Smart Garment Design

Transcription

1 Smart Garment Design 5. Basic Electronics Sungmin Kim SEOUL NATIONAL UNIVERSITY Definition of Circuit A closed loop of electricity that contains a power source and a load Components Power source Something that provides electricity Load Something that makes use of the electricity in the circuit Conductor Material that permits the flow of electricity Circuit Diagram A clear, concise representation of the components and connections in a circuit Battery Resistor Diode 2

2 Electricity Flow It flows from the positive terminal of the battery to positive terminal of the LED It then flows through LED to the negative terminal of the battery to complete the loop It likes to follow the path of least resistance Non-resistive alternate path is preferred It may create a short circuit 3 Short Circuit Definition A closed loop of electricity that has a power source but no load Happens when electricity is fed from the positive end of the battery directly into the negative end Results Malfunction of circuit Drainage of the battery Severe result can occur including smoke, melted wires, and damaged components Prevention Insulation material that do not conduct electricity is used 4

3 Ohm s Law Voltage (V) The difference in electrical energy between two points Current (A) The quantity or amount of electrical energy passing a particular point Resistance (Ω) The measure of a material s ability to prevent the flow of electricity V I R V I R V R I A quick-and-dirty way to light up an LED 5 Ohm s Law The problem in the circuit on the previous slide The LED is receiving a bit more than the desirable amount of current Excessive current can shorten the LED s life or even burn it out You should create a circuit that respects the needs of its components ( Vs V f ) R I V source voltage which is supplied by the battery V s f forward voltage which is needed for the component R desired resistance of the circuit According to the datasheet of an LED... Forward voltage is 2V Required current is 17mA or 0.017A ( Vs V f ) (3 2) R I

4 Ohm s Law 7 Ohm s Law Resistors are come in set values There may not always be the exact register that meets your needs Preparation of a 58.82Ω resistor Use the next largest value, in this case a 62Ω resistor Combine two resistors in a row, in this case 56+3=59Ω 8

5 Ohm s Law Reading a resistor s resistance Using color chart, calculator web site, or smart phone application Reading method Silver or gold band is on the right and read from left to right» First two bands will indicate the first two digit of the number» The third band indicates the multiplier for that digit» The fourth band indicates the tolerance 9 Series and Parallel Series Components are connected in a row Electricity flows through one, into the next, and then into the next Factors to be considered Power source must supply adequate voltage Voltage drops before it moves on to the next component Example) Forward voltage drop of LED = 1.8~2.2V With a 3V battery... First LED=3V, Second LED=1V, Third=0V Battery should provide at least 6V 10

6 Series and Parallel Parallel Components are connected side by side Each with an independent connection to power and ground Factors to be considered Each LED receives the same amount of voltage Current is divided between LEDs 11 Polarity Certain electronic components have a predetermined polarity It matters which way the component is connected in the context of a circuit Ex) Diode» A component that only allows electricity to pass through it in one direction» LED (Light Emitting Diode) 12

7 Multimeter A special tool to detect electricity A dial to select a particular function Probes that are used to make connections with whatever you are measuring 13 Multimeter Continuity The simplest but most useful function that measures the continuity or conductivity Check the continuity of a questionable connection Check for short circuits by placing the probes in two places that are not supposed to be connected Can be used to check the conductivity of a material Resistance Check the value of a fixed resistor Monitor the changing resistance of a variable resistor Determine the resistance of a material like conductive thread or fabric Voltage Check the state of a battery Determine if components of a circuit are receiving the voltage that they need Current The meter needs to be in series with the circuit 14

8 Multimeter Probe connection Voltage (Parallel) Current (Series) 15 Alligator Clip Circuit Advantage Alligator clips provide a quick way to prototype simple, temporary circuits Disadvantage Alligator clips do have a tendency to slide around a bit 16

