Nearwiki: Created page with "This example shows how to implement a real time Power Monitor in JavaScript for a mobile device. This implementation require an Xively account (www.xively.com) in order to get..."

2018-03-29T20:56:17Z

Created page with "This example shows how to implement a real time Power Monitor in JavaScript for a mobile device. This implementation require an Xively account (www.xively.com) in order to get..."

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This example shows how to implement a real time Power Monitor in JavaScript for a mobile device. This implementation require an Xively account (www.xively.com) in order to get the historical data sequence in a chart format.

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[[File:mobile_power_meter.png|160px]]

smartphone interface example
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===System Implementation===
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This implementation works in manual mode asking the remote agent (Arduino) the power reading in a periodic way. The system use the Cosm Connector to send the reading to Xively in order to show it in a graphical way. On the other hand a independently javascript code running from a mobile device ask to the NearBus system in a periodic way the last power reading to show it on the mobile device.
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Only two hadware components are needed to implement this real time Power Monitor: An Arduino Board (Ethernet / WiFi) and an AC Current Sensor [http://www.seeedstudio.com/wiki/Non-invasive_AC_current_sensor%2830A_max%29] as showed in the following picture.
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[[File:arduino_power_monitor.png]]
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The AC Current Sensor is connected to the A0 analog inpur on the Arduino board.
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'''IMPORTANT: the current sensor only should be installed on only one power wire (of two). If you place both power wires into the sensor,'''
'''then the reading will be 0 (zero)'''.
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===Configuring the Manual Mode===

In order to get samples from the sensor in a continous way, you should configure the '''RMS_INPUT''' service in manual mode for the selected channel (the port in which the sensor will be connected). In this example we will use the Channel 0 (A0 3 in an Arduino platform). The following picture shows this configuration.

[[File:manual_mode_power.png]]

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===Xively Configuration (formerly Cosm)===
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This screen allows you send to Xively (www.xively.com) the values received from or transmitted to the remote device over each channel.

[[File:xively_config_power.png]]

* '''Stream ID: ''' This field allows you to set the Xvely's (Cosm) datastream where you want to send the signal.

* '''IN / OUT:''' This option allows you to indicate if you want to send a readed value (input) from the remote device or the written value (output) to the remote device for each channel.

* '''Constant and Offset:''' The main advantage of this feature is that it allows you to apply a basic transfer function to your signal before sending it to Xively (Cosm):

<pre>
f(x) = x * K + offset
</pre>

* '''ON: ''' This option allows you to turn on or off the data feed to Xively (Cosm).

* '''Xively Feed and API Key:''' This option allows you to configure the required parameters to connect succesfully to www.xively.com.
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In this example we use a constant factor of 6.6. This factor is obtained in the following way:

*'''Power Line tension:''' 220 Vac
*'''Current Sensor Ratio:''' 30:1 (30Aac= 1Vac)
*'''RMS_INPUT scale''': mV (RMS)

K = 220 * 30 / 1000 = 6.6 [W/mV]

'''Note:''' this is a calibration example. In order to calibrate your Power Monitor you should use a well-known resistive load (and adjust the K factor to match its value).
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The following picture shows a real system power chart (Xively). It is important to remark the amount of information that can be obtained from it. In this example the chart represents a measure of our lab enviroment, where an electric heater (about 1400W) and a small refrigerator (about 175 W) are working together, each with its own power fingerprint, as indicated in red on the Xively output chart (note that a residual power consumption of 196W is always present).

[[File:xively_power_chart.png|600px]]
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===Javascript Code===
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The following code will allow you to display the sensed power in a graphical way from a mobile device or desktop computer. In order to run this example, download the following file in you mobile device or computer, change the parameters indicated with "****" and execute it. Double click onto the downloaded "html" file in order to run it on your default browser.

This example is calibrated to use a 30A AC Current Sensor [http://www.seeedstudio.com/wiki/Non-invasive_AC_current_sensor%2830A_max%29] but you can use any other current sensor sensor that you want (you only should change conversion factor). In this example a conversion factor of 6.6 is used.

'''Note:''' that the Xively transfer function '''does not affect''' the value read with the RMS_INPUT service.

'''Download:''' Power_Monitor_0v1.zip [http://www.nearbus.net/downloads/js_apps/Power_Monitor_0v1.zip]

In order to run this example you should edit it (eg. notepad) and replace the following parameters:
var device_id = "NB100xxx"; // You NearBus Device ID
var user = "****"; // Your NearBus Web user
var pass = "****"; // Your NearBus Web password

<pre>
<!DOCTYPE html>










<html>
<head>
<script src="http://code.jquery.com/jquery-1.9.1.min.js"></script>
<script type="text/javascript" src="PAGE" ></script>
<script type='text/javascript' src='http://nearbus.net/downloads/js_apps/nearapi_v05.js'></script>

<script>
// +--------------------------------------------------------------------+
// | To run this example you should replace the following parameters |
// | device_id Your device ID, or.. devices ID :) |
// | user Your NearBus Web user |
// | pass Your NearBus Web password |
// +--------------------------------------------------------------------+

//////////////////////////////////
// MAIN CONFIGURATION
//////////////////////////////////
var device_id = "NB100xxx"; // Your device ID
var user = "****"; // Your NearBus Web user
var pass = "****"; // Your NearBus Web password
var LOOP_DELAY = 2000;
var power = 0;

window.onload = function ()
{
///////////////////////////////////
// Function: Main Loop
///////////////////////////////////
setInterval( function()
{
ret = NearAPIjs( "RMS_INPUT", device_id , 0, 0, "RONLY" );
if( ret != "WAIT" && !isNaN(ret) ) {
power = Math.round( ret * 6.6 );
$('#field_1').text( power.toString() );
}
}, LOOP_DELAY );
}

</script>

<body bgcolor="#000">
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<p><div style="text-align:center; width:950px"><img src="http://nearbus.net/images/logo_nearbus.png" width="140" heisgth="78"</div></p>
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<p><div style="text-align:center; width:950px; font: bold 60px Arial; color:orange;">POWER MONITOR</div></p>
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<div id="div_temp_chart_cm"> <img src="https://api.cosm.com/v2/feeds/****YOUR_FEED_ID_HERE****/datastreams/****YOUR_CHANNEL_NAME_HERE****.png?width=750&height=400&colour=%23f15a24&duration=3hours&show_axis_labels=true&detailed_grid=true&timezone=****YOUR_ZONE_HERE****" > </div>

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<p><div style="text-align:center; width:950px; font: bold 60px Arial; color:orange;">watts</div></p>
<p><div id="field_1" style="text-align:center; width:950px; font: bold 300px Arial; color:orange;">. . . .</div></p>
</body>
</html>

</pre>

Power Monitor - Revision history

Nearwiki: Created page with "This example shows how to implement a real time Power Monitor in JavaScript for a mobile device. This implementation require an Xively account (www.xively.com) in order to get..."