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5V Regulated Power Supply Circuit (LM7805)

2015-03-17 05:40  
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This article describes a 5V Regulated Power Supply Circuit (LM7805). The principle is very simple, very practical. The circuit components can help you understand better grasp this principle. For example, in this circuit, you can go to find and buy these components: LM7805.

Simple 5V power supply for digital circuits

This circuit is a small 5V power supply, which is useful when experimenting with digital electronics. Small inexpensive wall tranformers with variable output voltage are available from any electronics shop and supermarket. Those transformers are easily available, but usually their voltage regulation is very poor, which makes then not very usable for digital circuit experimenter unless a better regulation can be achieved in some way.

The following circuit is the answer to the problem. This circuit can give 5V output at about 150 mA current, but it can be increased to 1 A when good cooling is added to 7805 regulator chip. The circuit has overload and thermal protection. The capacitors must have enough high voltage rating to safely handle the input voltage feed to circuit. The circuit is very easy to build for example into a piece of veroboard.

Circuit diagram:

Figure:1 5 Volt DC Power Supply Circuit Diagram

Figure 1 5 Volt DC Power Supply Circuit Diagram


C1 = 100uF-25V electrolytic capacitor, at least 25V voltage rating
C2 = 10uF-25V electrolytic capacitor, at least 6-16V voltage rating
C3 = 100nF-63V ceramic or polyester capacitor
IC = 7805 regulator IC

IC’s Pinout :

Unregulated voltage inGround (See Diagram)Regulated voltage out


Circuit features:

Gives out well regulated 5V output, output current capability of 100 mABuilt-in overheating protection shuts down output when regulator IC gets too hotVery simple and easy to buildVery stable 5V output voltage, reliable operationEasy to get components, uses only very common basic componentsBased on datasheet example circuit, I have used this circuit succesfully as part of many electronics projectsPart of electronics devices, small laboratory power supplyWide range of input unreglated DC 8-24V power supplyFew dollars for the electronics components the input transformer cost


More output current:

If you need more than 150 mA of output current, you can update the output current up to 1A doing the following modifications.Change the transformer from where you take the power to the circuit to a model which can give as much current as you need from output
Put a heatsink to the 7805 regulator (so big that it does not overheat because of the extra losses in the regulator)

More output voltages:

If you need other voltages than 5V, you can modify the circuit by replacing the 7805 chips with another regulator with different output voltage from regulator 78xx chip family. The last numbers in the the chip code tells the output voltage. Remember that the input voltage muts be at least 3V greater than regulator output voltage ot otherwise the regulator does not work well.



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