Author: Ethan Zonca

62 Articles

Cheap Power Meter

Digital Data From A Cheap Power Meter

October 21, 2014 by 46 Comments

Power meters like the Kill-A-Watt are great for keeping track of energy usage, and are also very hackable. The Kill-a-Watt in particular puts out analog signals proportional to current and voltage, which makes it easy to interface with a microcontroller.

Although reading analog voltages is easy enough, [Kalle] found a cheap Chinese power meter that is even more hackable. These inexpensive power meters cost about the same as a first-generation Kill-a-Watt, but they directly stream out digital data. The power meter [Kalle] hacked has a non-US plug, but the meter is available from the usual suppliers (eBay, Aliexpress, etc) with a 3-prong US plug and 120v rating.

After breaking out a logic analyzer, [Kalle] discovered that the meter constantly streams voltage, current, and power data from the measurement board to the display board on a SPI-like bus. The ribbon cable inside the meter even has the clock and data bus lines clearly labelled. [Kalle] went on to reverse-engineer the protocol and write an Arduino sketch that parses the stream, making it even easier to integrate this meter into your next power monitoring project.

Open-Source Water Quality Tester

Open-Source Water Quality Tester

October 17, 2014 by 12 Comments

Contaminated water is a huge problem in many third-world countries. Impure water leads to many serious health problems, especially in children. Installing a water purification system seems like a simple solution to this problem, but choosing the right purification system depends on the level of contaminants in the water.

Water turbidity testers are often used to measure the severity of water contamination. Unfortunately most commercial water turbidity testers are very expensive, so [Wijnen, Anzalone, and Pearce] set out to develop a much more affordable open-source tester. Their tester performs just as well as commercial units, but costs 7-15 times less.

The open-source water tester was designed in OpenSCAD and 3d printed. It houses an Arduino with a custom shield that measures the frequency from several TSL235R light-to-frequency converters. An LED illuminates the water and the sensors measure how much light is diffused and reflected off of particles in the water. Another sensor measures the brightness of the LED as a baseline reference. The turbidity of the water is calculated from the brightness values, and is displayed on a character LCD. More details about the tester are included in a fairly extensive paper.

[Thanks Andrew]

CARDIAC Cardboard Computer

A Clever Cardboard Computer

October 14, 2014 by 18 Comments

Back in the 70’s when computers were fairly expensive and out of reach for most people, [David Hagelbarger] of Bell Laboratories designed CARDIAC: CARDboard Illustrative Aid to Computation. CARDIAC was designed as an educational tool to give people without access to computers the ability to learn how computers work.

The CARDIAC computer is a single-accumulator single-address machine, which means that instructions operate on the accumulator alone, or on the accumulator and a memory location. The machine implements 10 instructions, each of which is assigned a 3-digit decimal opcode. The instruction set architecture includes instructions common to simple Von Neumann processors, such as load, store, add/subtract, and conditional branch.

Operating the computer is fairly simple–the cardboard slides guide you through the operation of the ALU and instruction decoder, and the flow chart shows you which stage to go to next. The program counter is represented by a cardboard ladybug which is manually moved through the program memory after each instruction completes.

Even though the CARDIAC is dated and very simplistic, it is still a useful tool to teach how microprocessors work. Although modern processors include multi-stage pipelines, finely-tuned branch predictors, and numerous other improvements, the basic principles of operation remain the same.

Feeling adventurous? Print out your own CARDIAC clone and try writing your first cardboard computer program.

[via Reddit]

Arduino Floppy Music Shield

A Simple Floppy Music Controller

October 12, 2014 by 12 Comments

While playing music with floppy drives has been done many times over, making any device with a stepper motor play music still appeals to the hacker in all of us. [Tyler] designed an Arduino shield and a library which lets you get up and running in no time. [Tyler]’s shield includes pin headers to connect 4 floppy drives, which plug directly into the shield. The drives don’t need any modification before being used.

While you could simply wire a few floppy drives up to an Arduino with some jumpers, this breakout shield makes connecting your drives trivial. In addition to designing the shield, [Tyler] released an Arduino library to make things even easier. The library lets you simply set the frequency you want each drive to play, which saves a bit of legwork.

The floppy-controlling Arduino library is available on GitHub and a video of the controller is included after the break.

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DeBrew Delta Coffee Robot

Delta Coffee-Brewing Bot

October 9, 2014 by 8 Comments

Pour-over coffee brewing is a simple and cheap hands-on alternative to using an automatic coffee maker. Although coffee aficionados often choose pour-over just for the manual brewing experience, this didn’t stop [Elias] from automating his pour-over coffee setup with an elaborate delta-robot: the DeBrew.

The coffee-brewing robot is built around a delta assembly from a 3d printer controlled by a BeagleBone Black. The BeagleBone drives stepper motors, displays information on a small open-source hardware HDMI LCD display, and serves up a web interface to control the machine. The radius of the pouring pattern, water temperature, and grind coarseness of the DeBrew can all be customized though its web interface.

For those who want to build their own pour-over robot, [Elias] has made a SketchUp drawing of the design and all of his Python source code available as open-source. Check out the video after the break where [Elias] explains how his delta pour-over bot works.

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Open-source BLDC motor driver

Brushless Motor Controller Shield For Arduino

October 8, 2014 by 19 Comments

Brushless motors are ubiquitous in RC applications and robotics, but are usually driven with low-cost motor controllers that have to be controlled with RC-style PWM signals and don’t allow for much customization. While there are a couple of open-source brushless drivers already available, [neuromancer2701] created his own brushless motor controller on an Arduino shield.

[neuromancer2701]’s shield is a sensorless design, which means it uses the back-EMF of the motor for feedback rather than hall effect sensors mounted on the motor. It may seem strange to leave those sensors unused but this allows for less expensive sensorless motors to work with the system. It also uses discrete FETs instead of integrated driver ICs, similar to other designs we have covered. Although he is still working on the back-EMF sensing in his firmware, the shield successfully drives a motor in open-loop mode.

The motor controller is commanded over the Arduino’s serial interface, and will support a serial interface to ROS (Robot Operating System) in the future. This shield could be a good alternative to hobby RC controllers for robots that need a customizable open-source motor controller. The PCB design and source code are available on GitHub.

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