Variable Voltage Regulators

Here is a simple variable voltage regulator circuit using LM317 and LM337 ICs

Components Required:

1) Breadboard

2) 1Amps Fuse

3) 15 - 0 - 15 center tapped Transformer

4) 1N4007 diode = 4

5) 2200uf capacitor = 2

6) 100nf capacitor = 2
7) 150 ohm resistor = 2
8) 3.9 kilo ohm Potentiometer (POT) = 2

9) LM317 Positive Voltage Regulator IC

10) LM337 Negative Voltage Regulator IC

Explanation for Dual Voltage Regulator:

• Connect the circuit as shown in the circuit diagram below.
• The output of the center tapped transformer is AC voltage.
• Voltage between the center and anyone of the other terminal gives +15Volt AC, Voltage between the two outer terminals gives +30Volt AC.
• Connecting in center tapped pattern gives +15Volt AC across terminals 1 & 2 and gives -15Volt AC across terminals 3 & 2.
• Four 1N4007 diode connected as shown below forms a bridge circuit which converts bidirectional AC into unidirectional DC.
• The converted signal is not pure DC, it still consists of some AC signals.
• The 2200uf capacitor is used as a filter, which allows only DC to pass through..
• LM317 Voltage Regulators are used for Adjustable Positive voltage values & LM337 Voltage Regulators are used for Adjustable Negative voltage values.
• LM317 and LM337 consists of three terminals namely regulated output voltage, adjustable terminal and unregulated input voltage.
• +15Volt DC input goes to LM317 and -15Volt DC input goes to Lm337, which gives +1.5 to +13Volt and -1.5 to -13Volt regulated DC output.
• Output of the regulator produces noise which can be removed using 100nf capacitor, which acts as a filter.

Circuit Diagram:

Figure 1: Variable Dual Voltage Regulator using LM317 & LM337 Circuit simulation made in Multisim

Explanation for Single Voltage Regulator:

• Connect the circuit as shown in the circuit diagram below.
• The output of the center tapped transformer is AC voltage.
• Voltage between the two outer terminals gives +30Volt AC.
• Four 1N4007 diode connected as shown below forms a bridge circuit which converts bidirectional AC into unidirectional DC.
• The converted signal is not pure DC, it still consists of some AC signals.
• The 2200uf capacitor is used as a filter, which allows only DC to pass through..
• LM317 Voltage Regulators are used for Adjustable Positive voltage values.
• LM317 consists of three terminals namely regulated output voltage, adjustable terminal and unregulated input voltage.
• +30Volt DC input goes to LM317, which gives +1.5 to +28Volt regulated DC output.
• Output of the regulator produces noise which can be removed using 100nf capacitor, which acts as a filter.

Circuit Diagram:

 

 Figure 2: Variable Voltage Regulator using LM317 Circuit simulation made in Multisim