There are many concepts that you cannot see with your own eyes and touch with your hands. The most striking example is electrical engineering, consisting of complex circuits and obscure terminology. Therefore, many simply give up the difficulties of the upcoming study of this scientific and technical discipline.
To gain knowledge in this area will help the basics of electrical engineering for beginners, outlined in an accessible language. Supported by historical facts and illustrative examples, they become fascinating and understandable even for those who first came across unfamiliar concepts. Moving gradually from simple to complex, it is quite possible to study the materials presented and use them in practical activities.
Concepts and properties of electric current
Electrical laws and formulas are required not only for any calculations. They are also needed by those who, in practice, carry out operations related to electricity. Knowing the basics of electrical engineering, you can logically determine the cause of the malfunction and eliminate it very quickly.
The essence of electric current is the movement of charged particles that carry an electric charge from one point to another. However, during random thermal motion of charged particles, following the example of free electrons in metals, charge transfer does not occur. The movement of an electric charge through the cross section of a conductor occurs only if ions or electrons participate in the ordered motion.
Electric current always flows in a certain direction. Its presence is indicated by specific signs:
- Heating of the conductor through which current flows.
- The change in the chemical composition of the conductor under the influence of current.
- The provision of force on neighboring currents, magnetized bodies and neighboring currents.
Electric current can be constant and variable. In the first case, all its parameters remain unchanged, and in the second, the polarity changes periodically from positive to negative. In each half-cycle, the direction of the electron flow changes. The rate of such periodic changes is the frequency measured in hertz
Basic current values
When an electric current occurs in the circuit, a constant charge transfer occurs through the cross section of the conductor. The amount of charge transferred over a specific unit of time is called, measured in amperes.
In order to create and maintain the movement of charged particles, it is necessary to apply the force applied to them in a certain direction. In the event of termination of such an action, the flow of electric current also ceases. Such a force is called an electric field, it is also known as. It is it that causes the potential difference or voltage at the ends of the conductor and gives impetus to the movement of charged particles. To measure this quantity, a special unit is used - volt. There is a definite relationship between the main quantities, reflected in Ohm's law, which will be considered in detail.
The most important characteristic of a conductor directly related to electric current is resistancemeasured in ohmah. This value is a kind of reaction of the conductor to the flow of electric current in it. As a result of the resistance, the conductor heats up. With an increase in the length of the conductor and a decrease in its cross section, the resistance value increases. The value of 1 Ohm occurs when the potential difference in the conductor is 1 V, and the current strength is 1 A.
Ohm's law
This law relates to the main provisions and concepts of electrical engineering. It most accurately reflects the relationship between such quantities as current strength, voltage, and resistance. The definitions of these quantities have already been considered, now it is necessary to establish the degree of their interaction and influence on each other.
In order to calculate a particular value, you must use the following formulas:
- Current strength: I \u003d U / R (amperes).
- Voltage: U \u003d I x R (volts).
- Resistance: R \u003d U / I (ohm).
The dependence of these quantities, for a better understanding of the essence of the processes, is often compared with hydraulic characteristics. For example, a valve with an adjacent pipe is installed at the bottom of a tank filled with water. When the valve opens, water begins to flow, since there is a difference between high pressure at the beginning of the pipe and low - at its end. The exact same situation arises at the ends of the conductor in the form of a potential difference - the voltage under which the electrons move along the conductor. Thus, by analogy, the voltage is a kind of electrical pressure.
The strength of the current can be compared with the flow of water, that is, its amount flowing through the cross section of the pipe for a specified period of time. With a decrease in the diameter of the pipe, the flow of water will decrease due to an increase in resistance. This limited flow can be compared to the electrical resistance of a conductor, which keeps the flow of electrons within certain limits. The interaction of current, voltage and resistance is similar to hydraulic characteristics: with a change in one parameter, all the others change.
Energy and power in electrical engineering
In electrical engineering, there are also such concepts as energy and powerrelated to Ohm's law. Energy itself exists in mechanical, thermal, nuclear and electrical form. In accordance with the law of conservation of energy, it cannot be destroyed or created. It can only be transformed from one form to another. For example, in audio systems, electricity is converted into sound and heat.
Any electrical appliances consume a certain amount of energy over a set period of time. This value is individual for each device and represents the power, that is, the amount of energy that this or that device can consume. This parameter is calculated by the formula P \u003d I x U, the unit of measurement is. It means moving one volt through a resistance of one ohm.
