Category: Passive

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Diodes

  • Diodes are electronic devices that conduct in one direction. Ideally, they have to block the conduction of current in the reverse direction, but in reality, there is always a small leakage current present.
  • Due to the presence of impurities in the diode, it gets hot when a large amount of current is passed through.
  • There are diodes for various applications which focus on a special property of the diode.
    • For example:
      • Zener Diode – Works in reverse bias condition. Provide excellent voltage regulation.
      • Schottky Diode – Has low forward voltage drop and high switching speed. Suitable for high-frequency applications and power supply circuits.
      • Silicon Controlled Rectifier (SCR) – Can handle high current and voltage levels. Used for power switching and motor control applications.
      • Light Emitting Diode (LED) – Emits light when forward biased. Used for lighting and display applications.
      • Tunnel Diode – Exhibits negative resistance. Used in microwave oscillators, amplifiers, and detectors.
      • Avalanche Diode – Can withstand high reverse voltage and exhibits avalanche breakdown. Used for overvoltage protection and voltage regulation.
      • Photodiode – Generates a current when exposed to light. Used in optical communication and sensing applications.
      • These are just a few examples, and there are many more types of diodes available for various applications.

The following properties should be looked at in a datasheet. There may be additional details but these are the minimum.

  • VF is the voltage drop across the diode when it is conducting current in the forward direction. For example, a silicon diode may have a VF of around 0.7V.
  • IF is the maximum current that the diode can handle without being damaged. For example, a diode rated for 1A can handle a maximum current of 1A flowing through it.
  • VR is the maximum reverse voltage that the diode can withstand before breakdown. For example, a diode with a VR of 100V can withstand a reverse voltage of up to 100V before it starts conducting in the reverse direction.
  • PD is the maximum power that the diode can safely dissipate without getting damaged. For example, a diode with a PD of 500mW can safely dissipate up to 500mW of power without getting damaged.
  • Tj is the maximum temperature that the junction of the diode can reach without getting damaged. For example, a diode with a Tj of 150°C can safely operate at a maximum temperature of 150°C.
  • trr is the time taken by the diode to switch from forward conduction to reverse blocking mode. For example, a diode with a trr of 50ns will take 50ns to switch from forward conduction to reverse blocking mode.
  • The package type and dimensions specify the physical size and shape of the diode and are usually given in the mechanical drawing section of the datasheet. For example, a diode may be packaged in a through-hole or surface-mount package with specific dimensions.

Electronic Diodes and Their Part Numbers

Rectifier Diodes

  • Small Signal Diode: 1N4148, 1N914
  • Schottky Diode: BAT54, BAT85
  • Silicon Controlled Rectifier: TYN616, C106D
  • PIN Diode: HP5082-2810, HSMP-386L

Zener Diodes

  • Zener Diode: 1N4728A, 1N5349B

LED and Laser Diodes

  • Light Emitting Diode (LED): 5mm Red LED, 3mm Green LED
  • Laser Diode: 650nm Red Laser, 405nm Blue Laser

Special Function Diodes

  • Tunnel Diode: 1N3716, NTT406AB
  • Varactor Diode: BB112, BB204
  • Transient Voltage Suppression Diode: P6KE36A, 1.5KE200A
  • Avalanche Diode: BZX84C5V6, P6KE100CA

Photodiodes

  • PIN Photodiodes: BPW34, SFH205F
  • Avalanche Photodiodes: S8664, C30932EH
  • Schottky Photodiodes: 1N5711, HSMS-2855-BLKG
  • MSM Photodiodes: YT201M, YT202M
  • InGaAs Photodiodes: G9933, G8941

Power Diodes

  • General Purpose Power Diodes: 1N4007, 1N5399
  • Fast Recovery Power Diodes: UF4007, FR107
  • Schottky Barrier Diodes: SB560, SB5100
  • Ultrafast Recovery Power Diodes: UF5404, UF5408
  • Super Barrier Diodes: SB540, SB570
  • Avalanche Diodes: MUR1100E, 1N4937GP
  • TVS Diodes (Transient Voltage Suppressor): P6KE15CA, 1.5KE400A
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Inductor

Inductors are electronic components that store energy in the form of a magnetic field. They are used in a wide range of applications, from simple circuits to power supplies and filters. Understanding the principles of inductors is essential for designing and analyzing electronic circuits.

