Project 2: The Zener Diode Voltage Regulator

Objective

The objective of this project is to measure the voltage applied to the lamp, and the current through the lamp for different supply voltages,
demonstrating the use of a zener diode to provide a steady voltage and current to a lamp when the supply voltage changes.

General Instructions

While the circuit is set up, measure the lamp current, zener diode current, and supply voltage as the voltage from the 9-volt battery drops.

Parts List

• One 9-volt battery
• One battery snap connector
• Two multimeters set to measure current (mA)
• One multimeter set to measure DC voltage
• One 56-ohm, 0.5-watt resistor
• One 1N4735A zener diode
• One breadboard
• One lamp rated for approximately 25 mA at 6 volts.
• Two terminal blocks

Step-by-Step Instructions

Set up the circuit shown on Figure 2.33. The circled “A” designates a multimeter set to measure current, and the circled “V” designates a multimeter set to measure DC voltage. If you have some experience in building circuits, this schematic (along with the previous parts list) should provide all the information you need to build the circuit. If you need a bit more help in building the circuit, look at the photos of the completed circuit in the “Expected Results” section.

Fig 2.33

Carefully check your circuit against the diagram, especially the direction of the battery and the diode. The diode has a band at one end.Connect the lead at the end of the diode without the band to the ground bus on the breadboard.

After you check your circuit, follow these steps, and record your measurements in the blank table following the steps

1. Measure and record the supply voltage.
2. Measure and record the lamp current.
3. Measure and record the zener current.
4. Wait 30 minutes.
5. Measure and record the new values of voltage and current.
6. Repeat steps 4 and 5 four times.: 

Figure 2.34 shows the arrangement of breadboard circuit of the project.

Fig 2.34

Figure 2.35 shows setup of project.

Fig 2.35

Compare your measurements with ones shown in the following table. You should see a similar trend in the measured values but not the exactly same ones.

As you can see in this data, even though the supply voltage is dropped by approximately 15 percent, the lamp current stayed roughly constant showing less than 1 percent drop.