BUILD CARD · EASY
Reed Switch LED
Use a magnet-operated reed switch to control a white LED without touching the circuit.
- Time
- 15 min
- Age
- 8+
- Pieces
- 6
- Board
- 10×7
- Build and check a 10×7 snap-grid circuit from a visual diagram.
- A nearby magnet closes the reed switch without direct physical contact.
02 / PARTS CHECK
Parts list
- 1×7-snap wireconnector
- 1×3-snap wireconnector
- 1×White LEDsemiconductor
- 1×100 Ω resistorresistor
- 1×Reed switchswitch
- 1×3V two-cell battery holderpower
03 / ASSEMBLY
How to build the circuit
- 1
Disconnect the battery and clear the base grid before placing any part.
- 2
Match the final diagram one grid position at a time, placing connecting wires and lower layers first.
- 3
Check the direction of every LED, diode, transistor, battery, and other terminal-sensitive part.
- 4
Press every shared snap firmly, check that no wire shorts the battery, then connect power last.
04 / FIELD NOTES
How it works
A nearby magnet closes the contacts hidden inside the reed switch.
The closed contacts complete the circuit and light the LED.
The resistor keeps LED current at a safer level.
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05 / TEST
Test and expected result
- What to do
- Move a magnet slowly toward the reed switch, try both magnet ends, then move it away.
- What to expect
- The LED turns on when the magnetic field closes the hidden reed contacts.
06 / SAFETY
Build smart
- Use only the 3V battery holder.
- Keep small magnets away from young children and sensitive devices.
- Disconnect the battery after use.
07 / TROUBLESHOOTING
If it does not work
- Move the magnet closer to the reed switch and try both ends.
- Reverse the LED if it does not light.
- Check every snap and battery direction.
08 / FREQUENTLY ASKED QUESTIONS
Questions about this circuit
What is the main idea behind this circuit?
A nearby magnet closes the reed switch without direct physical contact.
What should I check first if it does not work?
Move the magnet closer to the reed switch and try both ends.
09 / RELATED BUILDS
Try a similar circuit
Continue with another build that shares the same components, ideas, or difficulty.
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