Inductance is the property of an inductor that opposes any change in the current flowing through it. The unit of inductance is the henry (H). The inductance of an inductor depends on the number of turns in the coil, the shape and size of the core, and the material of the core. The formula for calculating the inductance of an inductor is:

L = (μ * N^2 * A) / l

where L is the inductance in henries, μ is the magnetic permeability of the core material, N is the number of turns in the coil, A is the cross-sectional area of the core, and l is the length of the core.

Another important parameter of an inductor is its reactance, which is the opposition of an inductor to a change in the flow of alternating current. The reactance of an inductor is proportional to its inductance and the frequency of the alternating current. The formula for calculating the reactance of an inductor is:

XL = 2πfL

where XL is the reactance in ohms, f is the frequency in hertz, and L is the inductance in henries.

In addition to storing energy, inductors can also be used to filter out unwanted frequencies in a circuit. A low-pass filter, for example, can be created by connecting an inductor in series with a resistor and a capacitor. The inductor blocks high frequencies while allowing low frequencies to pass through, while the capacitor blocks low frequencies and allows high frequencies to pass through.

To illustrate the concept of inductance, let’s consider the following example:

Suppose we have a coil with 100 turns, a core with a cross-sectional area of 0.01 m^2, and a length of 0.1 m. The core is made of iron, which has a magnetic permeability of 2000. Calculate the inductance of the coil.

Using the formula for inductance, we have:

L = (μ * N^2 * A) / l L = (2000 * 100^2 * 0.01) / 0.1 L = 2,000 H

Therefore, the inductance of the coil is 2,000 henries.

Induktoren sind elektronische Bauteile, die Energie in Form eines magnetischen Feldes speichern. Sie werden in einer Vielzahl von Anwendungen eingesetzt, von einfachen Schaltkreisen bis hin zu Stromversorgungen und Filtern. Das Verständnis der Prinzipien von Induktoren ist wesentlich für das Entwerfen und Analysieren von elektronischen Schaltungen.

Induktivität ist die Eigenschaft eines Induktors, die jeder Änderung des durch ihn fließenden Stroms entgegenwirkt. Die Einheit der Induktivität ist das Henry (H). Die Induktivität eines Induktors hängt von der Anzahl der Windungen in der Spule, der Form und Größe des Kerns sowie dem Material des Kerns ab. Die Formel zur Berechnung der Induktivität eines Induktors lautet:

L = (μ * N^2 * A) / l

wobei L die Induktivität in Henry, μ die magnetische Permeabilität des Kernmaterials, N die Anzahl der Windungen in der Spule, A die Querschnittsfläche des Kerns und l die Länge des Kerns ist.

Ein weiterer wichtiger Parameter eines Induktors ist seine Reaktanz, die dem Widerstand eines Induktors gegen eine Änderung des Wechselstromflusses entspricht. Die Reaktanz eines Induktors ist proportional zu seiner Induktivität und der Frequenz des Wechselstroms. Die Formel zur Berechnung der Reaktanz eines Induktors lautet:

XL = 2πfL

wobei XL die Reaktanz in Ohm, f die Frequenz in Hertz und L die Induktivität in Henry ist.

Neben der Speicherung von Energie können Induktoren auch zum Filtern unerwünschter Frequenzen in einem Schaltkreis verwendet werden. Ein Tiefpassfilter kann beispielsweise durch Anschließen eines Induktors in Serie mit einem Widerstand und einem Kondensator erstellt werden. Der Induktor blockiert hohe Frequenzen und lässt niedrige Frequenzen durch, während der Kondensator niedrige Frequenzen blockiert und hohe Frequenzen durchlässt.

Um das Konzept der Induktivität zu veranschaulichen, betrachten wir das folgende Beispiel:

Angenommen, wir haben eine Spule mit 100 Windungen, einen Kern mit einer Querschnittsfläche von 0,01 m^2 und einer Länge von 0,1 m. Der Kern besteht aus Eisen, das eine magnetische Permeabilität von 2000 hat. Berechnen Sie die Induktivität der Spule.

Mit der Formel für Induktivität haben wir:

L = (μ * N^2 * A) / l
L = (2000 * 100^2 * 0,01) / 0,1
L = 2.000 H

Daher beträgt die Induktivität der Spule 2.000 Henry.

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Custom Aluminum Heatsink for Raspberry Pi

Raspberry Pi is good a single-board Linux based computer system. But it runs OK for the most part and does not heat up if you’re not doing CPU hogging tasks.

I use my raspberry pi for watching videos. Which heats up the CPU to about 60 degrees celsius.

In Delhi, in the summer the ambient temperature is around 30 degrees celsius to about 34 degrees celsius.

In the past, I have placed a small TO-220 package heatsink on it. By placing it sideways.

