Electronic systems and control 2012
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Electronic systems and control 2012 Electronic systems and control 2012 Presentation Transcript

  • ELECTRONIC SYSTEMS AND CONTROL
  • CURRENT Current is the continuous movement of free electrons through the conductors of a circuit. Ammeter - Measures the flow of electrons in a circuit, which is known as current - connected in series. Symbol of current (I). The (I) unit of measurement of electric current, the ampere, is named after André-Marie Ampère.
  • VOLTAGE + The ability of a cell to produce current is called voltage. + Voltage is the electrical potential energy. + Is measured in Volts. + Voltmeter  Measures the voltage produced by a power supply – always connected in parallel. + Symbol for Volt (V) or
  • OHM’S LAW & RESISTANCE Resistance - Free electrons move through conductors with some degree of friction. Resistance is measured in Ohm (Ω). Symbol of resistance (R). A Resistor - Slows down the flow of electrons in a circuit.
  • EQUATIONS Resistance = voltage/current R= V/I Voltage = current x resistance V= I x R Current = voltage/resistance I=V/R Resistance in Serie: When resistors are connected in Series, the effect is to add more resistance to the circuit. E.g. The value of resistors in series: RT(Total) = R1+R2+R3[Resistor Values] *A resistor is a series circuit is called a voltage divider. Resistance in Parallel: When resistors are connected in parallel, the effect is to reduce the resistance in the circuit. E.g. The value of resistors in parallel: 1/Rt = 1/R1 + 1/R2 + 1/R3 *Resistors in a parallel circuit is called a current divider.
  • Measured in Volts (V). V = I x R V I = V R R = V I A ΩMeasured in Amps (A). Measured in Ohms(Ω).
  • RESISTOR COLOUR CODESThe First three bands give thevalue of the resistor in ohm(Ω).The fourth band indicates howaccurate the given value is.Resistor value: 2% - RED 5% - GOLD 10% - SILVERE.g.:
  • RESISTIVE COMPONENTS Variable Resistor  Light Dependent Can be used to adjust resistor (LDR) the flow of current in a  It’s a component whose circuit. resistance depends upon the amount of light falling on it – it reacts to light.  When the LDR in the circuit is covered up, the Thermistor bulb gets dimmer and Is a component whose finally goes out. resistance varies with temperature.
  • CONTROL ELECTRICS The switch  Single pole double It’s the simplest throw switch (SPDT). control unit form in an  Double Pole single electrical circuit. The throw switch (DPST). simplest type of switch is the single  Double pole single pole single throw throw switch(DPDT). switch (SPST). It has 2 parts: a pole & a contact.  Push to Make & Push to break switches:
  • MORE COMMON TYPE OF SWITCHES:Toggle switch Push SwitchSlide switch Reed SwitchA Rotary Switch
  • RELAYS The Relay - is a switch turned on and off by an electromagnet. Relay Latch - Fixes a circuit in “On” position. - A latch is like a lock. Relay Buzzer -The relay switches “on” and “off” very rapidly, producing a buzzing sound. -A relay can therefore be used to make a crude buzzer.
  • CONTROL ELECTRONICSTHE DIODE LIGHT EMITTING DIODES (LED) Is a semiconductor device.  A LED is a special form of diode It’s a component which allows that gives out light when current to flow in one direction connected the correct way only. around. A Semiconductor diode consists  LED’s normally need to be of a PN junction and has two connected in series with a terminals: resistor to prevent them drawing [P] - Anode(+) too much current and burning [N] – Cathode(-) out. Current flows from the anode to  LED’s are used mainly as visual the cathode within the diode. indicators that a circuit is working When a forward voltage is applied, the diode conducts. or an appliance is “On”. When a reverse voltage is  An LED converts electrical applied, their is no conduction. energy to light.
  • TRANSISTORS A Transistor is a semiconductor device. Made of three layers of N-Type & P-Type semiconductor material, Geranium and Silicone. The three layers are called - Emitter, Base & Collector. There are three types of transistors: NPN PNP The NPN Transistor has a small current flowing to the base of the transistor enables a large current to flow between the collector and emitter. The PNP Transistor uses a small base current and negative base voltage to control a much larger emitter-collector current. The FET transistor – Field Effect Transistor only needs a small field of current.
  • TIMING CIRCUITSCAPACITORS - A CAPACITOR IS A COMPONENT WHICH CAN STORE AND RELEASE ELECTRICAL ENERGY. - CAPACITANCE IS MEASURED IN FARAD. 1. POLARIZED - CAPACITOR 2. NON – POLARIZED CAPACITOR  Polarized capacitors tend to  Non-polarized capacitors be higher value types. which are low value types.  These have a positive(+)  These can be connected and negative(-) lead which either way round in a must be connected the circuit. correct way round in a  Do not have a (+) or (-) circuit (+ to + and - to -) . lead.  Normally used to smooth a current in a circuit.
  • THREE FACTORS THAT INFLUENCE THE CAPACITYOF A CAPACITOR: 1.) Lowering the surface area of plates. 2.) Increase distance between plates. 3.)The kind of material used for dielectric.
  • REFERENCES: Download.pptx. (n.d.). Retrieved from http://www.tes.co.uk/Download.aspx?storycode=6071059&type=X&id=6269844 explaining how Resistors work.ppt. (n.d.). Retrieved from http://teachersunderground.co.uk/Electronics/explaining%20how%20Resistors% 20work.ppt Garratt,J. (1996). Design and Technology. Cape Town: Cambridge University Press. Ohm’s Law - Resources - TES. (n.d.). Retrieved April 30, 2012, from http://www.tes.co.uk/teaching-resource/Ohm-s-Law- 6071059/addtofavourite/addtofavourite/ Resistor colour code wheel.ppt. (n.d.). Retrieved from http://teachersunderground.co.uk/Electronics/Resistor%20colour%20code%20w heel.ppt