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Tutorial Video
Hardware
- PHPoC Blue (+ USB WLAN) or PHPoC Black (+ Ethernet cable)
- Micro USB to USB Cable (to upload source code to PHPoC Device)
- Light Sensor
- Jumper wires
About Light Sensor
Light sensor is used to detect the current ambient light level - i.e. how bright/dark it is. The light sensor used in this example includes three pins:
- VCC pin.
- GND pin.
- Signal pin (outputs analog signal).
- The sensor outputs analog signal to signal pin. There bigger the ambient light level is, the higher the signal value is.
- By reading value of sensor's signal pin, we can infer ambient light level. To read value of sensor's signal pin, we just need to connect the sensor's signal pin to PHPoC device's ADC (Analog to Digital Converter) pin and use PHPoC code to read the value.
- Grove light sensor (for more convenience, use it in combination with PHPoC Grove Expansion Board).
- LDR Photoresistor Light Sensor.
Wiring Diagram
Quick Steps
Source code of this example is a part of PHPoC Support Packet (PSP). You need to:
- Download PHPoC Support Package.
- Upload example\p4s\02.html_text\02.adc_light_sensor to PHPoC Blue/Black.
- Configure network parameters (e.g. WiFi SSID, password, IP address ...).
- Access webpage on PHPoC using Web Browser on your PC or smart phone (See How To).
Source Code
Source files includes:index.php file, which contains source code of web page. It is only run in response to request from Web Browser.
index.php
[Full Code]
PHP Code:
<html>
<head>
<title>PHPoC / <?echo system("uname -i")?></title>
<meta name="viewport" content="width=device-width, initial-scale=0.7">
<style> body { text-align: center; } </style>
</head>
<body>
<h2>
ADC / Catalex Light Sensor<br>
<br>
<?php
include "/lib/sd_340.php";
define("ADC_MAX", 2520);
adc_setup(0, 0); // adc0, channel 0
$adc_in = adc_in(0, 30);
if($adc_in > ADC_MAX)
$adc_in = ADC_MAX;
printf("Illuminance level : %d(%%)<br>\r\n", $adc_in * 100 / ADC_MAX);
?>
<br><a href="index.php">reload</a><br>
</h2>
</body>
</html>
[Explanation]
Source code of index.php file is composed of HTML, CSS and PHPoC code.
PHPoC code is interpreted on on PHPoC device.
-
PHP Code:
<?php
include "/lib/sd_340.php";
define("ADC_MAX", 2520);
adc_setup(0, 0); // adc0, channel 0
$adc_in = adc_in(0, 30);
if($adc_in > ADC_MAX)
$adc_in = ADC_MAX;
printf("Illuminance level : %d(%%)<br>\r\n", $adc_in * 100 / ADC_MAX);
?>
- Setup ADC pin.
- Read value from light sensor.
- Calculate illuminance level based on the read value.
- Print the illuminance level value to Webpage
PHPoC code may add/update the content of HTML, CSS or JavaScript code. Once PHPoC code is interpreted in PHPoC, the remaining code is client-side code and it is returned to Web Browser. Web Browser receives this code and interpret it to display the webpage.
- HTML: describes the structure of Web pages
- CSS: describes how HTML elements are to be displayed
See Also
- Light Sensor - How to Use Light Sensor.
- Light Sensor - Monitoring Light Sensor from Webpage with Image.
- Light Sensor - Monitoring Light Sensor via WebSocket.
- Light Sensor - Monitoring Light Sensor via WebSocket with Web-based Gauge.
Other Resources