Thus, the basics of electrical engineering for beginners will help at first to understand the basic concepts and terms. After that, it will be much easier to put the acquired knowledge into practice.
Electrics for Dummies: The Basics of Electronics
We offer a small material on the topic: "Electricity for beginners." It will give an initial idea of \u200b\u200bthe terms and phenomena associated with the movement of electrons in metals.
Features of the term
Electricity is the energy of small charged particles moving in conductors in a certain direction.
At constant current, there is no change in its value, as well as the direction of movement for a certain period of time. If a galvanic cell (battery) is selected as the current source, in this case the charge moves in an orderly manner: from the negative pole to the positive end. The process continues until it completely disappears.
Alternating current periodically changes the magnitude, as well as the direction of movement.
AC transmission circuit
Let's try to understand what phase in a word is heard by everyone, but not everyone understands its true meaning. We will not go into details and details, we will choose only the material that the home master needs. A three-phase network is a method of transmitting electric current, in which current flows through three different wires, and one returns. For example, in an electric circuit there are two wires.
The first wire to the consumer, for example, to the kettle, is current. The second wire is used to return it. When such a circuit is opened, there will be no passage of electric charge inside the conductor. This circuit describes a single phase circuit. in electricity? Phase is the wire through which electric current flows. Zero is the wire through which the return is made. In a three-phase circuit there are immediately three phase wires.
An electrical panel in the apartment is necessary for current in all rooms. consider economically feasible, because they do not need two. When approaching the consumer, there is a separation of current into three phases, and each has zero. The earthing switch, which is used in a single-phase network, does not carry a workload. It is a fuse.
For example, if a short circuit occurs, there is a danger of electric shock, fire. To prevent this situation, the current should not exceed a safe level, the excess goes into the ground.
The manual "School for an electrician" will help beginners to cope with some breakdowns of household appliances. For example, if there are problems with the operation of the electric motor of the washing machine, current will flow to the external metal casing.
In the absence of grounding, the charge will be distributed throughout the machine. When you touch it with your hands, a person will act as a grounding conductor, having received an electric shock. If you have a ground wire, this situation will not occur.
Electrical Features
The manual "Electricity for Dummies" is popular with those who are far from physics, but plan to use this science for practical purposes.
The beginning of the nineteenth century is considered the date of the appearance of electrical engineering. It was at this time that the first current source was created. The discoveries made in the field of magnetism and electricity were able to enrich science with new concepts and facts that have important practical value.
The School for an Electrician manual introduces you to basic terms related to electricity.
Many collections of physics have complex electrical circuits, as well as a variety of obscure terms. In order for beginners to understand all the intricacies of this section of physics, a special manual "Electricity for Dummies" was developed. An excursion into the world of the electron must begin with a consideration of theoretical laws and concepts. Illustrative examples, historical facts used in the book "Electricity for Dummies" will help novice electricians learn knowledge. To test performance, you can use tasks, tests, exercises related to electricity.
If you understand that you do not have enough theoretical knowledge to independently cope with the connection of electrical wiring, refer to the directories for "dummies".
Safety and practice
First you need to carefully study the section on safety. In this case, during work related to electricity, there will be no emergency situations hazardous to health.
In order to put into practice the theoretical knowledge obtained after independent study of the basics of electrical engineering, you can start with old household appliances. Before starting repairs, be sure to read the instructions that came with the device. Do not forget that there is no need to joke with electricity.
Electric current is associated with the movement of electrons in conductors. If the substance is not able to conduct current, it is called a dielectric (insulator).
For the motion of free electrons from one pole to another, a definite potential difference must exist between them.
The intensity of the current passing through the conductor is related to the number of electrons passing through the cross section of the conductor.
The speed of the current is affected by the material, length, cross-sectional area of \u200b\u200bthe conductor. With an increase in the length of the wire, its resistance increases.
Conclusion
Electricity is an important and complex section of physics. The manual "Electricity for Dummies" considers the basic quantities characterizing the efficiency of electric motors. The units of voltage are volts, the current is determined in amperes.
Anyone has a certain power. It means the amount of electricity generated by the device for a certain period of time. Energy consumers (refrigerators, washing machines, kettles, irons) also have power, spending electricity during operation. If you wish, you can carry out mathematical calculations, determine the approximate fee for each household appliance.
