Interview: Inventing The Unix “sudo” Command

May 28, 2014 by 115 Comments

It was just one of these nights. We were sitting at the O’Neil’s San Mateo Pub, taking a break after a long day at the Maker Faire. Hackaday was hosting an informal drink-up and a steady stream of colorful characters has just started flowing in. That’s when we met [Robert Coggeshall].

XKCD comic #149
[xkcd, 149]
It started off as a normal discussion – he runs Small Batch Assembly and does a lot of interesting things in the maker space. Then he brought up a fascinating detail – “Oh, did you know I also co-invented sudo back in the 80’s?”

If you ever did as much as touch a Unix system, you’ll know this is a big deal. What came as an even bigger surprise was that something like sudo had to be “invented” in the first place. When thinking about the base Unix toolkit, there is always this feeling that it all emerged from some primordial soup of ideas deep inside of Bell Labs, brought to life by the infinite wisdom of [Ken Thompson] and the rest of the gang. Turns out that wasn’t always the case. We couldn’t miss asking [Bob] for an interview, and he told us how it all came about…

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OpenExposer, The DIY SLA Printer

May 28, 2014 by 25 Comments

printer

Precisely applied ultraviolet light is an amazing thing. You can expose PCBs, print 3D objects, and even make a laser light show. Over on the Projects site, [Mario] is building a machine that does all of these things. It’s called the OpenExposer, and even if it doesn’t win the Hackaday Prize, it’s a great example of how far you can go with some salvaged electronics and a 3D printer.

The basic plan of the OpenExposer is a 3D printer with a small slit cut into the bed, and a build platform that moves in the Z axis. The bed contains a small UV laser and a polygon mirror ripped from a dead tree laser printer. By moving the bed in the Y direction, [Mario] shoot his laser anywhere on an XY plane. Put a tank filled with UV curing resin on the bed, and he has an SLA printer. Put a mounting bracket on the bed, and double-sided PCBs are a cinch.

The frame is made of 3D printed parts and standard RepRap rods, with the only hard to source component being the polygonal mirror. These can be sourced from scrounged laser printers, but there’s probably some company in China that will sell them bulk. The age of cheap SLA printers is dawning, friends. Video below, github here.

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A Smart Clothes Dryer

May 28, 2014 by 52 Comments

dryer6 Here’s a question that will rack your brain: does your clothes dryer stop when the clothes are dry? It seems if you have a machine that guzzles power for one single purpose, you’d like it to stop when its job is done, or for the sake of convenience, keep going until the clothes are dry. Temperature and humidity sensors are cheap, and if you don’t have an auto sensing clothes dryer, a DIY smart clothes dryer seems both efficient and convenient. [Editor from the future: link rot, seems to be here now.]

[Andy] figured when clothes are dry, they stop emitting moisture. Based on that premise, he could monitor the operation of a clothes dryer and either shut off the machine or send a message that it’s time to take the clothes out. It’s a simple enough idea, and with an Arduino and a DHT11 temperature and humidity sensor, it was pretty easy to put together.

The clothes dryer used for this experiment was a self-ventilating model that doesn’t vent to the outside. Instead, it condenses the water in your towels and jeans into a tub to be emptied by hand later. This might introduce a little error into tests, but [Andy] did come up with a way to mount the temperature sensor without modifying his dryer in any way. From the initial data, the ventless dryer might be introducing a little experimental error, but it’s still too good of an idea to not try out with a traditional dryer that vents to the outside. Here’s the code should you want to try this yourself.

Mechanical Clock Relies On Marbles To Tick

May 28, 2014 by 25 Comments

As fun as micro-controllers and RTCs are, sometimes it’s truly fascinating to see a completely mechanical clock. Using only gravity this Pendulum Marble Clock (German version) by [Turnvater Janosch] runs for 12 hours at a time and has an accuracy error of less than one second per day!

It works by raising a 2.5kg weight which sinks approximately 1 meter during that 12 hours. A series of steel ball bearings count the minutes, 5 minute increments, and hours. Every minute one ball is released on the track — when the track fills up, trap doors open releasing the balls to the next level. The first level is minutes, the second, 5 minutes, and the third, hours.

The entire thing is made out of wood, plastic gears, brass and steel wire, and an old flat iron (although we’re really not too sure what that’s used for…)

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A Huge, Lightweight Wooden Quadrotor

May 27, 2014 by 15 Comments

quad_1

[Robert] once built a quadcopter frame by sawing laminate floor tile. It worked, we’re taking the lack of pictures of this build as evidence of how ugly it was. His latest design used a much better looking material – laser cut plywood – and the finished product is very strong and lightweight, even compared to commercial frames made with glass or carbon fiber and epoxy.

Although the design went smoothly thanks to some Solidworks skills, actually cutting the frame from 3mm birch ply resulted in a few issues. The cheap laser cutter used for cutting include some bottom of the line software called LaserWorksV5. There is a kerf compensation feature, called ‘sew compensation’ in the software’s native Chinglish. The software would always crash whenever it tried to calculate the compensation for circles. [Robert] spent two hours figuring this problem out, and in the end needed to break out a piece of sand paper to get a nice interlocking fit.

The completed frame bolts together without any glue at all, and the best part about it is the weight – only 167 grams. Compare that to a similarly sized glass fiber frame, and [Robert]’s shaved at least 200 grams off his finished build.

Overkill Phone Charger, Because, Well, Why Not?

May 27, 2014 by 26 Comments

ATX Phone Charger

There are times in a tinkerer’s existence where it is convenient to have the ability to plug in and power a lot of USB devices. Sure, you could use a USB hub but this may not be satisfactory if your devices require a lot of current. A computer may work but is not really a stand alone solution.

[Jeff] and the crew over at Make Lehigh Valley ran into this predicament. They were putting on an Adafruit Trinket class and needed a USB power supply to power all of the Trinkets that were going to be used. As any makerspace would do, they built their own USB Power Station, and the final product is certainly overkill for what they needed (that’s not a bad thing).

An old ATX computer power supply is a logical component to use for this type of project. These power supplies are usually available in abundance and will provide all the amperage any reasonable amount of 5v USB devices can ask for. The 5v output from the ATX power supply was wired to 8 USB jacks. Keeping up with the project’s resourcefulness, those USB jacks were scavenged from a couple of old PCI-slot USB hub panels. Not satisfied with only USB outputs, the guys also wired up some banana jacks so that 3.3, 5 and 12 volts were available for whatever project was being worked on. A 3D printed enclosure keeps everything neat and tidy.

This project used a bunch of recycled parts and solved a problem faced by the group. If you’re interested in using an ATX power supply to make a more bench-top style power supply then check out this build.

[Lenore] Eviscerates Her Racing Snail

May 27, 2014 by 10 Comments

[youtube=https://www.youtube.com/watch?v=pzymwuPdQp4&w=580]

 

You may have walked past [Lenore’s] unassuming card table at Maker Faire this year. But we’re really glad we stopped for a little chat. She went so far as to pull the working parts out of her racing snail to show them to us!

Wait, wait… racing snail? Yeah, this is a pretty neat one from a few years ago. The snail is a relatively large version of a bristlebot (incidentally, we believe bristlebots were originated by EMSL). The thing that’s missing here are the bristles. Instead of using a scrub-brush for this large version, [Lenore] discovered that velvet has a somewhat uni-directional grain. But using a piece of mouse-pad cut to the same footprint as the velvet she was able to get the flat-footed snail to move in a forward direction purely through the jiggle of a vibrating motor.

If this sparked your interest there are tons of other bristlebot variations to be found around here. One of our favorites is still this abomination which shifts weight to add steering.