9 Wire Circuit Method Wires are used to create connections between components Twisting, bending, or crimping establish a basic physical connection Soldering those points establishes a secure electrical connection Wrap resistor leg around LED leg Trim resistor leg Wrap stripped wire around LED and resistor legs Solder wires Apply heat shrink tubing 17 Wire Circuit 18

10 Breadboard Circuit Advantage Easy to connect and disconnect through-hole components Connections beneath a breadboard 19 Breadboard Circuit Placing Components Male headers Prepare resistor for breadboard 20

11 Protoboard Circuit Advantage Makes connections that are far more secure and robust than a breadboard 21 Conductive Thread Circuit Characteristics Allows the creation of soft and pliable circuits Sew connections rather than solder them Preparation of components for sewing 22

12 Conductive Thread Circuit Sew components using conductive thread Untrimmed tails of thread can lead to short circuits Trimmed thread trails Secure the knots with fabric glue 23 Conductive Fabric Circuit Advantage Intricate circuits can be created, cut, and adhered quickly Check the space between components Cover conductive fabric Iron to adhere the conductive fabric Conductive fabric circuit 24

13 Conclusion Circuit Advantage Disadvantage Alligator Clip Circuit Allows quick integration of nonstandard components like DIY sensors Useful for testing components Bulky and not optimal for complex circuits Unstable and potential for shorts Wire Circuit Extremely flexible and customizable Not practical for complex circuits Robustness depends on choice of wire and amount of strain placed on circuit Breadboard Circuit Protoboard Circuit Conductive Thread Circuit Conductive Fabric Circuit Quick and efficient Easy to modify Secure connections Potentially smaller than a breadboard Flexible, pliable, customizable, and fashionable Faster approach to soft circuits Potential for interesting designs Bulky and not terribly robust Looks weird on a shirt Still a bit bulky Difficult to integrate with textiles Potential for shorts Some conductive threads have significant resistance Time consuming Subject to shorts Still requires sewing 25 Switches Definition Something that enables, prevents, or diverts the flow of electricity Use Creates or breaks the physical connection of two conductors Intentional input Activate a circuit by doing something as pushing a button on a circuit board Passive sensor Activate a circuit by doing something as subtle and intuitive as standing up, blinking eyes, or a hug 26

14 Switches Poles and Throws Pole Refers to the number of separate circuits controlled by the switch Throw Refers to the number of positions each pole can be connected to SPST Rocker Switch SPDT Toggle switch between two LEDs SPDT Toggle switch used as a SPST 27 Switches Types of Switches Maintained switches Stay in whatever state you put them in» Light switch in a room Momentary switches Normally open» Refers to a momentary switch whose default state is for the contacts to be open» If it is activated by the user, the switch will close Normally closed» Refers to a momentary switch whose default state is for the contacts to be closed» When the switch is activated, the switch will open, deactivating the attached circuit 28

15 Off-the-Shelf Switches Switches Tactile buttons Momentary buttons that provide light tactile feedback Latching buttons Maintained switches that respond to being pressed - Press it once and the button will stay closed - Press it again and the button will stay open Toggle switches Maintained switch that is operated by a lever Slide switches Maintained switch that is controlled by moving the switch back and forth Microswitches Highly sensitive momentary switch that can be operated by a small movement Tilt switches Open or close based on the orientation of the switch - Single or multiaxial 29 Textile Switches Sandwich Switch Switches 30

16 Textile Switches Contact Switch Switches 31 Textile Switches Bridge Switch Switches Pinch Switch 32

17 Textile Switches Social Switches Switches When properly planned, a switch can create the opportunity for a social interaction 'Power Me Up' Circuit 'You Complete Me' Circuit 'We're All In This Together' Circuit 33 Hard-Soft Connection Connections Multi-conductor band Snap Button Breakout Board 34

18 Hard-Soft Connection Connections Zigzag stitch Magnet clasp/conductive thread Perforated board/conductive Thread 35 Traces Connections Screen-Printed Copper Paint Laser-Cut Mask Stretch Cable 36