Automatic Loudness Control Circuit

This is a simple design for automatic loudness control in audio. A simple approach to this problem can be done inserting a circuit in the preamplifier stage, capable of varying automatically the frequency response of the entire audio chain in respect to the position of the control knob, in order to keep ideal listening conditions under different listening levels. This is a figure of the circuit.


The circuit is shown with SW1 in the "Control-flat" position, i.e. without the Automatic Loudness Control. In this position the circuit acts as a linear preamplifier stage, with the voltage gain set by means of Trimmer R7. Switching SW1 in the opposite position the circuit becomes an Automatic Loudness Control and its frequency response varies in respect to the position of the control knob by the amount shown in the table below. C1 boosts the low frequencies and C4 boosts the higher ones. Maximum boost at low frequencies is limited by R2; R5 do the same at high frequencies.

This is a list component that must using for built the circuit.
P1 10K Linear Potentiometer (Dual-gang for stereo)

R1, R6, R8 100K 1/4W Resistors
R2 27K 1/4W Resistor
R3, R5 1K 1/4W Resistors
R4 1M 1/4W Resistor
R7 20K 1/2W Trimmer Cermet

C1 100nF/63V
C2 47nF/63V
C3 470nF/63V
C4 15nF/63V
C5, C9 1µF/63V
C6, C8 47µF/63V
C7 100pF/63V

IC1 TL072 Dual BIFET Op Amp

SW1 DPDT Switch (four poles for stereo)

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Automatic LED Emergency Light Circuit

This is one of the most cost effective (cheap) and simple emergency light circuit developed for CircuitsToday – This is an automatic emergency lamp with day light sensing, means it senses darkness/night and turns ON automatically. Similarly it senses day light and turns OFF automatically.

A simple emergency lamp which does not require any special equipment; even a multimeter to assemble and use. Any individual who can do a good quality soldering must be able to build this circuit successfully. This can be easily accommodated in the defunct two 6 watt tube National Emergency Lamp or any PL tube type emergency lamp. The difference will be in the working; it will work non stop for more than 8 hours. Deep discharge is taken care by the LED characteristic and over charge protection is taken care by the fixed voltage regulator.This uses a simple 3Pin fixed regulator which has a built in current limiting circuit. The only required adjustment is the preset which has to be set to ensure the LEDs just light up (it should be left at that position). The 5mm LDR is just mounted on top of the emergency light as shown in the photograph. LDR is used to avoid it lighting up during day time or when the room lights are ON. 2 LEDs are used in series; the dropping resistance is avoided and 2 LEDs light up with current that is required for a single LED,  by which energy is saved to a great extent.

Circuit diagram :

 

Simple Emergency Light Circuit Diagram

Note:

This circuit is developed by Mr.Seetharaman for readers of CircuitsToday. This particular circuit has been kept so simple for people who has limited access to components or in other words this is an emergency light that you can build with minimum components. In addition to circuit diagram, He has shared photographs of the prototype he made in National emergency light and a PCB design.

Source :www.circuitstoday.com

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Automatic Loudness Control Circuit

This is a simple design for automatic loudness control in audio. A simple approach to this problem can be done inserting a circuit in the preamplifier stage, capable of varying automatically the frequency response of the entire audio chain in respect to the position of the control knob, in order to keep ideal listening conditions under different listening levels. This is a figure of the circuit.


The circuit is shown with SW1 in the "Control-flat" position, i.e. without the Automatic Loudness Control. In this position the circuit acts as a linear preamplifier stage, with the voltage gain set by means of Trimmer R7. Switching SW1 in the opposite position the circuit becomes an Automatic Loudness Control and its frequency response varies in respect to the position of the control knob by the amount shown in the table below. C1 boosts the low frequencies and C4 boosts the higher ones. Maximum boost at low frequencies is limited by R2; R5 do the same at high frequencies.

This is a list component that must using for built the circuit.

P1 10K Linear Potentiometer (Dual-gang for stereo)

R1, R6, R8 100K 1/4W Resistors
R2 27K 1/4W Resistor
R3, R5 1K 1/4W Resistors
R4 1M 1/4W Resistor
R7 20K 1/2W Trimmer Cermet

C1 100nF/63V
C2 47nF/63V
C3 470nF/63V
C4 15nF/63V
C5, C9 1µF/63V
C6, C8 47µF/63V
C7 100pF/63V

IC1 TL072 Dual BIFET Op Amp

SW1 DPDT Switch (four poles for stereo)

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AUTOMATIC AIRFLOW DETECTOR ELECTRONIC DIAGRAM

AUTOMATIC AIRFLOW DETECTOR ELECTRONIC DIAGRAM

Sensor used in this circuit is a bulb filament. If there is no airflow, the filament resistance would give low value. On the other hand, if there is airflow, the filament resistance would varies. The variation of the resistance is caused by the heat difference between filament. It also effects to the voltage variation passing through that filament. That voltage difference will be processed by LM339 op-amp and displayed by the LED.

Parts list :

•     LED1 : LED 5mm
•     IC1 volt regulator : LM7805
•     Polar Capacitor C1 : 47 uF/15V
•     Resistor R1 : 100 ohm
•     Resistor R2 : 470 ohm
•     Resistor R3 : 10k ohm
•     Potensiometer R4 : 100k ohm
•     Resistor R5 : 1k ohm
•     IC2 op-amp : LM339
•     Bulb filament
•     Power supply/battery 12V

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