a) An electrical heater is used to heat the water in a tank. The heater starts when the temperature is lower than T and stops when it reaches T. In addition, when the water level is lower than L, a pump starts to pump water into the tank and stops when the level reaches L. for safety reason, the heater doesn’t start if water level is lower than L.

(Write ladder diagram as the picture above)

b) The door of the building is unlocked during 8-17 in working days. For the rest of time, it is locked. When it is locked, we can use the entrance card to open the door. Use the truth table and equation to show the logic.

(Write ladder diagram as the picture above)

c) the irrigation system normally works for 1 hr during 8-9am. however, when it is raining, it will not work. In addition, when the temperature is higher than 30C, it will also run for 30mins

(Write ladder diagram as the picture above)

 

Rail Rung 1 Rung 2 Rung 3 Inputs & Logic Expressions Input 1 Input 2 IF Internal Variable 1 Input 3 Input 4 Input 5 Internal Variables & Outputs Internal Variable 1 Output 1 O Output 2 Rail