555 Timer PWM-Controlled Cooling Fan

In this video, I demonstrate controlling a cooling fan (for an amplifier or PSU) using PWM (Pulse-Width Modulation) from a 555 timer. This "servo" is still temperature sensitive using an NTC (negative temperature coefficient thermistor), which can be adjusted to come on when necessary, rather than running at full speed all the time. The 555 is not the best solution for PWM, but it does work. What PWM will do, is when driving a BJT or MOSFET, will send bursts of current to the motor to control its speed, rather just varying the voltage. However, the voltage does vary to control the current flow, as current and voltage share a close relationship.

Link to inspiring article: https://www.paulvdiyblogs.net/2015/08/controlling-temperature-driven-fan-with.html

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