Variable resistor (Potentiometer) The variable resistor (potentiometer)
Figure 10A shows the schematic symbol of a variable resistor. 10A shows a schematic picture symbol of a variable resistor. It is Often Referred to as a potentiometer, Because It can be used as a potential (voltage) divider. This is often referred to as a potentiometer, it can be used as a divider (voltage) potential. Figure 10C shows how Potentiometers look like in reality, They Vary in size and shape, but They all work the same way. 10C shows how a potentiometer picture looks like in reality, they differ in size and shape, but they all work the same way. The pins at the right and left extremities of the potentiometer are equivalent to the fixed point (like Va and Vb in the figure 10A), while the middle pin is the moving part of the potentiometer, and is used to change the ratio of the resistance at its left to the resistance at its right. The pins on the left and right legs of the potentiometer which is equivalent to a fixed point (such as Va and Vb in Figure 10A), while the middle pin is the moving part of the potentiometer, and is used to change the ratio of the resistance on the left to drag on the right. Hence the voltage divider equation APPLIES to the potentiometer, the which can deliver any voltage from Va to Vb. then the voltage divider equation applies to the potentiometer, which can provide any voltage from Va to Vb.
Also a variable resistor can be used in a current-limiting configuration by connecting the output Vout to the point Vb like in the figure 10B. Also a variable resistor can be used in configurations that limit the current by connecting the output Vout point to Vb as in figure 10B. Imagine how the current will flow through the resistance from the left Extremity to the right until it Reaches the arrow (the moving part That varies resistance) Practically all current will then flow through the jumper wire (theoretically some very little current will pass through the rest of the resistor) Imagine how the current will flow through the resistance of the limb left to right until you reach the arrow (which moves the variable resistance) then almost all the current flows through a wire jumper (theoretically a very little current will pass through the remaining resistors)
This way you can also use a potentiometer to adjust the current flowing into any electronic component, or lamp for example. This way you also can use a potentiometer to adjust the current flowing into the electronic component, or a lamp for example. Actually this is how most of the old light dimmers work. Actually this is how most of the old lamp dimmer works.
LDR (Light Dependent Resistors) and thermistors LDR (Light Dependent Resistor) and thermistorThat there many electronic sensors rely on a resistor Whose resistance varies with respect to another parameter like light, temperature, or pressure. There are many electronic sensors that rely on a resistor of resistance varies with respect to other parameters such as light, temperature stress, or. We are going to briefly study LDRs (Light Dependent Resistors) and Thermistors (Temperature dependent resisters), and you will notice That all resistors based sensors work exactly the same way, as the the easiest way to use one of Those sensors is to put them in a voltage divider configuration, obtaining a voltage That changes with the Measured values, instead of a resistance change. We will briefly study the LDRs (Light Dependent Resistor) and thermistors (resisters depending on temperature), and you will see that all resistor-based sensor works the same way, as the easiest way to use one sensor is to put them in a configuration voltage divider, a voltage that changes with the measured values, rather than a change in resistance. Sensors Whose output is Voltage variations are much Easier to interface to computers or microcontrollers, as you shall see during the next tutorials. Sensor output voltage variation is easier to interface to a computer or microcontroller, as you will see over the next tutorial.
Fig. Image. 11A 11AAs you can see in figure 11A, LDRs Vary in size, but They are all resistors will Whose resistance when exposed to light Decrease, and increase of when shed in the dark. As you can see in Figure 11A, LDRs vary in size, but they are all the resistance of the resistor will be reduced when exposed to light, and increases when the shed in the dark. They are also Referred to as photoresistors, photoconductors or Cds Because They are made of cadmium sulphide Unfortunately, LDRs response can be slow, and Often They also growing niche to lack accuracy, but still, they are also known as photoresistors, photoconductors or CD because they are made of Cadmium sulfide Unfortunately, the response of LDRs can be slow, and they also often tend to lack accuracy, but still,
Fig. Image. 11B 11B
They are very easy to use (see example here). they are very easy to use (see example here). That requires more applications for accuracy, and faster response, photodiodes or phototransistors are preferred over LDRs. For applications requiring more accuracy and faster response, diode or photo transistor is preferred over LDRs. Usually, an LDR's resistance can Vary from 50 Typically, LDR resistance can be varied from 50 in the sun light, to over 10M in light of the sun, for more than 10M in absolute darkness. in absolute darkness. As we said before, the variation of resistance has be converted into a voltage variation, by introducing the LDR into a voltage divider configuration, as shown in figure 11B. As we said before, the variation of resistance has been converted into a voltage variation, by introducing into the LDR voltage divider configuration, as in Figure 11B.
Recalling equation 6B, you will see That the output voltage (Vout) of this circuit follows the Following equation: Given the equation 6B, you will see that the output voltage (Vout) of this series follows the following equation:
Supposing That the LDR's resistance varies from 10M Suppose that the resistance of LDR varies from 10M to 50 to 50, the calculations would yield That Vout varies from 0.005V to 4.975V respectively. , The calculation will result in Vout is varied respectively from 0.005V to 4.975V. This voltage variation can be then fed to an integrated circuit named an Operational Amplifier to create a reliable light sensor. Voltage variation can then be fed into the integrated circuit called an Operational Amplifier to create a reliable light sensor.Similarly, a Thermistor can be used in the exact same way to create a sensor varies with temperature Whose voltage variation. Similarly, the thermistor can be used with the exact same way to make the sensor voltage that varies with temperature variations. However, thermistors comes in much more than LDRs varieties and types, for instance, a thermistor can either be a negative temperature coefficient type (NTC) Whose Will Decrease resistance with temperature rise, or positive temperature coefficient type (PTC), Whose increase of resistance will with temperature rise. However, thermistors come in more varieties and types of LDRs, for example, the thermistor can be a kind of negative temperature coefficient (NTC) of resistance will decrease with increasing temperature, the type or positive temperature coefficient (PTC), which will increase the resistance to temperature rise . Nowadays, electronics manufacturers Provide thermistors of very high quality in terms of accuracy and response time, inneed, it's very common to see thermistors in very precise digital devices like thermostats. Currently, electronics manufacturers provide a very high quality thermistor in terms of accuracy and response time, inneed, very common to see the thermistor in a very precise devices such as digital thermostats.
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