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Archive for January, 2019

Astable Multivibrator: Monochrome Pirhana LED

The LED parts box disgorged some single-color Pirhana-style LEDs:

Astable - 2N7000 - Mono Pirhana LED
Astable – 2N7000 – Mono Pirhana LED

Didn’t quite catch the blink, but the Ping-Pong ball radome lights up just as you’d expect.

The radome sits on a stripped-down RGB LED spider:

Astable Multivibrator Battery Holder - mono LED Spider - fit view
Astable Multivibrator Battery Holder – mono LED Spider – fit view

The circuitry is the same as the First Light version, with a 1 MΩ resistor stabilizing the LED ballast resistor:

Astable - 2N7000 - Mono Pirhana LED - detail
Astable – 2N7000 – Mono Pirhana LED – detail

Those are 1 µF ceramic caps in the astable section, so I’m no longer abusing electrolytics, and a stylin’ 100 nF film cap metering out the LED pulse up above.

Just for pretty, I’ve been using yellow / black wires for the battery connections and matching the LED color with its cathode lead.

The OpenSCAD source code as a GitHub Gist:

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Minilathe MT3 Spindle Collet Fitting

I’ve used the LMS set of inch-size MT3 spindle collets on occasion, but releasing them required an unseemly amount of drawbar battering. It recently occurred to me to check their fit in the spindle taper:

Minilathe - MT3 collet - taper test

Minilathe – MT3 collet – taper test

Huh.

The only place they touch the spindle is right around the base, so it’s no wonder they clamp poorly and release grudgingly. I tried several others with the same result.

Cross-checking shows a much closer fit along the entire length of the dead center, so it’s not the spindle’s fault:

Minilathe - Dead Center - MT3 taper check

Minilathe – Dead Center – MT3 taper check

Stipulated: we’re not talking toolroom precision here

I set the collets on centers:

Minilathe - MT3 collet - drive setup

Minilathe – MT3 collet – drive setup

And proceeded to file away the offending section to move the clamping force closer to the business end of the collet:

Minilathe - MT3 collet - filed result

Minilathe – MT3 collet – filed result

I did the small collets, the ones I’m most likely to need, and left the big ones for another rainy day.

They don’t have much clamping range and seem good only for exact-inch-size rods.

I should lay in a stock of ER16 and maybe ER32 collets for small stuff.

 

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Monthly Image: Red Oaks Mill Dam Flow

Some of our regular walks take us over the Rt 376 bridge downstream of the Red Oaks Mill dam and I try to take a picture whenever we cross.

For reference, two years ago in December 2016:

Red Oaks Mill Dam 2016-12-11

Red Oaks Mill Dam 2016-12-11

January 2018:

Red Oaks Mill Dam - 2018-01-13

Red Oaks Mill Dam – 2018-01-13

April 2018:

Red Oaks Mill Dam - 2018-04-08

Red Oaks Mill Dam – 2018-04-08

October 2018:

Red Oaks Mill Dam - 2018-10-29

Red Oaks Mill Dam – 2018-10-29

November 2018:

Red Oaks Mill Dam - 2018-11-18

Red Oaks Mill Dam – 2018-11-18

December 2018:

Red Oaks Mill Dam - 2018-12-31

Red Oaks Mill Dam – 2018-12-31

The dam breast seem from the north (left in above pictures) in December 2018:

Red Oaks Mill Dam - north view - 2018-12-30

Red Oaks Mill Dam – north view – 2018-12-30

Searching for the obvious keywords will produce far more pictures than the subject may deserve.

Getting hydropower from the rubble would require considerable capital investment …

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Debossed Printed Legends

[Update: It seems I interchanged “em” and “de” throughout this post.  ]

Up to this point, I’ve been labeling printed parts with emdebossed legends that look OK on the solid model:

Astable Multivibrator Battery Holder

Astable Multivibrator Battery Holder

Alas, the recessed letters become lost in their perimeter threads:

3D Printed Legend - Embossed

3D Printed Legend – Embossed

Raising the legend above the surface (“deembossing”) works reasonably well, but raised letters would interfere with sliding the battery into the holder and tend to get lost amid the surface infill pattern.

The blindingly obvious solution, after far too long, raises the letters above a frame embossed into the surface:

Astable Multivibrator Battery Holder - Legend Debossed

Astable Multivibrator Battery Holder – Legend Debossed

Which looks OK in the real world, too:

3D Printed Legend - Debossed

3D Printed Legend – Debossed

The frame is one thread deep and the legend is one thread tall, putting the letters flush with the surrounding surface and allowing the battery to slide smoothly.

The legend on the bottom surface shows even more improvement:

NP-BX1 battery holder - Raised vs Recessed Legend

NP-BX1 battery holder – Raised vs Recessed Legend

An OpenSCAD program can’t get the size of a rendered text string, so the fixed-size frame must surround the largest possible text, which isn’t much of a problem for my simple needs.

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Lamp Posts vs. Reality

Spotted this in a mall built just before the 2008 financial implosion:

Round Lamp Post in Square Pavement Hole

Round Lamp Post in Square Pavement Hole

Maybe the original catalog items went obsolete by the time they signed up enough tenants in that section to justify any lighting at all?

In related news, a facelift some years ago at the motel next to the decaying Red Oaks Mill dam installed square lamp posts on the existing square concrete pedestals, but replaced the original metal conduit with a plastic sheath:

Square Lamp Post with Cut Cable Shield

Square Lamp Post with Cut Cable Shield

The cable may sit low enough in the recess to survive, but I wouldn’t bet my life on it.

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Red Fox Visitation

A Red Fox came trotting around the garden on the day before Christmas, then nosed up to the back of the house:

Red Fox visitation - 2018-12-24

Red Fox visitation – 2018-12-24

Presumably, it was in search of a snack. We wish it good hunting.

A few hours later, the fox walked quickly across the back yard with half a dozen turkey toms close behind, perhaps urging it away from their hens. Everybody remained calm and collected, knowing their roles in this particular play.

FWIW, Marist College fields Red Foxes athletic teams. The women’s teams are Lady Red Foxes, as “vixen” carries entirely inappropriate connotations.

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Just A Typo. It Could Happen To Anyone: Capacitor Edition

A bag of 100 nF ceramic caps arrived from across the continent (“US Stock”) and failed incoming inspection:

Mislabeled 100 nF ceramic capacitor - actual 50 nF

Mislabeled 100 nF ceramic capacitor – actual 50 nF

The capacitor mark says 104, which is what you’d expect on a 100 nF cap, but the first half-dozen out of the bag measured around 55 nF, far outside even the loosest -20%/+50% tolerance.

Stipulated: the factory can ship every capacitor it makes with a proper mark.

Given their (lack of) provenance, they could be mis-marked 47 nF caps.

Somewhat to my surprise, a refund occurred instantly after I reported the problem.

Trust, but verify.

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