ELECTRONIC REMINDERS ==================== # Ohm's Law * V = I x R * R = V / I * I = V / R >Voltage = Current(I) x Resistance (Ω=Ohm) >Units: Volts = Amps x Ohms ## Power's Law * P = V * I >Units: Watts = Volts x Amps * P = I² * R * P = V² / R * R = P / I² * I = √P / R * I = P / V ## Samples * Computing the resistance: 9V Battery + LED 3.4V using 20mA ==> (9V-3.4) / 20mA ==> 5.6 / (20/1000) => 5.6 / 0.02 => 280 Ω Power: 9V * 0.02 = 0.18 Watts 9V Battery + LED 3V using 20mA ==> (9V-3) / 20mA ==> 5 / (20/1000) => 5 / 0.02 => 250 Ω 18V Battery + LED 3.4V using 20mA ==> (18-3.4)/(20/1000) => 730 Ω Power: 18V * 0.02 = 0.36 Watts ## Serie vs Parallel - In Serie, Voltage drop (consumption increase), but current is constant across the circuit. - In Parallel, Voltage is constant, but current consumption increase. ## Resistance in serie ------------- | | 5V Battery ~ R1 100 Ω | | | | | ~ R2 200 Ω | | ------------- R = R1 + R2 I = 5V / (100+200)Ω => 5 / 300 => 17mA Current is constant across the circuit Voltage Drop R1: V1 = 17mA * 100 = 1.7V R2: V2 = 17mA * 200 = 3.4V 1.7V + 3.4V ~= 5V ## Resistance in parallel ------------- | | 5V Battery I1 /\ I2 | R1 R2 R1 100Ω, R2 200Ω | \/ | | ------------- R = 1 / ( (1/R1) + (1/R2) ) => 1/((1/100)+(1/200)) => 66.7 Ω I = 5V / (66.7)Ω => 75mA Current is constant across the circuit Current across resistor I1 = 5V / 100Ω = 50mA I2 = 5V / 200Ω = 25mA 50mA + 25mA = 75mA 2 100Ω Resistors in parallel => 100Ω/2 = 50Ω ## RC Circuit - Resistor Capacitor * Capacitor resist change in voltage * R x C (Capacitance) = Time (-t/RC) * Vout = Vin x (1 - e ) * e = 2.7182 * t = time * if t==0 then Vout == 0 * What is t when Vout is half Vin? * t = 0.693 x RC * At 1 x RC the capacitor is charged at 63.2% * At 2 x RC the capacitor is charged at 86.59% * At 3 x RC the capacitor is charged at 95.9% ### Sample 9V Battery + 1kΩ + 470uF + LED (3V, 20mA) RC = 1000Ω * 470uF == 1000Ω * (470/1000/100) = 4.7 Seconds RC = 1000Ω * 47uF == 1000Ω * ( 47/1000/100) = 0.44.67 Seconds * http://en.wikipedia.org/wiki/RC_circuit ## Capacitor in parallel ## Capactor in serie ## Diode ## Examples * 1V = 1A x 1Ohm ## References * [wikipedia - Ohm's_law](http://en.wikipedia.org/wiki/Ohm's_law) * [Voltage current resistance and ohms law](https://learn.sparkfun.com/tutorials/voltage-current-resistance-and-ohms-law#voltage) * http://vapor.rigsmedia.com/wp-content/uploads/2012/09/ohms_lawVIPR_relationship.jpg # Others ## Characters * √ ¼ ½ ¾ 2º 2¹ 2² 2³ Ω # Markdown * http://daringfireball.net/projects/markdown/syntax Arduino Tutorial https://www.youtube.com/watch?v=js4TK0U848I&list=PLA567CE235D39FA84 # Voltage Divider ------------- | | 5V Battery ~ R1 Omh | | | ----> Voltage out | | | ~ R2 Omh | | ------------- Vout = (R2 / (R1+R2)) * Vin R1 100Omh R2 100Omh => 100/(100+100) * 5v = 2.5v Light 5v | 10k Resistor | ----- Vout | * Ligth Censor (Resistor based on light) Voltage Regulator: 9V -- VR -- 5v | | | | | | *Cap1mF-Gnd--*Cap22mF Decoupling Capacitor needed PWM: _ _ _ Pulse With Modulate Signal : _| |_| |_| |_ Transistor: NPN: --------- | | | C B E (Collector, Base, Emettor) Current flow from C to E based on the state of B is high PNP: Opposite when B is low current flow Pull Up/Down Tutorial http://www.ladyada.net/learn/arduino/lesson5.html

## Saturday, April 11, 2015

### ELECTRONIC REMINDERS

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