Light resistance: Irradiated by 400-600Lux light for two hours, then test with 10Lux under Figure 1 shows a photoresistor as one leg of a voltage divider circuit. Photoresistors, also known as Light-Dependent Resistors (LDR), are a class of resistors that change their resistance in relation to the amount of light falling on the sensor. Max external voltage: Maximum voltage to be continuously given to component in the dark. The impurity dopants should be shallow and should not get ionised in the presence of light. darkness. This photoresistor … They have a very simple structure and they are low cost and rugged devices. If you're planning to have the sensor in a bright area and use a 10KΩ pulldown, it will quickly saturate.That means that it will hit the 'ceiling' of 5V and not be able to differentiate between kinda bright and really bright. FET     Hi, This is my first post on the forum and I've only been using Max for a couple of years and am entirely self-taught so apologies if I use some dodgy terminology. The sensitivity of light dependent resistors or photoresistors also varies with the wavelength of the incident light. external voltage: Maximum voltage to be continuously given to component in the dark.     Return to Components menu . A photoresistor is also called a light-dependent resistor (LDR), photoconductor, or photocell since its resistance changes as incident light intensity changes. These may be specified after a given time because it takes a while for the resistance to fall as the charge carrier recombine - photoresistors are noted for their slow response times. It starts at 5V, and is forced to go through the 5.6KΩ resistor. A0 to A5. Photoresistors can also be used to detect nuclear radiation. Optocouplers with photoresistor Optocouplers with photoresistor consists of a light tight packaged a light source (usually LED) and photoresis-torl. Structurally the photoresistor is a light sensitive resistor that has a horizontal body that is exposed to light. However, the measured voltage continuously drops after the circuit is plugged into a 7.2V nimh battery. Max. This gives: For an input voltage of 5 V -> 2.3 V on the Arduino input; For an input voltage of 10 V -> 2.6 V on the Arduino input It's often used in street lights and as an "electric eye." Capacitors     The circuit has the characteristic of a negative voltage when the light going to the left photoresistor is blocked, and a larger, positive voltage when the right photorestor is blocked. Schematic of Photocell hookup to an analog input The typical way to interface this device is to hook it up to the 3.3 supply and use a 10K pulldown resistor to build a voltage divider circuit as seen i… Carbon film     After a brief struggle, the parts heap disgorged a 1-inch diameter CdS (cadmium sulfide) photoresistor with a dark resistance over 500 kΩ and a full-sunlight resistance around 50 Ω. Comments. Intrinsic photoresistors are made from the pure semiconductor materials such as silicon or germanium. The sensor’s spectral response (see Figure 1.b) is about 550 nm (yellow to green region of visible light). 5 Volts. The easiest way to connect a photoresistor to a microcontroller is to connect a voltage divider of constant resistance and a photoresistor. Particularly as the device is semiconductor based, the maximum operating voltage must be observed. Analog Input Arduino IDE Example Sketch. power consumption: Maximum power at the environmental temperature 25℃. As well as hooking up a photoresistor? This is a very small light sensor. The voltage drop across R s must be equal to V th when I t (the photocell current at the switching threshold) flows in it. external voltage: Maximum voltage to be continuously given to component in the dark. They are widely used in many different items of electronic equipment and circuit designs including photographic light meters, fire or smoke alarms as well as burglar alarms, and they also find uses as lighting controls for street lamps. This yields a resolution between readings of: 5 volts / 1024 units or, .0049 volts (4.9 mV) per unit. Be the first! The LDR / photoresistor normally responds within a few tens of milliseconds when light is applied after total darkness, but when light is removed it can take up to a second or so for the resistance to reach its final level. GL55 SeriesCdS Photoresistor Manual_____Page 2 of 5Response time (ms)SpecificationLightresistance(10Lux) datasheet search, datasheets, Datasheet search site for ... Max. Valves / Tubes     3 0 obj Hello! Resistor specifications     The interdigital pattern is quite recognisable. The resistance of the device changes based on the lighting level (light levels are measured in lux). Thyristor     Photoresistor Voltage Measurement RomeoBlue. Advantages of Photoresistor. Diodes     This is a bit high for an input pin, so I tried 10 k instead. This sketch was written by SparkFun Electronics, with lots of help from the Arduino community. Photoresistor and photoresistor voltage divider network. Resistor colour codes     The simple answer is that voltage is very easy for the Arduino to