1 3.3V power supply

5V is commonly used in powering memory devices, sensors, microcontrollers ,USB, and other devices specially in computers. But not all of these devices uses 5V, some of these devices also uses 3.3V as a supply. We decided to design simple power supply circuits that can output 3.3V.

Regulated 3.3V using LM317
Among the power supplies presented here, this is a well regulated type that can deliver up to 1.5A current from a wide range of input voltage of 5V to 25V dc. See LM317 calculator if you want to know how to get the 3.3V output.

LM 317 regulator circuit

LM317 pinout

High Current 3.3V circuit
This 3.3V supply can deliver 5A or more depending on the type of transistor used, but input voltage is limited only to 5V to 6V range. Excessive heating to transistor may occur when there is no proper heatsink.

High current schematic

Part List:
R1-0.1 ohms or just short it
R2-10 ohms
Q-2N3055 or similar
D-3.9V zener 1W
C-220uF electrolytic capacitor (10V)

Simple 3.3V circuit
This is the simplest and easiest to build among the three, but the maximum current is around 300mA  and the input voltage is limited only to 5V to 6V. Simple yet enough to power up some microcontrollers.

Simple regulator circuit

Part List:
D-3.3V zener 1W
C-220uF capacitor 10V
R-10ohms 1W  for 6V supply
     and 5.6 ohms 1W for 5V supply