Nontrivial occupation, I tell you. :) In order to facilitate the assimilation of the material, I introduced a number of simplifications. Completely delusional and unscientific, but more or less clearly showing the essence of the process. The technique of "sewer electrics" has successfully proved itself in field trials, and therefore will be used here. I just want to draw attention to the fact that this is just a visual simplification, valid for the general case and for a specific moment, in order to understand the essence and has practically nothing to do with the real physics of the process. Why is it then? And to make it easier to remember that there’s no reason to confuse voltage and current and understand how resistance affects all this, otherwise I heard enough from students ...
Current, voltage, resistance.
If we compare the circuit with sewage, the power source is a drain tank, flowing water is current, water pressure is voltage, and shit rushing through the pipes is a payload. The higher the drain tank, the greater the potential energy of the water in it, and the stronger the pressure-current passing through the pipes will be, which means it will be able to flush more crap-load.
In addition to the current crap, the flow is prevented by friction against the pipe walls, forming losses. The thicker the pipe, the less loss (gee gee gee now you remember why audiophiles for their powerful acoustics take thicker wires;)).
So to summarize. The circuit contains a source that creates a potential difference between its poles - voltage. Under the influence of this voltage, the current rushes through the load to where the potential is lower. The movement of current is impeded by the resistance formed from the payload and losses. As a result, the voltage-pressure weakens the stronger, the greater the resistance. Well, now, let’s put our sewers in a mathematical direction.
Ohm's law
For example, let's calculate the simplest circuit, consisting of three resistances and one source. I will draw the circuit not as is customary in textbooks on SOE, but closer to the real circuit, where they take the point of zero potential - the case, usually equal to the minus power supply, and consider the plus point as a potential with a voltage equal to the voltage. To begin with, we believe that we know the voltage and resistances, which means we need to find the current. Add all the resistances (read the inset for the rules for adding resistances) in order to get the total load and divide the voltage by the result - the current is found! Now let's see how the voltage is distributed across each of the resistances. We turn Ohm's law inside out and begin to calculate. U \u003d I * R since the current in the circuit is the same for all series resistances, it will be constant, but the resistances are different. The result was that U source \u003d U1 + U2 + U3. Based on this principle, it is possible, for example, to connect in series 50 bulbs rated for 4.5 volts and quietly power from a 220 volt outlet - not a single bulb will burn out. And what will happen if one hefty resistance is put into this bundle, in the middle, let's say KiloOhm, and take the other two less - by one Ohm? And from the calculations it will become clear that almost all the voltage will drop out at this large resistance.
Kirchhoff's Law.
According to this law, the sum of the currents entering and leaving the node is equal to zero, and the currents flowing into the node are usually denoted with a plus, and flowing with a minus. By analogy with our sewer, water from one powerful pipe scatters along small heaps. This rule allows you to calculate the approximate current consumption, which is sometimes just necessary when calculating circuit diagrams.
Power and loss
The power that is consumed in the circuit is expressed as the product of voltage by current.
P \u003d U * I
Because the greater the current or voltage, the greater the power. Because the resistor (or wires) does not fulfill any payload, then the power falling out of it is pure losses. In this case, power can be expressed through the Ohm law as follows:
P \u003d R * I 2
As you can see, an increase in resistance causes an increase in power, which is spent on losses, and if the current increases, then the losses increase in a quadratic dependence. In the resistor, all the power goes into heating. For the same reason, by the way, batteries heat up during operation - they also have internal resistance, on which part of the energy is dissipated.
That's why audiophiles for their heavy-duty sound systems take thick copper wires with minimal resistance to reduce power losses, since there are considerable currents there.
There is a law of the total current in the circuit, although in practice it never came in handy for me, but it doesn’t hurt to know, so pulling out a textbook on TOE (theoretical fundamentals of electrical engineering) from the network is better for secondary schools, everything is much simpler and more understandable there - without going to higher mathematics.
