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What You Need to Know to Make Our Electronic Circuits at Bright Hub Engineering

written by: Swagatam • edited by: Lamar Stonecypher • updated: 4/18/2013

If you are done with the theoretical part of electronics, its time you learn some practical stuff. Here we discuss and find out how to identify electronic components physically. Without this it’s simply impossible to fulfill your dreams of becoming a successful electronics hobbyist

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    It took me almost ten years to get to the core of this intriguing subject of electronics. It took me this long just because I couldn’t find anybody who would actually acquaint me with the nitty-gritty of it and the simple tricks needed to grasp the subject. Even my diploma in the relevant field did no good, simply because it was mostly filled with the many unrelated and unnecessary theoretical explanations. It was just due to my sheer interest in the field and through some relentless trial and error process that I could ultimately learn to an extent the very basics of electronics.

    Circuit Assembled Over General Purpose Board   Well, I would be really happy if I could impart and share with you everything that I have come across regarding practical electronics until today. Let’s learn in a step-wise manner what a person primarily needs to become an electronics hobbyist.

    It goes without saying that if you want to become a successful electronic enthusiast you will need to learn how to solder before attempting to build electronic circuits. Also, proper knowledge regarding operating various mechanical tools like a nipper, nose-plier, screw driver, hand drill, etc. will be required.

    In the meantime, you may use bread boards and indulge yourself in some amusing practical stuff. It’s very simple- it’s like connecting lanes, streets and highways to different locations. Here, the locations are the electronic components, and the streets are the copper tracks, conductors, or wires.

    A breadboard is basically made up of a network of randomly laid fixed patterns of copper tracks (which act like connecting wires) with pinning holes arranged over these copper rows and columns. To configure your own particular circuit, you may connect these tracks by inserting external stripped wire ends or component leads into these holes as per the given schematic. Each hole internally is equipped with spring loaded clips that hold the inserted leads firmly so that the required connections are done perfectly. For more information, you may want to read my "Breadboarding Tutorial" also here on Bright Hub.

    How to Mount and Solder a Component Over a PCB, Image  

    Once you finish learning the art of soldering, you may proceed to constructing the circuits by soldering them over general purpose board. Again, these are printed and etched circuit boards having many individual tiny copper pads arranged closely in rows and columns. The copper pads are drilled through holes of approximately 1 mm in diameter. (See image and click to enlarge.)

    The constructor will need to first bend the leads of the axial components (resistors, diodes, etc.) and insert them appropriately into the selected pair of holes and solder them from the flip side. The radial ones (normal capacitors, LEDs, ICs, etc.) may be directly fitted over the PCB. Once the components are fixed you may just interlink them using the extended leads of the fixed parts themselves and then cut of the excess remaining leads.

    The next page will walk you through comprehensive illustrations regarding the physical recognition of the various electronic components and their pin out assignments. This is a must read for all budding electronics hobbyists.

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    Understanding Common Electronic Parts Physically

    Resistors: The main uses of resistors is current limiting and safeguarding the active components from damage. The resistance value selection may broadly depend on the type of active component to which it is connected and the load current. For carbon and metal film resistors, the values may be recognized through their printed color codes; for the wire wound types, the numbers are directly marked. A resistor does not have a polarity and may be connected any way round.

    Capacitors, Image  

    Capacitor: Commonly they may be seen in ceramic disc, polypropylene, tantalum, and electrolytic types. Mostly the electrolytic and tantalum types have polarity and need to be strictly and correctly oriented accordingly to a circuit as per the circuit schematic. Tantalum capacitors are valued for their negligible leakage characteristic and accuracy. In these capacitors the capacitive value is directly shown over their body, whereas for the other two types the value may be coded through special figures.

    For example, if a figure 104 is impressed, it indicates 4 zeros to be placed after the initial digit which is 10. So it becomes – 100,000.

    The above value will always be in picoFarad or pF. So, a 104 capacitor has a value of 100,000 pF.

    Simply dividing it by 1,000 gives 100 nanoFarad or 100 nF, and further dividing it by 1,000 produces 0.1 microFarad or 0.1 µF. It’s simple, isn’t it? What does the figure 103 indicate?

    Diode: These active components may be basically categorized as rectifier, zener, and light emitting diodes. The most commonly used 1 amp rated rectifier diode is 1N4007. You can increase this rating by simply wiring many diodes in parallel or using a single higher rated one like 1N 5408 (3 Amps). Zener diodes primarily do the job of restricting the voltage to a particular desired level as per their voltage ratings. LEDs are pretty popular as they have the special quality of emitting light and are available in different colors. However, basically they behave the same way as a rectifier diode (low power).

