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How to Make a 15 Volt Transformer

A transformer is a device that transforms the voltage level of your AC adapter. It is sometimes part of a larger device that converts the high AC voltages used by wall outlets into the low DC voltages needed by many electronic devices. They are also sometimes used to transform the output of a wind or water turbine into the 15 volts needed to charge many types of storage batteries. You can build your own battery charging transformer at home, with few parts or tools.

Things You'll Need

Steel or iron bar
Spool of 28 gauge magnet wire
Electrical tape
Emery board
Permanent marker
Multimeter
Selection of resistors
Electronic component connector

Instructions

- 1
  Tape one end of the wire near one end of the steel or iron bar, using the electrical tape. Leave a few inches of the wire sticking out. Wrap 600 loops of wire around the bar, always moving towards the other end. Never move back and forth while winding the coil. Once you have reached 600 turns, tape the wire to the coil. Cut the coil off of the spool.
- 2
  Sand about 1/2 inch of the enamel insulation off of the ends of the coil wire, using the emery board. Mark each of these ends with the marker for easy identification later. These marked ends are the output terminals of the transformer.
- 3
  Measure the voltage of the power source that you wish to transform into 15 volts, if you don't already know it. Use a multimeter, and follow the manufacturer's safety instructions.
- 4
  Divide the voltage of your power source by 0.25. Electric current in a wire builds up heat. Each gauge of wire can only handle a certain amount of current before becoming a fire hazard. The maximum current level for 28 gauge wire is 0.5 amps. Cutting that figure in half, for safety reasons, and dividing it into the voltage, gives you the value of resistance your transformer needs to keep its current below the maximum safe level.
- 5
  Select a resistor of at least the calculated value. Check its power rating. If it is lower than the voltage of your power source multiplied by 0.25, then the resistor cannot handle the power level. In that case, select a resistor with a higher power rating.
- 6
  Divide the voltage of your power source by 15. Multiply the result by 600. Round the result of that up to the nearest whole number. The final result is the number of loops you need in your next coil.
- 7
  Tape one end of the wire to the top of the coil you made first. Leave a few inches sticking out. Wrap a second coil on top of the first. Use the number of loops that you just calculated. Tape down the other end of this coil, and cut it off of the spool. Both coils share the same core, and the secondary coil is entirely encased in the field of the primary coil. Some transformers use this design instead of wrapping two separate coils. It is more efficient, as it does not expose the secondary coil to only a part of the field of the first.
- 8
  Sand about 1/2 inch off of each end of the new coil's wire. These are the input terminals of the transformer. Sand the leads of the resistor you selected. Attach one of the leads of the resistor to either of the input terminals, using the component connector. The transformer is now ready to be safely hooked up to your power source.

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