555

Do you want to focus on 555 as a math number or the 555 timer IC (electronics)? Here are quick notes for both. Tell me which you prefer or give a specific problem.

If you mean the number 555 (math):

• Factorization: 555 = 3 × 5 × 37
• Divisibility: divisible by 3 and 5; not by 9
• Base representations:
  • Decimal: 555
  • Binary: 1000101011₂
  • Hexadecimal: 0x22B
  • Base-7: 1422₇
• Roman numeral: DLV
• Other quick facts:
  • Palindromic in base 10 (reads the same forward/backward)
  • 555 minutes = 9 hours 15 minutes; 555 seconds = 9 minutes 15 seconds

If you mean the 555 timer IC (electronics):

• Used in: generating timers, oscillators, pulse-width modulation
• Common formulas:
  • Astable mode (free-running oscillator)
    • Frequency: f ≈ 1.44 / [(R1 + 2R2) C]
    • Duty cycle: D ≈ (R1 + R2) / (R1 + 2R2)
  • Monostable mode (one-shot)
    • Pulse width: t ≈ 1.1 × R × C (with a resistor and capacitor in the appropriate network)
• Typical pins: Vcc, GND, Trigger, Threshold, Discharge, Output (plus Control Voltage, Reset)
• Practical notes: tolerance of R and C, control via control voltage pin, start/stop considerations

Which direction would you like? I can solve a problem, convert representations, or explain the 555 timer in more depth.