Relay works under the principle of Electro-magnetic induction. An electric current passing through a coil wound on soft iron core. The iron core is magnetized as long as the current flows through the coil. As a result of this, a spring activated metallic contactor, is attracted towards this iron core, causing a mechanical movement. This principle is used to our advantage. There are two important principles demonstrated in this device, namely CAUSE & EFFECT. A relay connects

two devices working in different electrical conditions. I.e. mechanically connected and electrically isolated. For example: A digital system works at 5V DC and a fan works with 230V AC. Because the current flowing through a coil from a digital system, operating at 5V DC energizes the iron core; there is an effect of movable arm of the relay shifting its initial position. These switches ON a 230V AC operated bulb. The function of a Relay module is to show how a Microprocessor program can operate the relays and actuate high power devices. Some of the devices that can be actuated are like 230V AC lamps, blowers, contactors, fans, solenoids etc., which require 230 V AC supply for energisation. There are two relays placed on this module, which can be programmed by the Microprocessor either for ON or OFF condition. Each relay is housed in a transparent enclosure, to enable a student to see the movement of movable arm of the relay, while it gets actuated. The student is benefited by observing this phenomena.

Specifications:

• Two relays are used.
  
• Each relay operates @ 230V AC @ 0.5A.
  
• Two AC sockets are provided that for connecting two numbers of 230V AC actuated devices.
  
• Inputs are TTL compatible.
  
• Spark quenching electronics incorporated.
  
• An external power supply 5V DC @250mA is required or +5V DC power supply Model SP512 is recommended.