Math of the 555 Timer

If you’ve been following along with the 555 timer series, this video describes how to derive the formula that describes the timing of the circuit. Starting with just 2 components, we’ll work our way to an answer.

3 thoughts on “Math of the 555 Timer”

  • Jason,
    I have a NE555P set up for 70Hz, powered by a 9v, 350mA wall jack. I want to sink it using a 2N3904 transistor. I am told you need a resistor off pin 3 to the transistor. I can’t find anywhere how to calculate the current discharging pin 3 to determine the resistor size. Objective is to pulse a coil which has a resistance of 125 ohms and an inductance of 134.5 mH at 70Hz.

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