SERVO MOTOR
A servomotor (also abbreviated with servo) is a compact design of a small DC motor and a sensor for precision feedback. These type of motors are perfect for angular position or velocity. Let's have a look to the inside of a servo.
SPACERS
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RESISTOR
A resistor is an electrical component that consists of an electrical resistance. The component is used to limit current flow, to divide voltages, and a lot more. Nothing new, but have you ever wondered how a resistor is made? Every resistor exist of a resistive element to make the electrical resistance possible. These resistive elements are insulators (sounds logical). The most common types of resistors are carbon film and metal film resistors. Mind you, the carbon or metal film itself isn't actually the resistive element (carbon and metal are both conducting materials), but it's the ceramic core and in particular the way that the film is deposited on the core! The film is deposited in a helical cut. The total resistance will decrease by increasing the layer thickness or by increasing the pitch of the helix (and thus decreasing the length of the helical, electrical path). Remember that the longer a wire or path, the bigger its resistance (cfr. Pouillet's law*).
*Pouillet's law shows us the difference between the concepts 'resistance' and 'resistivity'. Resistivity r is a property of a material (e.g. copper) that quantifies how strongly that material opposes the flow of electric current. Resistance R is not a property of material, but is used for objects (e.g. a copper wire) that also has dimensions in particular. The resistance of an object is thus determined by its material and its dimensions. The resistance of a wire would be expected to be greater for a longer wire with length L, and less for a wire of larger cross sectional area A. If we translate this into math language, we get: R=r·L/A
A metal film resistor is more precise (tight tolerance) and can be noticed thanks to its blue colour, while a carbon film resistor is typically brown. Unfortunately, they are more expensive and as a result, I've always used carbon film resistors in all my projects so far.
Carbon film resistor 10W
Metal film resistor 681W
Colour coding
Every resistor (no matter what type it is) exists of a code in the form of coloured rings around its coating. This code makes it possible to easily read the resistance of the resistor. The colour of a ring and its place in the row is assigned to one specific number. All possible combinations are showed in the table below. Note that a carbon film resistor has four rings, while a metal film has five rings. The last ring always shows the tolerance and the second last ring is always a multiplier. The first two or three rings have the same meaning and represents each a number from 0 to 9. An attentive reader has probably noticed that the first ring will never be black (zero at the beginning of a number is nonsense). The tolerance ring of a carbon film is typically gold (5%), and that of a metal film is brown (1%).
Examples
Ohm's law
Let's expand on the most famous (and simplest) law in electronics: Ohm's law. This law simply states that the current I is proportional to the voltage V and inverse proportional to the electrical resistance R. Or as a mathematician would say: I=V/R, and thus V=I·R. But what does this mean in practice? I'll first explain the term electrical resistance and the difference between current and voltage.
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Current I
Current is a measurement for the flow of electric charge (carried by moving electrons) through a wire per seconds. The more electrons per seconds, the more 'electricity' we can consider. You've probably heard already the analogy with a water flow: The flow of moving water particles though a pipe can be considered as electrical current. Electrical current is measured in Amps.
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Voltage V
To make the electrons flow in an electric circuit (or analog the water particles through a pipe), we need a pressure to push them forwards. This pressure is called 'Voltage' and is measured in Volts. Voltages of 5 Volts or 12 Volts are frequently used values in electronics. These low DC (Direct Current) voltages are safe to us, so don't be afraid to pick up a battery or touching the output of a DC power supply. On the other hand, we also have the AC (Alternating Current) voltages. These voltages are much dangereous, and for sure AC voltages of 230V! So be careful while replacing a broken ceiling light at home. So summarized in my own words: 'The current will kill you, but it's the voltage that makes the current dangereous.'
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Resistance R
The electrical resistance of a material is the resistance against the flow of electrons. Materials with a high electrical resistance are called 'insulators' (such as plastic, paper, ...), and them with a small resistance are called 'conductors' (like copper, tin, ...).
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The relationship between these three concepts is given by Ohm's law (V=I·R), and is actually really easy to understand. Imagine you possess a copper wire with resistance R. If you want to have a current I flowing through the wire, you will need a voltage V across the wire as indicated in Ohm's law. Have a look to the following two fictional situations.
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Situation 1 (R = constant): A few minutes later you want to double the current I through that same wire. The only solution will be to make the voltage V across the wire also as twice as big (because the copper wire isn't changed and thus the resistance R remains constant). Analog to the water flow: you need more pressure to increase the flow.
Situation 2 (I = constant): After two years you need to replace the copper wire. You are a beginning engineer and you make the (bad) choice to take an iron wire (with the same length and cross section) instead. The iron wire has a higher resistivity and thus a higher resistance than the copper wire with resistance R (5.5 times as high to be specific). To have the same current I flowing through the iron wire as you had through the copper wire, you will need a higher voltage from Ohm's law (also 5.5 times higher than V) because the resistance has increased. Sounds logical, doesn't it? If the resistance of an element increases, the voltage across it must also increase to be sure that the current remains constant through that element.
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Use
In mechatronics and simple basic circuits are resistors mostly used for three applications: to use with LEDs, to create a voltage divider with a (variable) resistor, and as a pull-up (or pull-down) resistor to use with a switch. All these applications are explained in detail in another paragraphs which you can find by clicking on the underlined words.
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CAPACITOR
A capacitor is an electric component that stores electrical energy. It's something vage in the beginning of your carrier, but look at it as they would be temporarily batteries. Before I start explaining how they are made, I'm going to immediately give you a practical example of a capacitor to make the aim of this component more clear.
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DIODE
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INFRARED SENSOR
- DISTANCE SENSOR
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INFRARED SENSOR
- LINE TRACKING
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LIQUID CRYSTAL DISPLAY
- LCD
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