Flashcards
Engineering- Electronic systems 9
Flashcards do conjunto (36)
- 1What is an IC?• An IC is an integrated circuit
• An IC is a complete circuit minituarised so that it fits on a microchip. - 2What does a monostable circuit do?• A monostable circuit is a timer circuit.
• A timer circuit is used to turn an output on (or off) for a certain amount of time.
• This usually happens in response to an input signal change of some kind. - 3Draw a 555 IC monostable circuit so that an LED turns on when it is activated.
- 4What is the purpose of a counter circuit?• A counter circuit is used to count the number of times an event happens.
• The count may be triggered by a switch being pressed, or by something being sensed. - 5Describe what a decade counter is, and draw an example circuit based on the 4017B IC.• A decade counter can count up to 10 events happening.
- 6Describe what happens with the 4017B IC decade counter circuit above• SW1 is connected to the clock input of the 4017B counter
• Output Q0 is initially on, meaning LED D1 is also on.
• When SW1 is pressed, the clock input goes high, causing output Q1 to go on, and output Q0 to go off, meaning LED D2 goes on and D1 goes off.
• Every time SW1 is subsequently pressed causes the next LED to light up in sequence and the previous LED to go off.
• Switch SW2 is connected to the reset R. When this is pressed it causes the counter to reset to its initial condition (Q0 high, and therefore D1 on) - 7What is an op-amp?• Op-amp is short for operational amplifier
• It is a type of IC
• It has 2 inputs (marked + and -) and one output. - 8How can an analogue signal be converted into a digital signal?• To convert an analogue signal into a digital signal we can use an op-amp to build a comparator circuit.
• A comparator circuit compares two separate voltage levels which are connected to either of the inputs.
• When the voltage connected to the + input is greater than the – input, then the output turns on, and vice versa.
• This type of circuit is very good when you want something to turn on when a precise condition has been met, for example a warning light in a fridge when the temperature gets above 5 0C. - 9Draw a comparator circuit which turns an LED on when the temperature is too warm.
- 10What type of electronic signal activates a logic gate?• A digital signal (either high, 1, or low, 0)
• The three main types of logic gate that we need to be aware of are:
o NOT gates
o AND gates
o OR gates - 11When is a NOT gate useful?• NOT gates can be used to turn an output device off when a switch is turned on, for example an emergency stop button on a machine.
- 12When is an OR gate useful?• An example of an OR gate is a simple home alarm system. The alarm should sound when either the door or the window sensor detects a break in.
- 13What does PIC stand for?• Peripheral interface controller
- 14What is a PIC?• It is a type of microcontroller
- 15What is a microcontroller?• A microcontroller is a small programmable computer on an IC, used for control applications.
• It has different pins, called ports, for the connection of input and output devices - 16What are the advantages of using a microcontroller?• They are flexible – they can be programmed to perform a variety of different functions.
• They are adaptable – they can be reprogrammed thousands of time.
• They can replace a number of discreet components, thus saving space on a PCB, thus saving costs on materials used.
• A variety of inputs and outputs can be used on each PIC, thus allowing for highly complex systems. - 17What are the disadvantages of using a microcontroller?• Microcontrollers can be expensive, so for circuits which require only simple functions it is cost effective to use discrete components.
• Access to programming software and hardware is required:
o Programming software may be expensive
o Programming hardware may be expensive
o Programmers may have to be trained, which is expensive - 18How are PICs programmed?• PICs can be programmed using:
o block-based editors,
o flowchart software, e.g. genie flowchart
o or text-based programming languages, e.g. BASIC or C. - 19How can a PIC use an analogue signal?• For analogue signals, it is important that the analogue input sensor is connected to an analogue input port.
- 20What is an ADC?• An ADC is an analogue to digital converter
• Each analogue input port on a PIC has a built in ADC. - 21How does an ADC work in a PIC?• The input port reads the voltage value from the analogue sensor
• The ADC then converts this voltage value into a number from 0 to 255 - 22Do PICs provide a large current from their outputs?• The output current from a PIC is very small.
• The only output devices that can be connected directly from the output of a PIC is an LED or an LCD (liquid crystal display)
• This means that the signal from a PIC will need to be boosted in order to operate other outputs - 23How can the signal from a PIC be boosted?• The output signal from the PIC can be boosted by an interface device.
• Interface devices are also known as drivers.
• There are two main interface devices, or drivers:
o Transistor
o FET - 24Identify a transistor and explain what it does.• A transistor amplifies current
• They can boost the current from a PIC for outputs that require a small to medium current, for example a lamp, a buzzer, or a cluster of LEDs.
• It has three legs, called the base, collector and emitter.
• When the voltage at the base reaches 0.6V a current is allowed to pass from the collector to the emitter. - 25Identify a FET and explain what it does.• Field effect transistors (FETs) are voltage amplifiers.
• They can boost the signal from a PIC for outputs that require a larger current, for example a motor, or a relay.
• It has three legs, called the drain, gate and source. - 26Define the function of an output componentOutput components turn an electronic signal, such as voltage or current, into a real worls signal, such as light, sound, and movement
- 27What is a seven-segment display?• This is a package of LEDs arranged so that the numbers 0 – 9 can be displayed.
• Different combinations of LEDs light up to show the appropriate number - 28Describe when an eighth LED is sometimes used.• An eighth LED can be used as a decimal point
- 29Describe the difference between a common cathode type and a common anode type• A common cathode type has all the cathodes of each LED connected together
• This means that each LED segment will light up when the input to its anode is high
• A common anode LED has all the anodes connected together
• This means that each LED segment will light up when the signal sent to its cathode is low. - 30What is a piezo sounder?• These convert an electrical signal into sound using the piezo effect.
• They can produce a range of sounds, as opposed to a buzzer which can only produce a single tone.
• They are therefore ideal for playing musical tunes, such is in a novelty card or a child’s toy - 31Define what is meant by a passive component, and give examples• Passive components do not require a source of energy to perform their stated function
• Examples include resistors, capacitors, and diodes - 32What is the function of a resistor?• Resistors reduce the flow of current in a circuit
• The unit of resistance is the ohm, - 33What are the 2 main types of resistor?• Fixed resistor
• Variable resistor - 34Compare a fixed resistor to a variable resistor.• Fixed resistors have a set value within a tolerance
• Only certain values of fixed resistor are available, so it is sometimes necessary to combine resistors to achieve the required value of resistance.
• Colour coding is used to label the value of the resistor
• Variable resistors can be adjusted using either a spindle or a small screwdriver slot.
• LDRs and thermistors are also examples of variable resistors - 35What is the function of a diode?• Diodes allow current to flow through in one direction only
• It has 2 legs: anode (positive) and cathode (negative)
• They are used to prevent damage to a circuit from reverse polarity (accidentally connecting the power the wrong way around, e.g. if the batteries were incorrectly inserted)
• They are also used in rectifying circuits (converting a.c. to d.c.) - 36What is the function of a capacitor?• Capacitors store electrical charge
• The unit of measurement of capacitance is the farad, F.
• Capacitors can be polarized or non-polarised
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- Flashcards on Engineering- Electronic systems, created by AsimAli Rehman on 02/11/2019.
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- AsimAli Rehman
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