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Archive for category Machine Shop

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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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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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: Battery Power

With the DSO150 scope running, I printed Geoff’s DSO150 case + battery holder from Thingiverse, added a few bits & pieces from the heap, and came up with a completely portable scope:

DSO150 battery hack - first light

DSO150 battery hack – first light

The only scope mod consists of embedding a JST-ish connector in the back panel:

DSO150 battery hack - rear panel connector

DSO150 battery hack – rear panel connector

Then soldering it to the battery pads and applying generous hot-melt glue blobs:

DSO150 battery hack - PCB power

DSO150 battery hack – PCB power

Add a scrap 18650 Li-Ion cell, a regulated boost converter, and a switch:

DSO150 battery hack - interior

DSO150 battery hack – interior

The switch is directly below the DSO150 BNC connector to get a little protection for its handle, which would otherwise stick out in harm’s way. This being an afterthought, I drilled the switch hole, rather than modify the solid model.

Some testing with a bench supply showed that the DSO150 will not operate correctly from the voltages produced by a pair of lithium cells, despite what you’d think from looking at the case. Below 8 V, the internally generated negative supply becomes larger than the positive supply, so the 0 V point isn’t properly centered and the scope loses headroom for large signals; monitoring the internal 3.3 V test signal makes the problem painfully obvious.

More color commentary from my summary email:

  • Combining a case from Thingiverse with a Li-Ion cell and a regulated boost converter produces a portable scope.
  • The PCB has provision for battery input, so I drilled / filed a square hole for a teeny JST-ish connector on the back panel, secured it with a blob of hot melt glue, and globbed the wires onto the PCB battery pads.
  • The boost converter draws about 400 mA from the cell, so a 2500-ish mA·h cell should last Long Enough™. This is a scrap cell from the recycle box and gave out after maybe four hours.
  • It idles at 8 mA, so I drilled a hole in the back of the case for a toggle switch disconnecting the battery; you’d want the hole in the solid model. Perhaps a better converter would have lower idle current; you’d never be able to tell from the eBay descriptions.
  • Aaaaand it switches around 200 kHz under load, just barely beyond the scope bandwidth. It doesn’t add much noise to the signal, at least with a 50 Ω terminator jammed in the BNC, but the square-wave “cal” output looks awful at 50 mV/div; a real scope shows even more noise. I assume the noise comes directly from the logic supply; with luck, the DSO150’s analog circuitry has Good Enough™ filtering.
  • Which might not matter for logic-level and moderate analog signals, of course, which is the whole point of the DSO150.
  • Conspicuous by their absence: a Li-Ion cell protection PCB and any way to recharge the poor thing …

I’ve occasionally wanted a portable scope and now I have one!

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JYE Tech DSO150 Oscilloscope: Build Notes

I did a quick build of a JYE Tech DSO150 oscilloscope to see how it’d work in a proposed Squidwrench advanced soldering class / kit build session.

The main board requires adding only a few switches and headers, then removing a 0 Ω jumper resistor:

DSO150 - main board - bottom

DSO150 – main board – bottom

The analog board requires a handful of 1/8 W resistors, various capacitors, switches, and the BNC connector:

DSO150 - main board - front

DSO150 – main board – front

Some (lightly edited) color commentary from my summary email:

  • Just finished assembling the kit, which required two hours; I’m admittedly fussy. The one joint I missed on the input coupling switch required a complete disassembly, but all the rest worked fine.
  • The UI is much better than the DSO138.
  • Soldering the BNC connector requires lots of heat. My ordinary Hakko iron had inadequate grunt, so I deployed the hulking Radio Shack 150 W gun and did the job in seconds.
  • The resistors require a meter to measure them during installation, because they’re 1% 1/8 W jobbies with many teeny color strips in Chinese tints you’ve never seen before. I could not sort them visually, even with a lighted headband magnifier, and I know what I’m looking for.
  • The caps are marked, but using a meter builds confidence.
  • And, yes, the kit had all the right parts and they all worked. The instructions call for powering up the main board before starting assembly, then again after removing a 0 Ω jumper resistor, but that’s the extent of the “testing” required.
  • They recommend a flush cutter and I’d say it’s pretty much required. An ordinary diagonal cutter won’t get close enough to the PCB.
  • I needed an angle-tip tweezer to lay the PCB screws in place.
  • Don’t install the knob until the very last step and maybe wait until you’ve verified all the functions. You have been warned.
  • The minimum power supply voltage really is 8.0 V, not the 7.4 V from a not-quite-fully-charged pair of lithium cells. A 9 V alkaline battery will last a few minutes. A noisy boost converter / crappy 9 V wall wart translates directly into noise on the display, particularly on the internal calibration signal.
  • The “0.1 V” calibration signal turned out to be 150 mV, as measured on a real scope, at 1 kHz. The 3.3 V signal is closer to reality. Both are noisy from a noisy supply.
  • All in all, it’s a pretty good scope for thirty bucks!
  • Newbies will find it a challenging three hour build, for sure.

The next step involves adding a case and battery power:

DSO150 battery hack - first light

DSO150 battery hack – first light

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Sony NP-BX1 Battery Holder: SMT Pogo Pin Contacts

The original camera battery test fixtures used contact pins conjured from hulking gold-plated connector pins and coil springs:

Canon NB-6L holder - contact pin detail

Canon NB-6L holder – contact pin detail

The Sony HDR-AS30V camera chewed up and spat out a handful of batteries, all tested in the NP-BX1 test fixture:

NP-BX1 Holder - show layout

NP-BX1 Holder – show layout

Nowadays, SMT pogo pins produce a much more compact holder, so I figured I could put all those batteries to good use:

NP-BX1 Holder - SMT pogo pins

NP-BX1 Holder – SMT pogo pins

That’s the long-suffering astable multivibrator, still soldered to its CR123A holder.

Obviously, the battery holder should grow ears to anchor the 14 AWG copper posts and would look better in black PETG:

NP-BX1 Battery Holder - 1.5mm pins - solid model

NP-BX1 Battery Holder – 1.5mm pins – solid model

The battery lead wires get soldered to the ends of the pogo pins and are recessed into the slot in the end of the fixture. I used clear epoxy to anchor everything in place.

Fits perfectly and works fine!

The OpenSCAD source code as a GitHub Gist:

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