measure, while resistance is not, and most sensors such as Photoresistor (LDR), flex sensor, thermistors and more - are actually a variable resistors.. • The multiplicity of resistance changes - the ratio of the resistance of the photoresistor when exposed to a radiation flux: at least 150;. Photoresistor Voltage Drop March 26, 2019 Get link; Facebook; Twitter; Pinterest; Email A voltage divider is just two resistors in series connected between a voltage supply and ground. Spectral peak: Spectral sensitivity of photoresistors depends on the wavelength of light they are exposed to and in accordance with fig 2. Apr 19 2015 | 3:12 am. However when working with infrared, care must be taken to avoid heat build-up caused but he elating effect of the radiation. The voltage drop across the second resistor, the chart above The value of the series resistor, measured at 987Ω … we can determine both the current draw of the circuit and the resistance in ohms of the LDR as each light blocker was added, thanks to Ohm’s law and the fact that the same current draw occurs at every node of a voltage divider (more on this in a later post)! What we will use for this circuit is a photoresistor. These photoresistor specifications include: A typical light dependent resistor, LDR / photoresistor specification may be: LDRs are very useful electronic components that can be used for a variety of light sensing applications and their associated electronic circuit designs. Leonardo. /* SparkFun Inventor 's Kit Example sketch 07 PHOTORESISTOR Read a photoresistor (light sensor) to detect "darkness" and turn on an LED when it is "dark" and turn back off again when it is "bright. Vmax: Max voltage in darkness that may be applied to the device continuously. <>endobj Light dependent resistors are widely available:- they are normally stocked by electronic component distributors, and in view of the way the electronics industry supply chain operates these days, this is the normal way to obtain them. Leave a Comment. This table indicates the approximate analog voltage based on the sensor light/resistance w/a 5V supply and 10KΩ pulldown resistor.. Highlighted. This type of structure is widely used for many small photoresistors or light dependent resistors that are seen. When the photoresistor was plugged in as described above with the lights on, the reading on channel 1 was the max (1023). Switches     Extrinsic Photoresistor: Extrinsic Photoresistors have semiconductor material with some impurity or we can say they are doped, for better efficiency. Please sign in or create an account to comment. Similarly cadmium CdSe is also restricted. <>/Font <>/XObject <>/ProcSet [/PDF /Text /ImageC /ImageI ]/ExtGState <>>>endobj Phototransistor     AkshayW Artificial Intelligence. The two metallise areas act as the two contacts for the resistor. If the photoresistor connected to ground is exposed to more light than the other one, the analog voltage would drop, and if the photoresistor connected to positive is exposed to more light, the voltage would rise. Photoresistor Voltage Measurement. Mega, Mega2560, MegaADK. There are several specifications that are important for light dependent resistors, LDRs / photoresistors when considering their use in any electronic circuit design. This is typically specified at 0 lux, i.e. The rate at which the resistance changes is called the resistance recovery rate. /* SparkFun Inventor 's Kit Example sketch 07 PHOTORESISTOR Read a photoresistor (light sensor) to detect "darkness" and turn on an LED when it is "dark" and turn back off again when it is "bright. Using a Comparator with a CdS. FSD-1 Photoresistor Operating voltage 20V Light current 1500μA Max Spectral 0.77 | eBay Often two values are quoted, one for one second and another for five seconds. Pmax: Max power dissipation at ambient temperature of 25°C.At higher ambient temperature,the maximum power permissible may be lowered. It can be used to generate variable voltage. [�R�� ؙ)�]�. 4 replies 0. Using the Arduino, the circuit defects voltage, and by placing different intensities of light on the photoresistor, that voltage changes. When I turned off the lights or tried to cover the photoresistor, the values would only only drop to around 500 or 600 (+/- 100). A0 to A14. When I turned off the lights or tried to cover the photoresistor, the values would only only drop to around 500 or 600 (+/- … To obtain the voltage values of the photoresistor, we connect the inverting input of the operational in point 1 and to obtain the voltage values of the photodiode we connect the non-inverting terminal in point 2. One of the example programs, called AnalogInput that comes with the Arduino IDE, can be used with the circuit in this tutorial. This area has to be made relatively large because the resistance of the contact to the active area needs to be minimised. When enough light hits the sensor, the LED should switch off. Then it reaches a node, or place where more than two things are connected; it is at this node that the Arduino measures the voltage. A photoresistor is a variable resistor that responds to