    Typical SCR, Triac Pin-Outs, Image  

    SCR and TRIACS: These are high voltage switching devices, typically used for mains AC voltage load switching. They are quite comparable to transistors as they too have a separate triggering terminal with respect to ground. Their leads may be identified through their specific datasheets, but most of them have their lead orientations as shown in the diagram. An SCR or called thyristor is able to pass only one half cycle of an AC signal whereas a triac is able to pass both the halves of an AC signal input. These devices are different from transistors due to the following reasons:

    • SCRs require critical gate firing angle parameters and are not linear.
    • The triggering cannot take place at relatively lower currents, very unlike transistors.
    • They work only with alternating currents (ACs) and will latch up if a DC load is involved.

    Transistors: These active, and perhaps the most important electronic part ever, devices come in a variety of different shapes, sizes, and internal configurations. A transistor may be normally either a NPN or PNP, which are complementary to each other. It’s very easy to differentiate and recognize them through their external appearances and through datasheets. The following explanation will provide you the necessary general information regarding transistors.

    Relay Contacts, NC, NO (2)   Typical Relay Pin-Out Image  

    Like every active component, each category of transistors too will have their own specified breakdown thresholds. Typically, you should be careful about their Collector to Emitter and Base to Emitter breakdown voltages and Currents. They are represented as UCEO, UBEO, and IC (maximum) respectively. If you are not sure with the parameters of a particular device, refer the datasheet immediately.

    Relays: These are electromagnetic mechanical devices used to toggle loads involving heavy current and voltages. A relay is mostly used in conjunction with a transistor where low power switching from the transistor is used to operate the relay and the subsequent output is a much heavier load. This configuration is called a relay driver circuit.

    The next page will further explain how to identify electronic components through their external appearances and lead configurations.

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    Understanding Common Electronic Parts Physically (Continued)

    Typical Low Power General Purpose Transistor Pin Outs, Image  

    Electronic circuit building for hobbyists may be quite easy once they understand physically how to use the following important active members of the electronic family.

    Let’s discuss a few of the typical general purpose transistors commonly and extensively used in electronic circuits.

    General Purpose Low Power (BC 547B): This transistor is highly versatile and may be used in almost all low power applications in an electronic circuit unless specified. Keeping the flat side towards you, the right lead will be the emitter, the center is the base, and the left lead will be the collector. This is true for most of the general purpose transistors. However, a few may have a different configuration. For example in transistors 8050 (NPN)/8550 (PNP), which can handle a bit more power than the BC 547 (NPN)/ BC557 (PNP) and are also more sensitive, has emitter and collector terminal orientations just opposite to the above explanation. The housing incorporated for these types of transistors is typically indicated as a TO-92 package.

    TO-3 Transistor Pin-Outs, Image   TO-220 Transistor Pin-Out, Image  

    Power transistors normally may come in TO-126, TO-220, or TO-3 packages. Again, their specifications may be obtained from their respective datasheets. These transistors are equipped with a metal plate base and a hole or holes drilled over it to facilitate the fitting of a heat sink. Since they have to handle relatively huge currents, they often heat up. An external aluminum metal fitting is generally employed to absorb excessive heat and protect the transistor. This external metallic fixture is called a heat sink.

    To configure a transistor or transistors into a particular circuit, the following parameters will be required:

    It’s always required to assign a transistor base with a resistor for biasing it (making it conduct). The value of this resistor will exactly depend on the collector current (load) of the transistor. The collector current will depend on the resistance of the collector load. You may use Ohms law to find it. A rule of thumb is to select the base resistor whose value is approximately 40 times larger than the collector resistance. For NPN the trigger voltage here will always be a positive and for PNP it will be a negative voltage.

    Transistors Mounted over Heatsinks, image   Also it’s imperative to connect the emitter to negative for NPN and to positive for PNP transistors. The base will respond only after this is done.

    Op Amps: While designing your own circuits, another very important electronic part that you would like to involve is an Op Amp. You may consider them as the big brothers of transistors. Basically, these devices have two inputs and one output. The inputs are named as inverting and non-inverting inputs. These are complementary to each other, yet respond just in the opposite way. The output is specifically the function of its inputs. There may be a huge number of different configurations using op-amps that would be difficult to accommodate in the present article, but I will definitely discuss them comprehensively in one of my future articles very soon.

    CMOS ICs: Unlike Op Amps or any other linear ICs, CMOS chips behave uniquely to well defined voltage levels. Basically they are like toggle switches; their outputs may be either turned fully ON or fully OFF, depending upon their input triggers, making their responses accurate and predictable. I have already talked about these wonderful devices through a few of my previous articles; you may refer them to get a better picture of their functioning.

    Hopefully the above discussion will have provided you with some enlightenment about electronics and electronic circuit building for hobbyists. Please note that this article is no way over and further information will be updated from time to time, so keep following up.

    If you have specific questions related to the above discussion, feel free to ask through your comments (comments are moderated and may not appear instantly).