555

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• 555 timer IC (electronics): two common modes are astable (oscillator) and monostable (one-shot). Quick refs:

  • Astable: f ≈ 1 / [0.693 (R1 + 2 R2) C], TH = 0.693 (R1 + R2) C, TL = 0.693 R2 C.
  • Monostable: pulse width t ≈ 1.1 R C.
  • Common parts: NE555, LM555.

• The number 555 (math): prime factorization 3 × 5 × 37. Divisors: 1, 3, 5, 15, 37, 111, 185, 555.

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