A diode is a specialized electronic component. The current flows through the diode and there are two different polarity in a diode which are called anode(+) and cathode(-). The diode has one way value and it flows from anode to cathode with its operating voltage at around 0.6v. The current does not flow reversed direction. The diode can be used for switch and rectifiers.
A diode test
- Diode test mode on the meter.
- Positive probe and negative probe are touched anode and cathode of the diode each.
- Read the diode value.
- The diode is operating at around 0.6V. (normal diode)
Zener diode
The diode runs in reverse bias, and breaks down on the arrival of a certain voltage(5v or other voltages). A stable voltage is produced, if the current through the resistor is limited. In power supplies, these diodes are widely used to provide a reference voltage.
Light Emitting Diode (LED)
It is one of the most popular type of diodes and when this diode permits the transfer of electric current between the electrodes, light is produced. The LED consumes at about 1.8v for its operation.
reference by http://www.buzzle.com/articles/types-of-diodes.html
EXPERIMENT No. 2
DIODES
reference by http://www.youtube.com/watch?v=cyhzpFqXwdA&feature=player_embedded
Fig 4 – Diode symbol and P.N. junction
A diode has the characteristics of:
· An insulator when current tries to flow in one direction.
· A conductor when current flows in the other direction.
· An insulator when current tries to flow in one direction.
· A conductor when current flows in the other direction.
Components: 1 x diode, 1 x LED
Exercise: Using a multimeter, identify the anode and cathode of the diode and the LED.
Exercise: Using a multimeter, identify the anode and cathode of the diode and the LED.
Voltage drop in forward Biased Direction Voltage drop in reverse biased direction
LED 1.807 v 0
Diode 0.579 v 0
Explain how you could identify the cathode without a multimeter
Diode : The anode of the diode has a silver band on the its surface. However, there is black colour in the cathode of the diode..
LED : A long leg is the anode of the LED and another leg (short leg) is the cathode of the LED.
Table 1: Data sheet of 1N4007 is as follows
Exercise: For Vs=5V, R= 1KΩ, D= 1N4007 build the following circuit on a breadboard.
Calculate first the value of current flowing through the diode, now measure and check your answer?
Show your working
Calculated : Using Ohm's law V=I X R, I=V/R
I=4.4/1000 =0.0044A
Measured : 4.4mA At first, making open circuit between the resistor and the diode, and the multimeter is set up the amp range. Then, the red lead of a multimeter connects after the resistor and the black lead touches the anode of the diode. The current values are all the same any positions in series.
Is the reading as you expected; explain why or why not?
I could find the value of current which flows through the diode and it follows the ohm's law. Therefore, the calculated current and measured current are the same and the diode's operating voltage is at around 0.6v. In addition, the resistor is too high so the current reaches very low value.
Calculate the voltage drop across the diode, now measure and check your answer?
Calculated : Vs=Vr+Vd, Vd=Vs-Vr
Measured : 0.66v The multimeter is set up the voltage range. The red lead of a multimeter connects the anode of the diode and the black lead is touched the cathode of the diode.
Using the data sheet given in Table 1 above,What is the maximum value of the current that can flow through the given diode? 1A
For R = 1KΩ. What is the maximum value of Vs so that the diode operates in a safe region?
1000V
Replace the diode by an LED & calculate the current, then measure and check your answer?
Calculated : I=V/R LED's operating voltage=1.8v
I=3.2/1000 =0.0032A
Measured : 0.003A At first, making open circuit between the resistor and the diode, and the multimeter is set up the amp range. Then, the red lead of a multimeter connects after the resistor and the black lead touches the anode of the diode. The current values are all the same any positions in series.
Measured : 0.003A At first, making open circuit between the resistor and the diode, and the multimeter is set up the amp range. Then, the red lead of a multimeter connects after the resistor and the black lead touches the anode of the diode. The current values are all the same any positions in series.
When the LED is operated with at 1.8v, it consumes more voltage than the normal diode. The main consumer is still the resistor(1KΩ). As a result, the current value slightly dropped when the LED is replaced.
EXPERIMENT No. 3Components: 2 x resistors, 1 x 5V1 400mW Zener diode (ZD).
Exercise: Obtain a breadboard, suitable components from your tutor and build the following circuit.
What is the value of Vz? 4.97v
Vary Vs from 10V to 15 V
What is the value of Vz 10v : 4.72v, 15v : 5.1v
Explain what is happening here
Vz values are not changed too much between 10v to 15v (Vs). Because, the zener diode holds 5v for its operation.
What could this circuit be used for?
Supplying stable voltage for the device, the despiking protection of diodes
Reverse the polarity of the zener diode.
What is the value of Vz? Make a short comment why you had that reading.
0.8v, When the zener diode is reversed, it has the same characteristic of the normal diode, such as holding near 0.6v for switch on of the circuit.
EXPERIMENT No. 4
Components: 1 x resistors, 1 x 5V1 400mW Zener diode, 1X Diode1N4007 .
Exercise: Obtain a breadboard, suitable components from your tutor and build the following circuit.
Vs=10 & 15v, R=1K ohms
10 Volts 15 Volts
Volt drop V1: 4.64v 4.82v
Volt drop V2: 0.67v 0.7v
Volt drop V3: 5.31v 5.5v
Volt drop V4: 4.74v 9.5v
Calculated current A: 0.00474mA 0.0095mA
Vs=10v I=V/R =4.74/1000 =0.00474
Vs=15v I=V/R =9.5/1000 =0.0095
Describe what is happening and why you are getting these readings:
The V1, V2 and V3 of values are similar both 10v and 15v. However, V4 value is changed at 9.5v under 15v. Because the zener
The current value also increased due to rising supply voltage with under constant resistors which is shown the ohm's law.
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