AC to DC voltage converting device using the step-down transformer

Published May 07, 2024
 4 hours to build

It is an electrical device. Plug it in 220 volt A.C power supply socket and get 12 volt D.C as output. A step-down transformer is the building block of this device.

display image

Components Used

Digital Multimeters
Digital Multimeters Fluke 87V MAX DMM and PVLEAD1 MC4 Test Leads Bundle
Diode 1N400x
Diode 1N400x
LED 5mm
LED 5mm
Resistor 1 kOhms
Metal Film Resistors - Through Hole 1K ohm 1/4W 1%
Capacitor 1000 µF
Aluminium Electrolytic Capacitors - Snap In 400V 1000uF 20% 18k Hours
A zero PCB
P-N junction diodes × 4N
A step-down transformer
A latching PushButton DPDT switch
Green / Red 5mm LED

AC to DC voltage converting device using the step-down transformer


Description: We have made ac to dc voltage convertor using pn junction diode and step-down transformer.As the name suggests , it converts ac voltage into dc voltage. A multimeter will tell the exact output voltage reading.



P-N junction  diode is a type of semiconductor diode based upon the p–n junction. The diode conducts current in only one direction, and it is made by joining a p -type semiconducting layer to an n -type semiconducting layer.



A step-down transformer is an electrical device that reduces the voltage of an alternating current (AC) power supply.It consists of a primary winding, a secondary winding, and an iron core. Converts high voltage (HV) and low current from the primary side to low voltage (LV) and high current on the secondary side. 


Follow these steps to build this device:-

  • Since the transformer needs to be in the righ  position so either you can glue it to pcb or just tie it over pcb with the help of a wire or you may take help of nuts and bolts it is totally upon you.
  • adjoin the legs of adjacent p-n junction diodes the same way as it was shown in the circuit diagram and take care of the polarity while making connections.
  • Now its time to solder the secondary coil wires where both diode legs meet solder each of the two coil wires so that they face other.



On the left extemity we have ac voltage while on the right extremity we a pulsating dc voltage . Worry not it will not give you an electric short but ensure that do not attempt to touch live wire even if it is dc voltage. The project is now ready the 5 mm green LED glows on dc voltage. The device weighs than than a half kg.



  •  If you are not soldering diodes on pcb then it would not be a good choice because churning them can dislocate the limbs of this delicate pn junction diode.
  • Do not forget a capacitor otherwise the LED which blink continously.IN other wordds it will not maintain its glow.


Circuit Diagram:-


More photos:-


Project Video Link(Youtube):-


Circuit Diagram Download