Introduction: Full Wave-Bridge Rectifier(JL)


This intractable page will guide you through all the steps necessary to build a full wave bridge rectifier. It is useful in converting AC current to DC current.

Parts (with purchasing links)

(Pictures of the parts are included with corresponding order)

Four Diodes:

One 1kΩ Resistor:

One 470μF Capacitor:

One Breadboard:

One Wire Kit :

One Transformer:

The type of transformer provided above has a turns ratio of 115:6.3, which is slightly off from the 115:6 transformer I used. However, this extent of difference in the output voltage will not cause a major change in the results and will not blow the diodes nor the resistor. Also, pretty much all major types of diodes should be compatible with this project, but make sure you check that the peak repetitive reverse voltage is higher than the output of the transformer.

*For People Who Live in Countries that Use 220V AC

The output voltage from the transformer will double, but that would not blow the components if you get the correct types. Otherwise, you could double the resistance on the resistor or use a transformer that has a turns ratio close to 220:6.

Step 1: Circuit

You could use the schematic provided in the pictures (P1) as a guide to build the circuit. Or you could build the circuit using the pictures of the circuit I built on a breadboard (P2 and P3). Make sure that the capacitor is oriented in a way that its long leg (positive leg)is plugged into the top hole (hole G4 on my breadboard). The orientation of the resistor does not matter. A picture that indicates the current flow in a diode is provided. Check it out in the pictures (P4). The full wave bridge rectifier will not be functional unless the diodes are in the right directions. In my layout, they are all oriented to the right, so that you can quickly check if each diode is in the correct orientation.

Here is a link to an interactive simulation of this circuit:

Hopefully the interactive simulation helps your understanding of how this circuit works.

*Here is a link to instructions on how to use a breadboard in case you are not familiar with it.

Step 2: (Optional) Use a Function Generator and an Oscilloscope to Check!

Before plugging in the transformer, you can test your full wave bridge rectifier by connecting it to a function generator and look at the waveform of load voltage using an oscilloscope.

1. Connecting the oscilloscope: The probe should be connected to the right leg of the resistor and grounded through connecting its ground probe to the left leg of the resistor just as shown in the picture.

2. The picture I provided (P1) showing the way you should connect the apparatus has the breadboard turned 90 degrees clockwise. Make sure that everything is properly connected before turning the function generator on.

3. Adjust your function generator so that it creates a sinusoidal waveform with a root-mean-square voltage of 6V (you can test this with a multimeter if applicable).

Make sure that the positive wire goes into the red power rail of the breadboard(where there is a red line), and that the ground (negative) wire goes into the blue power rail (where there is a blue line).

If the waveform you observe is identical to the one I provided (P2), proceed to the next step.

Troubleshooting tips:

  1. If the waveform on the oscilloscope does not appear to be the same as mine, try to scale its vertical and horizontal axes.
  2. Make sure that none of the wires are touching each other when making the measurements.
  3. If there is no voltage readings, try to reconnection between the components and the breadboard as it might be that you have a circuit that fails open
  4. Link to a guide on how to use an oscilloscope:
  5. Link to a guide on how to use a function generator:

Step 3: Connect the Breadboard to the Transformer

Connect the transformer and oscilloscope with instructions in the previous section while referencing pictures provided in this section. Notice that when connecting the breadboard to the transformer, the positive/negative sides do not matter since the current is alternating. The way you connecting the breadboard to the oscilloscope remains the same.

Step 4: Results From the Oscilloscope

The Voltage across the resistor (load voltage) should vary between 5V and 6V, with a period of 8.33 ms.

Why is the period 8.33 ms?

The frequency of the waveform should be double the frequency from the power supply, which has a frequency of 60 Hz. The reason is that the full wave bridge rectifier without the capacitor basically takes the absolute value of the original sinusoidal waveform, so the waveform repeats itself every half the period. Thus the frequency doubles and the period halves. 1/(2*60)=0.00833s=8.33ms.

Step 5: Circuit Explanation

In this circuit, a 120 Vpeak-to-peak AC voltage is converted to 6 V with a transformer. So now effectively we have a 6V AC power supply. The 4 diodes are arranged in a way that even as the input current travels in both the forward and backward directions, the output current from the group of diodes travels only in one direction, but the voltage is not constant because the input voltage is sinusoidal (that means it oscillates like a sine or cosine wave). The output voltage with respect to time when no capacitor is connected looks like P2 (t-axis not to scale).

The diodes can do this because they only allow current to flow in one direction (in most cases).

The capacitor serves to store electric energy and release it when the current is low on the load side. This property of the capacitor suitable for smoothing out the output voltage.

You can take a look at the interactive simulation for a more visual representation of how the current flows: