2What are the specific safety practices and procedures that you need to observe when assembling and testing electronic circuits? (To include: any specific legislation, regulations or codes of practice for the activities, equipment or materials.)Is the test equipment in good condition?Are the test leads for the equipment in a safe condition, no nicks or breaks in the insulation?Have you tested the test equipment on a known working electrical supply before connecting it to your circuit?Has the test equipment been recently calibrated?Have you been trained to carry out this task? Do you have the skills?Are you wearing the correct PPE to complete this task?Are you practising safe soldering techniques, perhaps you could describe a safe and effective soldering procedure?Are the tools you are using to form and trim the component leads maintained in a safe condition?If you are making a PCB, are you following the correct procedures?
3What are the hazards associated with assembling and testing electronic circuits and how can they be minimised?(Such as: heat, toxic fumes, spilled / splashed chemicals / solder, static electricity, using sharp instruments for stripping cable insulation, connecting clips / probes into circuits.)What are the hazards associated with assembling and testing electronic circuits and how can they be minimised?(Such as: heat, toxic fumes, spilled / splashed chemicals / solder, static electricity, using sharp instruments for stripping cable insulation, connecting clips / probes into circuits.)What are the hazards associated with assembling and testing electronic circuits and how can they be minimised? (Such as: heat, toxic fumes, spilled / splashed chemicals / solder, static electricity, using sharp instruments for stripping cable insulation, connecting clips / probes into circuits.)Are you using ventilation next to your circuit?Are you wearing eye protection when making PCB boards and trimming component leads?Have you selected the correct components and checked them against a data sheet?How can you minimize the risk of static damage to a circuit containing integrated components?Is the PPE you are wearing suitable for the job?Have the tools you are using been maintained in a safe condition?Are you using a heat shunt when soldering delicate components such as transistors?Have you tested a circuit with the correct test equipment to ensure it electrically dead prior to handling it?Perhaps you could describe the correct procedure for setting up a multimeter to test for current, voltage and resistance (each one is different)Are testing the circuit with the correct voltage and power supply?Have you tested for short circuits and open circuits (perhaps you could describe the difference between them)
4Why is it important to wear appropriate protective clothing and equipment? Why is it important to keep the work area safe and tidy?To protect your clothes?To protect your skin and eyes, for example repeated exposure to some chemicals can cause dermatitis and cancerTo protect your lungs and respiratory system from dangerous fumes and gasesAre you using a barrier cream to minimize skin contact with the chemicals used to make the PCB’sIf you have an accident whilst making PCB’s and were not using the correct PPE, do you think you will have grounds for compensation?If someone else has an accident because of your negligence, do you think they will have grounds to seek compensation from you?Does a messy and untidy workplace assist you in making circuits?Is a messy and untidy workplace likely to contribute to accidents?Whose responsibility is it to ensure the workplace is in a safe and tidy condition?If you spot an unsafe practice, what would you do?Is it your responsibility to report hazards to an appropriate person?
5What precautions do you need to take to prevent electrostatic discharge (ESD) damage to circuits and sensitive components? (Such as: use of earthed wrist straps, anti-static mats, special packaging and handling areas.)Use wrist straps that can be earthedWear anti static boots and clothing that is less likely to cause a build up of static chargeStand on anti static mats when assembling circuits
6How do you use and extract information in relation to work undertaken How do you use and extract information in relation to work undertaken? (To include: circuit diagrams, block and schematic diagrams, equipment manuals, data sheets, test procedures and instructions [to include: symbols and conventions to appropriate BS or ISO standards].)Read circuits diagrams and list all of the components requiredCheck component values using charts, British standards and data sheetsCheck component tolerances once again using charts and data sheetsCheck component symbols against BS EN60617Recognize that not every drawing you encounter will use BS circuit symbols, for example some circuits use ANSI symbols (American National Standards Institute)Use the circuit diagram to plan a layout for your circuit taking into account the size and proximity of various componentsCheck your circuit design against the layout for every stage of the design process
7How do you recognise, read the values and identify polarity and any other orientation requirements for all electronic components being used in the assemblies? (Such as: capacitors, resistors, inductors, diodes, transistors, integrated circuit chips, and other discrete through-hole or surface-mounted components.)Check resistor values using the resistor colour codeCheck resistor tolerance values using the colour code and double check with a multimeterUse pin out diagrams to identify the function of pins on integrated circuits e.g. Power , ground, input and outputUse data sheets to identify the polarity of the terminals on diodesDescribe the difference between through hole and surfact mount components (such as size, reading component values and the absence of component leads on surface mount components)Check capacitor values using a chart, internet resources or data sheetsCheck polarity dependant components are connected the right way around (longer leg is connected to positive)Describe how the polarity of electrolytic capacitors and LED’s can be established
8How do you check that components meet the required specification / operating conditions? (Such as: values tolerance, current carrying capacity, voltage rating, power rating, working temperature range.)Check information from the circuit diagram which should contain the required informationCheck data sheets to find the current carrying capacity of componentsCheck data sheets for working temperature rangeOften working voltages are stamped on components such as capacitorsPower rating: How do you check the power rating of a resistor?What is the power rating the general purpose resistors used in the laboratory? (.25 Watt)
9What are the basic principles of operation of the electronic circuits being assembled? The amplifier takes a small input signal from a source such as an ipod or mp3 player and reproduces the signal at its output. The signal at the output is much larger than the input (thats what amplify means) which allows it to drive a loudspeaker.The fuse tester can also be used to test the continuity of a circuit. It uses a NOR gate to detect whether the fuse is good. If the fuse is good the NOR gate gives an output voltage of 5 volts. This voltage is used to switch on a transistor which drives a 555 timer and an LED. The 555 timer gives out a high pitched tone if the fuse is working and the LED lights up.The H bridge stepper motor control circuit uses 8 transistors to control the current through both phases of the stepper motor. The current must be fed to the stepper motor in the correct sequence in order for it to run forwards and backwards. A microcontroller is programmed to switch the transistors on and off. The entire circuit is powered through a bridge rectifier and voltage regulator which gives power to the microcontroller. The stepper motor power is taken from a point directly before the regulator as +12 volts smoothed DC.