I used fevicol which is a synthetic craft glue as I don’t have proper heat sink paste. But I found that fevicol glue works good and the heatsink stays quite firmly attached to the CPU.

Custom Aluminum HeatSink for Raspberry Pi

After Placing the Heatsink the CPU temperature never goes above 50 degrees celsius. Which is a 10-degree improvement.

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15V Unregulated DC Power Supply using 12Vrms step-down transformer

There are two ways to make DC power supply

  1. Linear
  2. Switching

Linear Power Supply
Continous control of voltage is done at any instance of time. It uses a pass transistor with an error amplifier to regulate the voltage supply.
example: 7805, 7905, LM317 etc

Switching Power Supply
It also uses the pass transistor along with an inductor and a capacitor to store the energy and release the energy. By controlling the switching of the pass transistor, the Voltage is regulated. It is more complex than the linear power supply.
The advantage of switching is that the transformer size gets reduced. Which reduced the cost of the power supply. The Reduced size also reduced the weight; which further increases the portability of the power supply.

[ A C Mains ] -> [StepDown Transformer] -> [Bridge Rectifier] -> [Filter] -> [Unregulated DC]

I am using a step-down transformer. Which transformer 220V 50Hz AC to 12 Vrms AC.

The Vrms is converted to Vdc which is dc equivalent voltage.

So, 12 Vrms = 12 x 1.414 Vdc

= 16.968 (approx.) Vdc

this Vdc is passed through the bridge rectifier which drops 1.5V to 1.8V

= 16.968 – 1.8

= 15.168 V

which is then filtered through the Capacitor filter

C = ( I x t ) / V

I is the amount of current passing through the capacitor at maximum load.

Let I = 1A

t is the ripple time which is taken 10 mS if using 50Hz cycles.

C = [1 x 10 x 10^(-3) ] / 15.168

= 6.59 x 10^(-4) F

= 659 micro Frad

So we will use a standard capacitor that is either equal to or bigger than the above value i.e 1000uF will OK.

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Capacitor ESR

A real capacitor has a series resistance which is due to the imperfect manufacturing process and also because of the cost regulations.

lower ESR = Better Capcitor = Higher Cost

A lower ESR capacitor is better but the manufacturing cost will also be on the higher side. So, there is a compromise made between ESR and cost.

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How to calculate the value of a resistor from colour codes

To calculate the value of a resistor from colour codes.

Then, First, you have to locate the Tolerance band.
The tolerance band mostly in most of the resistors is made from either gold colour or silver colour.

Then you need to look at the next band which tells you the multiplier.

Then you need to look at the opposite end of the resistor and note down the colour in order till the multiplier.

The first band from the left gives us the first digit.
The next band gives the next digit.

Resistor color coding chart
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Resistor

A resistor is an electronic component that offers resistance in the flow of current. The practical resistor has a slight shift in its values from the ideal counterparts.

Not all the values of the resistor are available in the market. There is a certain number that is chosen and is readily available. If a particular value is to be achieved then a combination made from the selected resistors is to be used.

An ideal resistor follows Ohm’s law.

A practical resistor changes its value if the surrounding temperature, pressure and changes in mechanical dimension etc. Though there are very nominal changes yet they differentiate the ideal resistor from the practical counterpart.

The resistors value is generally marked on the surface. If the resistor is big, standard values along with manufacturing company seal are also printed on top of it.

For very small resistors; either colour bands or some code is written on top of it. As the size goes on decreasing the surface area becomes small and reaches a point where it is not feasible to print anything that can be visible to the naked eye. Then the values are written beside the component.

10 Kilo Ohm Through Hole Type Resistor
SMD Resistor with value code written on it
SMD resistor with a reference to value is printed beside it.

There are two types of resistors.

  1. Fixed Value resitors
  2. Variable Value Resistors

It is important to consider the power dissipation of a resistor. Since resistor obstructs the flow of current. The obstruction causes a buildup of energy which needs to dissipate. If this energy is not released then it will burn the resistor or permanently change its resistance values. So resistors use heat to dissipate the energy.

for example:
Let’s consider an 8-ohm resistor that resists the flow of current.


A voltage source of 9V has connected across. The 8-ohm resistor drops the voltage from 8V to 0V. Blocking a significant portion of voltage that is 8V.
and Let’s say the current flowing in the circuit is one Ampere.
So the resistor needs to dissipate 8W of energy.
Now you need to select a resistor that can dissipate more than 8W of energy. and the next best option is to use a resistor of 10 watts.