The Power is equal to Voltage times Amperage. That is, P=VxA=Watts
For example, if you need to your cell phone 5V, 0.7A,, you will require 5x 0.7= 3.5Watts. Then, your wall/transformer should be of at least 3.5 Watts.
Also, the DC Power Plug or Jack should be connected of the form as it's showed in the Fig. #2 for drawing the terminal positive and negative.
It's important you realize that kind of unregulated transformer you are using for reading its specifications because the type of transformer must be with center positive for matching with the connection of the DC Power Plug or Jack of this project.
In contrary case, you should invert the connections of the DC Power Plug or Jack. That is, if you have an unregulated transformer with center negative, the terminal negative will be at center by having that invert the current connections for looking as in Fig. #4.
Let me show through a sign in the Fig. #4 that those connections aren't used in this project.
But, for this project is used an unregulated transformer of center positive (Fig. #3) that match with the connections propose and showed on the Fig. #2
Although the power jack looks of natural way in the picture showed after the fig.#4, in the last picture showed in this step we can note the identification of the connectos are A, B and C for connecting A and B as terminal negative and C corresponds to the terminal positive of our power jack male cited.
Step 1: Bill of Materials
3 Heat sink, TO-220
1 7805, 1A
1 7809, 1A
1 7812, 1A
1 Switch Rotary Shaft Solder Lug 4 pole, 3 position or any 3 position with 2, 3 or 4 poles.
1 Knob, 1/4" shaft, 24mm, black, w/set screw
1 Jack, DC power, male
1 AC/DC unregulated wall adapter/transformer (9V, 12V or 15V) from 200mA to 2A and it matched with your needs of Power.
1 Panel Meter, LED Voltage, Blue, 4.5-30Volt, 3-Digit, Jameco Part: 2152323
2 Connector terminal block 2 position
4 .1microF, 50V ceramic capacitor
3 Capacitor, Radial, 1microF, 25V
Or, you can eliminate the 2 Connector terminal block 2 position while you add a slide switch and an enclosure for your project.
Step 2: Install the Jack DC Power Male
Th rest of the pictures show as mounting the component on the PCB.
Or, you can leave free the component for being connected with the slide switch.
Step 3: Install the Voltage Regulators and Capacitors
These voltage regulators receive the same voltage that is about 15 Volt, such voltage is the input supplied to each voltage regulator by the AC/DC wall adapter/transformer.
Of this manner, the regulators provide through their outputs the voltages of 5, 9 and 12 V because they count witn the enough voltage for regulating it and obtaining the adequate output accords to this project..
Step 4: Install the Heat Sinks and Connector Terminal Blocks
Step 5: Wire the Rotary Switch and Panel Meter
When you select the first scale with the rotary switch, you select 5Volt and can read 5Volt on the panel meter.
The first scale is defined with a line on the knob that is the first position in this type of switch while the second scale once selected with rotary switch will permit to read 9Volt on the panel meter.
Finally, the last scale or third position defined by the line marked on the knob we will permit to read 12Volt on the panel meter.
Step 6: Complete Your Project
Once you assemble the whole project, you need to plug in the AC/DC wall adapter/transformer into the power jack male.
Next, you have to plug in the AC/DC wall adapter/transformer into your home AC power supply.
Or, you can use a PCB smaller than that you are using now.
Step 7: Use DC 5V, 9V and 12V
If you want to read 5V on the panel meter, you should select the first position of your rotary switch.
If you want to read 9V on the panel meter, you will have to select the following scale of your rotary switch.
If you want to read 12Von the panel meter, you will select the third position of your rotary switch.
And complete your project!!!