I created a simple circuit using the LM317 to output 3.3 volts from a 5V or greater input voltage. Why? Because, a number of modules for the Arduino (or Pinguino) take 3.3 Volts. It’s true, some of the Arduinos do have a 3.3V voltage regulator (and thus a source of 3.3V), however, that might not have sufficient amperage. Also, if you are a fan of the DIY (Do-It-Yourself) Pinguinos (as I am), you will need a 3.3V source to accompany them since they do not have one.
So, it is quite handy to have a 3.3V power source around! Here is what the circuit looks like:
I save the foam pads, that came with PC motherboards I bought, and cut out pieces to place under the circuits I make to protect against short circuits. The pads are held in place with two-sided sticky tape.
Here Is the Fritzing circuit diagram:
If you’d like the Fritzing source to the above diagram, download it from here.
The LM317 is an adjustable linear voltage regulator. It can take an input voltage of 3-40 Volts DC and outputs a fixed voltage from 1.2 to 37 Volts DC. The output is controlled by resistors on the adjustment pin. Here is a handy calculator to calculate the resistance needed to obtain the desired output voltage. I use 545 Ohms (470 + 75) to output the desired 3.3V.
Notice that I have a two pin header or a power jack as input source (on the right of the pictures) and the output is a two pin header (on the left in the pictures).
I thought about integrating this circuit on the DIY Pinguino boards I made and might do that next time I get around to making more of them. However, I think the stand alone circuit is more flexible to use. For example, you can attach a USB to RS-232 cable (like this):