Building a DC Constant Current/Power Electric Load

By just looking at the picture above, we’re pretty sure that most Hackaday readers will have guessed by now that much power can be dissipated by this electric load. For those who don’t know, an electric load (or dummy load) is a device used to simulate a load on a system for testing purposes. This is quite handy when measuring battery capacities or testing power supplies.

The heart of the device that [Kerry] designed is based on 6 power MOSFETs, a few operational amplifiers and an Arduino compatible ATmega328p microcontroller. Sense resistors are used to measure how much current is passing through the MOSFETs (and therefore the load), the MCP4921 Digital to Analog Converter (DAC) from microchip is used to set the current command, and the load’s voltage is measured by the ATmega ADC. Measuring the latter allows a constant power load mode (as power = current * voltage). In his article, [Kerry] shows that he can simulate a load of up to 200W.

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Hackerspace Tour: Milwaukee Makerspace


I had the opportunity last Thursday to visit the Milwaukee Makerspace. I took along a video camera and had a great time on a tour guided by [Brant], [Matt], and [Vishal]. We’ve actually seen quite a number of reputable hacks come from this group already. A couple that come to mind include beer dispenser security and a bottle-free water cooler. This tour shows off a lot of the cool stuff going on at the space. Don’t miss the video after the break, but we’ll also give you the gist of it if you’re looking for a quick rundown:

We start off looking at their craft area, wall of fame (including all their Power Racing Series medals) and laser cutter room. From there we take a peek at one of the big rooms that serves as for-rent floor space and pallet storage. This part of the tour includes a look at Red Lotus and Big Jake-stein, two of the PRS cars used this season. The storage tour rounds up with a look at their set of 19 vaults — these are like deep self-storage closets for members. The space spices things up with awards for best vault of the month.

Moving on to the next large space we encounter this huge Kuka KR 30 industrial robot arm that they acquired for free! A room has been built around the 2500 pound beast for safety and they are working on building their own controller for it. Right now it’s got a jig that holds a spindle motor making it a CNC router. This enclosure is in a larger space that makes up the machine shop and welding area. Through a door is a woodshop that includes a big panel saw which they pick up on Craig’s List. The tour wraps up with a walk-through of the electronics den and a tour of the 3D Printer hangout.

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Trinket Contest Update #3


We’re still receiving tons of Trinket contest entries (here’s a link to the last update). After the break you’ll find another dozen that were sent in. If you’re waiting to see your own appear here please be patient as we’ve got a lot to wade through. If you haven’t sent in an offering yet you’ve got to get it in before Friday!

The contest asks you slap the Hackaday logo onto something for a chance at winning one of 20 Trinket dev boards donated by Adafruit for this contest.

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The Nickelphone


[Tyler Bletsch] sent us a tip about his new build: a keyboard that redefines “coin-operated.” The Nickelphone can emit square wave tones via a piezo buzzer, but [Tyler] made this 25-key piano as a MIDI keyboard capable of driving a full synthesizer.

He chose an ATMega644 as the brain because it’s Arduino-friendly but has more data pins—32—than the usual ATMega328 chip, which allows him to provide each key with its own pin. Each coin was soldered to its own wire and connects up to a 1MΩ resistor array. Coin-presses are recognized by the simple capacitive sensing technique outlined here, but [Tyler] needed to take advantage of a workaround to accurately detect multiple presses.

Check out [Tyler's] detailed project guide for more information as well as the source code. Check out the video of the Nickelphone after the break, then browse through some other capacitive touch hacks, like the Capacitive Touch Business Card or the Capacitive Touch Game Controller.

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Hacking and Philosophy: An Introduction


This fall marks my third (and Flying Spaghetti Monster willing, final) year as a PhD student, and although I’m no longer taking courses, I often wonder how my seminars might have differed if other hacker-types were in the classroom contributing to the discussion.

Hacking and Philosophy is a new column that explores scholarly research about hacking, and does so with a community that lives the hacking experience. It’s a chance to discuss how researchers and deep thinkers handle our culture, its image, its philosophy, etc. Put simply, think of it as a weekly book club meeting. I’ll choose the text and proceed one chapter at a time, giving you my complete response to that week’s reading while engaging your replies in the comments as well as including your important or insightful contributions in future posts. Further, I promise never to venture into Ivory Tower territory: I hate being talked down to as much as the next person.

Hacking and Philosophy only works if it’s a conversation, so I encourage contributions, corrections, respectful disagreements, and as much hypertext (obviously literally, but philosophically a la Landow) that you can manage. Think of me not as an instructor but as a fellow participant who will occasionally guide us through obscure concepts and terminology.

Keep reading after the break for a tentative book list and the reading for next week!

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Making a Power Inductor Checker


Back to the basics: there are three kinds of passive electronic components: Inductors, Capacitors and Resistors. An inductor can be easily built and many types of core and bobbin kits are available. However, characterizing one hypothetical coil you just made is quite tricky as its inductance will depend on the measurement frequency and DC bias current. That’s why [ChaN] designed the circuit shown above.

As you may guess, RF enthusiasts are more interested in the inductance vs frequency curve while power circuit designers prefer inductance vs load current (for a given frequency). The basic principle behind the circuit shown above is to load an inductor for repetitive short periods and visualizing the current curve with an oscilloscope connected to a sense resistor. When loading the inductor, the current curve will be composed of two consecutive slopes as at a given moment the coil’s core will be saturated. Measuring the slope coefficient then allows us to compute the corresponding inductance.

[Via Dangerous Prototypes]

Portable PS2, Courtesy of Cross Plane


It’s not exactly a portable, but [Downing]‘s PS2 advance puts all the power of a Playstation 2 in the palm of your hands, all while being more popular that the Vita.

For the audio and video, the project uses a Cross Plane, a project from a slightly unsuccessful Kickstarter [Downing] pulled the plug on last month. When the handheld is plugged in to the Cross Plane, all the audio, video, and controller wires are transferred through a pair of cables, with the possible addition of wireless transmission should [Downing] ever want to revisit this project.

In deciding on what to use for a case, [Downing] had bought a few AG cases from Polycase but found the ergonomics severely lacking. Putting two of the case backs together, he found the resulting structure was actually very comfortable, and with a few simple modifications to add some holes for acorn nuts,

It’s a great looking project that really highlights [Downing]‘s talents as a console modder. He’s also thrown his hat into the Hackaday Trinket contest by engraving the Jolly Wrencher into the back of his project, which unfortunately isn’t seen in the video below.

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