Instructables

Triple Power Supply and Charger with Digital Monitor

Picture of Triple Power Supply and Charger with Digital Monitor
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This idea is based on an unregulated wall adapter/ transformer with DC voltage of 9V/300mA for regulating three outputs of voltage: 5V, 9V and 12V.  However, the unregulated output transformer is about 15Volt for supplying it to each input of the three regulators (Fig. #1).  Remember that you can use an unregulated wall/adapter from 9V to 15V for obtaining an input in the voltage regulators from 15V to 25V respectively and so with a good selection of amperage in your unregulated wall/adapter, you can use this electronic device as a charger too.

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.
 
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braulio777 (author) 1 year ago
Once you set the knob in the rotary switch, it should be with the line marked on the knob by pointing the first position or the beginning of the rotary switch without turning it and with this you will read 5Volt on your panel meter. For the following two positions, you will read in order 9 and 12Volt on your screen.
Thank you for your comments
Your schematic does show where the switch and screen hook up to.
Is it possible obtain 12 volts from a 9 volts battery using a 7812? I don't need at least 14 volts to obtain 12 voslts from a a 7812?
braulio777 (author)  ivancircoski1 year ago
No, you need at least 2Volt more of the voltage that you want to regulate because it's impossible by taking 12 apples where there are 9 apples only.

You can get a higher voltage from a lower input voltage but you need to use a DC to DC converter circuit. Which is different than a linear voltage regulator. The "Joule Thief" projects on this site are one way people do it. It is a simple switch mode power supply.
Its not even possible for a 7809 to produce 9V with only 9V going into it.
braulio777 (author)  mpilchfamily1 year ago
You need at least 2Volt more in its input for obtaining the adequate voltage. It's important to note that the project's diagram shows a common connection for all inputs of the voltage regulators. Then all of regulators receive the same voltaje or about 15Volt.
I would suggest actually giving some written instruction in all steps. The pictures don't always speak for themselves. If you want to have something featured or get a lot of attention you need to have a good writeup to go with it.

If your basing this on a 9V wall wart how do you expect to get 9V and 12V on the output. The 7809 needs a minimum input voltage of 11.5V to be able to produce 9V on the output. The 7812 needs a minimum of 14.6V to produce 12V on the output. There is no way the 9V wall wart will support those voltages.
braulio777 (author)  mpilchfamily1 year ago
As the wall adapter/transformer is an unregulated one and its output is about 15Volt, it can regulate 12V. Also, there is a common connection for all of inputs of the voltage regulators (check the project's diagram). Therefore, all of regulators receive enough voltage for regulating its output correctly.
BTW if you have measured the wall wart with a meter and your getting 15V that is what it outputs when it doesn't have a load. I suspect that is what your basing all of this on. Had you mentioned that in the writeup then it would prevent some confusion. But you need to understand that when you put a load that is within 75% of the max available amperage from the wall wart it will only output 9V. So your circuit will not work on the 9V and 12V settings.