LED Bulb Reviews, Evaluations And Teardowns

November 1, 2013 by Todd Harrison 25 Comments

[ElectronUpdate] has posted many great reviews of commercial LED bulbs that one can purchase to replace standard E26 incandescent light bulbs. In his reviews he evaluates the light emitting performance and does a thorough and detailed teardown, evaluating and understanding the circuit technologies used. For the light emission evaluation he uses a light meter and some homemade graph paper to plot the lumens at different angles. Flicker is easily evaluated using a solar panel from a discarded solar path light connected to his oscilloscope. Any flicker will show up quite nicely and can be measured. Of course a kill-a-watt meter makes an appearance in most reviews to read watts and power factor.

Recently [ElectronUpdate] wanted to understand the meaning of CRI which is advertised on many of these commercial LED packages. CRI stands for color rendering index and deals with how colors appear when compared to a natural light source. After doing some researching he found that a CRI over 80 is probably good for LED lighting. The next dilemma was how to measure CRI without expensive scientific equipment. He found a website that we have featured before with free software and instructions on how to build a spectrometer. The web instructions include building a meter box from paper but he found it was much more reliable if built out of wood. We’ll let you follow [ElectronUpdate’s] recommended build if you like, but you’ll need a few items which he does detail.

After a short calibration procedure the final rig will measure power spectral line densities of your light source. [ElectronUpdate] is promising more details on how the colorful measurement data can be related to CRI ratings, but you can get a jump on the details at Full Spectrum Solutions. We also recommend you browse through all of [ElectronUpdate’s] LED bulb reviews on YouTube if the progressing performance and innards of LED bulbs fascinates you as much as it does us.

Another Reflow Soldering Solution

October 30, 2013 by James Hobson 3 Comments

Still looking for a good way to reflow solder at home? Look no further! [Don] has a very handy and inexpensive solution that looks great. It makes use of a cheap hot plate, a solid state relay, an IR temperature sensor, and an arduino.

[Don] started by modifying the hotplate by reversing the handle mount — this provides a useful location to mount the IR temperature sensor. The control circuit uses PWM to adjust the temperature of the hot plate using the solid state relay. Because the IR temperature sensor has a cone of visibility it ends up reading an average area temperature as opposed to an individual point — for reflow soldering this is perfect. [Don] notes that some calibration is required, as depending on the emissivity of the object being measured the readout can differ — shiney objects will read a lower temperature than dark objects. He recommends doing the calibration with a scrap PCB and your chosen solder paste to get a general baseline for your project.

Need more info on the actual reflow process? We posted a handy guide a few months ago.

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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