![]() This voltage plus that from the power at the transistor are big enough to burn it. At this moment, without the freewheeling diode, a counter-electromotive force (EMF) will be generated at the ends of the coil, with positive at the bottom and negative at the top, a voltage higher than 100V. When pin 8 is given a Low level, the LED will stay dim.įunction of the freewheeling diode: When the voltage input changes from High (5V) to Low (0V), the transistor changes from saturation (three working conditions: amplification, saturation, and cut-off) to cut-off, the current in the coil suddenly has no way to flow through. Then its normally open contact is closed, and the LED will light up. Therefore, when a High level signal is given to pin 8, the transistor is energized, thus making the coil of the relay conductive. Both types of transistor are frequently used for contactless switches, just like in this experiment.Ĭonnect a 1K resistor (for current limiting when the transistor is energized) to pin 8 of the SunFounder Uno board, then to an NPN transistor whose collector is connected to the coil of a relay and emitter to GND connect the normally open contact of the relay to an LED and then GND. But a PNP one needs a Low level signal to manage it. When a High level signal goes through an NPN transistor, it is energized. From the abbreviation, we can tell that the former is made of two N-type semiconductors and one P-type and that the latter is the opposite. Based on the semiconductor type, transistors can be divided into two groups, the NPN and PNP ones. The direction of the arrow in the transistor circuit symbol indicates that of the emitter junction. They form two P-N junctions, namely, the emitter junction and collection junction. This composition enables the transistor to be an amplifier.įrom these three regions, three poles are generated respectively, which are base (b), emitter (e), and collector (c). The thinner in the middle is the base region the other two are both N-type or P-type ones – the smaller region with intense majority carriers is the emitter region, when the other one is the collector region. A transistor is a three-layer structure composed of P-type and N-type semiconductors. It functions by amplifying weak signal to larger amplitude signal and is also used for non-contact switch. Transistor is a semiconductor device that controls current by current. In this way, the switching on and off of the relay can control the state of a load circuit. Then breaking the circuit would a similar case, as the moving contact will be pulled up to the normally closed contacts under the force of the spring. So the circuit with the load is energized. Then the armature is attracted to the coil, pulling down the moving contact together thus connecting with the normally open contacts. When power is supplied to the relay, currents start flowing through the control coil as a result, the electromagnet starts energizing. The working principle of relay is simple. Molded frame – Relays are covered with plastic for protection. . Normally close – not connected when the relay is activated, and connected when it is inactive.ĥ. . Normally open - connected when the relay is activated, and disconnected when it is inactive. Set of electrical contacts – There are two contact points: Spring – When no currents flow through the coil on the electromagnet, the spring pulls the armature away so the circuit cannot be completed.Ĥ. And the armature can be moved with direct current (DC) as well as alternating current (AC).ģ. When current flows through them, the coil is it energized thus producing a magnetic field which is used to make or break the normally open (N/O) or normally close (N/C) points. Armature – The movable magnetic strip is known as armature. When electricity is passed through, it becomes magnetic. Electromagnet – It consists of an iron core wounded by coil of wires. ![]() Arduino CodeĬonst int pingPin = 7 // Trigger Pin of Ultrasonic SensorĬonst int echoPin = 6 // Echo Pin of Ultrasonic Sensor Coding in the Arduino language will control your circuit. Open the Arduino IDE software on your computer. Ranging Distance − 2cm – 400 cm/1″ – 13ftįollow the circuit diagram and make the connections as shown in the image given below.It comes complete with ultrasonic transmitter and receiver module. The operation is not affected by sunlight or black material, although acoustically, soft materials like cloth can be difficult to detect. It offers excellent non-contact range detection with high accuracy and stable readings in an easy-to-use package from 2 cm to 400 cm or 1” to 13 feet. The HC-SR04 ultrasonic sensor uses SONAR to determine the distance of an object just like the bats do.
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