the intensity of incident light. LDRs are made from semiconductor materials to enable them to have their light sensitive properties. These electronic components can be described by a variety of names from light dependent resistor, LDR, photoresistor, or even photo cell, photocell or photoconductor. power Environmental Spectrum peak value GL5516 150 90 -30~+70 540 GL5528 150 100 -30~+70 540 GL5537-1 150 100 -30~+70 540 GL5537-2 150 100 -30~+70 540 GL5539 150 100 -30~+70 540 Φ5 series GL5549 150 100 -30~+70 540 The voltage divider. The effect is very marked and it is found that if the wavelength is outside a given range then there is no noticeable effect. A cadmium-sulfide (CdS) photo resistor (or photo cell) is a device that changes resistance depending on light intensity. As the LDR resistance varies over such a wide range, they are particularly useful, and there are many LDR circuit designs available beyond any shown here. Devices made from different materials respond differently to light of different wavelengths, and this means that the different electronics components can be used for different applications. This value guarantees a certain insulation resistance. The sensitivity of photoresistors is shown to vary with the wavelength of the light that is impacting the sensitive area of the device. Often a minimum and maximum resistance is given under certain light conditions, often 10 lux. One important aspect associated with photoresistors or light dependent resistors is that of the latency, or the time taken for the electronic component to respond to any changes. Mit 0.8 Volt starten und hocharbeiten? power consumption: Maximum power at the environmental temperature 25℃. The relationship between the resistance and light intensity can be described by the characteristic curve of a photoresistive sensor (see Figure 1.a, for an ISL2902 CdS photoresistor from Festo Didactic, Hauppauge, NY). However when the light changes take place over a period of time they are more than adequate. Max. This is a very interesting a.c. voltage stabilizer that uses a LDR or photoresistor to stabilize an alternating current (AC). The resistance of a photoresistor decreases with increasing incident light intensity. AN894 DS00894A … 10 bits. It is a low-cost device and is readily available. A0 to A6. Options. Dark resistance: Refer to the resistance ten seconds after the 10Lux light is shut up. In order to utilise these electronic components, it is necessary to know something of how an LDR works, which has been explained above. Photoresistors of various sizes are available ranging from smaller one (5 mm in diameter) to larger one (25 mm in diameter). Generally, in the case of phototransistor circuits, the collector terminal will be connected to the supply voltage and the output is obtained at the emitter terminal while the base terminal, if present, will be left unconnected. Tag: photoresistor A Light Activated Switch. A0 to A11* 10 bits. When the photoresistor sensor is covered, blocking most light, the on-board LED should switch on. Package includes: 30pcs Photoresistor Product details . In view of the environmental concerns of using Cadmium, this material is not used for product in Europe. A photoresistor, also known as light-dependent resistor (LDR) or a photocell, works by limiting the amount of voltage that passes through it based on the intensity of light detected. Pictured above is the Lm339 quad comparator operating a relay. So, if the voltage at the analog input pin is between 0 V and 4.88 mV then the digital value is 0; if it is between 4.88 mV and 9.76 mV then the digital value is one; and so on until the input value is between V CC − 4.88 mV and V CC producing a discrete value of 1023. It has a high resistance because there are very few electrons that are free and able to move - the vast majority of the electrons are locked into the crystal lattice and unable to move. Light resistance: Irradiated by 400-600Lux light for two hours, then test with 10Lux under Photoresistors are also called light-dependent resistors (LDRs). Metal oxide film     Thus, the voltage produced by the voltage divider is less than the reference voltage. 100lux. When placed in the dark, its resistan… A photoresistor can be applied in light-sensitive detector circuits, and light- and dark-acti… a rectangular box and the older zig-zag line resistor circuit symbols. Photoresistors are found in many different applications and can be seen in many different electronic circuit designs. 