After receiving so many hits on this particular page I decided to update this page to provide the most accurate content possible. This tutorial is using the LM7805 Voltage regulator to take a 12 volt source down to 5 volts. This has many applicable uses, one of which being the Arduino micro-controller.

The Arduino operates at 1.8 volts to 5 volts and since most of the projects I work on require the ATMega328 chip it was important to properly regulate voltage. For my particular instance I am hooking the Arduino up to a 12 volt car battery to power a Knight Rider chase effect that I have come up with to implement on a friend of mines old firebird. One problem in particular with a car battery is that its not a constant voltage and sometimes can operate at up to 15 volts. Fortunately using the LM7805 and a couple of capacitors we can regulate a steady voltage to our project.

Now I am using this for an Arduino, however, this can be applied for many applications and I tend to see this particular regulator used a lot in automobiles.

Well lets get started
If you are unfamiliar with the LM7805 this is what it looks like...pretty simple huh



Your 12 volt power source will have its positive lead plugged into the INPUT pin on the LM7805, but lets not get into that right now I have a step by step on hooking up a voltage regulator.



Here is the datasheet for the LM7805 - lm7805.pdf

Here is what I will be using in this project. Now I should have used a 100uF capacitor as well as a 0.1uF capacitor but when I was building this tutorial they were still in the mail so I had to improvise.

• LM7805
• 1000uf 16v capacitor
• 100uf 50v electrolytic capacitor
• 1 resistor and 1 LED
• 12 volt dc power source
• Digital Multimeter
• Breadboard

Now that you have a parts list lets start putting putting it all together.

First we want to hookup the LM7805 to our breadboard. I had some spare parts laying around and found a heat sink that fit perfectly so I put it on mine. If properly hooked up it doesn't emit a whole lot of heat but I had one laying around so I placed in on their.


Now add the positive wire from your 12volt source to the INPUT pin on the LM7805 like so


Now lets put in the 1000uf 16volt capacitor, paying close attention to polarity. Mine has a minus symbol on the negative side, so plug the positive(unlabeled) side into the same row as the INPUT pin and place the negative lead of the capacitor into the row of the COMMON pin of the LM7805 like so
*The side facing camera is positive in mine*

Alright now take a wire and place one side in the same row as the OUTPUT pin and the other end goes into the long positive row.
*It may look like it is plugged into the negative row but it is actually in the positive row, see later pictures for more clarity*

Here is how the second capacitor should be hooked up. This is setting up a filter capacitor and get wired according to the schematic at the top of this page.


Wiring an led to work with 5 volts.


Wiring the common pin for the LM7805. Attach the Common pin to the long negative rail.


Now that you have everything wired up, lets try it out...ensure that your capacitors are of proper values for your project. Of course make sure that you have your negative lead from your 12 volt source plugged into the long negative rail.


Lets add two additional cables to test our voltage.


Make sure that you have your digital multimeter for correct voltage. I am using 12volts so 20 is the closest value while still being above.


Try it again and as long as your connections are good it should look similiar =)



I have tried to make this a step-by-step tutorial and I hope that it is easy to follow and descriptive enough to explain what needs to happen...If you have any questions feel free to post them and hopefully I will be able to help, if not I am sure other users will be able to!!