VARIABLE POWER SUPPLY 1.5-24V

This simple circuit is bridge rectifier circuit can be used to power the circuits described in my previous blogs. The main  components required are listed

• 240/24 V 1A Transformer
  
• LM317 Voltage Regulator
  
• IN4001/4007 Diodes
  
  
  
• Potentiometers/variable resistors
  
• Resistors
• Capacitors
• Breadboard or PCB
  

CIRCUIT DIAGRAM

              The transformer is used to step down the 240V AC supply to 24V. Bridge rectifier converts this AC to the Direct Current. This pulsating DC is filtered using the capacitor to get a clean DC and is given to the input of LM317 voltage regulator IC. Depending on the variations in the potentiometer the output gets varied. It is necessary to use a heat sink along with the IC because it became hot while the operation.

AUDIO AMPLIFIER USING TDA2003 IC

This is a simple audio-frequency (AF) amplifier using the amplifier IC TDA2003.  The main components are

• TDA2003 IC
  
• 10K Pot
  
• 8 ohm loudspeaker 
  
• Resistors 
• Capacitors
• Power Supply 6V
• Breadboard or PCB
  

The circuit diagram shown below 

            The IC can easily deliver 10W to a 4 Ohms load at 18V DC supply voltage. The IC can be also operated from 12V and that makes it applicable in car audio systems. The useful features of TDA2003 include short circuit protection between all pins, thermal overload protection, low harmonic distortion, low cross over distortion etc.

7 SEGMENT DISPLAY COUNTER CIRCUT

It is a simple circuit to drive the 7 segment display. The circuit consist of a 555 timer IC and CD4033 counter IC. The main components required are

• CD4033 counter IC
  
• 555 timer IC
  
• 7 Segment Display
  
• Resistors
• Capacitors
• Bread board or PCB
  
• A suitable power supply of 5V DC

     CIRCUIT DIAGRAM

                 The working of the circuit as same as mentioned in my Running LED project. The 555 Timer is used in astable mode of operation and the generated clock pulse is given to the clock input of the counter IC. You can also implement the circuit using CD4017 IC. The circuit and calculations are same as in my Running LED project. 

CRYSTAL TESTER

Crystal is used as an oscillator, to generate a high frequency. In all the major electronic projects crystal is used instead of coil. Using this circuit you can analyse that your crystal working or not.The main components are

• BC550 Transistor 
  
• IN4007 Diodes
  
• LED
  
• Reistors(Values are specified)
• Capacitors(values are specified)
• Breadboard or PCB
  

CIRCUIT DIAGRAM

                 This electronic circuit consists of a crystal oscillator, two capacitors and a transistor forming a Colpits oscillator. A combination of diodes and capacitors are used for rectification and filtering respectively. Another NPN transistor is used as a switch to make the LED glow.

                The entire circuit is operated with two transistors, two diodes, and few passive components. If the testing crystal is good then it operates as an oscillator in combination with transistor. The diode rectifies the output of the oscillator and the capacitor filters the output. This output is now fed to the base of the transistor and the transistor starts conducting.

                 An LED is connected to the collector of the transistor through the resistor. The LED gets proper biasing and starts emitting light, i.e. it starts glowing. In case if any fault occurring in the testing crystal then the LED does not glow.