To build your own transformer, wrap magnet wire around two steel bars a number of times, and join the bars using two more steel bars connected perpendicularly. Test the functioning of the transformer thus made using an ohmmeter. Finally, connect the transformer to a power source with a low voltage.
To make the transformer, use two steel bars of equal length and two more of a shorter length. With a power drill, make holes at both the ends of all the bars. Cover the longer bars with insulation tape wrapped around them in a thin layer.
Over the insulation tape layer, wrap 28-gauge magnet wire separately on both the longer bars to make hundreds of turns. Wind equal number of turns on both the bars. Join the shorter bars to the longer ones to form a rectangle. To do this, align the drilled holes of the bars, and attach them using bolts.
When testing the functioning of the transformer, check if the ohmmeter shows continuity between the steel bars and the wire turns. If so, it indicates a short in the winding. If the meter shows continuity between the ends of the wire turns, it indicates that some part of the wound wire is open. In either case, rewind the magnet wire.
Do not use a wall socket in place of a low-voltage power source to supply power to the transformer, as the former provides a high voltage.