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
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.
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
Optional:
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:
Voltage 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.
Video on constructing voltage regulator on breadboard.
Zx Lee 
What’s the maximum input voltage for 7805? Since you mention ‘try not to use input voltage that are too high’.
Well, according to the datasheet, its maximum rating input voltage is 35V. However, if you are using higher voltage, you are forcing the input voltage to go down to 5V. The voltage drop will turn into other kind of energy. So they will lose as heat, which will reduce the efficiency and you regulator may gets hot.
So what’s your recommend maximum input voltage?
What’s the difference between when you add a heat sink and not ? If you add it, the voltage regulator wont be that hot ? Is it ?
Thanks 🙂
Adding a heat sink to your regulator allows a larger surface area to dissipate the heat given off the regulator. If the heat can be dissipate well, it shouldn’t be that hot.
There is another 5V voltage regulator with lower dropout voltage – LM2940, you can try it =)
HAHAHAHA, but you know what, that regulator is very expensive !!!
Vick, save money for it! haha!
Hahaha, well, if I needed that I would buy it. But I dont think I need it so far 🙂
Thanks for the suggestion 🙂