electrical engineering

Energy Management: Google Power Meters

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Nowadays, the world is going green and everyone is behind optimising energy and resources. For better energy optimisation, we need to first better know about our energy consumption behaviour. And here comes the concept of energy monitoring tools.<br />
There are multiple energy monitoring tools available in the market such as Dreamwatts, Greenbox, etc. But the whole industry shook its head when Google decided to enter in this field with its free Google Power Meter.<br />
So, what is Google Power Meter? Why it is creating so much buzz?<br />
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<div style="text-align: center;"></div><div style="text-align: center;"></div><div style="text-align: center;"></div><div style="text-align: center;"></div><div style="text-align: center;"></div><div style="text-align: center;"><img alt="Google Power Meter" class="size-medium wp-image-2594 aligncenter" height="300" src="http://engineering.electrical-equipment.org/wp-content/uploads/2010/10/powermeter-ui-info-226x300.jpg" style="border: 1px solid black;" title="Google Power Meter" width="226" /></div><span id="more-2584"></span><br />
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It is a free energy monitoring tool which uses energy information provided by energy monitoring devices and smart utility meters. It is a real time energy monitoring tool which allows you to view<br />
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your energy consumption from anywhere online, and thus helping you to save energy and money.<br />
Some features of Google Power Meter:<br />
<ol><li>Energy tracking over a period of time</li>
<li>Prediction of costs</li>
<li>Budgeting</li>
<li>Information about always on power appliances</li>
<li>Easily customizable</li>
<li>Compatibility to smart phones</li>
</ol>Checking the reviews of Google Power Meter users, it seems that you can save minimum 20% of energy and bills. What is your opinion?<br />
Sudeep S</div>

Energy Management: Google Power Meters

Nowadays, the world is going green and everyone is behind optimising energy and resources. For better energy optimisation, we need to first better know about our energy consumption behaviour. And her…

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14 Dec 2010

First Order Transient Circuits

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</div><div style="text-align: justify;">first order circuit are those circuits whose response can be expressed by a first order differential equations.</div><div style="text-align: justify;"><br />
</div><div style="text-align: justify;">Example of such circuits include the RL and RC circuits</div><div style="text-align: justify;"><br />
</div><div style="text-align: justify;">RL circuit : circuit that contains an indicator and a resistor.</div><div style="text-align: justify;"><br />
</div><div style="text-align: justify;">RC circuit : circuit that contains a capacitor and resistor</div><div style="text-align: justify;"><br />
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This is a first order linear ordinary non-homogenous differential<br />
equation describing the response of the capacitor voltage.<br />
It is first order because the highest degree of derivative is one.<br />
it is called linear because the differential equation is linear<br />
function of (dvc /dt) and vc(t)<br />
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To solve this circuit I'm going to use the differential equation approach. I'm concerned with the<br />
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voltage across the capacitor at <a href=""><img align="top" alt="LaTeX Code: V_c(0^-) " border="0" src="http://www.physicsforums.com/latex_images/13/1349535-0.png" title="LaTeX Code: V_c(0^-) " /></a> and <a href=""><img align="top" alt="LaTeX Code: V_c(0^+) " border="0" src="http://www.physicsforums.com/latex_images/13/1349535-1.png" title="LaTeX Code: V_c(0^+) " /></a><br />
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At position 1 before the switch is thrown <a href=""><img align="top" alt="LaTeX Code: V_c(0^-)=0 " border="0" src="http://www.physicsforums.com/latex_images/13/1349535-2.png" title="LaTeX Code: V_c(0^-)=0 " /></a><br />
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At position 2 after switch is thrown I have the following from KCL:<br />
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<a href=""><img align="top" alt="LaTeX Code: \\frac{6-V(t)}{12k} = C\\frac{dv}{dt} + \\frac{V(t)}{6k} " border="0" src="http://www.physicsforums.com/latex_images/13/1349535-3.png" title="LaTeX Code: \\frac{6-V(t)}{12k} = C\\frac{dv}{dt} + \\frac{V(t)}{6k} " /></a><br />
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This reduces to: <a href=""><img align="top" alt="LaTeX Code: \\frac{dv}{dt} + 2.5V(t) = 5  " border="0" src="http://www.physicsforums.com/latex_images/13/1349535-4.png" title="LaTeX Code: \\frac{dv}{dt} + 2.5V(t) = 5  " /></a><br />
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My problem is that I know that this is correct but I don't know how to put it all together.<br />
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I know that the solution is of the form:<br />
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<a href=""><img align="top" alt="LaTeX Code: K_1 +K_2e^{-t/t_c} " border="0" src="http://www.physicsforums.com/latex_images/13/1349535-5.png" title="LaTeX Code: K_1 +K_2e^{-t/t_c} " /></a><br />
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The answer is <a href=""><img align="top" alt="LaTeX Code: V(t)=1.33 -1.33e^{-2.5t}V " border="0" src="http://www.physicsforums.com/latex_images/13/1349535-6.png" title="LaTeX Code: V(t)=1.33 -1.33e^{-2.5t}V " /></a><br />
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How do I extract this from my work?<img alt="" border="0" class="inlineimg" src="http://www.physicsforums.com/images/smilies/laughing.gif" title="Laughing" /><br />
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First Order Transient Circuits

