This document discusses different types of special relays used in automation control circuits. It describes solid state relays, which have advantages over conventional relays like producing no sound, operating faster, and withstanding higher temperatures. It also covers liquid level relays, electromagnetic latching relays, start-stop relays, and motor sequence relays. Notes are provided on how liquid level relays work using multiple electrodes to detect liquid levels and control outputs. Diagrams show examples of circuits for filling a tank and running/stopping a motor from a single push button.

1. Automation lecture 6
BY: Mahmoud Hussein

2. Special Relays
 A lot of tasks are repeated in classic control circuit that lead to some company to
manufacture compact components
 Types of the these components
 Solid state relay.
 Liquid level relay
 Electromechanical latching relay.
 Start-stop relay
 Motor sequence relay

3. Solid state relay
 Electronic relay content one NO open contact

4. Solid state relay
 There are some types have more one contact

5. Solid state relay

6. Solid state relay

7. Solid state relay
 Advantages
 No sound during running
 Faster than conventional relay
 Withstand with high temperature

8. Exercise
 Design a control circuit to control with tank

9. solution

10. Liquid level relay

11. Liquid level relay

12. Notes
 Is used for liquid (no fire)
 There are sensitivity adjustment that depend on the distance between electrodes.
 If the tank is metal you can use two electrode and the third electrode connect with
the tank.
 If liquid is upper than higher electrode(o/p=1 ½=open 1/3=close)
 If liquid is lower than lower electrode(o/p=0 ½=close 1/3=open)

13. Diagram for filling tank

14. Electromagnetic latching relay

15. Exercise
 Design a control circuit to run and stop motor from one push button

16. Start stop relay

17. Motor sequence relay