5. Silicon Controlled Rectifier (SCR):
A silicon-controlled rectifier or semiconductor-controlled rectifier is a four-layer solid state current controlling device. It has three junctions, labeled J1, J2 and J3 and three terminals. The anode terminal of an SCR is connected to the P-Type material of a PNPN structure, and the cathode terminal is connected to the N-Type layer, while the gate of the Silicon Control Rectifier SCR is connected to the P-Type material nearest to the cathode.
To turn-on of an SCR, a positive gate voltage between gate and cathode. This gives rise to a gate current where charges are injected into the inner p layer of the device. This effectively reduces the voltage at which forward break-over occurs. It can be gathered
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Holding current: When the gate terminal of SCR is kept open, then the maximum value of anode current at which Silicon Controlled Rectifier is turned OFF from conducting condition, is known as Holding Current.
Requirement of the R2 resistor:
The second resistor, R2 is the gate cathode resistor. This is sometimes denoted as RGK and it is included to prevent spurious triggering the action of the resistor can be seen with respect to the two transistor analogy of the SCR. It shows that a low external resistance between the gate and cathode bypasses some current around the gate junction. Accordingly a higher anode current is required to initiate and maintain conduction. It is particularly found that low current high sensitivity SCRs are triggered at very low current levels and therefore an external gate-cathode resistance is required to prevent triggering by thermally generated leakage current in the gate region.
CIRCUIT
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So voltage drop across resistor R4 varies accordingly. This is applied to the gate of SCR to control its angle of firing. Increase in voltage across resistor R4 increases the firing angle of SCR and makes the bulb glow brighter .the opposite happens if T1 conducts less. In this way, the light intensity of a 100W bulb gets varied from minimum to maximum. So it can be used as a 15W or lower wattage bulb, while going to bed and a 60W bulb or so while reading.
Remote control of variation on light intensity:
Here the circuit brings a advantage for the disabled persons. A remote sensing is used here to control the light intensity. Here the signal is transmitted and received which are commonly used television remotes. This receiver provides negative voltage across across RS1. Thus the current across RS2 flows opposite to the supply current. The summation of the supply current and negative current through drain terminal produces a decrease in total current acrcoss the resistor Rd.
Thus the flow of current is varied by the remote sensing by the disabled persons. Once the remote is turned on the switch closes the
It came to mind that after the movie, Two-bit realized that Cherry and Marcia did not have a ride home. So they walk to Two-bit’s house to get the car. As they walk, Ponyboy and Cherry talk about the differences between Socs and greasers and how they act and how poor or rich they are. Later on Ponyboy finds himself talking to Cherry about Sodapops old horse Mickey Mouse. Then Ponyboy realizes that two different worlds we live in are not so different after all because we look at the same sunset everyday. Until Marcia spots a blue mustang that belongs to the socs. At first, the socs didn’t notice them until they see their girlfriends hanging out with the greasers. When the socs get out of the mustang they defend their girls then turn to the greasers.
All of the sources of current to the equipment should be isolated and signs need to be fixed to ensure that the nature of the equipment is known
• On/off = It switches on output devices. For example - talkto “motora, on, wait 100, off.