first order circuit are those circuits whose response can be expressed by a first order differential equations. Example of such circuits include the RL and RC circuits RL circuit : circuit that conta…

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14 Dec 2010

Circuit Active Elements

<div dir="ltr" style="text-align: left;" trbidi="on"><span style="color: red; font-size: large;">There are 4 types of active elements (sources)</span><br />
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</span></div><div style="color: red;"><span style="font-size: large;">1. Independent voltage source:</span></div><div style="color: red;"><span style="font-size: large;"><br />
It is a 2-terminal sources that maintains a specific voltage across its terminals regardless of the current through it</span></div><div style="color: red;"><span style="font-size: large;"><br />
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</span></div><div style="color: red;"><span style="font-size: large;">2. Independent current source:</span></div><div style="color: red;"><span style="font-size: large;"><br />
It is a 2-terminal sources that maintains a specific current through it regardless of the voltage across it terminals.</span></div><div style="color: red;"><span style="font-size: large;"><br />
</span></div><div style="color: red;"><span style="font-size: large;">3. Dependent voltage source:</span></div><div style="color: red;"><span style="font-size: large;"><br />
It is a 2-terminal sources that generates a voltage that is determined by a voltage or current at a specified location in the circuit.</span></div><div style="color: red;"><br />
</div><div style="color: red;"><span style="font-size: large;"> 4. Dependent current source:</span></div><div style="color: red;"><span style="font-size: large;"><br />
It is a 2-terminal sources that generates a current that is </span></div><div style="color: red;"><span style="font-size: large;"> determined by voltage or current at a specified location in the circuit.</span></div><div style="color: red;"><br />
</div><span style="color: red; font-size: large;">Basic Quantities</span><br />
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<span style="color: red; font-size: large;">(1) Electron :electron is a mobile charge carrier.</span><br />
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The electron is measured in coulumb [ C ]</span><br />
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</div><div style="color: red;"><span style="font-size: large;">(2) Current :</span></div><div style="color: red;"><span style="font-size: large;"><br />
the time rate of change of charge produces an electrical current</span></div><div style="color: red;"><br />
</div><span style="color: red; font-size: large;">the electric current is measured in Amper [A]</span><br />
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<div style="color: red;"><span style="font-size: large;">(3) Voltage :</span></div><div style="color: red;"><span style="font-size: large;"><br />
The voltage is defined as the work or energy (in Joules) required per unit charge to move a test charge though an element</span></div><div style="color: red;"><br />
</div><div style="color: red;"><span style="font-size: large;">(4) Power :</span></div><div style="color: red;"><span style="font-size: large;"><br />
Power is the time rate of change of energy.</span></div><br />
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<span style="color: red; font-size: large;">(5) Energy</span><br />
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<span style="color: red; font-size: large;">Passive sign convention</span><br />
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<span style="color: red; font-size: large;">Power can be absorbed or supplied by an element.</span><br />
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<span style="color: red; font-size: large;">Power is absorbed (or dissipated) by an element if the sign of power is (+)</span><br />
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<span style="color: red; font-size: large;">Power is supplied (delivered or generated) by an element if<br />
the sign of power is (-)</span></div>

Circuit Active Elements

There are 4 types of active elements (sources) 1. Independent voltage source: It is a 2-terminal sources that maintains a specific voltage across its terminals regardless of the current through it 2. …

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14 Dec 2010