Electromechanical Relays

Electromechanical Relays

• 1.
  Electromechanical Relays
• 2.
  Outline Why Electromechanical Relays? CommonApplications of Electromechanical Relays The Principle Behind Electromechanical Relays What’s Inside an Electromechanical Relay Typical Sample Application Electromechanical Relay Advantages and Limitations Important Specifications of Electromechanical Relays Conclusion
• 3.
  Why Electromechanical Relays? Separationof AC and DC circuits Interface between electronic control circuits and power circuits
• 4.
  Common Applications ofElectromechanical Relays Solenoid Activation Control Many Automotive Applications (Electric Fuel Pump) Motor Control
• 5.
  Electromechanical Relays: What’sInside This diagram shows the basic parts of an electromechanical relay: a spring, moveable armature, Moveable Armature Moveable Contact electromagnet, moveable contact, and stationary Stationary Contact contact. The spring keeps Spring Electromagnet the two contacts separated until the electromagnet is energized, pulling the two contacts together.
• 6.
  Wiring Up anElectromechanical Relay This diagram shows how to wire an electromechanical relay. Power Supply When the control circuit turns the Load electromagnet on, the moveable Moveable Contact Moveable Armature armature is drawn towards the electromagnet and connects the Stationary Contact moveable contact and the Spring Electromagnet stationary contact. This completes the circuit and delivers power to the load. To Control Circuit
• 7.
  Typical Sample Application Suppose,there is a need to control a solenoid valve for a water drain application. Control is to be accomplished with a microcontroller. The solenoid valve requires 120 VAC to open. Assuming that a 120 VAC power supply is available, how can control of the solenoid valve be accomplished using a microcontroller that can only supply 5 VDC? This problem is easily solved using a relay. There are many relays that are turned on and off with a 5 VDC coil. The relay provides the interface between the microcontroller and the 120 VAC power supply that is needed to open and close the valve.
• 8.
  Typical Sample Application Ground To Microcontroller Coil Relay 120 VAC Solenoid Valve Circuit for Control of a 120 VAC Solenoid Valve
• 9.
  Electromechanical Relay Advantages Contactscan switch AC or DC Low initial cost Very low contact voltage drop, thus no heat sink is required High resistance to voltage transients No Off-State leakage current through open contacts
• 10.
  Electromechanical Relay Limitations Thecontacts wear and thus have limited life depending on loads Short contact life when used for rapid switching applications or high loads Poor performance when switching high inrush currents Package Size
• 11.
  Important Specifications ofElectromechanical Relays Coil Voltage – Voltage required for switching Contact Rating – How much current the relay can handle Normally Open (NO) or Normally Closed (NC)
• 12.
  Conclusion Electromechanical relays arean excellent solution to separate electronic control circuitry and power circuitry. Electromechanical relays are not the best choice in high frequency switching applications and do have a limited life due to wear on the contacts inside the relay. When used in the a proper application, the electromechanical relay provides safe and reliable integration between power circuits and control circuits.
• 13.
  Reference List  http://www.rowand.net/Shop/Tech/AllAboutRelays.htm  http://relays.tycoelectronics.com/schrack/pdf/C0_v4bg_2.pdf  http://www.cutler-hammer.eaton.com/unsecure/html/101basics/Module18/Output/ElectromechanicalRelays.html  http://www.msdignition.com/pdf/8961_8960_msd_relays.pdf  http://zone.ni.com/devzone/conceptd.nsf/webmain/7C83114818EAA85786256DD400569EB7?opendocument  http://www.ibiblio.org/obp/electricCircuits/Digital/DIGI_5.html
• 14.
  Links To ExploreFurther  http://www.allegromicro.com/techpub2/phoenix/relay5.htm - Solid State Relays  http://www.ssousa.com/appnote040.asp - Electromechanical Relays vs. Solid State Relays