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555 Astable Multivibrator

Mixed-signal

The timing capacitor integrates between $\tfrac{1}{3}V_{cc}$ and $\tfrac{2}{3}V_{cc}$ . The timing-branch stroke weight scales with instantaneous $V_C$ , and the LED node flashes in sync with the calculated frequency (time-scaled for visibility).

8 components · 10 connections · hybrid charge/discharge integrator

recommended lab 4 of 11

Relate RC charge thresholds to oscillator frequency and duty cycle.

Builds on: Dynamic RC Low-Pass Filter

predict · then test

Increase $R_B$ while $R_A$ and $C$ stay fixed. What changes first?

Commit before the explanation appears. This is a prediction, not a quiz score.

governing model

f = \dfrac{1.44}{(R_A + 2R_B)\,C} \;\cdot\; D = \dfrac{R_A + R_B}{R_A + 2R_B}

structural inventory

8-pin 555 IC block
$R_A + R_B$ timing pair
timing capacitor $C_T$
output LED + limiter

boundaries

$V_{cc}=5\ \mathrm V$
threshold $\tfrac{2}{3}$ · trigger $\tfrac{1}{3}$
astable + monostable modes

diagnosis challenge Fault identity withheld: infer it from the changed outputs first.

causal signal trace paused

Bias the timing ladder $V_{CC}$ drives RA and the timing network.

t_{\mathrm{stage}}=\htmlData{math-slot=value}{\mathtt{0.00}}\,\mathrm{s}

step 1 / 4 Bias the timing ladder

control console

R_A=\htmlData{math-slot=value}{\text{10.00 kΩ}}

R_B=\htmlData{math-slot=value}{\text{10.00 kΩ}}

C_T=\htmlData{math-slot=value}{\text{100.00 nF}}

switchboard · fault injection

inject hidden fault

test bed · mode=full

555 Astable Multivibrator

instrumentation rack

f=\htmlData{math-slot=value}{\text{1.00 kHz}}

D=\htmlData{math-slot=value}{\mathtt{00.0}}\%

pin 3 output: HIGH

V_C=\htmlData{math-slot=value}{\mathtt{0.00}}\,\mathrm V\quad \htmlData{math-slot=state}{\text{charging}}

pin 3 (OUT)

diagnostic probe