Each of us, when he begins to get involved in something new, immediately throws himself into the “abyss of passion” trying to complete or realize difficult projects homemade. So it was with me when I became interested in electronics. But as usual - the first setbacks reduced the fuse. However, I was not used to retreating and began to systematically (literally from the basics) comprehend the mysteries of the world of electronics. And so was born the "manual for beginner techies"
Step 1: Voltage, Current, Resistance
These concepts are fundamental and without familiarity with them, continuing to teach the basics would be pointless. Let's just remember that each material consists of atoms, and each atom in turn has three types of particles. An electron is one of these particles, it has a negative charge. Protons have a positive charge. In conductive materials (silver, copper, gold, aluminum, etc.) there are many free electrons that move randomly. Voltage is the force that makes electrons move in a certain direction. A stream of electrons that moves in one direction is called a current. When electrons move along a conductor, they collide with some kind of friction. This friction is called resistance. Resistance “compresses” the free movement of electrons, thereby reducing the current value.
A more scientific definition of current is the rate of change in the number of electrons in a certain direction. The unit of current is Ampere (I). In electronic circuits, the flowing current lies in the range of milliamps (1 amp \u003d 1000 milliamps). For example, the inherent current for the LED is 20mA.
The unit of voltage is Volt (V). Battery - is a source of voltage. Voltage 3V, 3.3V, 3.7V and 5V is the most common in electronic circuits and devices.
Voltage is the cause, and current is the result.
The unit of resistance is Ohm (Ω).
Step 2: Power Supply
A rechargeable battery is a voltage source or a “right” source of electricity. The battery produces electricity through an internal chemical reaction. On the outside, she has two terminals. One of them is a positive conclusion (+ V), and the other is negative (-V), or "ground." There are usually two types of power supplies.
- Batteries
- Batteries
The batteries are used once and then disposed of. Batteries can be used several times. Batteries come in many shapes and sizes, from miniature batteries used to power hearing aids and watches to room-sized batteries that provide backup power for telephone exchanges and computer centers. Depending on the internal composition, power sources can be of different types. Some of the most common types used in robotics and technical projects:
1.5V batteries
Batteries with this voltage can have different sizes. The most common sizes are AA and AAA. Capacity range from 500 to 3000 mAh.
3V lithium coin
All these lithium cells are rated at 3 V (at load) and with an open circuit voltage of about 3.6 volts. Capacity can reach from 30 to 500mAh. Widely used in handheld devices due to their tiny size.
Nickel Metal Hydride (NiMH)
These batteries have a high energy density and can be charged almost instantly. Another important feature is the price. Such batteries are cheap (in comparison with their sizes and capacities). This type of battery is often used in robotic homemade.
3.7 V lithium-ion and lithium polymer batteries
They have good discharge capacity, high energy density, excellent performance and small size. A lithium polymer battery is widely used in robotics.
9 volt battery
The most common shape is a rectangular prism with rounded edges and terminals that are located on top. The capacity is about 600 mAh.
Lead acid
Lead-acid batteries are the workhorse of the entire electronics industry. They are incredibly cheap, rechargeable and easy to buy. Lead-acid batteries are used in mechanical engineering, UPS (uninterruptible power supplies), robotics and other systems where a large supply of energy is needed, and weight is not so important. The most common are voltages 2V, 6V, 12V and 24V.
Series-parallel battery connection
The power source can be connected in series or in parallel. When connected in series, the voltage value increases, and when connected in parallel, the current current value increases.
There are two important points regarding batteries:
Capacity is a measure (usually in Amp-h) of the charge stored in the battery, and is determined by the mass of the active material contained in it. Capacity is the maximum amount of energy that can be extracted under specified conditions. However, the actual storage capacity of the battery may vary significantly from the nominal declared value, and the battery capacity is highly dependent on age and temperature, charging or discharging modes.
Battery capacity is measured in watt-hours (W * h), kilowatt-hours (kWh), ampere-hours (A * h) or milliampere-hour (mA * h). A watt-hour is the voltage (V) times the current strength (I) (we get the power - the unit of measurement of watts (W)), which the battery can give out for a certain period of time (usually 1 hour). Since the voltage is fixed and depends on the type of battery (alkaline, lithium, lead-acid, etc.), often only Ah or mAh is noted on the outer shell (1000 mAh \u003d 1Ah). For longer operation of the electronic device, batteries with a low leakage current must be taken. To determine battery life, divide the capacity by the actual load current. A circuit that consumes 10 mA and is powered by a 9-volt battery will run for about 50 hours: 500 mAh / 10 mA \u003d 50 hours.