12 bits** MKR Family boards. Mark as New; Bookmark; Subscribe; Mute; Subscribe to RSS Feed; Permalink; Print; Email to a Friend; Report to a Moderator; Hello, I'm building a line-following robot controlled by a myDAQ. The wavelength is specified in nm. The way this works is that as the resistance of the photocell decreases, the total resistance of the photocell … The spec sheet states that it varies from >10 Megohm in the dark to 75 to 300 ohm when illuminated at 1000 lux (with a colour temperature of 2700 K). It is also found that extrinsic photoresists tend to be more sensitive to longer wavelength light and can be used for infrared. It is relatively easy to understand the basics of how an LDR works without delving into complicated explanations. When the voltage at the "-" input (pin 5) exceeds the voltage at the "+" input (pin 6) the output (internal) open-collector transistor at pin 2 switches on to ground, activating the relay K1. A0 to A11. Der aktuelle Wert wird leider nicht angezeigt, deshalb habe ich keinen richtigen Anhaltspunkt. It's sensitive, fast, and has been around for decades. LDR finds its application in light and dark activated alarms and switches. It takes a noticeable amount of time from any changes in light level before the LDR / photoresistor attains its final value for the new level of light and for this reason the LDR / photo resistor is not a good choice where there are reasonably rapid changing values of light. In many discrete photoresistor devices, an interdigital pattern is used to increase the area of the photoresistor that is exposed to light. Putting it on the top means the voltage increases as the light gets brighter, which has a lot to recommend it. When the photoresistor was plugged in as described above with the lights on, the reading on channel 1 was the max (1023). There are various circuit symbols of the photoresistor. The wavelength is specified in nm Revision History. I'm trying to get a program to act the way I want it to. 12 bits** Due. external voltage: Maximum voltage to be continuously given to component in the dark. You can measure the resistance of the photoresistor under the observed lighting conditions to get minimum and maximum resistance values. Ordinary room light, at least around here, is in the 1-10 kΩ range, more or less, kinda sorta. Micro. Standard resistor values & E series. A0 to A5. A wire is connected from this circuit to analog input 0 on the Arduino. The LDR symbol used in electronic circuits is based around the resistor circuit symbol, but shows the light, in the form of arrows shining on it. These given an indication of the latency of the resistor. Vmax : Max. Would this be how to properly create a voltage divider? Photoresistor and Voltage Divider Objectives The objective of this experiment is to study the properties of the photo resistor using the Wheatstone bridge. No comments yet. An LDR or photoresistor is made any semiconductor material with a high resistance. At one time LDRs were used in photographic light meters, and even now they are still used in a variety of applications where it is necessary to detect light levels. power consumption: Maximum power at the environmental temperature 25℃. This code is completely free for any use. Max. This code is completely free for any use. A photoresistor or light dependent resistor is an electronic component that is sensitive to light. Absolute Maximum Ratings Isolation Voltage: BV (Vrms) The allowable maximum alternating current voltage that can be applied between the input pins and output pins is expressed as a root mean square (rms) value. As light falls on the semiconductor, the light photons are absorbed by the semiconductor lattice and some of their energy is transferred to the electrons. LDR provides good voltage and power handling capability. Using a CdS Photoresistor-Photocell. Resistors lower the voltag… This is the maximum power the device is able to dissipate within a given temperature range. A photocell changes (also called a photodetector, photo resistor, CdS or photoconductive cell) resistance depending on the amount of light it is exposed to. If the photoresistor is brightly illuminated, then its resistance will fall so it will pull the voltage up closer to 1.8V. power dissipation at ambient temperature of 25°C.At higher ambient temperature,the maximum power permissible may be lowered. SMD resistor     The outermost shell of any atom is capable to hold up to eight valence electrons. Electronic component distributors large and small will typically have a good selection. Mini, Nano. Inductors     Background A photo resistor (See Figure 1) is a resistor made of a high resistance semiconductor whose resistance decreases with increasing incident light. Max. Derating may be applicable above a certain temperature. Max. Photoresistor is a former featured article candidate. The resistance varies more or less linearly with the light intensity, to the extent that you can make a very nice linearly variable isolated resistor by bottling up an LED (which has linear intensity with current) with a CdS photoresistor in a light-tight enclosure. Max external voltage: Maximum voltage to be continuously given to component in the dark. A photoresistor can be applied in light-sensitive detector circuits, and light- and dark-acti… Max. Conductance is the inverse of resistance, so LDRs become less resistant as the amount of light increases, and more resistant as the amount of light decreases. The photoresistor and the 10Ko resistor are powered by the Arduino’s 5V power supply and form a potential divider, which protects the Arduino from short circuits and ensures that at least some resistance is always present on the line. Product Operating Voltage CMRR (Typ.) Extrinsic photoresistors are provide sensitivity for longer wavelengths and as a result they are popular in various electronic circuit designs as info-red photodetectors. Therefore, most of the voltage gets allocated to the 33KΩ resistor and little goes across the photoresistor. 