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Ed

By turns: tinker, engineer, husband, author, amateur raconteur, recumbent cyclist, father, ham radio geek. So many projects, so little time!

Homepage: http://softsolder.com

Astable Multivibrator: NP-BX1 Base

Adapting the NP-BX1 battery holder to use SMT pogo pins worked well:

NP-BX1 Holder - SMT pogo pins

NP-BX1 Holder – SMT pogo pins

The next step is to add sockets for those 14 AWG wires:

NP-BX1 Battery Holder - Wire Posts - solid model

NP-BX1 Battery Holder – Wire Posts – solid model

Start by reaming / hand-drilling all the holes to their nominal size and cleaning out the pogo pin pocket.

Solder wires to the pogo pins and thread them through the holder and lid:

Astable - NP-BX1 holder - pogo pin soldering

Astable – NP-BX1 holder – pogo pin soldering

That’s nice, floppy silicone-insulated 24 AWG wire, which may be a bit too thick for this purpose.

The pogo pins will, ideally, seat with the end of the body flush at the holder wall. Make it so:

Astable - NP-BX1 holder - pogo pin protrusion

Astable – NP-BX1 holder – pogo pin protrusion

Dress the wires neatly into their pocket:

Astable - NP-BX1 holder - pogo pin wiring

Astable – NP-BX1 holder – pogo pin wiring

Butter the bottom of the lid with epoxy, clamp in place, set it up for curing, then fill the recess:

Astable - NP-BX1 base - curing

Astable – NP-BX1 base – curing

While it’s curing, make a soldering fixture for the 14 AWG wires:

Astable - drilling strut soldering fixture

Astable – drilling strut soldering fixture

The holes are on 5 mm centers, in the expectation other battery holders will need different spacing.

Solder it up and stick the wires into the base:

Astable - NP-BX1 base - detail

Astable – NP-BX1 base – detail

Jam a battery in and It Just Works™:

Astable - NP-BX1 3.8V - 20ma-div - cap V

Astable – NP-BX1 3.8V – 20ma-div – cap V

The traces:

  • Green = supply current at 20 mA/div
  • Yellow = LED driver transistor base voltage
  • Purple = other transistor collector voltage
  • White = base – collector voltage = capacitor voltage

The measurement setup was a bit of a hairball:

Astable - NP-BX1 base - current probe

Astable – NP-BX1 base – current probe

For completeness, here’s the schematic-and-layout diagram behind the circuitry:

Astable - NP-BX1 base - schematic

Astable – NP-BX1 base – schematic

I love it when a plan comes together!

The OpenSCAD source code as a GitHub Gist:

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Six Gallon Can Lid Adapter to Platform Bird Feeder

A House Finch suffering from Finch Eye Disease prompted me to sterilize our feeder, which meant providing a temporary feeder to keep the birds flying. Having an abundance of lids from six gallon plastic cans / buckets, this made sense:

Can Lid Feeder - installed

Can Lid Feeder – installed

Which required an adapter betwixt pole and lid:

Can Lid Feeder - assembled

Can Lid Feeder – assembled

Which requires a bit of solid modeling:

Can Lid Platform Feeder Mount - solid model - bottom

Can Lid Platform Feeder Mount – solid model – bottom

The lids have a central boss, presumably for stiffening, so the model includes a suitable recess:

Can Lid Platform Feeder Mount - solid model - support structure

Can Lid Platform Feeder Mount – solid model – support structure

As usual, automatically generated support fills the entire recess, so I designed a minimal support structure into the model and cracked it out with very little effort:

Can Lid Feeder - support structure

Can Lid Feeder – support structure

The tangle off to the right comes from a bridge layer with a hole in the middle, which never works well even with support:

Can Lid Platform Feeder Mount - Slic3r - bridge layer

Can Lid Platform Feeder Mount – Slic3r – bridge layer

Didn’t bother the birds in the least, though, so it’s all good.

I loves me my 3D printer …

The OpenSCAD source code as a GitHub Gist:

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Dutchess Rail Trail: Maloney Rd Trailhead Ruts

It seems the DCW&WA SUV makes regular trips through the “No Motor Vehicles” bike access:

Maloney Rd Trailhead - 2018-11-07

Maloney Rd Trailhead – 2018-11-07

If it’s not them, then it’s somebody following their example.

Just because you can do something, doesn’t mean you should … but, of course, the ordinary rules apply only to little people, not public servants.

Someone in the bike advocacy apparat once told me I’m the most cynical, bitter person they’d ever met, at least on the subject of getting along with public servants. As I see it, I came by my attitude honestly.

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Sterling Table Knife Repair

A sterling knife followed me home after a Thanksgiving gathering:

Sterling knife repair - powdered cement

Sterling knife repair – powdered cement

The original cement, dating back to the middle of the last century, turned into friable dust around the blade tang:

Sterling knife repair - handle socket

Sterling knife repair – handle socket

I cleaned it out as best I could, buttered JB Quik epoxy around the tang and into the socket, joined the two, and let it cure in the natural position:

Sterling knife repair - curing

Sterling knife repair – curing

The rest of the knives in the set may need similar attention, but I’m not looking for trouble.

