12v positive negative dual power supply using LM7812, LM7912
A positive-negative power supply is used in electronic circuits that require both positive and negative voltages. For example, op-amps require both positive and negative DC voltage supplies to function properly. A negative voltage is one of a lower potential than its reference point. It is not possible to have an absolute voltage that is not referred to as a reference point. A negative voltage is used in some applications such as wired telephone lines from the local exchange to the Customer Premises equipment and the use of Amps for AC amplification. To design a 12V positive-negative dual power supply, You need to convert the 220V AC supply into 17V AC using a simple step-down transformer (220V/17V). The output of the transformer is given to the rectifier circuit, which will convert the AC supply into a DC supply. The output of the rectifier circuit that is DC contains the ripples in the output voltage. To filter out these ripples, two capacitors of 1000 uf, and 50V are used. The output of the capacitor that is pure DC is given to voltage regulators IC 7812 and IC7912 which will regulate the output voltage at 12V and -12V DC, despite the change in input voltage.
Circuit Diagram
Circuit Components
- Stepdown Transformer-01pc [See Buy Click Amazon]
- Voltage Regulator LM7812 -01pc [See Buy Click Amazon]
- Voltage Regulator LM7912 -01pc [See Buy Click Amazon]
- 1N4007 diode-06pcs [See Buy Click Amazon]
- Capacitor 1000uf,50v -04pcs [See Buy Click Amazon]
- Capacitor 10uf 50v-02pcs [See Buy Click Amazon]
- Resistor 22k ohm-02pcs [See Buy Click Amazon]
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Components used to Step down voltage converter:
- Step Down Transformer
- Voltage Regulator LM7812
- Voltage Regulator LM7912
- Diode 1n4007
- Capacitor,50V,1000uf
- Capacitor,10uf,50V
- Resistor 22k ohm
Using a transformer, electric energy can be moved from one AC circuit to another. A transformer uses the electromagnetic induction principle to either increase or decrease the AC voltage (step-up or step-down). To lower the power in the circuits of low-voltage devices like doorbells, transformers are frequently utilized.
This series of fixed-voltage integrated-circuit voltage regulators is designed for a wide range of applications. Input voltage 14.5v to 30v and output voltage 5v fixed. These applications include on-card regulation for the elimination of noise and distribution problems associated with single-point regulation. Each of these regulators can deliver up to 1.5 A of output current. The internal current-limiting and thermal-shutdown features of these regulators essentially make them immune to overload. In addition, to use as fixed-voltage regulators, these devices can be used with external components to obtain adjustable output voltages and currents and also can be used as the power-pass element in precision regulators.
The LM7912 series of 3-terminal regulators is available with fixed output voltages of −12V. These devices need only one external component—a compensation capacitor at the output. The LM7912 series is capable of supplying 1.5A of output current. These regulators employ internal current limiting safe area protection and thermal shutdown for protection against virtually all overload conditions. The low ground pin current of the LM79XX series allows the output voltage to be easily boosted above the preset value with a resistor divider. The low quiescent current drain of these devices with a specified maximum change with line and load ensures good regulation in the voltage-boosted mode
Diodes are used to protect circuits by limiting the voltage and also transform AC into DC. Semiconductors like silicon and germanium are used to make the most of the diodes.
1N4007 is a rectifier diode, designed specifically for circuits that need to convert alternating current to direct current. It can pass currents of up to 1A and have a peak inverse voltage (PIV) rating of 1,000 V.
The capacitor is a Two-Terminal passive component having the Property of Capacitance. This Property Electrifies (charging with electricity) Capacitors with input Voltage. Capacitors Condense Electricity, Hence it is also known as a Condenser. It consists of two Electrical Conductors that are Separated by Distance. The Capacitor Stores Charge and can act like a Battery. It is necessary for filter Circuits to Minimize voltage spikes, and Smoothing changes in voltage.
The capacitor is a Two-Terminal passive component having the Property of Capacitance. This Property Electrifies (charging with electricity) Capacitors with input Voltage. Capacitors Condense Electricity, Hence it is also known as a Condenser. It consists of two Electrical Conductors that are Separated by Distance. The Capacitor Stores Charge and can act like a Battery. It is necessary for filter Circuits to Minimize voltage spikes, and Smoothing changes in voltage.
Carbon Film Resistor.Value: 22k Ohm Wattage: 1/4W, Approximate Maximum Current: 21.13mA, Tolarence: ±5% Durable and easy to install small, low noise, precise and stable performance.Long service life.22k Ohm Resistor Color Code: Red-Red-Orange-Golden or Red-Red- Black-Red-Brown.
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Frequently Asked Questions:
Why use a positive negative power supply?
A positive-negative power supply is used in electronic circuits that require both positive and negative voltages. For example, op-amps require both positive and negative DC voltage supplies to function properly.
Where is a negative voltage used?
The negative voltage is one of lower potential than its reference point. It is not possible to have an absolute voltage that is not referred to as a reference point. A negative voltage is used in some applications such as wired telephone lines from the local exchange to the Customer Premises equipment and the use of Amps for AC amplification.
What is the maximum input voltage of LM7912?
LM7912 maximum input voltage is -30V.
Video: Circuit Test
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