Type of graphic language automatic control systems.
A drawing program of a switching circuit.
Called "ladder" diagrams because they resemble a ladder, with two vertical lines representing the power trails (supply power) and circuits are connected in horizontal lines called rungs. Connection between the element in the rung called link .
Referring to figure below, between these two rails, a horizontal straight line was drawn with two symbols . These two symbols refer to the input and output devices , which are used in the actual process/system.
On the left , we put all kinds of input . While on the right , we place all types of the outputs .
Once we complete one line of the program it seems like a ladder. This horizontal line which places the input and output make one rung.
-PB is pressed, output IR is activated -IR contact will closed -When PB is depressed, the output IR is still activated since current can go through contact IR unless is disturbed by stop button.
Vibrating/Jog circuit -When, PB is pressed, output IR is activated. -But after several microsecond, the normally closed IR is open then will stop the output IR. -This applicable to move an object which need to locate at precise location.
Control circuit has Overload Protection Device
Control circuit in ladder diagram. -When PB is pushed(forward/reverse),motor will move according to the command. -But, when there is an overcurrent,CB will stop the current flow by blow the fuse. -Means, NC of CB will open and stop the current flow to the circuit. -The circuit can be recovered by change the fuse. -If there is thermal overload, TOR will cut the current flow. -Lamp,L3 will turn on and TOR need to be reset.
Two wire control -only has one contact for switching device either ON or OFF state. -When ON state, M will energize and activate three phase motor. -Heater will heat if there is over current and open the circuit.
Three wire control -the connection almost the same as two wire circuit except has an extra set of contact connected in parallel as the pilot switch. -this extra contact provide extra third wire. -this auxiliary contact keep coil M energize even after start push button release.