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Astables produce pulsed outputs. They are often used to control flashing lights and audible outputs such as buzzers.
The number of complete pulses produced per second is called the frequency. Frequency is measured in hertz (Hz).
The length of time taken for one pulse is called the duration of the pulse, T. The ratio of time on to time off for a pulse is known as the mark/space ratio see Fig 1.
Astables can be used as the input to other circuits such as counters.
The number of complete pulses produced per second is called the frequency. Frequency is measured in hertz (Hz).
The length of time taken for one pulse is called the duration of the pulse, T. The ratio of time on to time off for a pulse is known as the mark/space ratio see Fig 1.
Astables can be used as the input to other circuits such as counters.
Fig 1.
An astable device is one which has no stable states. This means that it changes constantly from one state to another e.g. on/off, high/low, until it runs out of energy.
The diagrams below show a 555 IC set up as an Astable. You can see a circuit diagram (Fig 2) and a breadboard layout (Fig 3).
The diagrams below show a 555 IC set up as an Astable. You can see a circuit diagram (Fig 2) and a breadboard layout (Fig 3).
Fig 2
The 555 circuit shown here produces a mark/space ratio of 1:1, which means that it is off for the same amount of time it is on.
The pulse frequency and duration depend upon the values of the resistor and capacitor.
See if you can build the Astable circuit onto a breadboard and test it with the 9V battery or a suitable DC Power Supply.
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 10 µF Capacitor1 x 555 timer IC1 x 220Ω Fixed Resistor1 x LED
The pulse frequency and duration depend upon the values of the resistor and capacitor.
See if you can build the Astable circuit onto a breadboard and test it with the 9V battery or a suitable DC Power Supply.
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 10 µF Capacitor1 x 555 timer IC1 x 220Ω Fixed Resistor1 x LED
Astable1.mp4
Astable 555 Circuit Software Simulation
https://www.tinkercad.com/things/lLnwdGxcFgF-astable/editel - if you want to tinker. Save yourself a copy and play around with the circuit.
Could you neaten up the connections?
How could you add more LED's?
Does Series and Parallel make a difference when adding LED's?
PCB Layout
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