🎉 Party Spinner

What you're building

Press one button. A motor spins, a red LED lights, a buzzer beeps — all at once, all driven from the same transistor. Let go and everything stops together, quiet and dark.

Tape a paper arrow to the motor shaft and you've got a spinning game piece: who does the arrow point to? Board games, spinning question wheels, birthday-cake favours — all three cues (visual, audible, mechanical) fire together, powered by one AA pack.

The point of this project isn't the game. It's the wiring pattern: one brain, many mouths, run to the limit. Dusk Chorus did two mouths (LED + buzzer) at Level 3. Here you add a motor as a third mouth, and the transistor drives all three without breaking a sweat.

The multi-mouth pattern

The transistor's collector is a single "on/off" node that all your output lanes hang off of, each in its own parallel branch between + and the collector:

• Motor lane: motor (30 Ω) + flyback diode across it.
• LED lane: 220 Ω safety resistor + red LED.
• Buzzer lane: the active buzzer (its own 150 Ω resistance).

Each branch is independent — each one solves its own Ohm's-law problem and pulls its own current. The transistor's job is to add them all up and pass the sum through its collector.

Do the current math

Button pressed. Solve each mouth separately:

• Motor lane: (4.5 − V_CE(sat)) ÷ 30 Ω = (4.5 − 0.2) ÷ 30 = ≈ 143 mA.
• LED lane: V_LED ≈ 2.0 V (red), V_CE(sat) ≈ 0.2 V, so the 220 Ω resistor sees 4.5 − 2.0 − 0.2 = 2.3 V. I_LED = 2.3 ÷ 220 ≈ 10.5 mA. Same "First Light" brightness.
• Buzzer lane: the active buzzer looks like 150 Ω at 4.5 V. (4.5 − 0.2) ÷ 150 = ≈ 29 mA. Loud enough to hear from the next room.

Total collector current when the button is down:

I_C = 143 + 10.5 + 29 ≈ 183 mA.

Can the transistor handle it? Two ceilings to check:

1. The 2N2222's absolute continuous rating: 600 mA. We're at 183 mA — under a third. ✓
2. The base's saturation drive. With a 1 kΩ base resistor, I_base = (4.5 − 0.7) ÷ 1 kΩ = 3.8 mA. β × I_base = 200 × 3.8 = 760 mA available. We need 183 mA. 760 ÷ 183 = 4.2× headroom — deep saturation. ✓

The transistor is comfortable. It runs cool: V_CE(sat) × I_C = 0.2 × 0.183 = 37 mW. Warm to the touch after a minute; nowhere near hot.

Button released. I_base = 0. Transistor snaps off. All three mouths go quiet at once. The motor's collapsing coil still tries to push current — the flyback diode catches that pulse just like in First Spin, so the transistor never sees the spike.

Why the mouths don't fight each other

A common early instinct: "if I add a second mouth, won't the first one get dimmer?" Not here. Each parallel branch has its own path from + to collector, and each solves its own Ohm's-law equation independently. The LED lane pulls its 10.5 mA because the LED's forward drop and the 220 Ω resistor decide it. The motor pulls its 143 mA because its 30 Ω coil decides it. Adding the buzzer doesn't rob current from either — it just adds its share to the total the collector has to pass.

The one thing that would rob current is the transistor falling out of saturation — if you ask it for more than β × I_base and V_CE starts rising, every lane would droop together. But we have 4× headroom, so that won't happen.

This "parallel branches are independent" idea is what makes the transistor's "one brain, many mouths" trick scale. You can add a fourth or fifth lane the same way, as long as the total stays under the transistor's ceiling and the base drive is strong enough to saturate.

Build it

1. Power rails: battery + to a top row, battery − to a bottom row.
2. Trigger lane: battery + → push button → 1 kΩ → transistor Base.
3. The transistor: flat face toward you, legs are Emitter (left), Base (middle), Collector (right). E → − rail, B ← the 1 kΩ from the button lane, C into a fresh row A (the "collector node").
4. Motor lane: motor between the + rail and row A. Flyback diode across the motor: cathode (banded end) in the + rail row, anode in row A.
5. LED lane: 220 Ω from the + rail to a new row L; red LED from row L (long leg / anode) to row A (short leg / cathode toward the collector).
6. Buzzer lane: active buzzer from the + rail to row A. Watch its + / − stickers — the active buzzer only works one way around, unlike the motor.
7. Press the button. Three things happen at once: buzz, flash, spin. Let go: three things stop at once.

If any one mouth stays dark/silent/still while the other two fire, the wiring bug is in that lane, and only that lane — this is a big win over series-connected outputs, where one broken link kills everything.

What "one brain, many mouths" opens up

You've now seen the full menu of L1–L4 output types (LED, buzzer, motor) all fired at once. Everything at L5+ is a variation on this same pattern:

• Level 5: replace the motor with a servo. The button now triggers a specific angle — a game spinner with a predictable landing.
• Level 6: the button becomes a 555 timer — a spinner that fires on a schedule, no press required.
• Level 7: the trigger becomes an Arduino pin. Now the spinner spins on a countdown, or spins random durations, or logs every spin.

The mouths downstream don't change. Only the brain upstream does.