Fundamental Electronics: - It can be divided into two Major segments PASSIVE and ACTIVE components. We will also in the next section discuss about Hybrid Components which are made out of active and Passive component into one unit.

Passive Components

Resistor:  Resistance = Voltage/Current, Unit = Ohm. Lower the size of the resistor, higher the resistance. Every material has some amount of resistance. Higher the resistance lesser is the current flow. Super conductivity is all about finding material with the lowest resistance so that smaller Integrated chips can be made which would need less cooling.

 Check: Use a Multimeter to check the resistance across the two leads. Care should be exercised in touching a power resistor, since it can be extremely hot.

 Capacitor:  Capacitor stores energy. Used to stabilize the voltage across a circuit. "C" is measured in farads. There are several types of capacitors available like Electrolytic, tantalum, and disc. In electrolytic capacitors enough time should be allowed to discharge before touching  them or else it can possibly hurt. Higher the size higher the capcacity. Capacitors are always used in parallel.

 Check: Some Multimeter can measure capacitance, or special capacitance meter is used in case real high energy capacitor.

 Electrolytic Capacitor: Stores the highest amount of energy. Should be careful in dealing with it. The bigger it is, the more dangerous could it be. This is one of the components, which goes bad often and has a limited life. Polarity is very important and it cannot be switched.

Inductor (Also called as choke): Inductor is similar to capacitors in terms of storing energy. It is used to stabilize the current. In most cases it is used in series where the current flow needs to be stable. Typical applications are in the input/output side of motor drives.

 Check: The way to check an inductor is to measure and see whether there is resistance across the two leads. It should have some resistance based on the thickness and length of the wire used. If it is fully open, it is bad. Also check and see if it is shorted to the body. If it is shorted it is bad. Normally the failure rate of an inductor is very low.

 Active Components

 Diode: This is a basic electronic device, which will conduct only in one direction above a certain voltage and will conduct, in the reverse direction only at an extremely high voltage. This is equivalent to one way valve

 Check: When measured with a Multi meter across, in diode mode, it should read around 580 ohms one way and 1.6Meg Ohms when the leads of the multimeter are switched

 Zener Diode: This is a different kind of diode, which will maintain the voltage applied across it to a certain voltage.

 Check: When measured with a Multi meter in resistance mode it should read a higher resistance, in some cases even open, regardless of the Multi meter leads.

 Transistor: Transistors have three leads, called emitter, collector and base. There are two kinds PNP and NPN. They have three leads. The transistor is like a big valve with a pilot valve to open and close the main valve. Current flows from Emitter to Collector or vice versa. Base is like a pilot valve. When give me small amount of current the transistor fires allowing a bigger amount of current to flow.

 Check: In most cases, when the transistors go bad, they are either short are open between base and emitter. When measured with a Multimeter, in resistance mode base to emitter should have a resistance of about 150 ohms and none of the three leads should be shorted to each other. If any of the above two are any different, it is worth trying a new transistor, but this is not a complete test. Normally this is enough to quickly find if one should spend time in pursuing the transistor.

Thyristor (SCR): This is exactly similar to transistor, but used in high power applications. The bigger the size higher the current it carries. Welding applications will have water cooling the Thyristors.

Check: Exactly similar steps like a transistor would help identify the faulty unit.

 IGBT, Mosfet: They work exactly like a thyristor, but made of high conductivity material. The losses are low in these components. Less cooling is required. They also work at a higher speed.

 Author: Ven Swaminathan. Email - Ven@cnconestop.com

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