# Beginner Concepts: LEDs And Laws

Adafruit has a new LED tutorial for people wanting to get started with electronics. It is full of useful diagrams, pictures, and quizzes to help make sure you are understanding the concepts. This is the real basic stuff here: LEDs, resistors, and the laws from Kirchhoff, and Ohm. It starts out explaining the parts of an LED. Then variations of LEDs: illumination versus indication, clear versus diffused, brightness, color, and size. The mass of the tutorial covers how and why an LED’s brightness can be changed by a resistor and why a resistor is needed to keep an LED from burning out. Such as how Kirchhoff’s Voltage Law works with Ohm’s Law to help you determine the proper resistor for an LED. If you found useful the other beginner concepts posts about Analog Circuits and Electronics basics from the Giz, you should find this tutorial to be useful.

# Propeller And Machine Gun Timing

[Matt] was looking for a challenge. Inspired by the machine gun setups on World War I planes he wanted to make a gun that can shoot between the blades of a spinning propeller. The original guns used an interrupter gear that synchronized machine gun firing with the engine mechanically. [Matt] set out to do this using a microcontroller.

To make this work there are two important pieces of information; how fast is the propeller spinning right now, and how long does it take for the pellet to pass the blade? [Matt] used an oscilloscope and some infrared sensors to establish the firing delay at about 20-22ms. Another sensor shows the propeller is spinning at 500 RPMs, with some simple calculations showing that there is indeed a big enough window of time to fire between the blades. After testing with a visible LED and then building out the rest of the circuitry he accomplished his goal. He even added a test function that purposely hits the blades just to see how accurate the system was. We hope this shows up in a Red Baron RC replica, or other flying arsenal.

# Solderless Drawdio Terminally Implemented

So you’re stuck in a boring class and you can’t fight off the urge to hack something, even your pencil, to pass the time. Maybe you are performing a live electronics show and you drop your synth down a flight of stairs and all that you are left with is a handful of components, a screw terminal block and a pencil. There are thousands, perhaps millions of these kinds of situations and for each one the answer is the solderless drawdio clone by [Martin].

You may have seen the original Drawdio here before, a fun piece of technology that is simple enough to recreate. This latest approach would make an excellent introductory project for a hacking workshop seeing as the guide is straightforward and the lack of soldering would make logistics so much easier. The results are very similar to the original–check the video after the break. Continue reading “Solderless Drawdio Terminally Implemented”

# ROS Turns Three

Since its first debut three years ago, ROS has been gaining some popularity with the robotics folks.  It’s behind the scenes of those impressive quadcopters you may remember from a while back.  ROS helps abstract the lower level functions of a robot by supplying lots of code for commonly used components (wiimote for example). Being an “operating system”  it comes with lots of nice features you would expect, like a package manager.  It’s open source and many of their projects are well documented making it easy get started.

Check out the video after the break to see it in action Continue reading “ROS Turns Three”

# Android On IPhone: New Treats

It seems that the iPhone 2g and 3g are the newest phones to get Android 2.2, codenamed Froyo. The process for installing Froyo if you have a jailbroken device seems to get even easier every time, with this revision being as simple as adding a repository, downloading Froyo, and pressing go. Follow the link for a wonderful step by step guide, complete with screenshots to take out all of the guess work. Android on iPhone sure has come a long way since the first time we covered it.

[via reddit]

# AVR Controlled RGB LED Matrix Plays Tetris

[Stan] built this LED matrix using a 16×16 grid of RGB LEDs. He built the hardware and wrote some subroutines to randomize the colors. He’s not using PWM because frame buffering is not feasible for the 1k SRAM limit of the ATmega168 he used. Instead, shift registers drive the lights which can be mixed to achieve eight different colors (including off for black) reducing the framebuffer size to just 96 bytes. After he got done with the build he realized this is sized well for a game of Tetris. We’ve seen AVR tetris, PIC Tetris, and Tetris using composite video but it’s always a pleasure to see a new display build.

After the break we’ve embedded [Stan’s] demo video, several pictures, and a schematic. He’s using many of the same principles outlined in our How to Design an LED matrix tutorial.