In many types of batteries, you cannot “pick up” energy completely (in other words, the battery cannot be completely discharged) without causing serious, and often irreparable damage to chemical components. The discharge depth (DOD) of the battery determines the fraction of current that can be extracted. For example, if the DOD is defined by the manufacturer as 25%, then only 25% of the battery capacity can be used.
The charge / discharge rate affects the rated capacity of the battery. If the power source discharges very quickly (i.e., the discharge current is high), then the amount of energy that can be extracted from the battery is reduced and the capacity will be lower. On the other hand, if the battery discharges very slowly (low current is used), then the capacity will be higher.
Battery temperature will also affect capacity. At higher temperatures, the battery capacity is usually higher than at lower temperatures. However, intentionally raising the temperature is not an effective way to increase the battery capacity, as it also reduces the life of the power source itself.
C-capacity: The charge and discharge currents of any battery are measured relative to its capacity. Most batteries, with the exception of lead acid, are rated at 1C. For example, a battery with a capacity of 1000mAh, gives 1000mA for one hour, if the level is 1C. The same battery, with a level of 0.5C, gives out 500mA for two hours. With a 2C level, the same battery delivers 2000mA in 30 minutes. 1C is often referred to as a one-hour discharge; 0.5C - as a two-hour and 0.1C - as a 10-hour.
Battery capacity is usually measured using an analyzer. Current analyzers display information as a percentage based on the value of the nominal capacity. A new battery sometimes produces more than 100% of the current. In this case, the battery is simply rated conservatively and can withstand a longer time than specified by the manufacturer.
The charger can be selected in terms of battery capacity or C. For example, a charger with a rating of C / 10 will fully charge the battery after 10 hours, a charger with a rating of 4C would charge the battery after 15 minutes. Very fast charging rates (1 hour or less) usually require the charger to carefully monitor battery parameters, such as voltage and temperature limits, to prevent overcharging and battery damage.
The voltage of a galvanic cell is determined by the chemical reactions that take place inside it. For example, alkaline cells - 1.5 V, all lead-acid - 2 V, and lithium - 3 V. The batteries can consist of several cells, so you rarely see a 2-volt lead-acid battery. Usually they are connected together internally to produce 6 V, 12 V or 24 V. Do not forget that the rated voltage in a “1.5-volt” AA battery actually starts at 1.6 V, then quickly drops to 1.5, and then slowly drifts down to 1.0 V, at which the battery is already considered to be 'discharged'.
What is the best battery choice for crafts?
As you already understood, in the public domain, you can find many types of batteries with different chemical compositions, so it is not easy to choose which food is the best for your project. If the project is very volatile (large sound systems and motorized homemade) You should choose a lead-acid battery. If you want to build a portable under the tree, which will consume a small current, then you should choose a lithium battery. For any portable project (light weight and moderate power) we choose a lithium-ion battery. You can choose a cheaper battery based on metal-nickel hydride (NIMH), although they are heavier, but they are not inferior to lithium-ion in other characteristics. If you would like to make an energy-intensive project, then a lithium-ion alkaline (LiPo) battery will be the best option, because it is small in size, lightweight compared to other types of batteries, recharges very quickly and produces a high current value.
Want your batteries to last a long time? Use a high-quality battery charger that has sensors to maintain the proper charge level and recharge with low current. A cheap charger will kill your batteries.
Step 3: Resistors
A resistor is a very simple and most common element in circuits. It is used to control or limit the current in an electrical circuit.
Resistors are passive components that only consume energy (and cannot produce it). Resistors are typically added to the circuit, where they complement active components such as op amps, microcontrollers, and other integrated circuits. They are commonly used to limit current, separate voltages and input / output lines.
Resistor resistance is measured in ohms. Larger values \u200b\u200bcan be matched with the prefix kilo, mega, or gig to make the values \u200b\u200beasy to read. Often you can see resistors labeled kOhm and MΩ range (much less often mOhm resistors). For example, a 4.700Ω resistor is equivalent to a 4.7kΩ resistor and a 5,600,000Ω resistor can be written as 5,600kΩ or (more commonly) 5.6MΩ.
There are thousands of different types of resistors and many firms that produce them. If we take a rough gradation, then there are two types of resistors:
- with clearly defined characteristics;
- general purpose, whose characteristics can "walk" (the manufacturer himself indicates a possible deviation).
An example of general characteristics:
- Temperature coefficient;
- Voltage coefficient;
- Frequency range;
- Power;
- Physical size.
