💨 Puff Button

What you're building

First Spin with the slide switch replaced by a push button. Now the motor spins only while your thumb is on the button. Let go — the coil stops within a second. Press again — a fresh spurt of breeze.

Tape a small paper cone to the shaft and it's a dust puffer — a "hold to blow" gadget for camera lenses, keyboards, and laptop vents. Real photographers use rubber-bulb ones; this is the electric version, and it's still just three parts on a loop.

The two kinds of switch, at Level 4

You've used a slide switch (sustained: flip on, walk away) and a push button (momentary: only closed while pressed) for a whole level's worth of LED and buzzer projects. This project makes the same swap you did in Doorbell — but now the load is a motor that pulls 15× the current of an LED.

That change matters for the switch's rating. LEDs pull ~10 mA through their switch — a comfortable trickle. A motor pulls ~150 mA. The button's metal contacts are now doing real work. Most tactile push buttons are rated 50 mA to a few hundred mA; 150 mA is inside that range for name-brand buttons but on the edge for the cheapest ones. If yours feels warm after a long press, that's the contact warming up — a real design signal, not a fault.

Do the math

Same as First Spin — one loop, one motor, one switch, straight Ohm's law:

• Battery: 4.5 V.
• Button closed: contact resistance a few milliohms — invisible next to the motor's coil.
• Motor coil: ~30 Ω.
• Loop current when pressed: 4.5 V ÷ 30 Ω ≈ 150 mA.
• Power the motor eats: 4.5 × 0.15 ≈ 0.68 W. Almost all of it turns into spin, a bit into sound.

Button released → loop broken → battery drain drops to microamps of leakage. This is the whole "hold-to-run" story: the device is only drawing current in the moments you actually want breeze.

Battery life is measured in presses, not hours

First Spin's slide switch could easily be left on all day without noticing — that's how you drain a fresh AA pack in a sitting. This project's push button is its own energy saver: you can't accidentally leave it running.

Rough sums with a fresh 2500 mAh AA pack:

• Slide switch, always on: 2500 mAh ÷ 150 mA ≈ 17 hours of continuous spin.
• This project, one-second puffs, 60 times a day: each puff costs (150 mA × 1 s ÷ 3600 s/h) = ~0.04 mAh. Sixty puffs a day is 2.5 mAh; 2500 mAh / 2.5 mAh/day ≈ ~1000 days of daily use.

Same battery, same motor — different switch philosophy, three orders of magnitude difference in lifetime. Match the switch to the way the device is used.

The flyback diode still matters (in fact, more than before)

First Spin explained the diode-across-the-motor pattern: when the loop opens, the coil's stored magnetic energy tries to keep current flowing, and without a safe path it arcs across the switch contacts.

Push buttons snap open faster than slide switches. Slide switches roll open over a millisecond or two; push buttons release with a hard mechanical snap that separates the contacts in tens of microseconds. That faster snap makes the coil's inductive kick higher-voltage (because dI/dt is larger). A button-driven motor loop with no flyback diode arcs harder than a slide-driven one. Skip the diode and the button contacts pit noticeably within a few hundred cycles; keep it in and they last for years.

Every motor gets a flyback diode across it, banded end toward +. No exceptions.

Build it

1. Power rails. Battery + to a top row, battery − to a bottom row.
2. Push button inline with the + rail. Wire + rail → one leg of the button → out its diagonal leg into a fresh row A. (Diagonal legs = opposite sides of the button's internal switch — same trick as Morse Code Messenger and every other button project.)
3. Motor between row A and the − rail. Motor leads have no polarity for direction; either lead on top works. Reversing flips the spin direction.
4. Flyback diode across the motor. Diode banded end (cathode) in row A (the motor's + side), anode in the − rail. In parallel with the motor, cathode toward +.
5. Test it: press → motor spins at ~150 mA. Release → motor coasts to a stop in a second or two. No click, no snap at the button contact.

Compare to First Spin

	First Spin (slide)	Puff Button (button)
Switch type	slide (sustained)	push button (momentary)
On when …	flipped on	held down
Motor current	~150 mA	~150 mA (same)
Battery lifetime	hours of always-on	days of many short puffs
Idle drain	none when off	none when up
Diode	✓ across motor	✓ across motor
Real use	desk fan, robot drive	keyboard puffer, lens blower, hair puffer

Same loop, same current, same physics — different temporal behaviour. In electronics that difference is called the duty cycle: what fraction of the time the load is drawing current. A slide switch is 100% duty when on; a hand-pressed button is often 1% duty or less. Every real product picks a switch by looking at expected duty cycle and matching to a plausible battery life.

Where else you'll see this

• Keyboard air puffers and camera-lens blowers: rubber bulbs are the same idea (hold to blow) without a motor. The electric version is a fan + button — this project.
• Coffee-grinder grind buttons: hold to grind, release to stop. Prevents accidentally leaving the machine running.
• Handheld hair dryers (some models): continuous mode + a "boost" button that spins the fan a step faster while held.
• Foot pedals on sewing machines: a heavier version of the push button (foot-pressed) driving the machine's motor.

Any time you want power only while the user is actively attending to it, the push button + motor pattern is the answer. You built it in three parts.