Confused about AC and DC power?

This article explains the main differences between direct and alternating currents. You will also learn how to convert the AC power supply in your home to DC using a small, low-cost bridge rectifier circuit. By converting AC to DC, you can power the DC circuits in your DIY projects.

What Is Alternating Current?

Ac Voltage Symbol

Alternating Current (AC) is the type of electric current that keeps on changing its magnitude and direction many times a second. The flow of electrons in AC changes at regular intervals. Our homes have an AC supply because, unlike DC, AC voltage travels long distances without much loss of power.

What Is Direct Current?

Direct Current Supply Symbol

With Direct Current, electrons flow in one direction. It is a steady current that doesn't change its direction with time.

What Are the Main Differences Between AC and DC?

There are two main differences:

1. In DC, the current flow is constant, whereas, in AC, the flow of current is constantly changing.

2. With AC, the voltage doesn't drop over long distances as it does with DC.

How Do You Convert AC to DC?

Depending on what you want to do with the output, there are two different ways to convert AC to DC.

The first method is by mathematically converting AC to DC, knowing the source AC value. If you only want to use the value for calculations, you can convert it.

However, if you plan to convert AC to DC for any appliance physically, you can do it by making a small circuit.

Let's discuss both ways here:

1. Mathematical Conversion

To convert AC to DC, you only need to know the AC value of your source. Using a multimeter, you can measure it.

  1. Connect the multimeter plugs and set your multimeter on voltage measuring mode by rotating the knob to V~.
  2. Connect the other end of the probes to the positive and negative terminals of the power source and record the display readings.

Converting DC to AC

Here is the mathematical formula for converting AC to DC:

                                                              VDC=VAC/√(2)

For simple calculations, round off the √(2) to 1.4. So, you do not have to use a calculator to divide.

Let's say the measured value was 120V. Add the VAC value you just measured to the formula and calculate it.

VDC = (120/1.4)

VDC = 85.71 Volts

You can use this value to calculate different parameters based on DC voltage. Now, let's move on to making the physical circuit.

2. Making the Physical Circuit

You'll need the following equipment to build the physical circuit:

  1. Step-down transformer
  2. Four diodes
  3. Perfboard
  4. Wires
  5. Capacitor
  6. Multimeter

Let's look at the functions of each component in the circuit.

  1. Step-down Transformer: This is used to convert the high-voltage, low-current power into low-voltage, high-current power. If you want to convert AC to DC with a higher magnitude than the source, you can use a step-up transformer.
  2. Diodes: Allows electricity to flow into one direction when forward biased and blocks the flow in another direction. In this circuit, a bridge rectifier is built using four diodes.
  3. Perfboard: An electronic board used for prototyping circuits.
  4. Wires: components are connected and later joined with wires.
  5. Capacitor: A charge storage electronic component that smooths the current flow across the circuit.
  6. Multimeter: An electronic device used to measure current, voltage, resistance, and other parameters in the circuit. In this example, it is used to measure DC voltage.

Other components are directly connected in the primary circuit, but in a bridge rectifier, you must connect diodes in a diamond shape.

How to Make a Bridge Rectifier:

1. Connect two diodes in the shape of an L. Ensure that their negative ends are connected.

L-Shape Connection of Diodes in Rectifier Bridge

2. Connect the remaining two diodes in the same manner. Join their positive ends this time.

Second L-Shaped Connection of Rectifier Bridge

3. Join the two sets of diodes in diamond form, as shown below.

Bridge Rectifier Connection

Make sure the diodes are connected right, and your bridge rectifier is ready.

Related: Simulate and Test Arduino Projects with 123D Circuits

Making the Final Circuit:

Let's see how to use these components in a circuit to get DC output from an AC power supply.

1. With the help of nuts and bolts, attach the step-down transformer tightly to the perfboard.

Transformer

2. Connect the bridge rectifier to the circuit.

Bridge Rectifier Connection

3. The black and white wires of the transformer should be connected to the AC power supply. Connect the other two transformer wires to the bridge rectifier, as shown below.

Transformer Rectifier First Connection

4. Wrap the wires at these two points where the transformer is connected to the rectifier. Solder the connections afterward.

5. Connect the positive end of the capacitor to the left corner of the rectifier and the negative end to the right side indicated by points 3 and 4 on the circuit diagram. The circuit may run without a capacitor, but you should use one to block alteration in the current.

Capacitor Connection with Rectifier

6. Connect the transformer to the AC power source and turn on the AC power supply.

7. Set the multimeter to voltage measurement mode. On the positive and negative sides of the capacitor/bridge rectifier, connect the two plugs. It will show a reading of DC power converted from AC power.

Circuit Connection to Source

Precautions:

1. When soldering the endpoints, make sure not to touch the solders to avoid burning yourself.

2. Only after completing the circuit, turn on the AC supply.

Frequently Asked Questions:

1. Are AC and DC wires the same?

The structure of DC wire is pretty simple with two poles; negative and positive. However, AC cables consist of three-phase four or five wires with complex structures. In addition, the AC cable may cost you more than the DC one.

2. Can DC appliances work on AC?

No, in order to save your appliance from malfunctioning, always feed the right input.

Related: Best Electronics Kits for Kids

Convert AC to DC for Your DIY Projects

The low-cost bridge rectifier circuit is a good way of converting AC to DC. The direct AC supply in your home can be used to power the DIY DC circuits. Ensure that all connections are secure during assembly, and once you are satisfied, turn the circuit on. Do not forget to take the necessary precautions when making the circuit.