Year 9 Mood Light – Knowledge Map
Circuits
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Electric current is the flow of electrons
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Current is ‘pushed’ around the circuit by voltage
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A resistance in the circuit will reduce the amount
of current
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Insulators do not conduct any current and can be
used to protect us e.g. the PVC insulation on a
wire
Copper is used in wires because it is a good
conductor
Identify the similarities between water flow in pipes and electric current flow in wires as follows:
Water circuit
Pump
Pressure
Water
Pipe
Flow rate
Blockage/restriction
Electric circuit
Cell/battery
Voltage
Electrons
Wire
Current
Resistance
Be able to provide the following simple explanations of water flow and current flow in a circuit:
A pump provides the pressure that pushes water
around the circuit. The flow of water in the pipe
is known as the flow rate. A blockage will cause
a reduction in the flow rate.
A battery provides the voltage that pushes
electrons around the circuit. The flow of
electrons in the wire is known as the current. A
resistance will cause a reduction in the current.
Components
LED stands for Light Emitting Diode
Know that the ‘legs’ on an electronic component are known as leads.
Know that the negative lead of an LED and can be identified by the ‘flat’ on the side of the LED’s outer casing.
Know that the longer lead of a new LED is the positive lead.
Recognise a series circuit of LDR at the top and a
fixed resistor at the bottom as a basic light sensing
circuit, as shown on the right.
Know that an increase in light level causes a
decrease in resistance in an LDR.
Know that a decrease in the resistance in the LDR
will cause an increase in voltage at the mid-point
of our light sensing circuit (between the LDR and
the fixed resistor).
5V
Know the names for the following components and be able to draw their circuit symbols:
Component
Name
Appearance
Symbol
Component
Name
*LDR
Appearance
*Cell
Battery
(a gang of
more than
one cell)
RGB LED
*Toggle
Switch
Conductors (wire
or tracks)
*Resistor
*LED
Conductor
junction (wire or
tracks)
*PICAXE 08M2+
Microcontroller
with chip socket
Tracks on PCB
Symbol
Know that components connected in series are
connected in a ‘chain’ pattern, one after the
other, like this (see right)
The correct name for a silicon chip is an integrated circuit.
The legs on an integrated circuit are commonly called pins.
Know that integrated circuits have input pins, output pins, and power pins.
A program is a sequence of instructions, written to perform a specified task on a computer.
A microcontroller is a tiny computer built onto an integrated circuit.
A microcontroller can be programmed from a PC.
INPUT – PROCESS – OUTPUT
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Know that the LDR is an INPUT to the circuit because it is being used to create changes inside
the circuit, in this case, the resistance changes in response to external light level.
Know that the microcontroller is the PROCESS because it reads the input and processes
(converts) this into the desired output. It is the ‘doing’ part of the circuit.
Know that the LED is an OUTPUT from the circuit because it is being used to create changes
in the outside world, in this case, changes in light level.
Know the following flowchart symbols, and be able to create simple flowcharts to perform a
specified task.
A microcontroller program can be created using flowchart techniques.
More advanced programs can be created by writing the program using text commands.
Know that a microcontroller can be reprogrammed whenever desired and therefore:
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Any errors (bugs) in the program can be fixed
its function and performance can be improved with upgrades
A circuit diagram shows how each component is connected.
In a circuit diagram, wires can cross if necessary, but this is to be avoided.
If wires join in a circuit diagram this is known as a junction and shown with a dot at the point the
wires connect.
A breadboard is a plug-in board that allows the electronic components to be easily moved,
connected and reconnected without using solder so that circuits can be tested.
Breadboards save time and waste because the components legs are not cut/ damaged, no chemicals
are required and the circuit can be changed without de-soldering and re-soldering.
A PCB is a printed circuit board and is built on a Glass Reinforced Plastic board.
In circuit diagrams, breadboards and PCBs we try to follow the convention of positioning the power
supply positive voltage at the top, the negative voltage (or zero volts) at the bottom, the inputs on
the left and the outputs on the right.
