Building A DC Constant Current/Power Electric Load

October 28, 2013 by Mathieu Stephan 47 Comments

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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Making A Power Inductor Checker

October 28, 2013 by Mathieu Stephan 7 Comments

inductor-checker-for-oscilloscope

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]

Electrochemical Etching With A Microcontroller

October 27, 2013 by Brian Benchoff 31 Comments

IMAG1459_zps68634c16

While most of the time the name of the game is to remove a lot of metal, etching is an entirely other process. If you just want to put a logo on a piece of steel, or etch some labels in a piece of aluminum, You need to think small. Mills and CNC routers will do, but they’re expensive and certainly not as easy to work with as a small, homebrew electrochemical etcher.

This etchinator is the brainchild of [Gelandangan], and gives the techniques of expensive commercial etchers to anyone who can put together a simple circuit. This etcher can etch with both AC and DC thanks to a H bridge circuit, and can be fabbed up by anyone who can make their own circuit board.

To actually etch a design in a piece of metal, simply place the piece on a metal plate, put the stencil down, and hold a felt-covered electrode moistened with electrolyte down over the stencil. Press a button, and in about 30 seconds, you have a wonderfully etched piece of metal.

[Gelandagan] has some templates that will allow you to make your own electro etcher, provided you can etch your own boards and can program the PIC16F1828 microcontroller. All this info is over on the Australian blade forum post he put up, along with a demo video below.

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Converting A Mill To CNC

October 25, 2013 by Phillip Ryals 22 Comments

Have a mill that you’d like to automate? Perhaps you can gets some ideas from the work [James] recently finished. Using familiar NEMA 23 stepper motors (the same motors used in the RepRap), he hacked his Proxxon MF-70 mill for CNC control. Adding a Sanguino and the stepper controllers from other projects, [James] got a working machine for minimal investment. You can tell that [James] is a fan of Polymorph, because he uses it liberally for most of the project, even using it to create some Oldham couplings (Google cache).

After completing the build initially, he managed to burn out the spindle motor by milling steel too quickly. We found it interesting that he was able to use a TURNIGY 2217 860kv 22A Outrunner (for R/C airplanes) as a new spindle motor. Not only is it a low-cost solution, but pairing it with a traditional brushless ESC can give your CNC software direct control over the motor speed.

The image above is an example of what [James’] machine is capable of. Overall, it’s a very accessible project for most of us. Not every mill needs to be capable of 10 mil traces. If you’ve got the urge, you can probably put one together yourself. Of course, if you do, please let us know!

Table Saw Kickback Video Ends Badly

October 23, 2013 by Adam Fabio 85 Comments

Our comments section has been pretty busy lately with talk of table saws and safety, so we decided to feature this sobering video about table saw kickback. [Tom] is a popular YouTube woodworker. He decided to do a safety video by demonstrating table saw kickback. If you haven’t guessed, [Tom] is an idiot – and he’ll tell you that himself before the video is over. There are two hacks here. One is [Tom’s] careful analysis and preparation for demonstrating kickback (which should be fail of the week fodder). The other “hack” here is the one that came breathtakingly close to happening – [Tom’s] fingers.

Kickback is one of the most common table saw accidents. The type of kickback [Tom] was attempting to demonstrate is when a board turns and catches the blade past the axle. On a table saw kickback is extremely dangerous for two reasons. First, the piece of wood being cut becomes a missile launched right back at the saw operator. We’ve seen internal injuries caused by people being hit by pieces of wood like this. Second, the saw operator’s hand, which had just been pushing the wood, is now free to slid right into the blade. This is where a SawStop style system, while expensive, can save the day.

The average 10 inch table saw blade has an edge traveling at around 103 mph, or 166 kmh. As [Tom] demonstrates in his video, it’s just not possible for a person to react fast enough to avoid injury. Please, both personal users and hackerspaces, understand general safety with all the tools you’re using, and use proper safety equipment. As for [Tom], he’s learned his lesson, and is now using a SawStop Table.

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Introducing The Shapeoko 2

October 21, 2013 by Brian Benchoff 39 Comments

For all the 3D printers that hit the Hackaday tip line, it’s surprising we don’t see more CNC routers. They’re arguably more useful tools, and with the ability to mill wood, plastic, and non-ferrous metals, open up the door to a whole bunch more potential builds. One of the most popular – and certainly one of the least expensive – CNC routers out there, the Shapeoko, just received a huge update that makes this minimal machine even more capable.

The new Shapeoko 2 keeps the same V wheel on an aluminium extrusion design with Makerslide, but fixes a few problems that limited the original Shapeoko. There’s a larger work area on this version, and the Y axes feature dual stepper motors. The biggest feature, we think, is the ability to handle materials larger than the machine itself thanks to its open front and back.

The Shapeoko 2 is available in two versions, a $300 mechanical kit that requires you to go out and get some motors, a power supply, and a grblShield, the full version, for $650, includes everything you’ll need to start routing wood metal and plastic at home.

Circular Saw To Table Saw Conversion

October 19, 2013 by James Hobson 90 Comments

Corded circular saws are a dime-a-dozen at any old thrift store, yet table saws are a bit more of a costly investment — have you ever wondered if you could just make one out of a circular saw? [Matthias Wandel] did, and he just so happens to be very good at woodworking! He makes a lot of great woodworking videos to share on YouTube, and in his latest blog post, he shows us a rather elaborate way to convert a plain old circular saw, into a functional table saw.

While the concept seems simple, unless you do a lot of woodworking, you’ll probably marvel at how easily making things comes to [Matthias] — we know we did. By the end of the video he has a fully functional table saw that can raise and lower in height, and cut at different angles.

If you’re interested in making one yourself, he does a very thorough job explaining the process in his video — check it out after the break!

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