Tagalog: draft — for Kate / Janet to check. Shown slowed down: the real circuit switches about 1,400 times a second.
Maraming parte sa iisang pakete (IC). Hanggang 200 mA lang ang kaya, kaya MOSFET ang nagpapatakbo sa motor. Many parts in one package. It can only supply ~200 mA, so a MOSFET drives the motor.
3 resistor → 8 V at 4 V. Dalawang comparator, isang flip-flop, isang transistor. Three equal resistors make 8 V and 4 V references from 12 V; two comparators and a flip-flop flip the output.
Nag-iisang capacitor na umaakyat sa 8 V at bumababa sa 4 V. Hinahati ng pot ang dalawang daan. The capacitor ramps between 4 V and 8 V; the pot splits the charge and discharge paths, which sets the duty cycle.
Gate resistor 1 kΩ, pull-down 1 kΩ, flyback diode 1N4007. Each part has a job: limit gate current, drain the gate so it turns off, catch the motor's spike.
t ≈ 0.693 × R × C. f = 1 ÷ (ton + toff). 51 kΩ × 10 nF → 0.35 ms each side → about 1,400 Hz.