The copper pathways on a PCB are called tracks and act as the wires in the circuit.
The tracks cannot cross on a PCB.
The ends of the tracks are usually circular and have a hole in for the component legs to fit through
ready for soldering. These circular areas are known as pads.
The design of a PCB layout, showing tracks and pads, is known as artwork.
When artwork is printed onto transparent paper, this is known as a mask.
Know the basic order of PCB manufacture including
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Artwork
Expose
Develop
Etch
Drill
Solder
The legs of the components must be
soldered to the pads in order for electrical
current to flow properly through the joint.
Solder joints should appear pointed and
shiny when done correctly.
When a joint does not properly conduct
current, this is known as a ‘dry joint’.
The PCB has a layer of copper on top which is etched or cut away to leave the required pattern of
connecting tracks for out circuit.
The holes in the PCB are created using a PCB drill.
Electronics Safety Rules
General Workshop Safety
1. Always listen carefully to the teacher and follow instructions.
2. Do not run in the workshop, you could ‘bump’ into another pupil and cause an accident.
3. Know where the emergency stop buttons are positioned in the workshop. If you see an accident at
the other side of the workshop you can use the emergency stop button to turn off all electrical
power to machines.
4. Always wear an apron as it will protect your clothes and hold loose clothing such as ties in place.
5. Wear good strong shoes. training shoes are not suitable.
6. When attempting practical work all stools should be put away.
7. Bags should not be brought into a workshop as people can trip over them.
8. When learning how to use a machine or equipment, listen very carefully to all the instructions
given by the teacher. Ask questions, especially if you do not fully understand.
9. Do not use a machine or equipment if you have not been shown how to operate it safely by the
teacher.
10. Always be patient, never rush in the workshop.
11. Always use a guard when working on a machine.
12. Keep hands away from moving/rotating machinery.
13. Use hand tools carefully, keeping both hands behind the cutting edge.
14. Report any damage to machines/equipment as this could cause an accident.
Breadboarding Safety
 *ALWAYS wear your SAFETY GLASSES
 *DISCONNECT circuits when troubleshooting
 Always OBSERVE POLARITY when connecting components into a circuit, especially with electrolytic
capacitors
 DOUBLE CHECK circuits for proper connections and polarity prior to applying the power
 Make sure TEST instruments are set for proper FUNCTION AND RANGE prior to taking a
measurement
 When measuring UNCERTAIN quantities, start with the range switch on the HIGHEST setting
Soldering Safety
 *KEEP soldering irons in their protective STAND when not in use
 *DO NOT TOUCH the tip end of a soldering iron to check for heat – it will burn you very quickly
 *NEVER play with solder e.g. create balls or pools or use excessive amounts of solder as this will
create burn hazards
 *DO NOT touch your face or put solder or any other equipment or materials in your mouth (lead
is poisonous – wash your hands after use)
 Apply HEAT from a soldering iron for no more than a couple of seconds to AVOID HEAT DAMAGE
 Always CUT wire LEADS so the clipped wire falls on the table top and not toward others
PCB Manufacturing Safety
 AVOID SKIN CONTACT with chemicals
 Always READ the MSDS (Material Safety and Data Sheet) for all chemicals prior to their use
 *When drilling, always wear safety glasses
 *The dust from PCB drilling contains glass and is an irritant so should not be touched or blown
around
Know that this is the symbol for irritant or harmful chemicals, and that
these chemicals may cause damage to your skin, and especially your eyes
and lungs.
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Always use the correct PPE in the correct manner
Avoid contact with chemicals, don’t taste or sniff chemicals
Always wash your hands after working with chemicals
Never eat in a workshop
Know that the correct PPE for PCB work is goggles, plastic apron and plastic gloves. Plastic tongs
should also be used to avoid contact with chemicals.
Lastly, for the shade....
Translucent means allowing light, but not detailed shapes, to pass through