Monostable

Monostable timers are often called one-shot timers.
When the timer is switched on it will stay on for a certain length of time and then stay off until it is switched on again.
The time period depends on the value of resistor R1 and capacitor C1.
When triggered by a suitable pulse at its input (pin 2) it switches from its stable state, in which the output is low, to its unstable state where its output is high. This state exists for a time controlled by the values of R1 and C1, and at the end of this period the output switches back to its stable (low) state. Its primary use is therefore to produce a set time delay, initiated by an input pulse (Fig1).
The duration of the period is calculated using the formula:
Time on (seconds) = 1.1 x R1 x C1
R1 is the value of resistor R1 (in ohms) and C1 is the value of the capacitor (in microfarads).
Have a go at building the circuit in Fig 2 and try altering the timing by altering the Variable Resistor and changing the value of the Capacitor.
Can you add Oscilloscope probes and measure the time delay?

Fig 1

In addition to a Prototype board (Breadboard), wire for connections and a power source, you will need the following components to build this circuit:
1 x 100KΩ Preset Potentiometer (Variable Resistor)1 x 100 µF Capacitor1 x 555 timer IC1 x 220Ω Fixed Resistor1 x 10KΩ Fixed Resistor1 x LED1 x Push To Make Switch (can be simulated by just using two wires to touch then release)

Fig 2

MonostableV2

Fig 3. PCB Layout

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