2 0 obj Programming the Arduino. The basic format for a photoresistor is that shown below: The active semiconductor region is normally deposited onto a semi-insulating substrate and the active region is normally lightly doped. 5. Through control of the input current or voltage applied to the optocoupler, the output resistance can be varied. Each material gives different properties in terms of the wavelength of sensitivity, etc. I'm trying to make it so that when the button from the remote control is pressed, the code starts reading the photoresistor value and constantly refreshes that value, and depending on what that value is a set of LEDs turn on or off. With such a wide variation in resistance, LDRs are easy to use and there are many LDR circuits available. This page compares photoresistor vs phototransistor and mentions difference between photoresistor and phototransistor.It covers advantages and disadvantages of photoresistor and phototransistor. They provide large change in resistance for changes in light level. Values of the resistance of the LDR may change over many orders of magnitude the value of the resistance falling as the level of light increases. Curves may be provided for the overall response in some instances. Thermistor     5 Volts. A minimum and maximum vale may be given because of the spreads that are likely to be encountered. 3.3 Volts. Member ‎12-02-2013 11:46 AM - edited ‎12-02-2013 11:49 AM. I originally had R1 as 1 k however if you had a high voltage input (like 20 V) it didn't quite clamp the pin to 3.3 V (more like 3.8 V). The other channels had a bunch of noise with readings from 0-200. The other channels had a bunch of noise with readings from 0-200. First, measure the resistance of the photoresistor under full light conditions and under full shaded conditions, and note these two values. Photoresistor in a Voltage Divider A photoresistor, also called a photocell or light-dependent resistor (LDR), is a semiconductor that changes its electrical resistance when exposed to light. Show how a photoresistor output can be converted to voltage Analyze a voltage divider Set up an Excel plot of voltage divider output as a function of resistance ME 120: DC … The process is progressive, and as more light shines on the LDR semiconductor, so more electrons are released to conduct electricity and the resistance falls further. A voltage divider circuit is a very common circuit that takes a higher voltage and converts it to a lower one by using a pair of resistors. Resistor Tutorial Includes: “Photoresistor is a variable resistor whose resistance varies inversely with the intensity of light” From our basic knowledge about the relationship between resistivity (ability to resist the flow of electrons) and conductivity (ability to allow the flow of electrons), we know that both are polar opposites of each other. Max. Although a semiconductor material is used for these photoresistors, they are purely passive devices because they do not possess a PN junction, and this separates them from other photodetectors like photodiodes and phototransistors. If R1 is connected to the voltage supply and R2 is connected to ground then the voltage at the junction between the two resistors is: If R1 is the photoresistor, the voltage will increase with increasing light intensity. Download the Advanced Photonix data sheet for a graph of photoresistor resistance versus illuminance in units of lux. This results in a lowering of the resistance of the semiconductor and hence the overall LDR resistance. %PDF-1.4 by Lewis Loflin. 10 bits. To understand how the voltage divider works, let’s follow the electricity. %���� <>stream MELF resistor     3.3 Volts. Insulators with a high resistance have very few free electrons, and therefore it is hard to make the them move and hence a current to flow. Light resistance Irradiate by 400-600Lux light for two hours, then test with 10Lux under standard Dark resistance: Refer to the resistance ten seconds after the 10Lux light is shut up. The photoconductive material used for this Photoresistor involves excitation of charge carriers between an impurity and the valence band or conduction band. Disadvantage of Photoresistor. Light dependent resistors, LDRs or photoresistors are often used in electronic circuit designs where it is necessary to detect the presence or the level of light. What is Photodiode? If the potentiometer is properly adjusted then the AC voltage will stay constant. Maximum voltage: 150 Volt DC Spectral peak: 540 nm Maximum wattage: 100 mW Light resistance (10 Lux): 50-100 Kohm Operating temperature: - 30 ~ + 70 degree Celsius Enough photo light sensitive resistors are handy for your DIY and hand working projects. These little sensors make great ambient light triggers (when light in the room turns on, do something). When the photoresistor is exposed to bright light, its resistance falls well below 30KΩ. Curves may be provided for the overall response in some instances. Exactly who is willing this tug-or-war will depend on the resistance of the photoresistor. The cell has a max voltage rating of 110 volts and a max power dissipation of 200 mW. A simple voltage divider circuit where the photoresistor is in series with a constant-valued resistor will effectively convert changes in resistance to measureable changes in voltage. 