6 12V to 3V buck converter

There are many ways of converting 12V to 3V. You can use regulator IC, transistors, zener diodes and many more. The problem of these converters is very low efficiency and most of their power is converted to heat. A dc-dc converter is a need in this case.
The circuit below is a simple buck converter that converts a 12V DC (usually from battery) to 3V DC. The heart of the circuit is the 555 timer IC that controls the Mosfet and the entire circuit. This converter can deliver a current up to 5A at a 3V load. Current can be made even higher if Q1, D1, and L1 are replaced with much higher current capacity.

buck converter diagram

To make the output voltage more regulated, you can add the circuit below across the converter output.

regulator circuit

Part List:
R1 - 5 kilo ohms 1/4W
R2 - 2.7 kilo ohms 1/4W
R3 - 1.2 kilo ohms 1/4W
R4 -  just remove (its a dummy load)
C1, C2 - 100 nano-Farad capacitor
C3 - 2200uF electrolytic capacitor rated 16V
Q1 - IRF9530 or any similar P-channel Mosfet (10A current min)
D1 - SR506 or any diode rated 6A min (SCHOTTKY preferable)
L1 - 1mH Inductor minimum 6A current rating
555 - LM555 IC
Regulator circuit (optional)
      Dz - 1N5223B or 2.7V zener diode min 1/2W
      R - 120 ohms 1W
      Q - 2N3055, TIP41C or similar NPN transistor

555 pins

2N2222 pins

IRF9530 or PMOS pins

10 12V to 5V converter (555IC + Mosfet)

Buck converter circuit powered by a 12V battery down to 5V DC. Circuit is controlled by 555 timer IC that is operated in monostable mode.  The circuit is similar to 12V to 5V converter using BJT transistor but its much more stable, efficient, and higher current output (around 5A or even higher). The converter output voltage is given by the approximate equation:
Vout/Vin = (1-D); D is the Duty Cycle of 555 IC output.
See 555 timer calculator for more info about output frequency, duty cycle and combinations of resistors and capacitor.

schematic diagram

Part List:
R1 - 2 kilo ohms 1/4W
R2 - 5 kilo ohms 1/4W
R3 - 1.2 kilo ohms 1/4W
R4 - 27 ohms 1W (optional and can be removed)
C1, C2 - 100 nano-Farad capacitor
C3 - 2200uF electrolytic capacitor rated 16V
Q1 - IRF9530 or any similar P-channel Mosfet (10A current min)
D1 - SR506 or any diode rated 6A min (SCHOTTKY preferable)
L1 - 1mH Inductor minimum 6A current rating
555 - LM555 IC

555 pins

P-Channel Mosfet

When the converter is unloaded, its output is usually high but it drops to 5V when loaded. If you want to make your converter  more stable  (5V output loaded or unloaded), try to add the regulator circuit across its output pins.

regulator circuit

Regulator part list:
Dz - 1N4732A or 4.7V zener diode minimum 1W
R1 - 56 ohms 1W
Q - TIP41C, 2N3055 or similar NPN transistor

15 12V to 48V power supply using 555

This project is a DC-DC converter that outputs 48V using your 12V battery.  The driver of this converter is the 555 IC operated in astabe mode and has an output frequency of around 600Hz at 58% duty cycle (see 555 calc on how this one is computed) This project is similar to 12-48V but has more stable and regulated output.

Improvised converter schematic

Part list: 
R1 - 4 kilo-ohms 1/4W
R2 - 10 kilo-ohms 1/4W
R3 - 10 kilo-ohms 1/4W
R4 - 2.2 kilo-ohms 1/4W
R5 - 2.5 kilo-ohms 1/4W
R6 - 120 ohms 1W
C1 - 100nF
C2 - 100nF
C3 - 1000uF rated 50V or higher
C4 - 1000uF rated 16V or higher
D1 - 1N5401 or any diode rated 3A or higher
D2 - 1N4756A,1N5368B or 47V zener
D3 - 1N4740A, 1N5346B or any 8.2V to 9.1V zener
D4 - 1N4001 or similar
Q1 - IRF530 N-chanel MOSFET
Q2 - 2n3055
L1 - 40 turns #22AWG magnet wire in antenna rod
LED - 3mm to 5mm any color LED
555 IC

Diagrams click to enlarge:

555IC pins

Inductor wound in antenna bar

IRF530 pins

2N3055 pins

Similar converters using 555IC:
6V to 12V converter
12v to 24V converter
12V to 48V converter transistors

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

0 12V to 48V DC-DC converter

This converter is powered by a 12V battery and and has a 48V DC output and can deliver
a power up to 12W. This converter can be used to power a wireless modem.

12V to 48V converter

Bill of materials:

Resistor- 120 ohms 5W
Transistor- 2n3055 or similar
Capacitor- 470n cap preferably be mylar type
transformer -  12-0-12 to 48V
Diode -D1 D2 D3 D4 in4002 or any atleast 1A 100V type
C3 is atleast 22uF capacitor but the higher value the better

0 cheap 6 V to 12V converter

This electronic project is a cheap  6V to12V dc-dc converter that is easy to assemble.
The converter circuit is composed of simple oscillator, a rectifier, and voltage regulator. The feedback winding F is composed 4 turns of #24 AWG magnetic wire and main winding P is composed of 10 turns of #24 AWG wire. The 12V zener ( i used 13.2V zener) diode and 470uF capacitor regulates the output voltage and maintain it to 12V dc.but keep in mind that larger capacitance in its output is much better  but I used smaller capacitance since its cheaper but still works well. The converter consumes about 2.8A at 6V in its input deliver about 1A at 12V in its output and about 70% efficient in resistive loads. you can add a series 1k resistor and LED at the output for output indicator.
The parts minimal and very cheap (about 1$) and easy to find.
The windings are not critical,you can experiment using different number of turns. If ever the converter dont have any output, try to reverse the winding connection.