7 must know Sensors for Robotic Project…
Hello friends, sensors are the most important parts in development of any robotic project. Here in this article I will cover some basic concept of sensors and its working principle.
What is a sensor?
Before proceeding, do you know what a sensor is?
In simple worlds Sensor is a device that can detect the change in physical quantity and convert it in electrical signal. Here Transducer plays an important role because it is the main element of a sensor device. Sensors can detect many physical quantities like Pressure, Temperature, Sound, Light and magnetic / electric field etc.
Type of Sensors
There are many sensors available in the market. These are used in different application. Here I am describing some basic sensors by which are essential for robotic project. These sensors are
- Proximity Sensors
- Optical / light Sensors
- Position & Limit Sensors
- Electric current, electric potential, magnetic Sensors
- Acoustic / Sound Sensors
- Thermal, heat, temperature Sensors
- Pressure Sensors
A Proximity sensor is a sensor which can detect object but object should be inside its detection range. For detection of object no physical contact or touch is required. Proximity sensor`s detection range vary from Sensor to sensor. Generally it is from 10mm to several meters. For small range generally RF (radio frequency) type transducer used and for higher range IR (infrared) type transducer used.
In robotic application if our requirement is to sense object within 10-15mm we have to use RF proximity sensor and if it is higher than go for IR Proximity sensor.
Optical / Light Sensors
Optical or light sensor is a sensor which can detect light intensity and can convert it in to electrical signal. In market best, cheap and effective light sensor is LDR (Light Dependent Register). When LDR light sensitive surface expose to light, it shows very less resistance between its terminals. It is approximate few ohms but when there is no light, its terminal shows and open contact means very high resistance. It value is approximate more than 2 M-ohm.
Other segments of Light sensors are Infrared Sensors, as you know that Infrared lights are not a visible light. Basically IR sensors consist at least one set of IR light emitter and receiver. Its emitter circuitry is called transmitter Part of sensor and IR detector circuitry is called receiver Part of sensor. An IR sensor consists of an emitter, detector and associated circuitry. The circuit required to make an IR sensor consists of two parts; the emitter circuit and the receiver circuit. The emitter is simply an IR LED (Light Emitting Diode) and the detector is simply an IR photodiode which is sensitive to IR light of the same wavelength as that emitted by the IR LED.
Position & Limit Sensors
Basically these are mechanical lever type switches generally a position sensor is a devices or switch that provide a signal (generally digital signal) at a specific position. The main component of position sensor is a micro switch. It is attached with a lever. As shown in figure its lever moment is detected by micro-switch and a signal generate. This assembly can also be used as displacement measurement device but we have to install in a relative manner.
These position sensors can also be installed in angular and multi axial direction.
Electrical & Magnetic Sensors
It a glass encapsulated reed switch. It changes it`s contact when any magnetic force applied. It was invented in 1936. In industry it is called REED Switch. It is constructed with a ferrous material. Basically it is a magnetic switch and it can provide a digital signal. In robotic it can be used to detect any magnet or magnetic field.
Other one is Hall Effect Sensor. It is a magnetic transducer. It generates voltage in response to a magnetic field.
Acoustic / Sound or vibration Sensors
Microphones (Mic) are very popular sound sensors. They detect sound wave vibration on their diaphragm and provide electrical signal. Piezoelectric sensors can also detect sound wave pressure or vibration even at high frequency. Piezo-electric devices are used in Ultra sonic sensors.
In robotic it can be used to find obstacle in path. These sensors can be used in collision free robot.
Thermal, heat, temperature Sensors
Temperature or Heat is a very basic parameter to measure. In general there is number of sensors available in market but here we are going to cover very popular and easy to use sensors. One of them is IC LM35. Its output voltage is directly proportional to heat (temperature) in degree C. So for student application it is best component as a Temperature Sensors.
Second one is RTD. This is popular in process industry up to 300 degree C measurement. It works on the basis of temperature coefficient. PT100 is a good and popular example of RTD.
In a robotic pressure sensors play an important role. You might have seen a picture in which a robotic hand is picking an EGG. It is not possible without pressure sensors. Strain Gauge is a very popular pressure sensor, which works on the basis of deformation of conductive wire & change in its resistance. If any pressure or force is applied on Strain Gauge it`s resistance goes change. Change in resistance is directly proportional to applied force and can be easily detect by wheat stone bridge circuit.
Well list and application of sensors are very long and can’t be cover in a single page. So subscribe and be updated from YANTRA.