photo sensors circuit PDF

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Name: William R. Borro Jr. Dwaine Christian Docutan Niel Christian Salcedo Windyll Portugalete Venus Jarangue Adam Jeith Pamposa

Group No. 2 Report No.: 6 "PHOTO SENSORS CIRCUIT"

OBJECTIVES 

To know the meaning of photo sensors circuit.



To identify the different types of photo sensors circuit.



To know the application of photo sensors circuit.

Introduction Light Sensors are photoelectric devices that convert light energy (photons) whether visible or infra-red light into an electrical (electrons) signal. A Light Sensor generates an output signal indicating the intensity of light by measuring the radiant energy that exists in a very narrow range of

frequencies basically called “light”, and which ranges in frequency from “Infra-red” to “Visible” up to “Ultraviolet” light spectrum. TYPES OF PHOTO SENSORS CIRCUIT 1. Photoresistor A photoresistor (acronymed LDR for Light Decreasing Resistance, or light-dependent resistor, or photo-conductive cell) is a passive component

that

decreases resistance with respect

luminosity

(light)

on

the

component's

to receiving

sensitive

surface.

The resistance of a photoresistor decreases with increase in incident light intensity;

in

other words,

it

exhibits photoconductivity.

A

photoresistor can be applied in light-sensitive detector circuits and light-activated and dark-activated switching circuits acting as a resistance semiconductor. In the dark, a photoresistor can have a resistance as high as several megaohms (MΩ), while in the light, a photoresistor can have a resistance as low as a few hundred ohms. If incident

light

on

a

photoresistor

frequency, photons absorbed

by

the

exceeds

a

semiconductor

certain give

bound electrons enough energy to jump into the conduction band. The resulting free electrons (and their hole partners) conduct electricity, thereby lowering resistance. The resistance range and sensitivity of a photoresistor

can

substantially

differ

among

dissimilar

devices.

Moreover, unique photoresistors may react substantially differently to photons within certain wavelength bands. Parts of Photoresistors

2. Photodiode A photodiode is a semiconductor device that converts light into an electrical current. The current is generated when photons are absorbed in the photodiode. Photodiodes may contain optical filters, built-in

lenses,

and

may

have

large

or

small

surface

areas.

Photodiodes usually have a slower response time as their surface area increases.

The

common,

traditional solar

cell used

to

generate

electric solar power is a large area photodiode. Parts of Photodiode

3. Photovoltaic Cell A solar cell, or photovoltaic cell, is an electrical device that converts the energy of light directly into electricity by the photovoltaic effect, which is a physical and chemical phenomenon.[1] It is a form of photoelectric cell, defined as a device whose electrical characteristics, such as current, voltage, or resistance, vary when exposed to light. Individual solar cell devices are often the electical building blocks of photovoltaic modules, known colloquially as solar panels. The common

single

junction silicon solar

cell

can

produce

maximum open-circuit voltage of approximately 0.5 to 0.6 volts.

a

Parts of Photovoltaic Cell

4. Phototubes A phototube or

photoelectric

cell

is

a

type

of gas-

filled or vacuum tube that is sensitive to light. Such a tube is more correctly

called

a

'photoemissive

cell'

to

distinguish

it

from photovoltaic or photoconductive cells. Phototubes were previously more widely used but are now replaced in many applications by solid state photodetectors. The photomultiplier tube is one of the most sensitive light detectors, and is still widely used in physics research. Parts of Phototubes

5. Photomultiplier Tubes Photomultiplier tubes (photomultipliers or PMTs for short), members

of the

class of vacuum

tubes, and

more specifically

vacuum phototubes, are extremely sensitive detectors of light in the ultraviolet, visible, and near-infrared ranges of the electromagnetic spectrum. These detectors multiply the current produced by incident light by as much as 100 million times or 10 8 (i .e., 160 dB), in multiple dynode stages, enabling (for example) individual photons to be detected when the incident flux of light is low. Parts of Photomultiplier Tubes

6. Phototransistors A Phototransistor is

an

electronic

switching

and

current

amplification component which relies on exposure to light to operate. When light falls on the junction, reverse current flows which are proportional to the luminance. Phototransistors are used extensively to detect light pulses and convert them into digital electrical signals. These are operated by light rather than electric current. Providing a large amount of gain, low cost and these phototransistors might be used in numerous applications.

It is capable of converting light energy into electric energy. Phototransistors work in a similar way to photoresistors commonly known as LDR (light dependent resistor) but are able to produce both current and voltage while photoresistors are only capable of producing current due to change in resistance. Phototransistors are transistors with the base terminal exposed. Instead of sending current into the base, the photons from striking light activate the transistor. This is because a phototransistor is made of a bipolar semiconductor and focuses the energy that is passed through it. These are activated by light particles and are used in virtually all electronic devices that depend

on

light

in

some

way.

All

silicon

photosensors

(phototransistors) respond to the entire visible radiation range as well as to infrared. In fact, all diodes, transistors, Darlington’s, triacs, etc. have the same basic radiation frequency response. Parts of Phototransistors

APPLICATIONS The light sensor circuit can be used to design various practical embedded systems based sensor based projects such as security alarm system by photo electric sensor, Arduino managed high sensitive LDR based power saver for street light control system, a solar highway lighting system with auto turn off in daytime, sunset to sunrise lighting switch, and so on. An application for every industry: 1. Automotive In the construction of a car body, each part needs to be transported down the line with precision. Skids must speed up, slow down, and stop in front of each station to be welded, riveted, and glued with no errors in timing. The R201 with polarization filter can be used to regulate skid speed in this application, ensuring that the skid will slow or stop when the sensor’s beam is blocked by said skid. Glossy materials and materials with a reflective surface do not affect these sensors, making them ideal for many industrial processes.