Third Stage[t2-t3](Fig.9): At instant t2 The switch is turned off at the time t2. energy stored in L1 transfer to the Capacitor CM and also energy transfer through capacitor CS1 and CS2
Under these conditions, the resulting current response of a sine wave Iac will be given by:
Automation is a step beyond mechanization, Automation is the use of control systems and information technologies to reduce the need for human work in production of goods and services. Where mechanization provided human operators with machinery to assist them with the muscular requirements of work, automation greatly decreases the need for human sensory and mental requirements as well. Automation plays an increasingly important role in the world economy and in daily life. Automatic systems are being preferred over manual system. Through this project we have tried to show automatic control of a house as a result of which power is saved to some extent. The Global System for Mobile Communications
Tuite, Don. "Understanding LED Application Theory and Practice: Learn Some Basics about How LEDs Work, How Their Manufacturers Characterize Them, and How Circuits That Drive And/or Control Them Are Designed." Electronic Design 2 May 2013: 36+. Vocations and Career Collection. Web. 13 Mar. 2014. Http://go.galegroup.com/ps/i.do?id=GALE%7CA330250618&v=2.1&u=mlin_n_great&it=r&p=PPVC&sw=w&asid=00a96b3240cb52efc97fb076b2036932
“The privilege of a lifetime is being who you are”- and with the Supernova the deaf can be who they are. A person that is deaf is in a terrible disaster and the rescuers don’t know any sign language and they are in a big crisis This will never happen with Supernova, Supernova is an AdaFruit® design and it has a one of a kind “LED Board” that is made from scratch. Most people that are deaf and don’t have anyone to talk to feel like outsiders. AdaFruit® is like an upgrade to the original RedBot®. The Supernova can be mobilized and controlled to be moved around in any situation, for instance, when there is an earthquake and someone gets hit in the head and that person can’t hear Supernova can come in and see what is wrong. Before all of this the idea was to make a RedBot® that wasn’t even a RedBot® is was going to
So, participant should provide several questions to the “the learner” and when this one failed they have to send a shock of electricity, they would increase the volts throughout the experiment from 15 to 450 volts.
Villanueva,J and Farcy,R.2012. Optical device indicating a safe free path to blind people. Instrumentation and measurement, IEEE [online].pp.170-177. Available from IEEE Xplore digital library. [Accessed 5 April 2014]
Introduction: I chose this topic; because I thought it would be fun to make a four-way switch that turns on the same light. I got the idea to make one when I went online to search for the perfect project idea. I found information about a three way light switch and decided that this is what I want to do, but to make it more difficult I decided to create a four way light switch instead. It sounds like the perfect experiment to try. I felt that if I did this project I would learn more about electricity and the way it works. What is a four way light switch? A four way light switch is an electric switch that uses electricity to power a light bulb that can be turned on by four different places and not just one or two. The great thing about a four way light switch is that there can be more then one way to turn on one single light. In order to achieve the perfect four ways light switch the four-way switch must be in the center of two three light way switches in order for the whole proses to work. A hot wire or wire of 120 volts will connect from a battery to the light bulb. A wire that is neutral will also be connected from the battery to the light bulb. The third wire can’t be neutral or 120 volts (hot wire) and will just float near the 120-volt wire. The third wire that is neither neutral or 120 volts, and 120 volt wire will connect when the switches are turned on and will produce the light. When the light will be turned on the switches should be one circuit in order for the light bulb to turn on and the electrons to travel through the circuit. The switches must be either up or down at the same time in order for the electricity to flow. If one of the switches is up and the other is down the light will not work. If one o...
How it works a right handed person hand has an active hand its hand will show all of the
However according to Semerc [2000] these alternative methods of access are more complex than direct input and therefore place an additional cognitive burden on the child. The system therefore needs to be set up so that it does not become an additional barrier. Children need to be competent with input devices such as switches. The technique may take time to develop and opportunities need to be provided to practise these to avoid frustration.
Traffic lights are signaling devices located at road intersections and pedestrian crossings, they are now part of our everyday life. Before traffic lights were invented, policeman would control traffic, but accidents would still occur frequently. This is when J.P Knight took action in 1868 and made the first traffic light. It was installed outside the British Houses Of Parliament but didn’t last long since it exploded in 1869 due to a gas leak. It was only in 1912 that a man named Lester Wire created an electrical traffic light that is still used today. There are three main types of traffic lights: fixed timed, semi actuated and fully actuated. Fixed time traffic light are light where “signals change according to a pre-set timing. The signals will cycle all the time even if there is no vehicle or pedestrian demand.” (a). In semi actuated signals vehicle detectors and push buttons are installed on streets and roads. The traffic signals will remain green until either a group of vehicles is detected or a pedestrian pushes a button. Lastly in fully actuated lights “ signals are programmed to change with minimum green times depending on the traffic and pedestrian demand on all approaches. The signals will change based on the demand from each approach.” (b).
Older controlling techniques use 16 pulse or 8 pulse rectifiers which are now replaced by 24 pulse rectifiers, which makes it effective in power factor regulation.