555

What would you like to do with 555?

Options:

• Electronics: 555 timer IC basics and circuits (monostable, astable, bistable) with quick formulas.
• Math/number theory: problems involving the number 555 (factors, conversions, properties).
• Other: something else related to 555.

If you want electronics, here’s a quick refresher you can use right away:

• Pinout: 1 GND, 2 Trigger, 3 Output, 4 Reset, 5 Control, 6 Threshold, 7 Discharge, 8 Vcc.
• Modes:
  • Monostable (one-shot): output high for a period T = 1.1 R C. R is the timing resistor, C the timing capacitor.
  • Astable (free-running): f = 1.44 / ((R_A + 2 R_B) C). TH (high time) = 0.693 (R_A + R_B) C, TL (low time) = 0.693 R_B C. Duty cycle = (R_A + R_B) / (R_A + 2 R_B).
  • Bistable (latch): no timing capacitor; toggled by triggers.
• Quick example: If R_A = 10 kΩ, R_B = 20 kΩ, C = 100 nF, then f ≈ 1.44 / ((10k + 2*20k) * 100 nF) ≈ 1.44 / (0.005) ≈ 288 Hz.

Tell me which path you want, and I’ll tailor the help (with examples or practice problems).