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Handy Electronics Youtube Videos
! Fundamentals (and Misc) [physics.unsw.edu.au - Oscillation|http://www.animations.physics.unsw.edu.au/waves-sound/oscillations/index.html] * Oscillation requires "restoring force": ** Pendulum: String tension ** Helmholtz oscillator (blowing over the mouth of a bottle): Air pressure * Spring tension is linear * Using air track to make friction negligible * Equations for a spring-load-spring oscillation: ** F = ma ** k = sum of 2 spring tensions ** F = -kx ** v = dx/dt (v = rate of change of x) ** a = dv/dt (a = rate of change of v) ** a = d{sup}2{/sup}x/dt{sup}2{/sup} (rate of change of rate of change of x) ((TODO: Internalize meaning of d{sup}2{/sup})) ** ...but then it says: F = -kx/m, and I'm going to have to pause, because I don't get that. It does point to [these clues|http://www.animations.physics.unsw.edu.au/jw/DifferentialEquations.htm#SHM], though. * ... [Radio Wave Production?|http://www.youtube.com/watch?v=bCPxbhjDiGw] * Electric current → magnetic field ∴ oscillating current → oscillating magnetic field ** Not "EM wave" (as Maxwell supposed) ** Electric oscillation can only occur in a conductor * Faraday Effect: Rotation of the plane of polarization of light by application of a magnetic field * Electric fields are created when: ** A charged particle (negative or positive) creates an electric field around that particle ** An oscillating magnetic field creates an oscillating electric field within a conductor. * Magnetic fields are created when: ** A charged particle (positive/negative) has magnetic properties and acts as a small magnet. ** Charged particles are aligned in a material, a magnetic field will be created around that material. * Flowing electrons cause the electrons to align (but there is no direct connection between current and creation of a magnetic field) * An electron's electric field is at right angles to its magnetic field---so the magnetic wave emanates perpendicular from the current direction [Quaint Radio Basics|http://www.youtube.com/watch?v=kifC0HsYRy4] * Annotations = TODO [Wire Antenna Currents|http://www.youtube.com/watch?v=7Sgtq-ncZAE] * Remember 2-wire transmission line ** Wave goes forward and bounces back (standing wave) * Linear Dipole [@1m45s|http://www.youtube.com/watch?v=7Sgtq-ncZAE#t=1m45s] ** "Dipole" because of two, equal and opposite, current excitations on each side ** Still is an open circuit (like a transmission line) ** E.g., length{sub}total{/sub} = λ/2 *** 1/4 wavelength away (at the middle) = maximum *** Notice the directions of current are ...concurrent [@2:55|http://www.youtube.com/watch?v=7Sgtq-ncZAE#t=2m55s] ** λ/2 < length{sub}total{/sub} < λ [@3:54|http://www.youtube.com/watch?v=7Sgtq-ncZAE#t=3m54s] *** I{sub}in{/sub} (in center) is less than the peaks ** λ < length{sub}total{/sub} < 3λ/2 [@3:54|http://www.youtube.com/watch?v=7Sgtq-ncZAE#t=3m54s] *** Maximum on both legs, a null, and a reverse-direction current ** Those reversed currents can null out the other peaks * Current distributions for various λs [@5:56|http://www.youtube.com/watch?v=7Sgtq-ncZAE#t=5m56s] * Ideal Sinusoidal Current Distribution Equation [@8:32|http://www.youtube.com/watch?v=7Sgtq-ncZAE#t=8m32s] ** + [Continuation Video|http://www.youtube.com/watch?v=L33iI3LwwlQ] Ground * [Understanding Ground Loops|http://www.youtube.com/watch?v=4YM1iwC6vhg] ** GFI tester ** Don't just live with (60Hz always?) hum ** Start by using single power strip instead of two different plugs ** Actual details and explanation at the [Wikipedia: Ground Loop|http://en.wikipedia.org/wiki/Ground_loop_(electricity)] page. [Testing An Electronic Circuit - Making A Circuit Board|http://www.youtube.com/watch?v=5kwvkkcOlmg] * Static checks before live checks. * Check +V * Check all ground locations * That's all (it's a short video. Notable bonus is the way the text twiddles in at the start. Obskur4tionz Styl3.) [Tube Radio Repair Essential Tools|http://www.youtube.com/watch?v=AjKWInA8Jb8] * Isolation transformer * Multimeter (obviously) * Variac * When starting up for first time, smoke test: slowly go from 50V to 75V to 100V to 117V, pausing 3-4 minutes in between each step No video for this one, just a tip: * You can find AAAA batteries inside 9V batteries [SMD Soldering|http://www.youtube.com/watch?v=3NN7UGWYmBY] * Several techniques, all you need to know.
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Last changed: 2010/11/02 18:31