Voltage Resistors

The MCP6SX2 PGA Thermistor PICtail Demo Board features the MCP6S22 and MCP6S92 Programmable Gain Amplifiers (PGA). These devices help: Overcome the non-linear response of the on-board NTC thermistor Provide multiplexing between two inputs; the other input can be any desired source. This opens the possibilities of temperature correcting another sensor, and of increasing the number of PIC® microcontroller I/O pins available for other purposes. Two on-board variable resistors allow users to experiment with different designs on the bench. DIP switches on the board select certain resistors (in a binary weighted sequence) to add together, thereby emulating the series resistor in the voltage divider and the thermistors change in resistance over temperature. For more information, please visit: www.microchip.com

General Electric Motors Cheap Popcorn Machine

In power applications, switches perform function to energize or unenergized an electric load. On the high end of the scale are load-break switches and disconnecting switches in power systems at the highest voltages (several hundred thousand volts).

Load-break switches are required to maintain the capability of interrupting the load current. The load break switch in a circuit with several hundred thousand volts, designed to carry a large amount of current without overheating the open position, having enough insulation to isolate the circuit in closed position, and equipped with arc interrupters to interrupt the load current.

Load break switches of air break are of versatile switch gear for transformer control & protection. They can also be used for Motor feeder in conjunction with Vacuum contactors. They are highly useful for Ring feeders for isolation of faulty section either manually or through remote control if fitted with motor operation. Load break switch in conjunction with HRC fuse can tackle high fault current and offer very good protection against dead short circuit capacity up to 40KA.The fault clearance and isolation through this combination will be achieved in a few milli seconds provided a proper selection of LBS and fuse is done. HRC fuses are manufactured with silver strips/silver coated Cu. Strips wires surrounded by granular quartz. When short-circuit occurs the metal element melts and the molten metal melts the surrounding quartz, making the combination an insulating material, called fulgarite. There will be a number of sections in the element which will create similar insulating media in quick succession and thus the arc will be extinguished in a matter of few milliseconds, say 5 to 8 milli-seconds, ie., less than 1/2 a cycle.

Electronic Engineering Services [http://www.engineeringservices.beganto.com/]

Corporate Gift Ideas Philosophy Skin Long Term Car Rental

Troubleshooting linear power supply was quite easy as compare to switch mode power supplies (SMPS). AC voltage enters to the primary side of linear transformer and then converted the AC into a lower or higher AC voltage depending on the secondary winding. The output AC voltage is then rectified and filtered by a diode and capacitors to produce a clean DC voltage. If there is a problem in the linear transformer circuit, I can say that it is very easy to locate the fault. This is somehow different in the case of a switch mode power supply. The designs were complicated and some technicians found it quite hard to fully understand how the switch mode power supplies work.

The working principle of switch mode power supply is different from the linear type. First the AC voltage will flow to a full wave rectifier (bridge rectifier) which produces an uneven DC output and then filtered by a large capacitor (usually 220 micro farad and up to 450 volts). The clean DC voltage will then flows to start up resistors and to the input of switch mode power transformer. Once the voltage passed through the high ohms resistor (start up resistors) the voltage would drop to a value where it then flows to the VCC supply pin of Pulse width modulation IC.

Once the PWM IC received the voltage it will output a signal to drive the transistor (or FET) and produces a changing in magnetic field in the transformer primary winding. The changing magnetic field induces voltage in the secondary windings. Each of these AC voltage produced by the secondary windings is then rectified, filtered, and regulated to produce a clean DC voltage. One of the main DC output voltage is the B+ that supply to flyback transformer (for TV and Monitor Circuit)

The output from the B+ voltage supply is then connected, through a “feedback” loop (which consist of optoisolator ic and an error amplifier TL431 IC), back to the PWM IC. When the voltage from the B+ supply rises or drop a bit, the PWM IC will act to correct the output.

If you still do not understand the above explanation, please do not be discourage because you can always buy technical books and schematic diagrams and read it till you get the whole idea of how a SMPS work. You can ask a repair friend or even surf the internet for a better and easy explanation.

Here I would like you to download a free SMPS article by Sencore and I found it to be a great help for you who are still struggle on how SMPS work and how to troubleshoot when it fails. You must ask your self what is the purpose and its function of the components in the SMPS circuit and how to check them if they fail. Find out on your own the function of these components in SMPS circuit:

Bridge rectifier,

Filter capacitor,

Start up resistors

Chopper/Power FET

Pulse Width Modulation (PWM IC)

Current sense resistor

Switch mode power transformer

Optoisolator/optocoupler

Error Amplifier IC (TL431)

Secondary diodes

Secondary filter capacitors

Push yourself further by searching the internet for the datasheet of a PWM IC part number. For example, UC3842 PWM IC is mostly used in SMPS. Do you know what the function of pin 5 of this IC is? Do you know which pin the VCC supply enters? Do you know what the actual voltage that flow to the IC is? Do you know which pin that drives the power FET? Can I get a replacement for this IC? And so on………

Let’s take a soldier as an example. Soldiers not only good in handling rifle but also knows all the details about it. They know how to dismantle and assemble back their rifle fast (imagine in the middle of war the rifle jammed-they can repair it fast). They know how much each bullet cost, how far the shooting distance, how big is the diameter of the bullet, how many cm the length of the bullet and so on. Hope you don’t get bored with the soldier’s story, did you get the ideas?

Any SMPS that comes across my repair bench, I would not immediately repair it, in fact I will take couples of minutes to analyze the circuit design and see it from all angles before I begin to repair. Troubleshooting SMPS is not limited to only one procedure in fact many electronic repairers have their own unique ways and methods to solve SMPS problems. Some prefer to use light bulb to isolate SMPS faults while others like to use resistors. Troubleshooting SMPS is fun and flexible but in some cases could make you get very frustrated too.

Remember, don’t limit yourself to only one or two sources to get you understand and be able to repair SMPS. If you have the budget, get the books that have related to SMPS repair-study and start doing practical about it. Share your problems with other fellow electronic repairers and the most important thing is don’t give up. There’s lot of mountain in the journey of our live and you yourself have to climb and conquer it. All the best!

Prk Lasik

Inlet circuit of the PU. VaristorThe major reason for the impulse power units to fail is the presence of overstrain impulses within the network. They may be caused by electromagnetic distortions due to lightning discharge, commutation and discharge of inductive/capacitive elements, complying with the transition processes. The varistors have been acknowledged to be the most effective means to protect electronic equipment from any impulse overstrain. Varistors are non-linear resistors, the resistance of which depends from the voltage applied. Electric parameters of varistors are determined by the major liquid resistance and the capacity, which alters insignificantly due to alterations in voltage and temperature. When the voltage on the varistor is high and high voltage currents are passing it, the current density in pin contacts is also high. Heating the pin contacts decreases resistance and as a result the current-voltage diagram is non-linear. The major parameter of the varistor is the acceptable dispersion capacity, determined by geometrical dimensions and the construction of outlets. In order to increase the capacity of dispersion massive inlets, acting as radiators, are frequently implied. When a high voltage impulse occurs the resistance of the varistor decreases rapidly to fractions of Ohm and shunts the load, protecting it and dispersing the consumed energy in the form of heat. Impulse current up to thousands of amperes may flow through the varistor simultaneously …

Franklin Electric Motors Monthly Car Rental Surgeries

This video (screen-cast) will show how to analyse a simple circuit consisting of a power supply (battery) and two resistive loads (resistors) connected in series. It shows how to calculate the total resistance, current through all parts, the voltages across all parts, and the power dissipated by the entire circuit as well as each load.

Wedding Suite