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:

5 thoughts on “Astable Multivibrator: NP-BX1 Base

  1. Very nice. Those projecting bus bars make me wonder if they make a miniature sized cap that they put on the ends of rebars at construction sites to prevent workers from becoming impaled on them. I wouldn’t want OSHA coming in and shutting down the basement laboratory :)

    1. They do call for a bit of dressing up, don’t they? A printed cap seems way too bulky; perhaps something from the brass tube snippet collection is in order.

      Ah! Obviously, the Tiny Lathe™ needs a Tiny Ball Turner™!

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