IR remote control extender

IR remote control has a limited range and doesn’t work when it is out of line of sight. But what if you need to control your appliances even if don’t see them. [Michail] suggest to build an IR remote extender that stands between your remote control and device to be controlled. Building one seems to be pretty easy task. It has to repeat everything you send. Repeater circuit design is based on Andy Collinson circuit. It is based on 555 timer circuit that makes overall repeater small and cheap. Repeater receives IR signal by TSOP1738 receiver. As you may know receiver demodulates IR signal by removing 38kHz. 555 timer is set up to generate 38kHz signal which is modulated by TSOP1738 output. Whole magic that simply works well. If you need to control appliance that is in different room you can simply locate receiver in your presence while transmitting LED in other room.

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Nicer PC HDD activity indicator

Usually, computer hard drive activity is indicated with a single flashing LED when there is write or read operation performed. [Harvey Wilson] wanted something different than just a flashing LED and came out with an indicator. He replaced a single LED with 10 LEDs mounted in a circular shape. After digging some info from the Internet, he found the HDD signal nature and built the 4017 counter based circuit which accepts each incoming LED signal and then increments a counter. All 10 LEDs are connected to counter output pins, so each event lights makes the feeling of running lights.

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Multivibrator – back to basics

Multivibrator circuit is one of the first projects you start learning electronics. It is a beautiful circuit widely used for educational purposes and even in end projects as waveform generators. Lots of hobbyists grab a microcontroller/Arduino to blink LEDs. But using basic circuits like multivibrator may be cheaper, faster and even fun. [Ray] decided to go through multivibrator theory and explain its working in detail step by step. The circuit itself consists of two transistors, two capacitors, and four resistors. When powered, the circuit generates a square wave signal that can be used to flash LEDs or clock other circuits. You will get an intuition on what causes multivibrator continuously generate. Formulas allow calculating resistor and capacitor values for a particular frequency. Especially if you are a starter in electronics build one on a breadboard and do some experiments, why not to start with Christmas lights.

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Have you seen RGB seven segment LED display?

Seven segment LED displays usually come in single color like red, green, blue or yellow. But probably there isn’t any RGB displays in a market yet. After this mod situation can change. Markus decided to fill this gap and made one by himself. All he did is took a an existing 7-segment display and removed single colored LEDs with dremel and replaced them with SMD RGB LEDs. SMD LEDs already were with magnet wires that made the process easier. Obviously the number of pins tripled so additional socked was needed. He made a simple board with all pins and glued a display to it. Great inspirational work. isn’t it?

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Transistor based class AB amplifier

In most small audio project hobbyist are using specialized audio amplifier chips. That’s really fine you get high quality amplification without scratching your head. Some probably don’t care how these things work. But don’t forget that amplifiers can be built out of discrete electronics components like bipolar transistors. Check out this great hackaweek project where Dino builds class AB audio amplifier out of three bipolar transistors and other passive components. He slightly goes through theory of operation and of course demonstrates its working in following video.

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Adding DAC to Arduino or any other microcontroller

Most of the 8-bit microcontrollers lack integrated DAC (Digital to Analog Converter) functionality. This is handy when you need to generate analog signals out of digital information. Adding DAC to any existing microcontroller is a piece of cake. But before you start why not to look at various options available. Embedded newbie provides a review of Arduino DAC solutions. Beginning with the R-2R ladder solution list goes through multiple ways of converting digital to analog. Depending on your needs and speed required there can be a PWM DAC converter that is nothing more than digital signal passed through low pass filter. This is how motor control works. Its relatively slow, but serial that gives an advantage when small pin count microcontrollers are used. In the other hand is signal speed is an issue then parallel DAC – same R-2R ladder probably with an output buffer circuit. And lastly, there is always an option to use specialized DAC chips that can be interfaced through one of the available interfaces like SPI. These save space and MCU pin and still provide high resolution and speed.

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ScienceProg Link Dump -07/26/2011

Circuitpeople have a nice online tool for viewing Gerber Files. You upload Gerber or zip file and see design on web page right away. Tired of sharing your circuit files? Sometimes it is really hard to send your design as they are big in size or format. CircuitBee has a solution. It’s an online circuit sharing service that allows sharing circuits and schematics without pressure. Once uploaded put generated code in to your blog, forum or share directly. Tool allows zooming, panning, and adding mouse over tips. Have an image which you would like to mill with CNC? Most likely it is not in vector format. This software takes care of it – it simply takes bitmap image and converts it to vectorized G-code that is suitable for milling, drilling and where ever you like.

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