2. Material Handling Automated storage technology, stacker cranes, and the LS682 optical data coupler with wireless data transfer make it easier to store and transfer goods in warehouses. This data coupler provides reliability and efficiency and is a wireless way to track and communicate with objects in transit inside warehouse storage facilities.

3. Machine Engineering The sensors also ensure reliable and safe operation in theme parks. Retroreflective sensors with polarization filter (MLV12-54/47/92) detect the position of a carriage to be set on and off the tracks of a rollercoaster. A carriage can successfully be removed from the tracks once it has been detected. This ensures no mistakes are made during carriage placement and removal.

4. Food and Beverage Bottle cap feeding machines must align and orient each bottle cap in the correct position for bottling. With an R201 series diffuse mode sensor, even the smallest feed error registers, and incidents are stopped before a capping mistake occurs. This provides accuracy that saves time and money.

5. Doors, Gates, and Elevators Buses have automatic doors that open and close as people pass beneath the incorporated sensors. The sensors need to see the entire area of the doorway to allow people in and out of the bus. The PROSCAN active infrared scanner scans the entire step and door area to ensure that people approaching or standing in front of the door are detected.

Sample Schematic Diagram Light Sensor Circuit Working Operation The light sensor circuit is an electronic circuit designed using (light sensor) LDR, Darlington pair, relay, diode, and resistors which are connected as shown in the light sensor circuit diagram. A 230v AC supply is provided to the load (in this case, the load is represented with a lamp). The DC voltage required by the light sensor circuit is supplied from a battery or by using a bridge rectifier circuit. This bridge rectifier circuit converts the 230v AC supply into a 6v DC. The bridge rectifier circuit utilizes a step-down transformer to step-down the 230v into 12v. The diodes connected in the form of a bridge are used to convert the 12v AC into 12v DC. The IC7806 DC voltage regulator is used to convert the 12v DC into 6v DC, and then, this 6V DC is supplied to the circuit. A 230v AC supply for both the load and the bridge rectifier is to be maintained continuously for uninterrupted operation of the light sensor circuit.

Light Sensor Circuit Diagram During the daytime, the light sensor LDR has very-low resistance of around a few 100Ω. Thus, the supply passes through the LDR and ground through the resistor and variable resistor as shown in the light sensor circuit. This is due to the fact that the resistance offered by the LDR during daytime or when the light is illuminated on LDR is less compared to the resistance of the remaining part of the circuit (that is through relay and Darlington pair). We are aware of the principle of current, that the current always flow in the low resistance path. Thus, the relay coil does not get enough supply to get energized. Hence, the load is switched off during the daylight. Similarly, during the night time (when the light illuminated on LDR is very less), the LDR resistance increases to a very high value of around a few Mega ohms (approximately 20MΩ). Thus, due to very high resistance of LDR the current flow is very less or almost zero like an open circuit condition. Now, the current flows through the low-resistance path such that it increases base voltage of Darlington pair to reach more than 1.4v. As the Darlington pair is activated, the relay coil gets enough supply to get energized, and hence, the load is switched on during night time or when no light is illuminated on LDR. In order for you to understand how the system of Photo Sensor Circuits and how it works you can watch some videos. Below are the links of additional information for these device. How Photoelectric Sensor Works? 

https://www.youtube.com/watch?v=Fbz-VkX5Sog

How to test photo sensor switch https://www.youtube.com/watch?v=fAMH6s-q4XU Autonics : Photoelectric Sensor Applications 

https://www.youtube.com/watch?v=mHigI-DREFU

Application of Photo sensor & Encoder ( Autonics ) 

https://www.youtube.com/watch?v=rPCssXQBzxA

REFERENCES Aspencore (2020). Light Sensors. Retrieved fromhttps://www.electronicstutorials.ws/io/io_4.html Elprocus

(2020).

Phototransistor.

Retrieved

from

https://www.elprocus.com/phototransistor-basics-circuit-diagramadvantagesapplications/#:~:text=Phototransistors%20are%20transistors%20wit h%20the,that%20is%20passed%20through%20it. Wikipedia

(2020).Photoresistor.

Retrieved

from

https://en.wikipedia.org/wiki/Photoresistor Wikipedia

(2020).Photodiode.

Retrieved

from

https://en.wikipedia.org/wiki/Photodiode Wikipedia

(2020).Photovoltaic

Cell.Retrieved

from

https://en.wikipedia.org/wiki/Solar_cell#:~:text=A%20solar%20cell% 2C%20or%20photovoltaic,a%20physical%20and%20chemical%20phe nomenon.

Wikipedia

(2020).Phototube.

Retrieved

from

Tube.Retrieved

from

https://en.wikipedia.org/wiki/Phototube Wikipedia

(2020)

Photomultiplier

https://en.wikipedia.org/wiki/Photomultiplier_tube#:~:text=Photomul tiplier%20tubes%20(photomultipliers%20or%20PMTs,ranges%20of%2 0the%20electromagnetic%20spectrum. Wordpress (2020).Light Sensor Circuit Working Operation and Application. Retrieved

from

https://www.edgefx.in/light-sensor-circuit-working-

operation/ Wagner A. (2019). 5 Applications for Photoelectric Sensors. Retrieved from https://blog.pepperl-fuchs.us/5-applications-for-photoelectricsensors#:~:text=Photoelectric%20sensors%20use%20visible%20red, contact%20detection%20for%20multiple%20applications....