Week02_Physical-Computing by Michell Cardona

physical computing interacting with the physical world

physical computing what is electricity? it is the flow of charge through a conductive material in electronics changing electrical properties are used to convey information sensors convert one form of energy into electrical energy; we then interpret whats going on the process of changing one energy into another is called transduction transducers are devices that change energy from one form into another weâ&#x20AC;&#x2122;re interested in using electrical energy to convert human action into other forms of energy

physical computing what is electricity? what are electrons? how do these move? electrons tend to go from a point of greater electrical energy to a point of lesser electrical energy we must provide electrons with a positive connection (greater energy/power), a negative connection (lesser energy/ground/earth) and a conductor through which these electrons flow (this is conventional current) with these in place the electrons will flow from power to ground and along the way we insert electrical devices that distract the electrons as you may remember, electrical energy follows the path of least resistance a good conductor means the electrons with flow with ease

physical computing what is a circuit? a circuit is a closed loop containing an electrical source such as a battery and a load such as a light bulb we need to know how much energy we need to light up the bulb, if we give it too little, it wonâ&#x20AC;&#x2122;t turn on, or might be dimmer than expected, if we give it too much, we might melt the wire inside the bulb, thus breaking the circuit

physical computing what is voltage? current? resistance? we need to know what voltage is. voltage/potential difference is the difference between two given points. it is measured in volts, V. we also need to know current. it is the amount of electrical energy passing through any point in the circuit. it is measured in amperes, A the transducers/components we use in our circuit resist the electrical flow. sometimes we even use resistors in our circuits to limit the flow of electricity. the amount of resistance is measured in ohms, 立

physical computing what is a short circuit? load? when there is very little resistance, you get a short circuit. avoid this at all cost all the energy that is coming from the power source should get used up by the components resistance. This is often referred to as a load

physical computing the relationship between voltage, resistance, and current:

voltage = current X resistance;

V=IXR

current = voltage / resistance;

I= V/R

resistance = voltage / current;

R= V/I

physical computing OHMâ&#x20AC;&#x2122;S LAW

physical computing forms of electrical power: direct current(DC) supplies constant voltage between power and ground alternating current(AC) supplies alternating current. good for distance typically electronics run on dc so we use AC-to-DC converters and transformers to convert AC to DC

physical computing in series | in parallel when components are in series they share the same electrical path. the current remains the same but the voltage is used up by the components when components are in parallel they are on different electrical paths. in this case the current is split between the paths depending on relative resistance

series

parallel

physical computing sensors

physical computing common components & schematic symbol switches

physical computing common components & schematic symbol resistors

physical computing common components & schematic symbol variable resistor

photocell

thermistor

pot

physical computing common components & schematic symbol non polarized capacitor

polarized capacitor

physical computing common components & schematic symbol diode

led

physical computing common components & schematic symbol transistor

relay

physical computing common components schematic symbols switches

resistors

variable resistor

photocell

non polarized capacitor

polarized capacitor

diode

led

thermistor

pot

transistor

relay

physical computing building circuits connected & unconnected

power

ground

physical computing digital | analog digital inputs have two states: ON/OFF or TRUE/FALSE. if voltage is flowing, the circuit is on. if its not then its off digital outputs are either ON/OFF. often used to control other devices through a transistor or relay analog inputs measures variability. its not about on and off its about how much analog outputs show how “bright”/”dim”/”loud” things are

physical computing what is pwm? pulse width modulation(pwm) is a method by which we control analog devices via digital signals we create digital square waves, a signal switch between on and off. this pattern can represent voltages rates between 5V and 0V by changing the portion of the on signals vs. the off signals duty cycle describes the proportion of on time to the period time