Misc.(Edit)

Radio Wave Production?

• 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

Testing An Electronic Circuit - Making A Circuit Board

• 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.)

WA2KWL (Jonathan Gordon), who is the man:(Edit)

User Page

Digital RFI

• AM Radio detects RFI
• Square wave is fundamental + odd harmonics (the faster the rise/falls, the more the harmonics)
• 166 MHz (6'), 1 GHz (1'), will find 1/4-wave, 1/2-wave and full-wave wires/traces to use as antennas
• Spread-spectrum clocking (enabled in BIOS) reduces RFI output.
• TRIAC dimmers/speed controllers clip AC sine wave to change duty cycle. The chops create sharp edges (aka, harmonics) == Divide by triangle wave?

Tips for troubleshooting a complicated analog circuit on a solderless breadboard

• Run wires as short and parallel to each other as possible.
• Color-code wires
• Keep component leads far enough apart that they don't short
• Try to avoid going over the top of ICs
• Be aware of adjacent rows' stray capacitance
• Diagnose in stages (!) Either one at a time in sequence, or BinaryChop Debugging

D-type Flip-Flop (computer PSU)

• Shows how the momentary-on switch resets a flip-flop to start a PSU
• Also mentions the Data and Clk inputs on the flip-flop that could work as a power-off timer.

Test for Electrical Circuit Continuity

• Doesn't like mini phono plugs (because they can short during insertion), does like barrel plugs (which don't)
• Set MM to continuity, place one lead on plug and the other on the opposite wire termination, then hold them and move the wires around at different angles to test for intermittent connection
• To find ground, connect one lead on the shielding of a serial port terminal, then probe using other lead. Anywhere on the circuit you get a beep is a ground connection.
• Also, continuity testing fuses (out of or in-circuit)

AC Adapters

• AC-to-AC Unregulated: Just a transformer; measures higher without load than with.
• AC-to-DC Unregulated: Transformer, bridge rectifier; measures higher without load than with.
• AC-to-DC Regulated: Transformer, rectifier, filter caps, voltage regulator.
• AC-to-DC Switcher: Bridge rectifier, HV filter cap., stepdown transformer, pulse width modulator, switching transistor, rectifier diode; Probably lighter than the transformer version.

LED Semiconductor Physics Made Easy

• Valence shell <-> Band Gap <-> Conduction band
• Energy required to move from valence to conduction band defines insulation/conduction. Home run hit vs. Cannon vs. Thump.
• Silicon doping:
• Silicon has 4 valence electrons, creates strongly bound electrons
• Boron, aluminum, gallium = 3 valence electrons; dope with these and you have one electron "missing", hence P-type
• Nitrogen, Phosphorous, Arsenic = 5 valence electrons; opposite: N-type
• Electrons going from N-type to P-type gives off energy: different wavelengths for different band gaps
• Doping with other substrates gives different band gaps, e.g., Gallium Arsenic, Aluminum Gallium Arsenide (=Red: 620-780nm), Aluminum Gallium Phosphorous (=Green: 490-570nm)
• Wikipedia elaborates ( http://en.wikipedia.org/wiki/Band_gap )
• Gap is measured in Volts.
• The reverse: "the band gap determines what portion of the solar spectrum a photovoltaic cell absorbs."

Ethernet 10Base-T Manchester Encoded Signaling

• TX+ (non-inverting) TX- (inverting)
• Non-return to Zero Encoding
• TX+ rising = "1" bit, TX+ falling = "0" bit
• 100ns period (10MHz) possible, but this only happens on consecutive bits (1 to 1, 0 to 0). Whenever there is a change (1 to 0, 0 to 1) the signal is 5MHz wide (!).
• Spectral Analysis verifies that most of the signal is near the 5MHz range---which reduces bandwidth.

AC Copper Wiring vs MotherBoard Copper Trace

• House wiring has no transmission line properties---just connects switch to load
• U.S. AC = 60Hz cycle, 16.67ms (0.0167s) period, 5 Mm length (New York to California)
• Because the wavelength is so much greater than the wire length, the wire is not a transmission line (only presents a small amount of resistance)

• When you get to the 7th+ harmonics, PCB traces are going to act like antennas, like a series of inductors and capacitors
• Xc (capacitive reactance) = 1/(2 pi Freq C)
• XL (inductive reactance) = 2 pi Freq L
• As frequency increases, Xc decreases (thus more voltage is shunted to ground), and at the same time XL increases (attenuating the voltage more).
• Causes timing problems, motherboard = unstable.
• Also, on traces, electricity's speed of propagation slows down to 50% of C.

Computer PSU

• ATX 20+4 (the 4 break away for use on 20-pin)
• One of the pins has 2 orange wires: one is the supply and the other is a sensing wire to make sure it's exactly 3.3V
• Multiples of same voltage because connectors have a significant voltage drop
• Causes of burnt-out PSUs:
• Long duration voltage surges (solution: Line-interactive UPS)
• Motherboard capacitor fails
• Lightning (solution: Surge protector)
• Faulty ATX Connector Pins
• Excessive moisture
• Excessive current draw
• Leads to heating
• Caused by too many peripherals
• Best way to test is to feel for excess heat with your finger
• One solution is to use different connectors (e.g., use both PCI Express connectors rather than the "Y" one)
• As processor speeds increased, circuits went from 5V to 3.3V and then further: the motherboard gained its own switched-mode power supply fed by the 4-pin connector.
• 4-pin Molex HDD connector
• Yellow = 12V (powers motor)
• Red = 5V (electronics)
• Testing
• Ground Green (power on) to Gnd to turn PSU on
• Have to cut to test Amps (= in series)

Repair:(Edit)

• LCD TV repair made simple
• Watertown TV Repair

Ellsworth:(Edit)

• Debugging Bus Contention - Electronics Repair Techniques

Just interesting (as in, not necessarily useful):(Edit)

• Commodore 64 Laptop Demo
• Best of the SpaceLab

Totally Irrelevant:(Edit)

• Search by Image
• Villager TSBs