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Component 2: Timing circuits

3 dot points across 3 inquiry questions. Click any dot point for a focused answer with worked past exam questions where available.

How does a 555 astable generate a continuous stream of pulses, and how do we find its frequency and mark-space ratio?

The 555 timer in astable mode: how it produces a continuous square-wave output, the equations for frequency and period, and the meaning and calculation of the mark-space ratio.
A focused answer to WJEC Eduqas GCSE Electronics on the 555 astable timer, covering how it produces a continuous square-wave output, the equations for frequency and period, and the mark-space ratio.
10 min answer →

How does a 555 timer produce a single pulse of a set length?

The 555 timer in monostable mode: how it produces a single output pulse of fixed duration when triggered, and the equation for the pulse duration in terms of the timing resistor and capacitor.
A focused answer to WJEC Eduqas GCSE Electronics on the 555 monostable timer, covering how it produces a single output pulse of fixed duration when triggered, and the pulse duration equation in terms of the timing resistor and capacitor.
9 min answer →

How does a capacitor charge and discharge through a resistor, and how does this create a time delay?

The capacitor and the resistor-capacitor (RC) network: how a capacitor charges and discharges through a resistor, the shape of the voltage-time curves, and how the RC combination produces a time delay.
A focused answer to WJEC Eduqas GCSE Electronics on RC charging and discharging, covering how a capacitor charges and discharges through a resistor, the shape of the voltage-time curves, and how an RC network creates a time delay.
9 min answer →