Electronics and robotics
Electronics and robotics projects for class 6 to 8: 43 ideas.
Each project below opens to its own page with what it shows, the science behind it, the materials, safety, step-by-step instructions, what you should see and viva questions. Many can be made from things at home; where a kit helps, the page links one.
Other subjects for class 6 to 8: Physics, Chemistry, Biology, Maths, Earth and space, Environment, Computing and coding.
Automatic street light with an LDR
A light dependent resistor (LDR) has a high resistance in the dark and a low resistance in light. A transistor uses that change to switch the LED on when it gets dark.
Water level indicator
Tap water conducts a little electricity because of the salts dissolved in it. As the water rises it touches wires at different heights, and transistors light an LED or sound a buzzer for each level.
Foil and foam pressure pad that lights an LED when pressed
A switch is just a gap in a circuit that can be closed. Two foil sheets held apart by a foam ring touch when pressed, completing the circuit so current flows through the LED.
Pocket dark detector that beeps when you cover the LDR
A light dependent resistor has a low resistance in bright light and a very high resistance in the dark. In a voltage divider with a fixed resistor, this change swings the base voltage of a transistor, which switches a buzzer on when it gets dark.
Sunlight meter: an LED that glows brighter as the light increases
When an LDR is placed in series with an LED, more light lowers the LDR resistance, more current flows and the LED glows brighter. The LED becomes a simple meter for how bright the room is.
Bucket overflow alarm that beeps when water touches two wires
Tap water conducts a small current because of dissolved salts. Two BC547 transistors joined as a Darlington pair multiply that tiny current enough to drive a buzzer, so the alarm sounds the moment water bridges the probe wires.
Rain alarm with an interleaved foil strip sensor on a card
Raindrops bridge the gap between two sets of foil strips that are close but not touching. The water lets a tiny current flow, which a Darlington pair of BC547 transistors amplifies to sound a buzzer, warning you to bring the washing in.
Morse code key from a paper clip and drawing pin with a buzzer
A telegraph key is a spring switch that closes a circuit for short or long moments. Pressing the paper clip onto a drawing pin completes the loop, and the pattern of short and long beeps carries letters in Morse code.
Two-station Morse telegraph line across a room with LEDs
Two keys and two indicator LEDs on one long wire pair let either station send to the other. It shows that a signal is really a current switched on and off, and that one shared return wire is enough for a two-way line.
Electric quiz board with brass fasteners and a foil answer path
Each question fastener is secretly wired to its correct answer fastener behind the board. Touching the two probes to a matching pair completes the circuit and lights the LED, so the board tests both knowledge and the idea of a closed loop.
Scrubbing brush bristlebot driven by an off-centre motor weight
A motor spinning an unbalanced weight shakes the whole brush. The angled bristles push forward on every shake and slip backward on the return, so the vibration turns into movement in one direction.
Cup scribble bot that draws with three markers and a vibrating motor
An unbalanced motor on a plastic cup makes it wobble on three marker legs, and the wobble is traced out as a looping drawing. The pattern depends on the weight, the speed and how far apart the legs are.
Energy transfer: one toy motor spins another that lights an LED
A DC motor is also a generator. When a second motor is turned by the first, its coil spins inside its magnets and produces a voltage that lights an LED, showing that electrical and mechanical energy can be converted in both directions.
Salt water conductivity tester with a transistor and an LED
Water conducts electricity only through dissolved ions. Two probes in a liquid feed a tiny current into a transistor, which amplifies it to light an LED. Distilled water gives nothing, tap water a faint glow and salt water a bright one.
Pocket continuity tester with a buzzer and an LED in a tic-tac box
A continuity tester tells you whether a path conducts: touch its two probes to the ends of a wire, a fuse or a switch and it beeps if current can flow. It is the first tool for finding broken wires and checking which materials conduct.
Steady hand wire loop game with a buzzer and a penalty LED
A bent bare wire and a wand loop form a switch that closes whenever your hand shakes and the loop touches the wire. The buzzer and LED make the contact obvious, turning a simple circuit into a game.
Cardboard table fan with a bottle propeller and a slide switch
A DC motor turns electrical energy into rotation. Angled blades cut from a bottle push air backwards as they turn, so a breeze comes forward, and a switch in the circuit starts and stops the fan.
Cardboard conveyor belt driven by a toy motor and rubber band
A motor turns a small pulley, a rubber band carries that rotation to a larger roller, and a loop of cloth belt stretched between two rollers moves objects along. It shows belt drives, friction grip and speed reduction through pulley sizes.
Motorised cardboard crane that lifts a load with a thread spool and reversing switch
A motor winding thread onto a spool converts rotation into lifting. A DPDT slide switch swaps the battery polarity so the same motor raises and lowers the hook, which is how real crane winches are controlled.
Electric bell model with a nail electromagnet and a hacksaw blade clapper
An electromagnet pulls a springy steel strip towards it, which breaks its own contact, loses the magnetism and springs back to close the contact again. The strip vibrates to and fro, striking a tin lid to ring like a doorbell.