According to their properties, resistors can be classified as:
Line resistor - a type of resistor whose resistance remains constant with an increase in the potential difference (voltage) that is applied to it (the resistance and current that passes through the resistor does not change from the applied voltage). Features of the current-voltage characteristic of such a resistor is a straight line.
Non linear resistor - this is a resistor whose resistance varies depending on the value of the applied voltage or the current flowing through it. This type has a non-linear current-voltage characteristic and does not strictly follow Ohm's law.
There are several types of non-linear resistors:
- OTC (Negative Temperature Coefficient) resistors - their resistance decreases with increasing temperature.
- PEC resistors (Positive Temperature Coefficient) - their resistance increases with temperature.
- Resistors LZR (Light-dependent resistors) - their resistance changes with a change in the intensity of the light flux.
- Resistors VDR (Volt-dependent resistors) - their resistance critically decreases when the voltage value exceeds a certain value.
Non-linear resistors are used in various projects. LZR is used as a sensor in various robotic projects.
In addition, resistors come with a constant and variable value:
Constant resistors - types of resistors, the value of which has already been established, during production and cannot be changed during use.
Variable resistor or potentiometer -type of resistor whose value can be changed during use. This type usually has a shaft that rotates or moves manually to change the resistance value in a fixed range, for example, from. 0 kΩ to 100 kΩ.
Resistance Store:
This type of resistor consists of a “package” that contains two or more resistors. It has several terminals, thanks to which the resistance value can be selected.
The composition of the resistors are:
Carbon:
The core of such resistors is cast from carbon and a binder, creating the required resistance. The core has cup-shaped contacts holding the resistor rod on each side. The entire core is filled with material (like Bakelite) in an insulated casing. The case has a porous structure, so carbon composite resistors are sensitive to relative humidity.
These types of resistors usually produce noise in the circuit due to electrons passing through the carbon particles, so these resistors are not used in “important” circuits, although they are cheaper.
Carbon deposition:
A resistor that is made by applying a thin layer of carbon around a ceramic rod is called a carbon-deposited resistor. It is made by heating ceramic rods inside a methane flask and depositing carbon around them. The value of the resistor is determined by the amount of carbon deposited around the ceramic rod.
Film Resistor:
The resistor is made by deposition of the sprayed metal in vacuum on a ceramic rod base. These types of resistors are very reliable, have high stability, and also have a high temperature coefficient. Although they are more expensive than others, they are used in major systems.
Wirewound Resistor:
A wire resistor is made by winding a metal wire around a ceramic core. A metal wire is an alloy of various metals selected according to the declared features and resistances of the required resistor. This type of resistor has high stability and also withstands high power, but, as a rule, they are more bulky compared to other types of resistors.
Metal-ceramic:
These resistors are made by firing some metals mixed with ceramic on a ceramic substrate. The proportion of the mixture in the mixed metal-ceramic resistor determines the resistance value. This type is very stable, and also has precisely measured resistance. They are mainly used for surface mounting on printed circuit boards.
Precision Resistors:
Resistors whose resistance value is within the tolerance, therefore they are very accurate (the nominal value is in a narrow range).
All resistors have a tolerance that is given as a percentage. The tolerance tells us how close to the nominal value of the resistance can vary. For example, a 500Ω resistor that has a tolerance value of 10% may have a resistance between 550Ω or 450Ω. If the resistor has a tolerance of 1%, the resistance will change by only 1%. Thus, a 500Ω resistor can range from 495Ω to 505Ω.
A precision resistor is a resistor with a tolerance level of only 0.005%.
Fuse Resistor:
The wire resistor is designed to easily burn out when the rated power exceeds the threshold. Thus, the fuse resistor has two functions. When the power is not exceeded, it serves as a current limiter. When the rated power is exceeded, oa functions as a fuse, after a burnout the circuit becomes broken, which protects the components from short circuit.
Thermistors:
A heat-sensitive resistor whose resistance value changes with a change in operating temperature.
Thermistors show either a positive temperature coefficient (PTC) or a negative temperature coefficient (NTC).
How much resistance changes with changes in operating temperature depends on the size and design of the thermistor. It is always best to check the reference data to find out all the specifications of the thermistors.
Photoresistors:
Resistors whose resistance varies depending on the light flux that falls on its surface. In a dark environment, the resistance of the photoresistor is very high, a few M Ω. When intense light hits the surface, the resistance of the photoresistor drops significantly.
