Circuits 1 Lab Project

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A transformer is a device that transfers electrical energy from one circuit to another through inductively coupled conductors—the transformer’s coils. A varying current in the first or primary winding creates a varying magnetic flux in the transformer’s core and thus a varying magnetic field through the secondary winding. This varying magnetic field induces a varying electromotive force (EMF) or “voltage” in the secondary winding. This effect is called mutual induction.

If a load is connected to the secondary, an electric current will flow in the secondary winding and electrical energy will be transferred from the primary circuit through the transformer to the load. In an ideal transformer, the induced voltage in the secondary winding (Vs) is in proportion to the primary voltage (Vp), and is given by the ratio of the number of turns in the secondary (Ns) to the number of turns in the primary (Np).

By appropriate selection of the ratio of turns, a transformer thus allows an alternating current (AC) voltage to be “stepped up” by making Ns greater than Np, or “stepped down” by making Ns less thanNp.

In the vast majority of transformers, the windings are coils wound around a ferromagnetic core, air-core transformers being a notable exception.

Transformers range in size from a thumbnail-sized coupling transformer hidden inside a stage microphone to huge units weighing hundreds of tons used to interconnect portions of power grids. All operate with the same basic principles, although the range of designs is wide. While new technologies have eliminated the need for transformers in some electronic circuits, transformers are still found in nearly all electronic devices designed for household (“mains”) voltage.

Project: Construct a step-down transformer

Input: 220V

Output: 0 – 15V

Current: 3A

To be submitted on the first Wednesday of September 2012:

  1. Transformer design and computations
  2. Transformer

Electronics 1 Lab Project

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Regulated Variable Power Supply

 Specifications:

  • Output Voltage            :           0-15VDC
  • Current                        :           3A
  • Short-Circuit Protection:         auto shut-off or current limiter
  • Transistor Type           :           BJT or FET
  • With Course and Fine Adjust

To be submitted on the third Wednesday of August 2012:

  1. Physical lay-out of enclosure with dimensions
  2. Transformer design and computations
  3. Schematic diagram and bill of materials

To be submitted on the first Wednesday of October 2012 together with the finished product:

  1. Physical lay-out of enclosure with dimensions
  2. Transformer design and computations
  3. Schematic diagram and bill of materials
  4. PCB lay-out and component placement
  5. Documentation Pictures