<div dir="ltr">If I'm not mistaken, the Arduino circuit described measures apparent power, not true power, because it simply averages the current and doesn't take into account the voltage to current phase shift caused by inductive loads. Good enough to tell if your water heater is on, but it may not match what your electric meter says.</div><div class="gmail_extra"><br><div class="gmail_quote">On Wed, Jan 14, 2015 at 9:49 PM, Martin Brooke <span dir="ltr"><<a href="mailto:martin.brooke@duke.edu" target="_blank">martin.brooke@duke.edu</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr"><div class="gmail_default" style="font-family:arial,helvetica,sans-serif;font-size:small">I used an audio jack breakout on an arduino proto shield with a simple RC circuit to level shift the AC.</div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif;font-size:small"><br></div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif;font-size:small">here is a <a href="https://drive.google.com/file/d/0B0lP-6BNGel_a09EbFBkeDJWamc/view?usp=sharing" target="_blank">photo</a>.  The proto shield is this one from  <a href="http://smile.amazon.com/SainSmart-Prototyping-Prototype-Breadboard-Arduino/dp/B0079WI2MK/ref=sr_1_4?ie=UTF8&qid=1421289842&sr=8-4&keywords=Prototype+Shield" target="_blank">sain smart </a> although there are many alternatives for this.</div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif;font-size:small"><br></div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif;font-size:small">The break out was from <a href="https://www.sparkfun.com/products/10588" target="_blank">sparkfun</a>  for which you need some <a href="https://www.sparkfun.com/products/116" target="_blank">headers </a>and the <a href="https://www.sparkfun.com/products/8032" target="_blank">jack</a>  maybe you can find one assembled </div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif;font-size:small"><br></div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif;font-size:small">There is also two resistors and a capacitor needed to get the AC signal into the ADCs input range.</div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif;font-size:small"><br></div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif;font-size:small">I really just copied the circuit from this <a href="http://www.instructables.com/id/Yun-based-Electricity-Monitor-with-Cloud-Support-T/?ALLSTEPS" target="_blank">intructable</a>. </div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif;font-size:small"><br></div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif;font-size:small">The instructable goes way further, using an Arduino Yun to make it readable via wifi, very cool, but maybe beyond what you want or need.</div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif;font-size:small"><br></div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif;font-size:small">Cheers,</div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif;font-size:small"><br></div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif;font-size:small">​​</div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif;font-size:small"><a href="http:///" target="_blank"></a><span></span><span></span><br></div><div class="gmail_extra"><div><div dir="ltr"><div><div dir="ltr"><div></div></div></div></div></div>
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