Thus, photoresistors are variable resistors, the resistance of which depends on the amount of light that falls on its surface.
Output and non-lead types of resistors:
Terminal Resistors: This type of resistor was used in the very first electronic circuits. Components connected to the output terminals. Over time, printed circuit boards began to be used, into the mounting holes of which the terminals of the radio elements were soldered.
Surface Mount Resistors:
This type of resistor has been increasingly used since the introduction of surface mount technology. Usually this type of resistor is created by using thin-film technology.
Step 4: Standard or Common Resistor Values
The notation system has its origins that go back to the beginning of the last century, when most resistors were carbon with relatively poor manufacturing tolerances. The explanation is quite simple - using a 10% tolerance you can reduce the number of manufactured resistors. It would be ineffective to produce resistors with a resistance of 105 ohms, since 105 is within the 10% tolerance range of the resistor per 100 ohms. The next market category is 120 ohms, because a 100 ohm resistor with 10% tolerance will have a range between 90 and 110 ohms. A 120 ohm resistor has a range between 110 and 130 ohms. According to this logic, it is preferable to produce resistors with a 10% tolerance of 100, 120, 150, 180, 220, 270, 330 and so on (respectively rounded). This is the E12 series shown below.
Tolerance 20% E6,
Tolerance 10% E12,
Tolerance 5% E24 (and usually 2% tolerance)
Tolerance 2% E48,
E96 1% tolerance,
E192 0.5, 0.25, 0.1% and above tolerances.
Standard resistor values:
E6 Series: (20% tolerance) 10, 15, 22, 33, 47, 68
E12 Series: (10% tolerance) 10, 12, 15, 18, 22, 27, 33, 39, 47, 56, 68, 82
E24 series: (5% tolerance) 10, 11, 12, 13, 15, 16, 18, 20, 22, 24, 27, 30, 33, 36, 39, 43, 47, 51, 56, 62, 68, 75, 82, 91
E48 series: (2% tolerance) 100, 105, 110, 115, 121, 127, 133, 140, 147, 154, 162, 169, 178, 187, 196, 205, 215, 226, 237, 249, 261, 274, 287, 301, 316, 332, 348, 365, 383, 402, 422, 442, 464, 487, 511, 536, 562, 590, 619, 649, 681, 715, 750, 787, 825, 866, 909, 953
E96 Series: (1% tolerance) 100, 102, 105, 107, 110, 113, 115, 118, 121, 124, 127, 130, 133, 137, 140, 143, 147, 150, 154, 158, 162, 165, 169, 174, 178, 182, 187, 191, 196, 200, 205, 210, 215, 221, 226, 232, 237, 243, 249, 255, 261, 267, 274, 280, 287, 294, 301, 309, 316, 324, 332, 340, 348, 357, 365, 374, 383, 392, 402, 412, 422, 432, 442, 453, 464, 475, 487, 491, 511, 523, 536, 549, 562, 576, 590, 604, 619, 634, 649, 665, 681, 698, 715, 732, 750, 768, 787, 806, 825, 845, 866, 887, 909, 931, 959, 976
E192 series: (0.5, 0.25, 0.1 and 0.05% of tolerance) 100, 101, 102, 104, 105, 106, 107, 109, 110, 111, 113, 114, 115, 117, 118, 120, 121, 123, 124, 126, 127, 129, 130, 132, 133, 135, 137, 138, 140, 142, 143, 145, 147, 149, 150, 152, 154, 156, 158, 160, 162, 164, 165, 167, 169, 172, 174, 176, 178, 180, 182, 184, 187, 189, 191, 193, 196, 198, 200, 203, 205, 208, 210, 213, 215, 218, 221, 223, 226, 229, 232, 234, 237, 240, 243, 246, 249, 252, 255, 258, 261, 264, 267, 271, 274, 277, 280, 284, 287, 291, 294, 298, 301, 305, 309, 312, 316, 320, 324, 328, 332, 336, 340, 344, 348, 352, 357, 361, 365, 370, 374, 379, 383, 388, 392, 397, 402, 407, 412, 417, 422, 427, 432, 437, 442, 448, 453, 459, 464, 470, 475, 481, 487, 493, 499, 505, 511, 517, 523, 530, 536, 542, 549, 556, 562, 569, 576, 583, 590, 597, 604, 612, 619, 626, 634, 642, 649, 657, 665, 673, 681, 690, 698, 706, 715, 723, 732, 741, 750, 759, 768, 777, 787, 796, 806, 816, 825, 835, 845, 856, 866, 876, 887, 898, 909, 920, 931, 942, 95 3, 965, 976, 988
When developing equipment, it is best to stick to the lowest section, i.e. better to use E6 rather than E12. So that the number of different groups in any equipment is minimized.
