Fixed Voltage Regulators

Here is a simple Fixed voltage regulator circuit using 7805 and 7905 voltage regulator ICs

Components Required:

1) Breadboard

2) 1Amps Fuse

3) 9 - 0 - 9 center tapped Transformer

4) 1N4007 diode = 4

5) 2200uf capacitor = 2

6) 100nf capacitor = 2

7) LM7805 Positive Voltage Regulator IC

8) LM7905 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 +9Volt AC, Voltage between the two outer terminals gives +18Volt AC.
• Connecting in center tapped pattern gives +9Volt AC across terminals 1 & 2 and gives -9Volt 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..
• 78XX Voltage Regulators are used for Positive voltage values and 79XX Voltage Regulators are used for Negative voltage values.
• Here i have used +5Volt and -5Volt Voltage Regulator ICs ie) 7805 and 7905.
• 78XX and 79XX consists of three terminals namely unregulated input voltage, ground and regulated output voltage.
•  +9Volt DC input goes to 7805 and -9Volt DC input goes to 7905, which gives +5Volt and -5Volt 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: Fixed Dual Voltage Regulator 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 center and anyone of the other terminal gives +9Volt AC, Voltage between the two outer terminals gives +18Volt 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..
• 78XX Voltage Regulators are used for Positive voltage values and 79XX Voltage Regulators are used for Negative voltage values.
• Here i have used +5Volt Voltage Regulator IC ie) 7805. Similarly we can replace 7805 with 7905 to get -5Volt regulated output.
• 78XX consists of three terminals namely unregulated input voltage, ground and regulated output voltage.
•  +9Volt DC input goes to 7805, which gives +5Volt regulated DC output.
• Output of the regulator produces noise which can be removed using 100nf capacitor, which acts as a filter.
• For other voltage values we can simply replace 7805 with the corresponding 78XX or 79XX Voltage Regulator ICs.

Circuit Diagram:

 

Figure 2: Fixed Single Voltage Regulator Circuit simulation made in Multisim