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Archive for category Science

Squidwrench Electronics Workshop: Session 5 Whiteboards

Whiteboards from the SqWr Electronics Session 5, covering transistors as switches …

Reviewing I vs V plots, starting with a resistor and then a transistor as a current amplifier:

SqWr Electronics 5 - whiteboard 1

SqWr Electronics 5 – whiteboard 1

Reminder of why you can’t run a transistor at its maximum voltage and current at the same time:

SqWr Electronics 5 - whiteboard 2

SqWr Electronics 5 – whiteboard 2

A resistor load line, with power calculation at the switch on and off coordinates:

SqWr Electronics 5 - whiteboard 3

SqWr Electronics 5 – whiteboard 3

Detail of the power calculations, along with a diagram of the current and voltage when you actually switch the poor thing:

SqWr Electronics 5 - whiteboard 3 detail

SqWr Electronics 5 – whiteboard 3 detail

Oversimplification: most of the power happens in the middle, but as long as the switching frequency isn’t too high, it’s all good.

Schematic of the simplest possible switched LED circuit, along with a familiar mechanical switch equivalent:

SqWr Electronics 5 - whiteboard 4

SqWr Electronics 5 – whiteboard 4

We started with the “mechanical switch” to verify the connections:

SqWr Session 5 - Switched LED breadboard

SqWr Session 5 – Switched LED breadboard

Building the circuitry wasn’t too difficult, but covering the function generator and oscilloscope hookup took far more time than I expected.

My old analog Tek 2215 scope was a crowd-pleaser; there’s something visceral about watching a live CRT display you just don’t get from the annotated display on an LCD panel.

I’d planned to introduce capacitors, but just the cap show-n-tell went well into overtime. We’ll get into those in Session 6, plus exploring RC circuitry with function generators and oscilloscopes.

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MPCNC: Modified Drag Knife Adapter Spring Constant

The bars on the original MPCNC drag knife / plotter pen adapter had a 100 g/mm spring constant:

MPCNC - Plotter pen force test

MPCNC – Plotter pen force test

Making the bars slightly thicker improved their print-ability:

MPCNC knife adapter mods - OpenSCAD model

MPCNC knife adapter mods – OpenSCAD model

The reddish tint marks the new bars, with their location carefully tweaked to be coincident with the stock STL.

Shoving the pen into the scale with 0.1 mm steps produces another unnervingly linear plot:

Modified MPCNC pen adapter - Spring Constant data

Modified MPCNC pen adapter – Spring Constant data

Real plotter pens want about 20 g of force, so this isn’t the holder you’re looking for.

A bunch of plots at Z=-1.0 mm turned out well with the ballpoint pen insert, though:

MPCNC Modifed pen adapter - first plots

MPCNC Modifed pen adapter – first plots

The globs apparently come from plotting too fast for conditions; reducing the speed to 1500 mm/min works better.

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Long-lived CFL Bulb

This compact fluorescent lamp seems to have survived nearly two decades of use in a desk lamp:

Desk Lamp - long lived CFL

Desk Lamp – long lived CFL

It had plenty of starts, although maybe not so many total hours, as the other CFLs you’ll find mentioned around here.

I swapped in a similar CFL and we’ll see what happens.

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Monthly Science: Cheese Slicer Epoxy vs. Water, Continuing

The epoxy coating on our cheap aluminum (?) cheese slicer continues to corrode (clicky for more dots):

Cheese slicer - epoxy failure - front

Cheese slicer – epoxy failure – front

The back side:

Cheese slicer - epoxy failure - rear

Cheese slicer – epoxy failure – rear

The epoxy coating remains intact, although I expect it’ll break through as the corrosion products swell underneath.

For whatever it’s worth, I applied the epoxy almost exactly one year ago.

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Maximum Strength Homeopathic HGH: Not

Spotted at an exhibition for Olde Fartes:

Somaderm homeopathic HGH

Somaderm homeopathic HGH

I think they just blew up the bottle label to human size, with no attention to the resulting pixelation.