10What is the purpose of the individual modules/components within the circuits? Each component will fulfil a given purpose within the circuitThe circuit function will rely on each component being correctly chosen and connected to the circuitOften circuits can be broken down into a series of function blocks or modulesFor example the amplifier circuit has:A mixing stageA preampifierVolume controlA power amplifierAn output stageThe continuity tester circuit has:A voltage regulator to fix the working voltage at 5 voltsA logic circuit to test the continuity of a circuitA signal generator stage to give an audible signal when continuity is present
11How and why is circuit protection equipment used? Circuit protection equipment is there to protect the user, the circuit and the environmentCircuit faults can lead to overheating which left untended can cause firesThe two most common circuit faults which present danger to people are short circuits and earth faultsShort circuits:Bypass components in the circuit either by bad design, poor soldering, faulty components or moistureThis means more current is drawn from the power supplyMore current = more power = more heatUnder certain circumstances the circuit can draw so much current that the insulation begins to break downFuses and Residual Current Devices (RCD) prevent this happening by cutting the power supply to the circuitEarth Faults:When a live conductor comes into contact with the metal housing of an appliance you have an earth faultThis means the housing will be electrically live, if you touch it then current will flow through you to groundEarth Current Leakage Breakers (ECLB’s) and RCD’s can be used to protect people from earth faults
12What are the methods of mounting and securing electronic components to various surfaces? Use of heat sinks and heat shunts to prevent damage to sensitive componentsYou can find some information on surfact mount techniques hereYou are already familiar with manual soldering methods, keep soldering tip clean and tinned etcMechanical fixing methods include the use of chocolate block and wire wrapping
13What are the methods for attaching markers/labels to components to assist with identification? You can use masking tapeColoured electrical tapeColour coded tagsColoured cable tiesMarking and identification techniques are essential when maintaining and upgrading circuits, for more information you can visit here
14Why should you use BS7671/IEEE wiring and othe regulations, when selecting wires and cables and when carrying out tests on electronic circuits?It is difficult to get hold of the 17th edition book without buying it. However the most important reasons for using the standards and regulations above can be listed as:It is a legal obligation to ensure you are complying with the given standardsComplying with the standards means you are testing your circuits in the safest way possibleThe standards are there to ensure that circuits are built and tested using suitable components and cablesThe standards give information of cables and conductors so that you are able to select ones which are safe to use with the current you circuit will be conductingSo that you don’t over engineer your circuits designs and builds, choosing the correct cable for the job in not only safe, it is also cost effective.
15How do you care for, handle and use electronic test and measuring equipment? How do you check that test equipment is safe to use? How do you check that test equipment is suitable for the tests you are to carry out and can cover the range and values you are to measure?Check the equipment is physically sound with no signs of mechanical or electrical damage before useCheck the equipment has been tested and calibrated, normal practice is to test the equipment each gear, there should be a sticker on the equipment detailing the date and outcome of the last testAlways make sure that the equipment is suitable for the job, don’t use equipment that doesn’t have the range to measure your circuit. For example there is no point trying to measure an input voltage of 20 volts if your meters range only goes up to 10 volts.Make sure you are trained to carry out the testsAlways replace test equipment carefully after use, make sure it is switch off and leads are disconnectedAlways test equipment on a known supply before carrying out a live test (known as a functional test)If in doubt ask a qualified personYou can also check the manual/datasheet for the equipment in question
16How do you connect equipment to an approved power supply and where appropriate signal source? Always make sure the power supply is switched off before connecting to a circuitAlways make sure the signal source is switched off before connecting to a circuitIf the power supply is a variable type, make sure it is set up to the correct voltage and current before connectingCheck the signal is the correct frequency and amplitude before connectingAlways connect the ground clip or wire firstAlways disconnect the ground clip or wire last
17How do you make adjustments to circuit components? Only certain components can be adjusted such as variable resistors, potentiometers, variable capacitors and inductorsAdjustments can be made under live conditions, you should be using an anti static wrist strap and an insulated screwdriver
18How do you make adjustments to circuit components? Once you have decided a component is faulty:Disconnect power from the circuitUse test equipment to ensure that the circuit is electrically dead (all capacitors discharged etc)Identify the component type and value using either the schematic or visual inspectionCarefully desolder and remove the componentReplace and resolder
19What are the fault finding techniques to be used when equipment fails to operate correctly? Carefully check the type and value of each component against the values given on the schematicCheck all polarity dependant components are connected the correct way aroundCheck the power supply is connected correctly and the correct voltage for the circuit is appliedVisually check all of the soldering tracks and joints to ensure there are no short circuitsManually ‘pull test’ each component to ensure it is securely soldered to the boardWith the power supply disconnected, use a multimeter to measure the resistance between power and groundCheck the continuity between all power points and check the continuity between all ground pointsWith the power supply connected check for the correct voltage at all of the supply pointsSpecific fault finding methods that can be used are half split and input to output