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LED-Scope Kit Part 1: Basic Electronics Part 2: LED Array Oscilloscope Part 3: Microcomputer Controlled Graphics |
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| Introduction | ||
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| LED-Scope Learn Electronics by Doing LED Array Oscilloscope Kit - |
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| Fully assembled LED array oscilloscope kit displaying a 440hz sign wave produced by the Signal Generator/Practice board. |
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Learn Electronics by Doing The best way to truly learn something requires that you make use of what you have just studied by actively using it. Therefore, the best way to learn electronics is to build something. This kit is intended to provide a high interest project that will teach the basic operation and functions of an oscilloscope by building it one functional module at a time. A source of test signals will be needed to demonstrate and study the scope as it is being built , so the Signal-Generator Practice board is the first part of the project. This provides a non-critical place to learn soldering and unsoldering skills, how to identify and test components, how to read schematics, use a Digital Multi Meter (DMM), and apply some basic math to analyze these test circuits. Because a standard Cathode Ray Tube (CRT) oscilloscope uses very high voltages to drive the display, this kit replaces the CRT with an array of low voltage LEDs. Though this complicates the design, it provides two additional advantages: 1) there are more examples of how to use digital logic, and 2) the display can be reused in part-3 to teach microprocessor programming to create graphic displays. Just what is an Oscilloscope? The Merriam-Webster Dictionary defines it as: “An instrument in which the variations in a fluctuating electrical quantity appear temporarily as a visible wave form on the fluorescent screen of a cathode-ray tube.” Oh, yes; that clears up that mystery rather nicely. Lets start again with an example of why and what we need. If you use a volt meter to test the wiring for the lights in your car, you can see the changes as you flip switches. As long as the voltage changes only a few times per second, you can track it and troubleshoot the circuit. But what do you do to test something with very fast changing signals like a radio? Most audio signals change 200 to 12,000 times per second. Computer circuits have signals that change at the rate of 3 billion times per second. These are the signals the oscilloscope was created to visualize. In a cathode-ray tube (the original format) oscilloscope, a beam of electrons is scanned across the center of a phosphor screen. As the electrons strike it, they generate light and so produce a luminous horizontal line. The input signal being tested is then used to deflect this beam up and down as the voltage changes. By taking advantage of the fact that the signals we want to measure repeat themselves, the same pattern will be drawn on the screen many times in the same place and we can see the shape of the changing voltage. Changing how fast the beam moves across the screen lets us see the changes in everything from slow to very fast signals. With this tool we can see and track the shape of an audio signal as it passes through the different parts of a radio. We can find problems by looking for changes in its shape. In digital computer circuits, all the shapes should ideally be rectangular- just on or off. If we find a signal that is taking too long to change from on to off, it will look like a ramp and we know we have found a problem. How does it teach? The kits are divided into many small modules. Each module builds on the one before it, and consists of a small theory section. Next a circuit that demonstrates and uses this theory is built, step by step. Finally, the circuit is tested and analyzed using the skills and tools from earlier modules. By having a hands-on experience in the middle of a learning module, different parts of the brain are used and this helps to maintain interest level and reinforce skills learned in earlier modules. Part-2, the LED Array Oscilloscope, is presented in a manner similar to the story "Stone Soup."* As each module is built and tested, a new feature is suggested that would improve the scope’s functionality. This leads to describing, building, and testing the next module until all the features of a commercial oscilloscope have been demonstrated. Because the results are visual, there is an immediate gratification to applying the theory just taught. In Development: Part 3: Microcomputer Controlled Graphics With the addition of a new circuit module containing a Microchip PIC microcomputer, the 240 LED array is reused as a graphics display. The electronic hardware in this section has been minimized because the main focus is to demonstrate how a microcomputer can be used to replace hardware with software. Using only software, the display can be reconfigured to become a digital clock/calendar, a scrolling message display, a chart recorder, or video game like Pong. The results of each programming experiment are visual, so motivation is kept high. With the new understanding of how the system works, new applications can be created. What is in the kits? The kits contain all the parts and instruction needed to build and understand six circuit boards, including test leads- Part-1:
Part-2:
Though this LED Oscilloscope does not have the resolution of a comercial scope, it does have the same functionality and basic controls. Building it in sections allows for a better understanding of why each function is needed, and how they relate to each other. Tools Required A simple set of tools will be needed to build this kit. You may have some of them already.
Additional useful tools:
These tools will be life time resources if a real interest in electronics is developed, and they can be used for other projects as well. |
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| * Stone Soup is a story of three solders returning from the Napoleonic wars who "trick" the miserly villages into holding a neighborhood feast. They fill a large kettle with water, build a fire under it, and add a large stone. As each inquisitive villager asks what they are doing, they tell them they are making Stone Soup. "It’s very tasty, but would be even better with a little seasoning." As each person offers something new for the pot, the Stone Soup turns into feast for the entire town. There is also a version called "Nail Soup". General Patton used a similar method to acquire resources for offensive operations when he met official disapproval by his superiors. He would start with a scouting mission and escalate it from there. |
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Taking Ideas into Reality | |||||||||
Edison was very insightful in his definition of genius. There are lots of good ideas and inspirations, but all by themselves they have little value. It takes effort and insight, tools, materials, and lots of time to bring them into solid existence. Applied Inspirations, LLC was founded to assist in bringing new ideas into physical reality by providing:
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