To be continued
Before proceeding with work related to electricity, it is necessary to “be a little savvy” theoretically in this matter. Simply put, electricity is usually understood to mean this movement of electrons under the influence of an electromagnetic field. The main thing is to understand that electricity is the energy of the smallest charged particles that move inside the conductors in a certain direction.
D.C practically does not change its direction and magnitude in time. Suppose a regular battery has a constant current. Then the charge will flow from minus to plus, without changing, until it runs out.
Alternating current is a current that changes direction of movement and magnitude with a certain periodicity.
Imagine the current as a stream of water flowing through a pipe. After a certain period of time (for example, 5 s), water will rush either one way or the other. With current, this happens much faster - 50 times per second (frequency 50 Hz). During one oscillation period, the current rises to a maximum, then passes through zero, and then the reverse process occurs, but with a different sign. When asked why this happens and why such a current is needed, it can be answered that receiving and transmitting alternating current is much simpler than direct current.
Receiving and transmitting AC is closely related to a device such as a transformer. A generator that produces alternating current is much simpler in a device than a direct current generator. In addition, alternating current is best suited for transmitting energy over a long distance. With it, less energy is lost.
Using a transformer (a special device in the form of coils), alternating current is converted from low voltage to high and vice versa, as shown in the illustration. It is for this reason that most devices operate from a network in which the current is alternating. However, direct current is also widely used - in all types of batteries, in the chemical industry and some other areas.
Many have heard such mysterious words as one phase, three phases, zero, ground or earth, and they know that these are important concepts in the world of electricity. However, not everyone understands what they mean and how they relate to the surrounding reality. Nevertheless, you must know this. Without going into technical details that a homemaster does not need, we can say that a three-phase network is such a method of transmitting electric current when alternating current flows through three wires, and one back. The above should be clarified a bit. Any electrical circuit consists of two wires. One current flows to the consumer (for example, to the kettle), and the other returns back. If you open such a circuit, then the current will not go. That's the whole description of a single-phase circuit.
The wire through which the current flows is called phase, or simply phase, and through which it returns - zero or zero. A three-phase circuit consists of three phase wires and one reverse. This is possible because the alternating current phase in each of the three wires is 120 ° C relative to the adjacent one. More details on this question will help answer the textbook on electromechanics. Transmission of alternating current occurs precisely with the help of three-phase networks. It is economically beneficial - two more neutral wires are not needed.
Approaching the consumer, the current is divided into three phases, and each of them is given zero. So he gets into apartments and houses. Although sometimes a three-phase network starts right in the house. As a rule, we are talking about the private sector, and this state of affairs has its pros and cons. This will be discussed later. Earth, or, more correctly, grounding is the third wire in a single-phase network. In essence, he does not carry a workload, but serves as a kind of safety lock. This can be explained by example. If the electricity goes out of control (for example, a short circuit), there is a danger of fire or electric shock. To prevent this from happening (that is, the current value should not exceed the level safe for humans and devices), grounding is introduced. Through this wire, an excess of electricity literally goes into the ground.
One more example. Suppose a small breakdown occurs in the operation of the electric motor of the washing machine and part of the electric current enters the outer metal shell of the appliance. If there is no ground, this charge will wander around the washing machine. When a person touches it, it will instantly become the most convenient outlet for a given energy, that is, it will receive an electric shock. If there is a ground wire in this situation, an excess charge will drain through it without causing any harm to anyone. In addition, we can say that the neutral conductor can also be a ground and, in principle, it is, but only at a power plant. The situation when the house does not have grounding is unsafe. How to cope with it without changing all the wiring in the house will be described in the future.
Attention!
Some craftsmen, relying on initial knowledge of electrical engineering, install a neutral wire as a ground wire. Never do that. If the neutral wire breaks off the case of the grounded devices will be under voltage 220 V.