Every MagneTronics block

Power and connection blocks carry current around the circuit. The Battery Block pushes it, and the wire, corner and junction blocks give it a path, so every loop starts and ends here.

• Battery Block3 V from two AAA batteries. The longer plate and + side is the positive end.17 circuits
• WireCarries current straight through.17 circuits
• L WireTurns the path 90 degrees.17 circuits
• T JunctionSplits or joins three paths. Use it to put parts in parallel.11 circuits
• 4 Way JunctionJoins four paths together.
• Overpass JunctionTwo paths cross without touching.
• X Junction (touch pads)Two paths cross. Touching the pads lets a tiny current flow through your finger from one path to the other.1 circuit

Input and control blocks decide when current flows. Switches open and close the path, and the potentiometer changes how much resistance is in it.

• ON/OFF SwitchA slide switch. It stays where you leave it.6 circuits
• Tactile SwitchA push button. Current flows only while you hold it down.6 circuits
• PotentiometerA variable resistor. The two ends are across the track, the third terminal is the slider.2 circuits

Output blocks turn current into something you can see, hear or feel: an LED lights, a buzzer sounds and a motor spins.

• LED 1 (red)Lights only when current flows into the left side (the triangle points the way). Has a 220 Ω resistor built in.14 circuits
• LED 2 (orange)An orange LED, with a 220 Ω resistor built in. Needs about 2 V.2 circuits
• Active BuzzerMakes its own tone whenever it is powered. Connect + to the left side.1 circuit
• Passive BuzzerNeeds a changing signal, such as the Melody IC. A transistor makes it louder.2 circuits
• DC MotorSpins when powered. Swap the polarity (rotate the block) to reverse it.1 circuit

Resistors and capacitors shape a circuit without switching it. Resistors limit current and set levels; capacitors store charge and release it over time, which is how timers and fades work.

• 10kΩ ResistorLimits current. Use one before a transistor's base.2 circuits
• 100kΩ ResistorA higher value resistor for sensor and timing circuits.
• 100µF Polar CapacitorStores charge. Connect + to the left side.
• 470µF Polar CapacitorStores more charge, so timers last longer. Connect + to the left side.2 circuits

Transistors and ICs let a small signal control a bigger one. A transistor acts as an electronic switch or amplifier, and the Melody IC generates a tune on its own.

• S8050 NPN TransistorAn electronic switch. Base on the left, collector at the top, emitter at the bottom. Always use a resistor on the base.6 circuits
• S8550 PNP TransistorWorks the other way round. Base on the left, emitter at the top, collector at the bottom.
• UM66 Melody ICPlays a tune on its OUT terminal (right). + at the top, − at the bottom.2 circuits

Sensor blocks react to the world: light, infrared and magnets. Put one on a transistor's base and the circuit responds to what the sensor sees.

• LDR (light sensor)Low resistance in light, high in the dark. Click it to cover it.1 circuit
• A3144 Hall Effect SwitchSenses a magnet. + at the top, − at the bottom, OUT on the right pulls low when a magnet is near.1 circuit
• IR LEDAn infrared LED. You cannot see its light, but an IR photodiode can.
• IR PhotodiodeDetects infrared light, such as from a flame. Click it to shine infrared on it.

A relay is a switch worked by an electromagnet. A small current through the coil pulls the contacts closed, so one circuit can switch another.

• RelayA switch worked by a coil. Coil + on the left, coil − at the bottom. COM on the right, NO at the top.