Voltage regulator is a device used to provide a constant output voltage. Most of the circuits uses 5V supply. With a voltage regulator, LM7805 you can make your own 5V supply easily.

Lets look at voltage regulator 78xx family. The xx specifies the output voltage of voltage regulator. For example, 7805 means 5V output voltage, 7812 means 12V output voltage. There is also 79xx family which provides negative output voltage. 7905 would provide a -5V output voltage.

78xx series voltage regulators are easily obtained and economical. Some features of 78xx regulators:

– Output current up to 1A

– Thermal Overload Protection

– Short Circuit Protection

Pin Connection

By checking the datasheet, the dropout voltage is 2V. So your input must be at least 2V above your output voltage to get a constant output voltage.

Dropout Voltage

When using voltage regulator for heavier load which draws a lot of current from regulator, attach a heat sink so that the heat could be dissipated. Try not to use input voltage that are too high especially when your circuit is drawing quite an amount of current. The voltage regulator has to convert from a large input voltage to 5V. The voltage difference would end up as heat loss by P=IV.

Parts needed:

1x LM7805

2x 10uF electrolytic capacitor


1x 1N4001 diode (to allow current flow in one direction)

1x LED (indicator for power on)

1x 330ohm resistor (current limiting resistor for LED)

How to connect your voltage regulator:

ImageVoltage regulator on breadboard


Well, if you going to use 5V supply quite often while prototyping, you can consider making yourself a DIY breadboard supply soldered on a stripboard. I had made myself one which can be use by plugging in the DC supply adapter or a 9V battery.

Breadboard 5V supply on stripboard.


Video on constructing voltage regulator on breadboard.