Traffic light with red, amber and green LEDs on three push switches
Three LEDs each with their own resistor and switch share one battery. Each switch controls only its own branch, which is a parallel circuit, the way the lights in a house are wired so that one can be on while the others are off.
Magnetic door alarm with a reed switch that sounds when the door opens
A reed switch closes when a magnet is near and opens when it moves away. With the magnet on the door and the switch on the frame, opening the door removes the magnet, and a transistor circuit turns the buzzer on, the same way shop door sensors work.
Bicycle wheel revolution flasher with a spoke magnet and a reed switch
A magnet on a spoke closes a reed switch on the fork once every turn, flashing an LED. Counting flashes in a known time and knowing the wheel circumference gives the bicycle speed, the same method a bike speedometer uses.
Solar powered spinner: a small solar cell drives a toy motor top
A solar cell turns light directly into electrical energy. Connected to a toy motor with a paper disc, it spins in sunlight, slows in shade and stops indoors, showing how output depends on the amount and angle of light.
Staircase light with two switches that each turn one LED on and off
Two single-pole double-throw switches wired together let you switch one lamp from either end of a staircase. Flipping either switch changes whether the loop is complete.
LED strings on a 9 V battery: working out resistors for series and parallel
Three red LEDs in series share one resistor and draw one LED worth of current, while three in parallel each need their own resistor and draw three times as much. Working out the resistor with R = (supply minus LED voltages) divided by current shows why.
Knob dimmer for an LED using a 10 kΩ potentiometer on a 9 V battery
A potentiometer wired as a variable resistor changes how much current an LED gets, so turning the knob dims or brightens the light. Less resistance gives more current and more light.
Weak cell finder: loaded and unloaded voltage of old and new AA cells
A cell that reads 1.4 V with nothing connected can still be nearly flat, because its internal resistance has grown. A voltage reading while it lights a small bulb shows the true condition.
Quiz board where matching question and answer wires light an LED
A circuit is only complete when a wire joins the right pair of terminals. Touching a probe wire to the correct answer closes the loop and lights an LED, while a wrong answer leaves it open.
Tripwire alarm: a clothes peg with foil contacts and a pull-out card
A plastic card between two foil contacts keeps a circuit open. Pulling the card out by a thread lets the contacts touch, which closes the circuit and sounds a buzzer.
Pencil lead rheostat that dims an LED as the clip slides along the graphite
Graphite conducts, but not as well as copper. The longer the length of lead the current has to pass through, the more resistance it has, so the LED gets dimmer as you move the clip away.
Push button LED that fades out slowly, powered by a charged capacitor
A capacitor stores charge like a tiny rechargeable tank. A quick press of a button fills it, and when the button is released the capacitor keeps the LED glowing for several seconds as it empties.
Secret code box: four toggle switches in series that light an LED in one setting
Switches in series work like the word AND: the loop is complete only if every switch is in its correct position. With four two-way toggles there are 16 settings and only one lights the LED.
Tilt alarm from a steel ball in a straw tube that rings a buzzer
A small steel ball rolls to the low end of a tube when it is tilted and bridges two bare wires there. This completes a circuit, so the object is warned when it moves out of the upright position.
Forward and reverse toy car using one DPDT switch and a motor
The direction of a DC motor depends on the direction of the current through it. A double-pole double-throw switch wired crosswise swaps the battery connections and so reverses the car.
How fast a toy motor spins with one, two, three and four AA cells
The speed of a DC motor rises almost in proportion to the voltage across it. More cells in series give more speed and also a larger current.
Plant pot dry soil alert with two steel nails, a BC547 and an LED
Damp soil conducts electricity far better than dry soil. A transistor circuit lights a red LED when the soil resistance between two nails rises, which tells you the plant needs water.
Propeller thrust test: how blade angle and blade number change the push
A propeller pushes air backwards and is pushed forwards in return. The size of the push depends on how many blades there are and how they are angled to the air.
Foam tray toy boat with a toy motor, propeller and slide switch
A motor-driven propeller pushes water backwards and the boat moves forward, which is Newton’s third law. A well-shaped, light hull floats because the water it pushes aside weighs more than the boat.
Coin-cell LED night lamp with an ice-cream stick switch
A complete circuit of a cell, an LED and a switch lights the lamp. It shows that current flows only in a closed loop and that an LED works in one direction only.
Cardboard traffic signal with three LEDs and a rotary switch
Each lamp has its own circuit with a cell and a switch path. The model shows red, yellow and green lights and teaches how a circuit is completed.
Conductor or insulator? Tester with one cell and a bulb
Some materials let electric current pass and some do not. A bulb lights up when the circuit is complete and a conductor is in the gap.
Cardboard lighthouse that lights with one cell and a bulb
A complete circuit with a cell, a bulb and a switch makes light. A lighthouse model shows how light guides ships at night.