Diodes

Read more about the article Electrical Experiments with PSLab

Electrical Experiments with PSLab

PSLab has the capability to perform a variety of experiments. The PSLab Android App and the PSLab Desktop App have built-in support for over 70 experiments which are commonly performed by students. In addition to that, it can be used in other experiments conveniently. This blog post is in continuation with the previous two posts regarding performing experiments (links in the reference) and this blog deals with another category of experiments that can be performed using PSLab. The blog lists experiments which mainly involve the basic circuit elements like resistors, capacitors and inductors. These experiments involve the study of R-C, L-R, L-C and L-C-R circuits. These circuits have properties which make them important in real life applications and this blog attempts to give a rough picture of their importance. Ohm’s Law, Capacitive Reactance and Inductive Reactance These experiments involve the study of each of the basic circuit element individually. The current and voltage characteristics of each of the elements is studied. The definitions of the above are: Ohm’s Law - This is a law familiar to most. It relates the voltage and current of a purely resistive circuit stating that the voltage and current are proportional to each other and their ratio is a constant called the resistance. In this case, the current and voltage are in the same phase. Capacitive Reactance - Across a capacitor in an AC circuit, the current and voltage are not in the same phase and the current leads the voltage. For a purely capacitive circuit, this difference is 90o. Inductive Reactance -  Across an inductor in an AC circuit, the current and voltage are not in the same phase and the current lags behind the voltage. For a purely inductive circuit, this difference is 90o. The reactance is given for capacitor and inductor is given by 1/wC and wL respectively, where C & L are the values of capacitance and inductance respectively and w is the frequency of the AC signal. The circuit for the setup is shown below. We need to observe the plot of the input waveform and the plot of the voltage across individual elements to observe the phase shift. Connect CH1 & GND across the input terminals and CH2 & GND across the terminals of any of the elements. An external signal can be used or can be generated using the PSLab. Use the PSLab to generate a sinusoidal signal of frequency 1000 Hz. by connecting the ends of PV1 in the circuit. Observe the waveforms. In case of the resistor, there should be no observable phase lag between the two. In case of the capacitor and inductor, there will be an observable phase difference of 90o. For the capacitive and inductive circuits, just replace the resistor in the above circuit with capacitor/inductor. RC Circuits Drawing their names from their respective calculus functions, the integrator produces a voltage output proportional to the product (multiplication) of the input voltage and time; and the differentiator (not to be confused with differential) produces…

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Read more about the article Fascinating Experiments with PSLab

Fascinating Experiments with PSLab

PSLab can be extensively used in a variety of experiments ranging from the traditional electrical and electronics experiments to a number of innovative experiments. The PSLab desktop app and the Android app have all the essential features that are needed to perform the experiments. In addition to that there is a large collection of built-in experiments in both these experiments. This blog is an extension to the blog post mentioned here. This blog lists some of the basic electrical and electronics experiments which are based on the same principles which are mentioned in the previous blog. In addition to that, some interesting and innovative experiments where PSLab can be used are also listed here. The experiments mentioned here require some prerequisite knowledge of electronic elements and basic circuit building. (The links mentioned at the end of the blog will be helpful in this case) Op-Amp as an Inverting and a Non-Inverting Amplifier There are two methods of doing this experiment. PSLab already has a built-in experiment dedicated to inverting and non-inverting amplification of op-amps. In the Android App, just navigate to Saved Experiments -> Electronics Experiments -> Op-Amp Circuits -> Inverting/ Non-Inverting. In case of the Desktop app, select Electronics Experiments from the main drop-down at the top of the window and select the Inverting/Non-inverting op-amp experiment. This experiment can also performed using the basic features of PSLab. The only advantage of this methodology is that it allows much more tweaking of values to observe the Op-Amp behaviour in greater detail. However, the built-in experiment is good enough for most of the cases. Construct the above circuits on a breadboard. For the amplifier, connect the terminals of CH1 and GND of PSLab on the input side i.e. next to Vi and the terminals of CH2 and GND on the output side i.e next to Vo. Usually, an Op-Amp like LM741 have a set of pins, one dedicated for the inverting input and the other dedicated for the non-inverting input. It is recommended to consult the datasheet of the Op-Amp IC used in order to get the pin number with which the input has to be connected. The terminals of W1 and GND are also connected on the input side and they are used to generate a sine wave. The resistors displayed in the figure have the values R1 = 10k and R2 = 51k. Resistance values other than these can also be considered. The gain of the op-amp would depend on the ratio of R2/R1, so it is better to consider values of R2 which are significantly larger than R1 in order to see the gain properly. Use the PSLab Desktop App and open the Waveform Generator in Control. Set the wave type of W1 to Sine and set the frequency at 1 kHz and magnitude to 0.1 V. Then go ahead and open the Oscilloscope. CH1 would display the input waveform and CH2 will display the output waveform and the plots can be observed. If the input is connected…

