View source for Relay(HIGH) for Arduino and Raspberry Pi

=='''Introduction'''==
[[File:Relay module.png]]<br>
This is a HIGH level trigger relay,apply to Arduino and Raspberry Pi. Relays are suitable for driving high power electronic devices such as lights, electric fans and air condition. A relay can be used to control high voltages with a low voltage by connecting it to an MCU.<br>
The schematic of the relay module is shown as following:<br>
[[File:Relay schematic（HIGH）.png]]<br>
Sending a HIGH level to SIG; the NPN transistor is energized and the coil of the relay is electrified. Thus, the normally open contact of the relay is closed, while the normally closed contact of the relay will be open. Send a LOW level to SIG; the transistor will be de-energized and the relay will restore to the initial state.
=='''Principle of relay'''==
See the picture here :A is an electromagnet, B armature, C spring, D moving contact, and E fixed contacts. There are two fixed contacts, a normally closed and a normally open. When the coil is not energized, the normally open contact is the one that is off, while the normally closed one is the other that is on. <br>
[[File:Relay3.png]]<br> 
Add a certain voltage to the coil and some currents will pass through the coil thus generating the electromagnetic effect. So the armature overcomes the tension of the spring and is attracted to the core, thus closing the moving contact of the armature and the normally open contact (or you may say releasing the former and the normally closed contact). After the coil is deenergized, the electromagnetic force disappears and the armature moves back to the original position, releasing the moving contact and normally closed contact. The closing and releasing of the contacts results in power on and off of the circuit. <br>
=='''Features'''==
*Support control of DC and AC signals (AC 220V load)<br>
*Working voltage: 5V; PCB size: 2.0 x 4.3 cm<br>
*With power light and signal output indicator <br>
=='''Application'''== 
The module can be used as a development module on an MCU or for control of household appliances. 
=='''Resource'''==
[https://www.sunfounder.com/learn/sensor-kit-v2-0-for-raspberry-pi-b-plus/lesson-4-relay-module-sensor-kit-v2-0-for-b-plus.html Test Experiment for Raspberry Pi][[File:LINK.jpg]]<br>
[http://www.sunfounder.com/wiki/index.php/File:Relay_datasheet.pdf Relay_datasheet][[File:PDF.jpg]]