MISSION 08 · BASIC ELECTRONICS
Can a circuit notice darkness and switch on without anyone pressing a button?
4 · Make It Respond
Your new skill: Make an input control an output without your hand.
Revisit the skill you will reuse: Previous main-path mission
Match the names to your parts before you build. New parts appear when you first need them. You can point, say the name or show a grown-up.
A battery supplies energy that can make a light glow or a motor turn. A holder keeps its connections in place.
Look for: Find the + and - marks and the matching holder or snap connector.
Before using it: Use only the supply named in this mission. Never join + straight to -; disconnect before rewiring.
Your turn: With power disconnected, trace the path from + through the parts and back to -.
This reusable building board joins some holes with hidden metal strips, so we can connect parts without soldering.
Look for: Find the centre gap, row numbers and power rails. The gap separates the two halves.
Before using it: Five holes in one numbered strip usually join; the strip across the gap does not. Some power rails have a break. Match your board diagram.
Your turn: Point to two holes on the same connected strip, then two that are separated by the gap.
A wire makes an electrical connection between two points. A clip lead grips a terminal.
Look for: Jumpers have small plug ends; clip leads have metal jaws. Colour helps us track a connection.
Before using it: Colour does not change a wire's job. Check both ends and keep bare metal away from other terminals.
Your turn: Follow one wire from start to finish and name what it joins.
A resistor limits current in a path. Beside our LED it helps protect the light from too much current. Its resistance is measured in ohms.
Look for: Look for a small body with two legs and coloured bands; match its labelled value to the mission.
Before using it: A resistor can face either way. Values such as 1 kΩ and 10 kΩ are different: k means one thousand. Keep the specified value.
Your turn: Point to the resistor in the LED path. Explain why replacing it with a plain wire is not our test.
An LED turns electrical energy into light and works in one direction. We use it to show what a circuit is doing.
Look for: An untrimmed ordinary LED often has a longer anode leg and a shorter cathode leg. A flat rim often marks the cathode.
Before using it: Confirm polarity with the part card if legs are trimmed. Use the mission's resistor in series; never connect an LED straight across the battery.
Your turn: With power off, identify the two legs and point to its protective resistor.
An LDR is a resistor whose resistance changes with light. Our circuit uses that change as a clue about brightness.
Look for: Look for a little round face with a zigzag pattern and two legs.
Before using it: Do not guess whether a reading goes up or down: the circuit arrangement matters. Compare uncovered and shaded readings first.
Your turn: Point to the face you will shade without moving any wires.
A transistor lets a small electrical signal control current in another path. Here we use it as an electronic switch.
Look for: Find the three-legged part labelled 2N3904 and its matching E B C pin card. E is emitter, B is base and C is collector.
Before using it: Look-alike transistors can have different leg orders. Use this exact part card and the mission's resistors.
Your turn: Point to E, B and C on the card, then match them to your unpowered part.
A video demonstration will appear here when it is ready. You can follow the written step now.
Before we build, match these names to the parts in front of you. Battery and holder. A battery supplies energy that can make a light glow or a motor turn. A holder keeps its connections in place. Find the + and - marks and the matching holder or snap connector. Use only the supply named in this mission. Never join + straight to -; disconnect before rewiring. Breadboard. This reusable building board joins some holes with hidden metal strips, so we can connect parts without soldering. Find the centre gap, row numbers and power rails. The gap separates the two halves. Five holes in one numbered strip usually join; the strip across the gap does not. Some power rails have a break. Match your board diagram. Jumper wire and clip lead. A wire makes an electrical connection between two points. A clip lead grips a terminal. Jumpers have small plug ends; clip leads have metal jaws. Colour helps us track a connection. Colour does not change a wire's job. Check both ends and keep bare metal away from other terminals. Resistor. A resistor limits current in a path. Beside our LED it helps protect the light from too much current. Its resistance is measured in ohms. Look for a small body with two legs and coloured bands; match its labelled value to the mission. A resistor can face either way. Values such as 1 kΩ and 10 kΩ are different: k means one thousand. Keep the specified value. LED or light emitting diode. An LED turns electrical energy into light and works in one direction. We use it to show what a circuit is doing. An untrimmed ordinary LED often has a longer anode leg and a shorter cathode leg. A flat rim often marks the cathode. Confirm polarity with the part card if legs are trimmed. Use the mission's resistor in series; never connect an LED straight across the battery. LDR or light dependent resistor. An LDR is a resistor whose resistance changes with light. Our circuit uses that change as a clue about brightness. Look for a little round face with a zigzag pattern and two legs. Do not guess whether a reading goes up or down: the circuit arrangement matters. Compare uncovered and shaded readings first. 2N3904 transistor. A transistor lets a small electrical signal control current in another path. Here we use it as an electronic switch. Find the three-legged part labelled 2N3904 and its matching E B C pin card. E is emitter, B is base and C is collector. Look-alike transistors can have different leg orders. Use this exact part card and the mission's resistors. Pause and point to the part that will do the main job in this mission. If it is missing or looks different, ask a grown-up before building.
WHAT YOU'LL USE
Kit list: match the named parts to your box and its component cards. Home list: gather these before starting; some may also be supplied in your kit. Reuse components between missions. Stop and ask a grown-up if an essential part or label is missing.
BEFORE YOU BUILD
Use the 9V source. With the transistor flat face toward you, the supplied 2N3904 legs are E-B-C from left to right. Power off while placing it.
YOUR REWARD
PREDICT BEFORE YOU BEGIN
What do you think will happen? Say it, point to it or draw it. Then test your idea.
YOUR CHALLENGE
NEW POWER-UP
Make an input control an output without your hand.
You already know: LEDs, resistance and complete paths New power-up: LDR sensing, a sensor pair and transistor switching This prepares you for: using the same sensor brain with a sound output
Each coloured strip is one connected group. Different numbered rows stay separate. This explains the board; use the mission’s exact connection reference for component positions. Check rail breaks on your supplied board.
CONNECTION MAP
BUILD PATH
STEP 1 OF 9
Connect the 9V red and black leads to the + and - rails.
A video demonstration will appear here when it is ready. You can follow the written step now.
Connect the 9V red and black leads to the + and - rails.
WHAT'S REALLY HAPPENING?
The LDR changes resistance with light. Together with the 560k resistor it creates a changing voltage at the sense point. The transistor uses that tiny signal like an electronic switch.
Automatic night lights, garden lights and display backlights use light sensing to respond without a person pressing a button.
FAIR-TEST CHALLENGE
Change one feature, keep the rest the same and repeat your comparison.
WHEN IT DOESN'T WORK YET
Likely cause: Transistor pins or sensor join are wrong
Try this first: Power off, verify E-B-C and trace the sense point to base B.
Likely cause: Sensor pair may be reversed
Try this first: Compare the 560k resistor and LDR positions with the diagram.
Likely cause: Base connected directly to + or LDR not connected
Try this first: Trace the sensor path and remove shortcut wires.
CLEAN, RESET AND STORE
Switch off and disconnect all power. Let moving parts stop. Put the parts back in their kit compartments.
NEXT SKILL
Reuse the same sensor rule with a different output.