Power amplifier electronic circuits-tube audio rf amplifiers

Electronic Amplifier Circuits-Power amplifier, audio amplifier designs and circuits

May 24th, 2010

Automatic Car Head Lights Turn-off Circuit

Circuit Description

The circuit diagram of Automatic head lights turn off circuit has been explained here. This circuit can be installed in a car so that it will automatically turns off the head light after a certain time after ignition switch has been turned off. The time duration for which the light should burn can be set by the end user. If this particular circuit is used in a car, the user can walk out easily from the dark garage in the light from head lamp of the car.

NE 555 timer IC is the heart of this circuit. The voltage from battery is fed to the relay through diode D1 when the ignition is switched on. It produces a negative pulse at the pin2 of timer IC when ignition is switched off. Then the output of timer becomes high for a certain time determined by resistor R1. This triggers the transistor Q1 into conduction and relay is energized and that drives the head light. When the preset time exceeds, the head light goes off.

Circuit Diagram

Automatic Car Head Lights Turn-off Circuit

Automatic Car Head Lights Turn-off Circuit

Notes

  • Use a good quality PCB or common board to assemble this circuit.
  • User can easily set the timing by fitting the potentiometer on somewhere on the dashboard of the car.
  • With the value of components used you can make a setting from 10 S to 60 S.
May 24th, 2010

Simple Photo Switch Circuit

Circuit Description

The circuit diagram given here is a photo switch which switches on a relay when the intensity of light falling on its sensor changes from a preset limit. The central part of this circuit is the IC NE 555 and two transistors Q1 (BC 548) and Q2 (SL 100). The transistors Q1 and Q2 are used here as driving elements for relay. The voltage across LDR is kept at 1/3 of the supply voltage by adjusting the potentiometer R2 (100K). The output of IC is high at this stage. This makes transistor Q1 turn on and Q2 will be in off state since its base is connected to the collector of Q1. As a result of this, relay will be put into inactive state. The voltage across LDR increases when light falls on it. When this voltage crosses 2/3 of the supply voltage, the output of IC goes high. By the effect of this, relay will get activated. That is relay works with respect to the intensity of light falling on LDR.

Circuit Diagram

Photo Switch Circuit

Photo Switch Circuit

Notes

  • Use a good quality PCB or common board to assemble this circuit.
  • This switch is suitable for home as well as industrial purposes.
  • Use a 12V DC supply for powering this circuit.
May 24th, 2010

Power Supply Circuit Using LM 317 IC

Circuit Description

The circuit diagram 40V 2A power supply circuit has been described here. The central part of this circuit is the voltage regulator IC LM 317. This power supply circuit is ideal for circuits such as power amplifier circuit can deliver a current of 2A. In this circuit the transistor Q1 acts as pass transistor for increasing current capability. The output voltage is set to 40V by using resistors R5 and R8.

Parts List

Resistors: R1 (39 ohm 1 or 2W Resistor), R2 (22 ohm 1/4W Resistor), R3 (68K 1/4W Resistor), R4 (220R 1/4W Resistor), R5 (47K 1/2W Resistor).

Capacitors: C1 (3300µF 50V Electrolytic Capacitor), C2, C5 (100nF 63V Polyester Capacitors), C3 (10µF 63V Electrolytic Capacitor), C4 (220µF 50V Electrolytic Capacitor).

Active Components: D1 (Diode bridge 4A), D2 (1N4002 Diode), D3 (LED any color), U1 (LM317), Q1 (TIP42A Transistor), T1 (230V Primary, 40V 2A, Secondary, mains transformer).

Circuit Diagram

Power Supply Circuit Using LM 317 IC

Power Supply Circuit Using LM 317 IC

Notes

  • Use a good quality PCB to assemble this circuit.
  • Use four 1N 4007 Diodes if Diode Bridge is not available.
  • If you want any other out put voltage use a 10 K pot instead of R5 and adjust it.