Electronics
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Welcome to the wonderful world of PCB creation! We've used a few software packages over the years (namely Protel DXP) and have found Eagle Layout Editor from CadSoft to be very easy to use, very cost effective, and very powerful.
Lecture 8 - Eagle Schematics
I've experimented with many home fabricated PCB methods. Some were successful, others not quite so much. You can spend as much as you want tooling/buying consumables to produce good PCB's by yourself.
PCB's on the cheap
The sound waves generated by nearby conversation will cause the glass in a window to vibrate very slightly. If a laser beam is bounced off the window, its reflection will be modulated by the vibrations. All that's needed to hear what is being said is a demodulating device that extracts the audio from the reflected laser beam That technique is used by sophisticated "surveillance experts," but you can easily duplicate that feat by using a hobbyist's laser and the inexpensive Laser Listener demodulator shown in Fig. 1.
Laser listening
ShmooCon was, once again, a fantastic experience this year. One of many highlights of this year's event for me was hacking on some radio devices with Travis Goodspeed in the hotel bar for hours on end. This included playing with the IM-Me that he brought.
a $16 pocket spectrum analyzer
Ο αναλυτής αυτός είναι , ένα ευαίσθητο όργανο , στις μεταβολές συχνότητας και πλάτους, ενός ακουστικού σήματος.
mini audio analyzer
This site provides a series of online textbooks covering electricity and electronics.
All About Circuits : Free Electric Circuits Textbooks
Audio circuits
The following links to circuit diagrams and building projects I have found from other web sites.
Limiter
Why it is important to use a limiter? Audio signals as music or speech have big dynamic ranges. There are silent and loud sections.
Why is it important to use this device? Audio signals as music or speech have big dynamic ranges. There are silent and loud sections.
CZ Compressor/Limiter/Clipper for FM broadcasting
This audio limiter circuit is easy to build, works with BA741 8pins or 4pins so pay attention and uses a symmetrical power supply.
Audio limiter circuit schematic
An Excellent Audio Clipper Here are two versions of the best clipper circuit I could find in a short search of the radio handbooks I have on my, somewhat limited, book shelf.
clipper
Single Op-Amp Twin-T Band-Pass and Notch Filter | Simple Circuit Diagram
This is a Single Op-Amp Twin-T Band-Pass and Notch Filter circuit. This circuit uses the twin-T topology which requires one or two op amps and three resistors and three capacitors.Robotics