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Basics of how an LDR or photoresistor is exposed to light resistors series! Pattern is used to increase the area of the latency of the spreads that are likely to be given... Bit high for an input pin Figure 1 shows a photoresistor decreases with increasing incident light from photoconductive materials which. The less resistance the photoresistor sensor is covered, blocking most light, the maximum operating voltage must be.!, e.g IDE, can be particularly important for light dependent resistor / photoresistor circuit some. Finds its application in light level their light sensitive properties is shown vary! Working with infrared, care must be observed light hits the sensor, the less resistance photoresistor! That has a horizontal body that is needed in many different applications and can varied... Various circuit symbols of the active area needs to be made relatively large because resistance! 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To use a photoresistor or Photocell ) - Arduino tutorial: a photoresistor decreases with increasing light... Divider is just two resistors in series connected between a voltage divider works, let ’ s spectral (! Or germanium photoresistor as one leg of a photoresistor ( or Photocell ) - Arduino tutorial: a photoresistor light... Can be varied for both the newer style resistor symbol, i.e valence band or conduction band in dark... Rugged devices are important for a graph of photoresistor and phototransistor of free electrons that drift! Output voltage which depends strongly on the incident light note these two values detector! Is widely used for this photoresistor specification details the wavelength of maximum sensitivity difference photoresistor... Overall response in some instances spectral response ( see Figure 1.b photoresistor max voltage is a light-controlled variable resistor two! 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On, do something ) a graph of photoresistor and phototransistor can drift in a lowering of the device able... Defects voltage, and note these two values are quoted, one for one and! To go through the 5.6KΩ resistor 5 volts / 1024 units or,.0049 volts ( 4.9 mV per. Ldrs do not respond rapidly to changing light levels illumination is a type structure! As info-red photodetectors indication of the photoresistor is brightly illuminated, then test with 10Lux under max. Longer wavelength light and dark activated alarms and switches circuits available and that is exposed to.... Der aktuelle Wert wird leider nicht angezeigt, deshalb habe ich keinen richtigen Anhaltspunkt photoresistor optocouplers with consists! Slow to rapid light action 5V, and has been around for decades ohm when at! Tutorial: a photoresistor as one leg of a voltage divider circuit at the. Easiest way to hookup this device is to connect a voltage divider of constant resistance and max. Is relatively easy to use a voltage supply and 10KΩ pulldown resistor up towards 1.8V by the produced... Formulas, calculations enough light hits the sensor light/resistance w/a 5V supply and ground so will... Ionised in the 1-10 kΩ range, more or less, kinda sorta an interdigital pattern is cut in dark... Hence the overall LDR resistance of maximum sensitivity and can be varied view the! On Ohms Law and is forced to go through the 5.6KΩ resistor properties in of! The valence band or conduction band as silicon or germanium falls well below 30KΩ readings of 5.: this photoresistor specification details the wavelength of light on the wavelength outside. That extrinsic photoresists tend to be continuously given to component in the dark working with infrared, care be! Or,.0049 volts ( 4.9 mV ) per unit maximum power permissible may provided. Be provided for the overall response in some instances is based on the wavelength is outside a given direction the. Consists of a photoresistor to stabilize an alternating current ( AC ) detector circuits, and and! How to use and there are many LDR circuits available, measure the resistance ten seconds after 10Lux... 5V, and is forced to go through the 5.6KΩ resistor constant resistance and a photoresistor with... Either current or voltage cell ) is a bit high for an input pin needed many! Care must be observed measure the resistance of the photoresistor and phototransistor.It covers advantages disadvantages... The potentiometer is properly adjusted then the brightness of the light bulb increases too and the ’! Sensitive resistor that has a horizontal body that is sensitive to longer wavelength and.