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GCSE Electronic Products Revision Flashcards 555 timer •8 pin Integrated Circuit (I.C.) •Analog •can be used as an astable or monostable •Low cost Monostable (the egg timer) •Has a single (mono) stable state • when it is timing •The output is normally off Pin 2 = Trigger • The trigger sets the timer going • Timer starts when trigger is < 2V • Connects to a 10K pull-up resistor Pull-up resistor • Pulls the voltage up on a wire to supply voltage • Makes a “nice” logic high Pull Down Resistor • Pulls the voltage on a wire down to 0V • Gives a “nice” logic 0 Pin 6 = Threshold • Detects when the bucket (capacitor) is 2/3rds full • The capacitor fills up through a resistor • Time to fill to 2/3rds full = Resistor Value x Capacitor Value (T = RC) Pin 7 = discharge • Empties the bucket (capacitor) Astable (The “flasher” circuit) • Has no stable states • Keeps on flashing forever • Number of flashes per second = frequency • Automatically triggers The Op-Amp • - input = inverting • + input = non-inverting • used as an inverting amplifier or a comparator • An analog device • A 741 I.C. is an example of an op-amp Inverting • Means it turns the signal upside down Gain • The ability of a device to make a signal bigger • Op-amps have huge “open loop” gain • Transistors also have gain Feedback • Gain can be reduced by using feedback • Some of the output is taken away and added to the input • We use resistors to do this + Comparator (Which input is bigger) - • If “+” is bigger than “” we get a logic 1 • If “+” is smaller than “-” then we get a logic 0 • A simple analog to digital converter Ohms Law • As resistance increases, current decreases • As resistance increases, voltage increases Sources of power P.I.C. (Peripheral Interface Controller) • Digital • A mini-computer in a single Integrated Circuit • Programmable using flowcharts • Can be programmed many times • Remembers program even when the power is off Diode (A one way valve) • Current flows from anode to cathode • Prevents current flowing the wrong way • Protects circuits if the power supply is connected up wrong Transducer (A device for converting energy from one form to another • Motor – converts electrical energy to kinetic energy • LED – converts electrical energy to light • Microphone - converts sound energy to electrical energy Transducer Drivers (Things that provide power to output transducers) • Bipolar Transistors • FET’s • Darlington Pairs Tolerance • The amount of “spread” in a components value • 100Ω and 10% tolerance gives a spread between 90Ω and 110Ω E12 Series • The values that 10% tolerance resistors are made in to avoid value overlap • 10, 12, 15, 18, 22 etc • 100, 120, 150, 180 etc Polymorph – Smart Material • Used to rapidly model complex shapes + • Granules put in hot water turn solid and can be immediately shaped clock • A digital signal that has a regular repeating on/off pattern • Often generated by an astable • Used by PICs & counters HIPS • Plastic material used for vacuum forming • Available in different colours • Used to make complex 3d shapes • Boxes must have angled sides to get the mold out Breadboard • Used to model circuit using real component • No soldering • Easy to change connections • Components can be reused CAD (Computer Aided Design) • Testing by simulation • Links to CAM (Computer Aided Manufacture) • Easy to share designs with others and keep track of changes • Making changes is a quick & easy process Latch Circuit • Can be made using a thyristor • Can be made with NOR or NAND gates • When activated, stays activated until reset – Remembers that it has been activated Thyristor • Used in latch circuits • A pulse on the gate causes current to flow from Anode to Cathode until reset • Reset by making the Anode voltage the same as the Cathode Potential Divider • A circuit for dividing voltages • Voltage splits based upon the ratio of two resistors Schmitt Trigger • A type of circuit used to remove switch bounce Thermistor • Device for measuring temperature • As temperature increases, resistance decreases • Often used as part of a potential divider LDR (Light Dependent Resistor) • As light increases, resistance decreases • Often used as part of a potential divider Multimeter • Device for measuring: – Current – Voltage – Resistance • Has red & black probes The 3 R’s (Helping The Environment) • Reduce cut the materials you use • Reuse make use of existing products • Recycle stop the product going to landfill when obsolete Resistors • Measured in Ohms (Ω) • Used to reduce current • Colour bands indicate the value Integrated Circuits • Pin 1 is to the left of the notch • Lots of components on a single piece of silicon • Examples are: – PICS – 555’s – 741’s Switch Bounce • A problem with mechanical PTM & PTB switches • One press of the switch generates more than one pulse AND Gate • Both inputs must be at logic 1 to get a logic 1 out • A = 1 AND B= 1 OR GATE • Either one of the two inputs can be at logic 1 to create a 1 on the output • A=1 OR B=1 Relay • A device that allows one circuit to turn on another circuit that works at a different voltage • Uses electro-magnets Variable Resistor • Used for – volume controls – Changing astable frequencies – Changing mono-stable time periods 4017 • Output 0 is on • When a clock pulse is received: – Output0 turns off – Output1 turns on • On next clock pulse – Output1 turns off – Output2 turns on SPDT SWITCH (Single Pole Double Throw) • • • • One circuit Two positions Three pins Two different sets of components can be switched into one circuit Life Cycle Analysis • What happens to a product when it is disposed of: – Reused in a new product – Recycled – Goes to landfill Multipliers 1,000,000,000 1,000,000 1,000 = 1G = 1 x 109 = 1M = 1 x 106 = 1K = 1 x 103 1 = 1 = 1 x 101 0.001 = 1m = 1 x 10-3 0.000,001 = 1µ = 1 x 10-6 0.000,000,001 = 1n = 1 x 10-9 0.000,000,000,001 = 1p = 1 x 10-12 Units of Measure Measurement Unit Symbol Resistance Ohms Ω Capacitance Farads F Voltage Volts V Current Amps I Power Watts W Time Seconds S