Build 5V regulated power supply from 9V DC adapter

Many different devices require DC power and thus, need something called an I.T.E power supply. ITE stands for “Information Technology Equipment” (Learn more here )

I had an iPod speaker system that no longer works. It came with a 9V adapter. Most of us, hobby electronics guys know very well that a regulated 5V DC supply is a must in our shack. My old 5V circuit was no longer working and so I decided to build one from the 9V adapter.

5V Regulated Power Supply

We need to safely convert the 9V output from the adapter to a 5V regulated output. The circuit on the left shows the one I have built.

The circuit is very simple needing only 4 components. Let me explain each component in detail.

  1. You first need a jack to enable the adapter connection. (See a power adapter here)
  2. Next you need a 0.33uF capacitor. Any type (electrolytic, polyester) will do. This we will use for input ripple filtering
  3. You now need an IC called LM7805. This is a very simplistic IC with only 3 pins; input, output and ground. An excellent IC to quickly create regulated power supplies. The IC numbering scheme is prettly simple.For 5V, you should get LM7805. For 9V you need to look at LM7809 and for 12V you should use LM7812. There is another set to get negative volts (so much for Op-Amps).So for -5V you should look for LM7905, -9V is by LM7909 and -12V is by LM7912. Here is the datasheet
  4. The last capacitor required at the output is 0.1uF (again, electrolytic or any other).

Please note, you need to find the right jack for your board based on the adapter jack size.

Also, while the capacitors are required, they do not need to be of the exact value. If you cannot find an exact value get something close from your junk box. The LM7805 circuit is given below.

Circuit Diagram for 5V Power Supply using LM7805

Circuit Diagram for 5V Power Supply using LM7805

Now simply solder the jack and make the connections as shown. From the jack power line, connect Pin-1 of the IC. Create a common ground and connect the jack ground and Pin-2 of the IC. At the input and output, solder the capacitors between the IC pins and the ground. You are done!

Warning: It is dangerous to play around with power. Unless you are properly qualified (meaning you know what you are doing), do not attempt anything outlined in this post. I will not be not responsible for your loss/damage.


5 thoughts on “Build 5V regulated power supply from 9V DC adapter

  1. Pingback: Controlling DC Motors using AVR Microcontrollers « Vishnu's Blogs

  2. I have 9vdc adaptor, and I use lm7805 to reduce it to 5vdc but d ic is very hot beyond heatsink. Can I get better circuit for it

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