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Read more about the article Electronics Experiments with PSLab

Electronics Experiments with PSLab

Numerous college level electronics experiments can be performed using Pocket Science Lab (PSLab). The Android app and the Desktop app have all the essential features needed to perform these experiments and both these apps have quite a large number of experiments built-in. Some of the common experiments involve the use of BJT (Bipolar Junction Transistor), Zener Diode, FET (Field Effect Transistor), Op-Amp ( Operational Amplifier) etc. This blog walks through the details of performing some experiments using the above commonly used elements.   The materials required for all the experiments are minimal and includes a few things like PSLab hardware device, components like Diodes, Transistors, Op-Amps etc., connecting wires/jumpers and secondary components like resistors, capacitors etc. Most of these elements would be a part of the PSLab Accessory Kit. It is recommended to read this blog here, go through the resources mentioned at the end and also get acquainted with construction of circuits before advancing with the experiments mentioned in this blog. Half Wave and Full Wave Rectifiers The Bipolar Junction Transistor (BJT) can be used as a rectifier. Rectifiers are needed in circuits to obtain a nearly constant and stable output voltage and prevent any ripples in the circuit. The rectifier can be half wave or full wave depending on whether it rectifies one or both cycles of Alternating Voltage. The circuit for the Half and Full Wave rectifier is given as follows: Construct the above circuits on a breadboard. For the half wave rectifier, connect the terminals of CH1 and GND of PSLab on the input side and the terminals of CH2 and GND on the output side. The terminals of W1 and GND are also connected on the input side and they are used to generate a sine wave. Use the PSLab Desktop App and open the Waveform Generator in Control. Set the wave type of W1 to Sine and set the frequency at 100 Hz and magnitude to 10mV. Then go ahead and open the Oscilloscope. CH1 would display the input waveform and CH2 will display the output waveform and the plots can be observed. The plot obtained will have rectification in only half of the cycle. In order to obtain rectification in the complete cycle, the full wave rectifier is needed. For the full wave rectifier, the procedure is the same but an additional diode is used. Use an additional channel CH3 to plot the extra input. The plot obtained from the above steps would still have ripples and so a capacitor is placed in parallel to cancel this effect. Place a 100uF/330uF capacitor in parallel to the resistor RL and an additional 1 ohm resistor in the circuit. BJT Inverter Transistor has a lot of functions. The most common of them is its use as an amplifier. However, transistor can be used as a switch in a circuit i.e. as an inverter. The circuit for this experiment is shown below. For this experiment, it is recommended to use an external 5V DC supply like…

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Read more about the article Understanding PN Junctions with the Pocket Science Lab

Understanding PN Junctions with the Pocket Science Lab

The boundary layer between two thin films of a semiconducting material with Positive type and Negative type doping is referred to as a P-N junction, and these are one of the fundamental building blocks of electronics. These junctions exhibit various properties that have given them a rather indispensable status in modern day electronics. The PSLab’s various measurement tools enable us to understand these devices, and in this blog post we shall explain some uses of PN junctions, and visualize their behaviour with the PSLab. One might easily be confused and assume that a positive doping implies that the layer has a net positive charge, but this is not the case. A positive doping involves replacing a minute quantity of the semiconductor molecules with atoms from the next column in the periodic table. These atoms such as phosphorus are also charge neutral, but the number of available mobile charge carriers effectively increases. A diode as a half-wave rectifier A diode is basically just a PN junction. An ideal diode conducts electricity in one direction offering a path of zero resistance, and it is a perfect insulator in the other direction. In practice, we may observe some additional properties. Figure : The circuit used for making the half-wave rectifier and studying it. A bipolar sinusoidal signal is input to a diode, and the output voltage is monitored. The 1uF capacitor is used to filter the output signal and make it more or less constant, but it has not been used while obtaining the data shown in the following image We can observe that only the positive half of the signal passes through the diode. It can also be observed , that since this is not an ideal diode, the conducted portion has lost some amplitude. This loss is a consequence of the forward threshold voltage of the PN junction, and in case of this diode, it is around 0.6 Volts. This threshold voltage depends on the band structure of the diode , and in the next section we shall examine this voltage for various diodes. Measurement of Current-Voltage Characteristics of diodes In practice, diodes only start conducting in the forward direction after a certain threshold potential difference is present. This voltage, also known as the barrier potential, depends on the band gap of the diode, and we shall measure it to determine how the electrical properties affect the externally visible physical properties of the diode. A programmable voltage output of the PSLab (PV1) will be increased in small steps starting from 0 Volts, and a voltmeter input (CH3) will be used to determine the point when the diode starts conducting. The presence of a known resistor between PV1 and CH3 acts as a current limiter, and also enables us to calculate the current flow using some elementary application of the Ohm’s law. I = (PV1-CH3)/1000 . The following image shows I-V characteristics of various diodes ranging from Schottky to Light Emitting Diodes (LEDs). It may be interesting to note that the frequency…

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