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Three Dead Mice

The rodents around here have great trouble with outdoor bowls, but this trio ended in a deep six gallon bucket next to the garage workbench:

Three Dead Mice

Three Dead Mice

Even though mice don’t seem like cuddly creatures, they ended their days snuggled together; we’ll just ignore the cannibalism thing.

Heck of a way to go, even for rodents. I renewed the steel wool blocking a gap in the garage door.

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Halogen Desk Lamp Conversion

As part of converting the halogen desk lamp to LEDs, I replaced the hulking iron transformer with a flatter counterweight:

Halogen Desk Lamp - 12 V 20 W transformer

Halogen Desk Lamp – 12 V 20 W transformer

Under normal circumstances, you’d use something like steel or lead sheets, but Tiny Bandsaw™ can’t cut any appreciable thickness of steel and I gave away my entire lead stockpile, so I sawed disks from a pile of non-stick pancake griddles and drilled suitable mounting holes:

Parallel clamps in action

Parallel clamps in action

Another disk (from a formal aluminum sheet!) goes into the lamp head, with a trio of 3W COB LEDs epoxied in place:

Ex-Halogen Desk Lamp - 3x3W COB LED assembly

Ex-Halogen Desk Lamp – 3x3W COB LED assembly

The other side of the disk sports a heatsink harvested from a PC, also epoxied in place:

Ex-halogen Desk Lamp - heatsink fitting

Ex-halogen Desk Lamp – heatsink fitting

Realizing the head required only a little filing to accommodate the heatsink sealed both their fates.

A test firing showed the heatsink needed more airflow, which didn’t come as much of a surprise, so I milled slots in the lamp head:

Ex-halogen Desk Lamp - vent slot milling

Ex-halogen Desk Lamp – vent slot milling

Deburring the holes, blackening the sides with a Sharpie, and tucking a bit of black window screen behind the opening made the vents look entirely professional.

The small dome in the base originally cleared the transformer and now holds the entire 10 W LED driver, along with all the wiring, atop the counterweight sheets:

Ex-halogen Desk Lamp - base wiring

Ex-halogen Desk Lamp – base wiring

A cork pad covers the base for a bit of non-skid action:

Ex-halogen Desk Lamp - cork pad

Ex-halogen Desk Lamp – cork pad

I couldn’t convince myself filling in those sectors would improve anything, so I didn’t.

And then It Just Worked:

Ex-halogen Desk Lamp - in use

Ex-halogen Desk Lamp – in use

All without a trace of solid modeling or G-Code …

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JYE Tech DSO150 Oscilloscope vs. Actual Signals

The DSO150 oscilloscope’s specs give a 200 kHz bandwidth, so a 50 kHz sine wave looks pretty good:

DSO150 - sine wave 50 kHz 10 us-div

DSO150 – sine wave 50 kHz 10 us-div

A 100 kHz sine wave looks chunky, with maybe 25 samples per cycle:

DSO150 - sine wave 100 kHz 10 us-div

DSO150 – sine wave 100 kHz 10 us-div

The DSO150 tops out at 10 µs/div, so you can’t expand the waveform more than you see; 25 samples in 10 µs seems to be 2.5 Msample/s, exceeding the nominal 1 Msample/s spec. I have no explanation.

A 10 kHz square wave shows a blip just before each transition that isn’t on the actual signal:

DSO150 - square wave 10 kHz 20 us-div

DSO150 – square wave 10 kHz 20 us-div

At 50 kHz, there’s not much square left in the wave:

DSO150 - square wave 50 kHz 10 us-div

DSO150 – square wave 50 kHz 10 us-div

And, just for completeness, a 200 kHz square wave completely loses its starch:

DSO150 - square wave 200 kHz 10 us-div

DSO150 – square wave 200 kHz 10 us-div

A 10% (-ish) duty cycle pulse at 25 kHz has frequency components well beyond the scope’s limits, so it’s more of a blip than a pulse:

DSO150 - pulse 25 kHz 10 us-div

DSO150 – pulse 25 kHz 10 us-div

The pulse repetition frequency beats with the scope sampling and sweep speeds to produce weird effects:

DSO150 - pulse 25 kHz 100 us-div

DSO150 – pulse 25 kHz 100 us-div

Tuning the pulse frequency for maximum weirdness:

DSO150 - pulse 15 kHz 200 us-div

DSO150 – pulse 15 kHz 200 us-div

None of this is unique to the DSO150, of course, as all digital scopes (heck, all sampled-data systems) have the same issues. The DSO150’s slow sampling rate just makes them more obvious at lower frequencies.

Key takeaway: use the DSO150 for analog signals in the audio range, up through maybe 50 kHz, and it’ll produce reasonable results.

Using it for digital signals, even at audio frequencies, isn’t appropriate, because the DSO150’s low bandwidth will produce baffling displays.

 

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