exploring.   Those snails aren’t doing their job, and spend half their time falling off plants instead of keeping the windows clean, and…  Anyway, I digress.

Over the edge of the tank,  and out into enemy territory.  Across a desk, and found just what I thought I saw through all that algae on the glass.  It’s a computer, with those lovely, sensitive keys that work if you just touch them!  Alright, you might wonder what a leech would do with a computer?  Well, let me tell you, there is a long history of literate and intelligent invertebrates.  Unfortunately, they could never get the word out until the biped vertebrates invented the writing machine.  But true creativity was (just barely) possible, in the early days before digital came along.


The first true voice of the invertebrate world called himself Archy, and though the world would call him a cockroach, he was a noble and philosophical soul (, and sacrificed so much to be heard!  As if spending all night bruising your carapace on typewriter keys wasn’t bad enough, think about being isolated in a dusty office with a bunch of Socialist newsies, your only companion a spaced-out kitty who thought she was Cleopatra and nothing to eat for years and years but old library paste! The biped named Don DID help Archy in his bumbling way – at least he kept the paste pots filled.

Such sacrifice to let the world know of your genius!

Now there’s none of this clambering up a typewriter, trying to keep from getting your antennae or suckers stuck in all those rods and levers, then jumping off the top and hoping that you come crashing down on just the right key!!!  The old way might be OK for insects, but we leeches just aren’t built for jumping and crashing – we just tend to plop messily in a nasty little puddle of guts and, well, brains if we had them (but that’s another story).  But I do run on…

None of that today, though.  Particularly for us slender and silkily dampish, sinuously flexible lovely beings, just a flick on the key or a touch on the screen and we’re off to the races and on to the big time.  Today, even a leech of modest literary capability can find himself with a national audience.  After all, if Fox News can do it, why not a leech with just a LITTLE more brain and much more class?

The Road to Literary Fame

Time to go over the top! So I strap on my imaginary tin helmet, gather courage and all of my dignity, and charge up the glass into that dry, biting air (SO much nicer when it’s dissolved in lovely warm water), over the edge of my new home, across the desk (Dust and WHO KNOWS WHAT all over my mucus!  I’d fire that housekeeper!), up a cable, and onto the keys!  A little lunge, click, click, and words appear!  I’m into his system!  The great hacker leech has arrived! And there’s even music!  I do a lovely, slippery, sinuous Charleston with “%5” as my own little dance floor!LEECH 05So you think you’re pretty tolerant because you don’t openly snigger at fat people?  Let me tell you, you don’t know what it’s like to be green till you’ve BEEN green!  You have prejudices! The same folk who vote for integrated classrooms and put tofu on the menu  and recycle their newspapers would step on a slug or squash a snail without thinking and believe they were doing a GOOD thing by mushing another hapless invertebrate!  World, look out!

The little folk of the Valley are going to have a voice!  It will ring out from beneath the waters of every swamp, pond and puddle!  Humanoids wonder about what’s beneath Jupiter’s clouds, but they drain a green puddle and don’t even THINK about it.  The only people among those bony behemoths are children (if they don’t squish our soft parts

Small friend:
Small friend: “Look, Mommy!”

too hard) and they forget when they grow up. They lose the joy of befriending a nice snail or starfish when they start to get big and worry about a new bicycle. I’ll be off to work every night to tell the planet about our world beneath the green layer, and next time YOU see a blob of green Spirogyra, you’ll pause and say, “Oh, how beautiful!” instead of scraping it off your rubbers!  GetImage.aspxAnd we’re hard working professional creatures – we’ve been helping heal your disgusting big bodies for CENTURIES!  And this is the treatment we get in RETURN!

(Still haven’t solved the food problem.  I’m starting to get a bit too slender.  I’m even starting to dream about McBloodburgers!  How could a leech sink so low?)


The blood (I mean dinner) situation has been resolved!  I am so full – and what a great meal!

It’s really all hard work and careful watchfullness, and though I don’t like to boast, I am one of the best!  I could have been snoozing on a leaf, or wasting an evening waving back and forth with those empty-headed worms, but I was on alert like the good, hard-working parasite that I am.  And when The Proprietor fell asleep at his microscope, I was waiting and ready! Over the edge, a little slither, slither across the desk, then so, so quietly up on his finger and oh, what a tasty meal!  Mrs. Proprietor has been filling him up with something called the Mediterranean Diet – lovely olive oil, good Italian whole-wheat pasta, and lots of organic fruits, and not a whiff of the Big M!  I will be so slim and healthy, and my slime will positively glow!  What a lovely leech I will be, feeding like this!  And just a few tiny, tiny drops that he’ll never miss!  Then back home (yes, it has become home) for a a little swim off the diving board…SHOULD I TRY A DIVE CEthen a nap in the sun…A NAP IN THE SUN

So that’s life these days.  Oops!  Aquarium light just went out and all is dark.  Time to get to work.  Keep connected and I’ll share the world of the pond with you….

Proprietor’s Note:

Little stinker!  So he thinks I don’t know what he’s up to?  Wet tracks all over my screen, sucker prints on my keys, and that little tail disappearing over the edge first thing in the morning?  No wonder he’s never around in the daytime!

Oh, well, he reminds me to dust my screen, and he’s kind of amusing.  He better watch his step, or it’s back to the pond, and it’s COLD outside!

Funny how this finger keeps itching….



Archy and Mehitabel at Work

The author offers sincere apologies to the ghost of Don Marquis.

See “Invertebrates In Ink” and:

The Literary Leech