LM317 to output 3.3 Volts

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 tested this circuit using the ESP8266 and the NL6621-Y1 modules that I wrote about in earlier articles. These modules require 3.3V and both worked fine.

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):

directly to the circuit (5V Input and GND) and to the wireless module (Tx and Rcv from the cable, 3.3V and GND from the circuit)  and not even need an Arduino / Pinguino.