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Uh dun't nuh
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∙ 10y ago
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What is your proudest moment to date and why?
Battling through the VCE and keeping my head held high!
How can a relay circuit be used?
A relay circuit is typically a smaller switch or device which drives (opens/closes) an electric switch that is capable of much larger current amounts or a circuit which operates the coil or electronic actuator from one source and uses a separate power source to drive an isolated device. For the use in electrical engineereing:Generally speaking, using a relay may involve anything from a very robust approach to an extremely delicate approach. Consider some aspects of a relay. A relay has contacts, arcing and sparking because of back e.m.f from load circuits may damage these contacts and reduce the life span of the device. Some inductive applications might require a low value capacitor across the relay contacts. Just remember that the peak voltage (not rms or AC) of the mains running through the contacts is not more than the rated capacitor voltage value. Do not use polarized capacitors where AC is used. Often a 10nF might make a difference already depending on your back e.m.f of the load obviously. It will also reduce some EMI (electromagnetic interference)Even if your DC control signal may only see resistance of the coil at the time the coil is on or off. A coil that has inductance and store magnetic energy, the same as any coil will also produce back e.m.f when potential is removed. The collapse of the magnetic field cause a high potential difference, possibly thousands of volts at high frequency. The frequency may in fact be so high that regular diodes or transistors might not stop it. One would recommend a series resistor and use the collector of a NPN transistor with it's emitter to the ground to switch the relay on or off via the base, be sure to have a base resistor to protect the source of the control signal as well as the B-E junction of the transistor, calculation as follow:Rs = collector series resistorRb = is base series resisterbeta = current gain for the transistorVsource = the control signal voltage minimum that will turn relay on or offBy applying ohm's law we get:Rc = [Rrelay x (VCC-Vrelay -Vce)]/(Vrelay )Rb = (Vsource-Vbe)/[(Vrelay/(Relay x Beta)) x 10]{use factor 10 to compensate for error in beta values}Don't ever be to comfortable with the fact that there are no electrical connection between the contacts and the coil of a relay. Do not think relays are safe to use with computers or related micro controller devices because they are electrically isolated. It will be a bad mistake!! There are back e.m.f. from the coil aswell as e.m.i from contacts what is induced back into the coil when it has high impedance across it.It's then recommended to have a fast recovery diode in reverse bias condition across the coil to prevent back e.m.f. of finding its way back home.This is recommended to protect the driving signal source. Often in small relays using HC or TTL family logic to drive it via a transistor to a transorb or fast recovery diode across the coil may be good enough. Especially if you use it for your self and not to design a heart-lung machine for a hospital.But if you have micro controllers, computer ports. The damage of a strong back e.m.f may be more than what you bargain for and will probably happen at the worst time in the wrong place. The best is to use a opto-coupler.The control source will via a series resistor, let say about (330R for a 5V signal) switch an internal LED inside the opto-coupler device on. The light will drive a photo-transistor into forward bias condition. That can be used to drive the transistor that will energize the relay. Since there is no electrical connection between the output pin of the microcontroller that produce the control signal and the relay coil. There is only a one way communication via a light beam. This is by far safer. It creates a typical, 2500V isolation between the robust electrical circuit and it's e.m.f 's, and the sensitive and delicate micro controller or computer circuit environment. A dip in Vcc or pin for less than a millionth of a second dipping with 2 volt or spiking can cause freezing, erratic response or failure of the micro controller. For good electronic design opto-couplers are a very important part of a reliable control system that use micro controllers to control relay output with.
When an NPN transistor is saturated its Vce?
is zero
What is vce and ie of a transistor?
A: Vce is the voltage across the transistor . Ie is the emitter current. Ico is the collector current with the base open. Or really the leakage.
What should be the value of Vce if the base terminal of a transistor is open?
It would be zero because there is a leakage.
Where you can use transistor?
Transistors are Bi-polar PN Junction devices (BJT's) which switch or amplify current and come in PNP and NPN types which dictate base to emitter bias conditions. BJT's commonly have three terminals b (base), e (emitter), and c (collector) which by internal design provide an hFE or dc current gain which is needed to produce larger currents from varying smaller currents. There are two p-n junctions : base/emitter and base/collector with BJT transistors. For this reason transistors are commonly used as simple current switches or amplifiers. Without the transistor there would essentially be no computers since there would have never been any mechanism by which to construct logic devices like OR Gates, AND Gates, NAND Gates, Flip-Flops, Inverters and Buffers. Transistor Switches In a simple switch application the transistor is placed in cutoff mode (off) or saturation (on). The on/off condition of a transistor is affected by a base-emitter bias versus the dc hFE. In a simple logic application where a digital signal is produced the NPN type transistors base-emitter bias current is high enough to saturate the transistors emitter-collection region with current. When the emitter collector region becomes saturated (both junctions forward-biased) a logic low (Vce =0) will be produced across the collector emitter terminals since current is flowing. By simply removing or lowering the base/emitter forward-bias current the transistor will move from saturation (Vce=0) to cutoff where the Vce is equal to Vcc.
What does vce stand for?
VCE stands for Victorian Certificate of Education.
Where does whine go under vvc vcc vc vce?
vce
What is the purpose of a heat sink in transistors?
Heat sinks are needed for transistors passing large currents. Waste heat is produced in transistors due to the current flowing through them. If you find that a transistor is becoming too hot to touch it certainly needs a heat sink! The heat sink helps to dissipate the heat by transferring it to the surrounding air. The rate of producing waste heat is called the thermal power, P. Usually the base current IB is too small to contribute much heat, so the thermal power is determined by the collector current IC and the voltage VCE across the transistor: P = IC × VCE The heat is not a problem if IC is small or if the transistor is used as a switch because when 'full on' VCE is almost zero. However, power transistors used in circuits such as an audio amplifier or a motor speed controller will be partly on most of the time and VCE may be about half the supply voltage. These power transistors will almost certainly need a heat sink to prevent them overheating. Power transistors usually have bolt holes for attaching heat sinks, but clip-on heat sinks are also available. Make sure you use the right type for your transistor. Many transistors have metal cases which are connected to one of their leads so it may be necessary to insulate the heat sink from the transistor. Insulating kits are available with a mica sheet and a plastic sleeve for the bolt. Heat-conducting paste can be used to improve heat flow from the transistor to the heat sink, this is especially important if an insulation kit is used.
What is the average VCE Enter Score?
53.95 is the average ENTER score for VCE students
How do you open VCE file or to run in on window 7?
To open and run VCE files on Windows 7 you need software known as Visual CertExam. This software is used to simulate VCE exams.
What dc load line?
well, this is very simple to understand ,the DC load line of a circuit is nothing but the Kirchoff's voltage law on the out put circuit of the transistor-amplifier. As the KVL is linear equation involving voltage drops the equation of load line is a straight linelet us assume that the transistor is in CE configuration.VCC-VCE-ICRC=0vICRC=VCC-VCE of the form by=aX+c which is in the form of a straight line with positive intercepts on X(VCC) and Y(VCC / RC) axis and a negative slopewhere,x= VCE/RCy= ICm(slope)= -VCC/RC
What is the vce in dc load line?
A: Vce is the voltage that will follow a particular load line. It is linear by itself but not related to the base drive.
What is the difference between IB and VCE?
IB has a different curriculum to VCE, IB is more known world wide and can get you an easier enter score. Although IB is a bit harder than VCE but in the end, it's all worth it
