Here's a good powerpoint presentation about Factors Influencing Automation Projects. It tackles matters on DCS, PLC, SCADA, Industrial Local Area Networking, Standards and others. Greats for basic discussions!
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The Linear Variable Differential Transformer is a position sensing device that provides an AC output voltage proportional to the displacement of its core passing through its windings. LVDTs provide linear output for small displacements where the core remains within the primary coils. The exact distance is a function of the geometry of the LVDT.
(1)
As the core is displaced, the number of coils in the secondary coil exposed to the coil changes linearly. Therefore the amplitude of the induced signal varies linearly with displacement.
The LVDT indicates direction of displacement by having the two secondary coils whose outputs are balanced against one another. The secondary coils in an LVDT are connected in the opposite sense (one clockwise, the other counter clockwise). Thus when the same varying magnetic field is applied to both secondary coils, their output voltages have the same amplitude but differ in sign. The outputs from the two secondary coils are summed together, usually by simply connecting the secondary coils together at a common center point. At an equilibrium position (generally zero displacement) a zero output signal is produced. The induced AC signal is then demodulated so that a DC voltage that is sensitive to the amplitude and phase of the AC signal is produced.
Carrier Demodulator
In practice, LVDTs are used with carrier demodulator modules that provide the carrier signal (the AC signal to the primary coil) and converts (or demodulates) the induced AC signal to a DC signal.
The phase sensitive demodulator is an AC to DC converter that produces a DC voltage (typically between 0 and 10 volts) proportional to the magnitude of the LVDT output and sensitive to the phase of the output signal relative to the input (carrier) signal.
When the core is displaced to one side of the primary, the LVDT output is in phase with the input and the demodulator produces a positive signal. When the core is displaced to the other side, the LVDT output is 180 degrees out of phase with the signal to the primary. The demodulator output is then a negative voltage proportional to the displacement. (from university of california, berkeley)
Fuzzy logic is a powerful problem-solving methodology with a myriad of applications in embedded control and information processing. Fuzzy provides a remarkably simple way to draw definite conclusions from vague, ambiguous or imprecise information. In a sense, fuzzy logic resembles human decision making with its ability to work from approximate data and find precise solutions.
Unlike classical logic which requires a deep understanding of a system, exact equations, and precise numeric values, Fuzzy logic incorporates an alternative way of thinking, which allows modeling complex systems using a higher level of abstraction originating from our knowledge and experience. Fuzzy Logic allows expressing this knowledge with subjective concepts such as very hot, bright red, and a long time which are mapped into exact numeric ranges.
Fuzzy Logic has been gaining increasing acceptance during the past few years. There are over two thousand commercially available products using Fuzzy Logic, ranging from washing machines to high speed trains. Nearly every application can potentially realize some of the benefits of Fuzzy Logic, such as performance, simplicity, lower cost, and productivity.
Fuzzy Logic has been found to be very suitable for embedded control applications. Several manufacturers in the automotive industry are using fuzzy technology to improve quality and reduce development time. In aerospace, fuzzy enables very complex real time problems to be tackled using a simple approach. In consumer electronics, fuzzy improves time to market and helps reduce costs. In manufacturing, fuzzy is proven to be invaluable in increasing equipment efficiency and diagnosing malfunctions. (from aptronix)
| Tutorial_On_Fuzzy_Logic.pdf |
A. AC Circuits: Install a varistor or a resistor capacitor (RC) network:
This circuit will protect the switch. Use a 100 ohms 1/4 watt resistor and 0.1 microfarad non- polarized capacitor or values within that range.
B. For DC circuits, install a diode.
You can use a general purpose diode of the number 1N4004 or equivalent diode.
Additional Notes:
* Don't be mislead by the resistive ratings of the switches. Most applications involve inductive loads.
* Don't be mislead by the wattage ratings of the loads. Low wattage loads are often high inductive devices making contact protection very important.
By using 2 pieces 110V ac to 220V ac step up transformers, one can produce 440V ac to power up certain industrial equipment for testing by following the setup above (parallel input, series output). Low power transformer can be used to power up variable frequency drives and similar equipment at no load to test programming and simulation. High power transformers should be used if used to power up with loads such as motor. At the place where I work, I usually use two variable transformers of high power rating that weighs about 10kgs for each to be be able to produce output voltages from 220 to 600Vac. It is such a big help for me instead of laying out power cables from to the 440V ac source towards the area where I usually do my work. But be be careful when doing this for one mistake could be hazardous. I mean high voltages here and that is fatal. Watch out for shorts and grounds.
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