This application note describes the operation of 12 volt DC cooling fans typically used to supply cooling air to electronic equipment: These fans are typically based on two-phase Brushless DC (BLDC) motors drawing between 1 and 50 watts of power. Single-phase brushless DC motors are also used in fans, but this is outside the scope of this application note.
Further discussion describes the addition of an Atmel ATtiny13 microcontroller and the benefits this offers, such as variable speed by external thermistor input. An additional input is a PWM pulse width-varying signal, which also controls fan speed.
App note: PC fan control using an ATtiny13 – [Link]
Adafruit has launched their Circuit Playground app for iPhone, iPad and iPod Touch. It provides a collection of reference formulas at the touch of a button, simplifying calculations to make your project more fun – [via]
Decipher resistor & capacitor codes with ease. Calculate power, resistance, current, and voltage with the Ohm’s Law & Power Calc modules. Quickly convert between decimal, hexadecimal, binary or even ASCII characters. Calculate values for multiple resistors or capacitors in series & parallel configurations. Store, search, and view PDF datasheets. Access exclusive sneak peaks, deals & discounts at Adafruit Industries. All that, plus updates with additional features & enhancements – MANY NEW CALCULATORS AND TOOLS being added!
Adafruit launches Circuit Playground app – [Link]
Digital pins 0-7, Analog 2-5, and a RST, V+, and GND pin are broken out to two rows of pins, maintaining about half the pins in a familiar shape and organization. A JST connector for LiPo batteries like the ones available through SparkFun and Adafruit and an MCP73811/2 charger circuit makes the Demiduino well suited for portable applications. On the back, I’ve also included CR1225 clips for ~3v3 power from easy to find coin cell batteries, and a power switch to save battery life.
Demiduino, another tiny Arduino compatible board – [Link]
Arena PartsList is a BOM manager that’s integrated with the Octopart component database. It has neat functions like auto-fill, that automatically adds a part to your database directly from a sales page of a electronics component distributor like Farnell, Digi-Key, Mouser, etc… [via]
Octopart just tweeted a free tool for BOM management. You can import a CSV file into a project and auto fill details using Octopart.
Their main tool is a more comprehensive product with collaboration features and stuff. They charge $79 per user per month, which includes training, tech support, upgrades, etc.
Arena PartsList free BOM management tool – [Link]
Here is a part from National Semiconductor designed for controlling high-power DC/DC boost regulators. What makes it interesting is that its PWM frequency can be pushed to 2Mhz. This allows for smaller and cheaper discrete components, like inductors and capacitors. The datasheet on this device also provides some nice PCB guidelines to maximize its efficiency and minimize noise.
App note: LM5022 DC/DC boost controller – [Link]
Here is a hack to extract, and use the LCD from a cheap picture-frame key chain. The project involved desoldering the LCD from its mainboard and building a breakout for it. With the help of a DSO it was possible to find out the pin-out for the LCD.
The AVR library used to drive this LCD is available for download at the bottom of the source article. You can check out a video of this project below.
Re-purposing an LCD from a cheap picture-frame key chain – [Link]
Paul Asselin has written a description of his design of a USB Lithium Polymer battery charger – [via]
I wanted to build a cheap USB LiPo charger and didn’t like the unavailability nor the price of the Maxim’s MAX1555. Searching for something better, I stumbled upon the Microchip MCP73831. It is still way too expensive in single quantities but there ain’t too many options.
The board is intentionally small and has a status LED. There really isn’t much more to it, it’s a single purpose device and just does the job. It is proudly Open Source Hardware.
Eric built himself a battery monitoring system based on the ATmega328 Development Kit. He drained a 9V battery with 100mA of current and monitored the voltage drop until total depletion. He used this data to estimate how much time is left until depletion – [via]
The 100mA constant load was chosen because my ProtoStack Arduino Clone with LCD draws about 92mA and I wanted to write a sketch to display a battery bar and the approximate hours battery life left. Since all batteries have an internal equivalent series resistance (ESR), it is important to take that into account when only using a battery’s voltage to monitor its state of charge. Since we discharged the battery through a load that is similar to the ProtoStack board with LCD, the ESR of the battery has automatically been accounted for in the voltage measurements.
Monitoring battery voltage to calculate capacity with an Arduino – [Link]
The activity of the Sun varies on a cycle with a period of approximately 11 years. Periods of low solar activity are followed by a few years of sharply increased number of solar spots, flares, and coronal mass ejections (CMEs), disrupting Earth’s magnetic field and causing magnetic storms. With the next Solar cycle maximum approaching I wanted to get on the fun too, so I set to build my own device for detecting and recording those magnetic storms, a.k.a. a magnetometer.
DIY geomagnetic storm monitoring – [Link]
Cameron tipped us to a circuit simulator for Android devices. It looks a lot like the java based circuit simulator we wrote about a few weeks ago. Everycircuit seems like a useful tool if you want to play around with electronics anywhere you find yourself. Unfortunately it seems to only support abstract level simulation models, not actual real components.
Circuit simulator for Android devices – [Link]