The Capacitor is a little bit like a battery as it is used to store and release electricity. They are generally used in circuits for two main functions:
1. As a filter – When AC signals are directed to a capacitor it takes a certain amount of time to charge and discharge resulting in a more consistent voltage on the other side of the capacitor.
2. As a timer – When a capacitor is used in a circuit with a resistor you can use an equation to predict the amount of time the capacitor will take to charge and discharge. By selecting specific values you can make basic timing circuits.
- Identify all component needed in the parts list bellow
- Use the Breadboard layout and Schematic diagram to connect all components except battery power supply.
- Double check all components are in the correct location and orientation (especially capacitors, transistors and LEDs)
- Connect power supply. If circuit works check components do not get hot. If circuit does not function disconnect power supply and diagnose problems.
- When circuit is flashing at an even rate try swapping the capacitors with the smaller 10uF Electrolytic Capacitors.
- Next try adding an extra 10K or 22K resistors in series to the negative side of the capacitor
- Record your finding in your 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|
|R1-2||1||330 Ohm Resistor|
|R3-4||1||22K Ohm Resistor|
|LED1||1||Red LED 5mm|
|LED2||1||Green LED 5mm|
|Q1-2||2||NPN Transistor BC546|
|C1-2||2||100uF Electrolytic Capacitor|
Fritzing Breadboard Layout and Schematic Diagram:
Note: the following circuit uses transistors with a CBE pin configuration (please ensure you are using BC546 transistors (see transistor page for more details).
Finished? Check out the review page before your exam!