One can find Somaderm on the Interwebs, which leads to the “Active Ingredients” list:

Somaderm homeopathic HGH - Active Ingredients

Somaderm homeopathic HGH – Active Ingredients

Looking up their NDC number helps translate the bullshit Latinesque nomenclature:

  • Glandula Suprarenalis Suis = boar adrenal glands
  • Thyroidinum = cow thyroid glands
  • Somatropin = human growth hormone

They’re exceedingly proud of that NDC number, touting “SOMADERM Gel is the only transdermal, FDA registered product”. Indeed, it’s registered, about which the FDC has this to say:

Assigned NDC numbers are not in any way an indication of FDA approval of the product.

and

Marketing Category UNAPPROVED HOMEOPATHIC

With that in mind, consider the dilutions:

  • Glandula Suprarenalis Suis = 1 part per million
  • Thyroidinum = 10 part per billion
  • Somatropin = 1×10-30 = there are no words

Homeopathic “drugs” never list the starting concentration or amounts in the product, but diluting something by a factor of ten-to-the-thirty ensures not one single molecule of the original compound will make it into the bottle. This, of course, means the HGH is at “maximum strength”, in the homeopathic way of magical thinking.

You’ll surely find some molecules of pig brain and maybe even a few molecules of cow glands, but I suspect they’re not buying the “active” ingredients in shipping container lots. In round numbers, one pig adrenal, one cow thyroid, and one drop of actual HGH would supply their needs well into the future.

I would like to see how they dilute those ingredients, because I doubt they have legions of trained homeopaths succussing bottles against elastic surfaces.

Of course, such dilution requires careful attention to detail, lest a stray molecule make its way into the final product, which surely justifies the punch line:

Somaderm homeopathic HGH - Price

Somaderm homeopathic HGH – Price

There is also a $150 “Membership Price”, suggesting a multi-level marketing scam running in parallel. Some rummaging on their website reveals cryptic phrases confirming the suspicion: “Be the change that will inspire others to follow” and “Information on how to become a distributor“.

Ya gotta admire ’em for not even blinking.

A note on commenting: there is zero evidence of efficacy¸ so don’t even try to advocate homeopathy. If it worked, it’d be medicine, not a MLM scam.

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Monthly Image: Organ Pipe Mud Dauber Wasp Nest

The side of our house seems to attract Organ Pipe Mud Dauber Wasps during nesting season.

One pair of wasps built this impressive structure behind the patio door, beside the bathroom window:

Organ Pipe Mud Dauber Wasp Nest - side view

Organ Pipe Mud Dauber Wasp Nest – side view

The female wasp built six tubes over the course of an August week, carrying blobs of mud the size of her head and abdomen from sources about 30 seconds away (1 minute round trip). Each blob produces half of one serration around the tube, with a seam running down the middle, and requires 20 seconds to smooth into place. We got tired just watching her!

Each tube has many compartments, each containing a wasp larva and a paralyzed spider, with a mud cap inside the end:

Organ Pipe Mud Dauber Wasp Nest - bottom view B

Organ Pipe Mud Dauber Wasp Nest – bottom view B

We watched the wasps attack, sting, and remove spiders of a specific size from the corners of our window frames.

The young wasps in the innermost tube may not make it out alive, because they must chew through at least one outer tube before flying away:

Organ Pipe Mud Dauber Wasp Nest - bottom view A

Organ Pipe Mud Dauber Wasp Nest – bottom view A

Perhaps layering the outer tubes around a central tube makes for a more compact and durable nest, with the possible sacrifice of offspring in the center.

The new wasps will likely emerge next spring.

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Monthly Science: Monarch Caterpillars!

After several years of seeing few-to-no Monarch butterflies, last year we managed to save a single Monarch egg, raise the caterpillar, and release it:

Monarch on Milkweed - left

Monarch on Milkweed – left

This year, we’ve seen more, if not many, Monarchs in flight. They’re not abundant, but perhaps there’s hope.

A Monarch evidently laid eggs in our milkweed patch, with at least two offspring surviving:

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We decided to let them seek their own destiny; may the odds be ever in their favor …

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