The 555 timer is an Integrated Circit that is most commonly found as a DIP (Dual in Line Package) with 8 legs. It has many different different applications but it is primary use is often in trimming or oscillating circuits. In this example we are going to make a circuit that turns an output pin on and off rapidly so that a device such as a speaker can make sound by moving back and forward to create sound waves that we can hear.
- Identify all of the parts required for all three circuits bellow in the parts list:
- Before starting ensure power supply is not connected
- Use the Fritzing Breadboard Layout and Schematic Diagram images to connect the components with prototyping wires to complete
- Record findings in learning journal.
- If any component is getting hot disconnect the battery.
- Ensure a resistor is used in the circuit or LED will be burned out and damaged
- Ensure LED positive leg (longest) is connected to positive side of circuit
- Check battery voltage with multimeter in Volts DC mode
- Try a different LED in case it has been burned out (ensure you are using a resistor!)
- Look at breadboard picture bellow and ensure all connection are correct.
|VCC1||1||4.5V – 6V Battery Supply|
|R1||1||1k Ohm Resistor|
|R2||1||10k Ohm Resistor|
|R3-5||3||1K Ohm Resistor|
|C3||1||10uF Electrolytic Cap|
Fritzing Breadboard Layouts and Schematic Diagrams:
f = frequency in hertz (Hz), R1 & R2 = resistance in ohms (Ω), C1 = capacitance in farads (F).
To calculate the stylus touching position A:
R1 = 1kΩ = 1000 Ω
R2 = 10kΩ + 1kΩ = 11,000Ω
C1 = 10nF = 0.01uF = 0.0000001 F
f = 1.4 / ((R1 + 2 x R2) × C1)
f = 1.4 / (1000 + 2 x (11,000)) x 0.0000001
f = 1.4 / (23,000) x 0.0000001
f = 1.4 / 0.0023
f = 608.7 Hz
Try calculations for Position B and C.
Extra Teaching Material:
- What happens when you add a second capacitor of the same value in parallel to C1.
- What happens as you add more resistance to R2 in series? Why?
- Use an instrument tuner (or mobile app) to listen to the sound that is being generated and determine the frequency. Some multimeters can also measure frequency
- Consider why the results of the formula does not have exactly the same frequency results as the measured frequency?
Finished? Lets have a go at the Solder the Stylophone Project