PIDDYBOT – A Self Balancing Teaching Tool

January 17, 2014 by Mathieu Stephan 9 Comments

We’re sure that most Hackaday readers are already familiar with the inverted pendulum system, which basically consists of a pendulum having its center of mass above its pivot point. Most applications (like the one we are going to describe) limit the pendulum to 1 degree of freedom by affixing the pole (or circuit board here) to an axis of rotation. The overall system is therefore inherently unstable and must be actively balanced in order to remain upright.

[Sean] created the piddybot, a tiny balancing robot aimed to teach the basics of PID control by trying to get the robot to stand still. More interestingly, the Proportional / Integral / Derivative values can directly be adjusted using the three on-board potentiometers. This will allow users to get the feel of each parameter’s impact on the robot behavior. The piddybot is based around the Arduino nano, a custom PCB, 2x 26:1 geared motors, one 1A dual motor driver board, a six degrees of freedom Inertial Measurement Unit, 2 batteries and finally a 3D printed body. You can check out a video of the robot in action after the break.

This project stems from a non-PID self balancer which [Sean] hacked together in September.

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Here’s Pi In Your Eye – HUD Goggles

January 17, 2014 by Kristina Panos 7 Comments

[John Ohno] has found what is perhaps the best possible use for steampunk goggles: framing a monocular display for a Raspberry Pi-based wearable computer. [John]’s eventual goal for the computer is a zzstructure-based personal organizer and general notifier. We covered [John]’s zzstructure emulator to our great delight in July 2011. Go ahead and check that out, because it’s awesome. We’ll wait here.

[John] has been interested in wearable computing for some time, but is unimpressed with Google Glass. He had read up on turning head-mounted displays into monocular devices and recognized a great opportunity when his friend gave him most of an Adafruit display. With some steampunk goggles he’d bought at an anime convention, he started on the path to becoming a Gargoyle. He encountered a few problems along the way, namely SD card fail, display output issues, and general keep-the-parts-together stuff, but came out smelling like a rose. [John] has ideas for future input additions such as simple infrared eye tracking, the addition of a chording keyboard, and implementing a motorized glove for haptic learning.

Want to make your own wearable display but have an aversion to steampunk? Check out this homebrew solution with (mostly) 3-D printed frames. And it has servos!

[Thanks John]

AxCut: An Open Source Laser Cutter

January 16, 2014 by Marsh 47 Comments

If you’ve always wanted a laser cutter and you have £1500 lying around (approx. $2500 as of today) — and you have access to a 3D printer — then you’ll want to take a look at [Damian’s] open source laser cutter: axCut. The project has evolved over the last few months from some mockups in OpenSCAD to a working prototype.

You’ll want to dig through his blog posts as well as his YouTube channel for all the juicy details, but from what we can gather, [Damian] is on the home stretch. The current implementation includes a 40W CO2 laser with functioning laser control and an impressively quiet watercooling system. Although the build’s wiring remains a bit of a tangle, the prototype cuts (almost) as expected. His next hurdle is ironing out the air assist, which should prevent some fire hazard issues and keep the lens free of debris.

Check out a couple of videos after the break, and if you’re interested in getting into laser cutting but want to start smaller, have a look at the MicroSlice from a few months ago.

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Retro Modern Nixie Clock

January 16, 2014 by James Hobson 20 Comments

[Reboots] is a humble hacker who enjoys nixie tubes. So when he saw an old General Electric battery charger for sale at a hamfest, he thought: “that case would make a nice clock…”

He was first exposed to nixie tube clocks a few years ago when his brother gave him a DIY nixie clock kit from [Peter Jensen’s] website TubeClock.com — it was an easy build, and worked very well. It also introduced him to a unique driver for nixie tubes, an HV5622 high-voltage shift register made by Supertex inc. Compared to the traditional (and rare) 74141 nixie driver chips or discrete transistor drivers, the HV5622 is much smaller, requires less microcontroller I/O’s, and is not as picky when it comes to powering it.

The nixie tubes he chose for the project came from a lot sale on eBay, Russian surplus IN-12 tubes. He even managed to find an english datasheet for them!

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Making A Variable RF Signal Sampler

January 16, 2014 by Mathieu Stephan 18 Comments

One of [Brian]’s hobbies is Amateur Ham radio, in which it is usually required to check that the transmitted signals are within specifications. As it isn’t safe to connect the radio’s output directly to measuring equipment due to the high voltages involved, [Brian] made his own dedicated RF signal sampler. It works by using capacitive coupling between the signal you wish to sample and a high impedance output. The latter can then safely be connected to an oscilloscope or spectrum analyzer for monitoring.

In the picture you see above, the air gap between the core signal conductor and the output plays the role of a capacitor. By adjusting its length you can therefore vary the output signal’s voltage range. The sampler is built using a die-cast aluminium enclosure which is 52x38x27mm. As you may have guessed, due to the case geometry the output attenuation will depend on the signal’s frequency. [Brian] tested the unit using a 30MHz signal generator and printed this frequency attenuation graph while also varying the air gap.

Fail Of The Week: Color Meter For Adjusting LEDs

January 16, 2014 by Mike Szczys 29 Comments

fotw-color-meter

[John Peterson] answered our call to document your hacks by discussing what he learned while building this color meter. He conceived the project as a way to precisely match the color output of LEDs driven with a PWM signal. The thought was that it could sample an LED’s output, then use that data to calculate values necessary to match the color of other LEDs. This is a good idea when using LEDs of different types, but even diodes from the same production line can show variations in color output.

Of course this project wouldn’t be featured as a Fail of the Week if it worked as he had expected. It turns out the sensor that he used, an Avago ADJD-S371-QR999 on a SparkFun breakout board, takes very quick color readings. This is great for solid objects, but not great for a light source being switched on and off like the PWM LEDs.

We like it that [John] posted a list of lesson learned on the project. The real fail is in trying to use this particular sensor, but we figure there must be some way to get meaningful data through sampling. Check out the page for the retired sensor which also includes a link to the datasheet. Can you think of a firmware hack which would allow this hardware to sample so that the PWM value could be extrapolated through averaging or other calculations? Let us know in the comments.

Fail of the Week is a Hackaday column which runs every Wednesday. Help keep the fun rolling by writing about your past failures and sending us a link to the story — or sending in links to fail write ups you find in your Internet travels.