555

Do you mean one of these? 555 can pop up in a few ways.

• Math (as a number): prime factorization 555 = 3 × 5 × 37; divisors: 1, 3, 5, 15, 37, 111, 185, 555; binary 1000101011; hex 0x22B; Roman numeral DLV.

  • Quick practice: how many divisors does 555 have? (Answer: 8)

• Electronics: the 555 timer IC.

  • Basic pins: 1 GND, 2 Trigger, 3 Output, 4 Reset, 5 Control, 6 Threshold, 7 Discharge, 8 Vcc.
  • Modes: astable (oscillator) and monostable (one-shot).
  • Formulas:
    • Astable frequency: f ≈ 1.44 / [(R1 + 2R2) C]
    • Duty cycle: D = (R1 + R2) / (R1 + 2R2)
    • Monostable pulse width: t ≈ 1.1 R C

• Other common interpretations: 0x22B = decimal 555 in hexadecimal; 0b1000101011 in binary.

Tell me which interpretation you’re after (or the exact problem), and I’ll help work through it.