Entries in Category Engineering and Inventions

3D-Printed Screw Threads

I've been playing with a 3d printer lately, specifically a Solidoodle machine that deposits ABS plastic filament. As part of a larger project I've been designing various mechanical parts, challenging myself to do without support structures and keeping manual finishing steps to a minimum. One of the things I've tried to make is an entirely printed, functional screw thread, for both male and female parts. The result is the nut and bolt combination documented here.

As for the larger project, I'll publish more about that here soon, so keep visiting!

A First Attempt at a Solder Fume Extractor

I believe strongly in publishing negative results, so I've written an account of an old project (December 2006), in which I tried and failed to build a solder fume extracting and filtering machine and learned some useful lessons along the way.

DIY Paracord Bootlaces

Six years ago I walked into an Army-Navy surplus store and bought a pair of Hi-Tec hiking boots for something like 30 dollars. They're sturdy and very comfortable, have given me good service in all sorts of places and conditions, and are likely to keep doing so for years to come. The laces, however, were beginning to show their age and experience; the anglets had come off and the inner core of the laces had retreated into the outer sheath. I had an opportunity, therefore, to replace them with a much stronger and more useful type of bootlace: mil-spec 550 parachute cord.

Black never goes out of style

This fits into the trend of survival experts and EDC enthusiasts carrying miles of paracord on their persons at all times, usually by tightly weaving it into something like a watch band or key chain. I'm impressed by their techniques but I'm far from being a serious student of wilderness survival—I only sniff around the edges of that community—but I enjoy hiking now and again and I'm very much a fan of preparedness and capability in all aspects of life.

Tilt Sensor Demonstration Toy

I've finally created a page for this fun little tilt-sensing toy I made using a MEMS accelerometer, some LEDs, and the LM3914 bar-graph driver. It was knocked together in an afternoon in 2002, so don't look too closely at the somewhat crude construction techniques in this one!

Postel's Prescription and Power Polarity

Be liberal in what you accept, and conservative in what you send.

Postel's Prescription, by Jon Postel

I have a day job as a hardware engineer for a telecommunications company, and in this capacity I'm often designing equipment to be installed in phone company Central Offices (COs). Unlike the designers of consumer electronics or data center hardware, I can rely on having DC available to power my devices; COs have “rectifier plants” that convert mains AC to 48-volt DC and distribute this power through the facility with giant copper or aluminum busbars over the racks.

Most CO equipment uses two-pin Phoenix-style connectors as power inlets. These come with a pluggable terminal block with screw-down style connectors that accept bare wire from the rack's fuse and power distribution panel. Because installers wire this plug on site and mistakes are easy to make, it's good sense (and company policy) for the hardware designer to put a bridge rectifier across the input leads so that this connection can be insensitive to polarity.

This is an application of the first part of Postel's Prescription, “be liberal in what you accept”, to power engineering. If the second part, “conservative in what you send”, has an analogue in this field, it could be this: make sure your power outputs, if any, have clearly defined polarity. Another possible analogue would be: keep the output to a tighter voltage range than the telecom standard 36-72 volts.