Bilal_Baig
Member
Hello I am a college student and using Melsec for the first time and I am really stuck. I would be eternally grateful if someone could post a ladder diagram for the following. If I have the answer I can work backwards. I have wasted hours on his and haven't got very far at all.
Question:
A workshop has the sawdust created by two machines extracted through ducts by a three-phase motor operating an extractor fan. The control fo the fan is austomatic and is initiated by the machine ON/OFF pushbuttons.The system must operate to the following specification:
a) the fan must run for 20 seconds before power can be supplied to either of the machines
b) only one machien can be switched onat a time, a 10 second delay being required before the second machine can be started. The machines may be started in any order.
c) from the time that the last machine is turned off a 20 second delay is required before the exhaust fan may be stopped.
d) in the event of the fan motor overload protection operating, both the machines and the fan must stop immediately.
e) operating of the overload protection of a machine motor will only stop that machine as the workshop processes are independent of each other.
f) each machine is covered by a guard. The position of the guard is indicated by a changeover switch which changes position as soon as the guard starts to open but before any access can be obtained to the blades. The machien must not start until the guard is fully closed and must stop immediately if any attempt is made to open the guard.
Summary of inputs and outputs.
Inputs Contact type
Machine A
ON pushbutton NO
OFF pushbutton NC
overload NC
guardswitch terminal 1 NC
gaurdswitch terminal 0 NO
Machine B
ON pushbutton NO
OFF pushbutton NC
overload NC
guardswitch terminal 1 NC
guardswitch terminal 0 NO
Fan overload NC
Outputs
M/C A motor contact
M/C B motor contact
Fan motor contact
I know this is a lot to ask but help would be great.
Question:
A workshop has the sawdust created by two machines extracted through ducts by a three-phase motor operating an extractor fan. The control fo the fan is austomatic and is initiated by the machine ON/OFF pushbuttons.The system must operate to the following specification:
a) the fan must run for 20 seconds before power can be supplied to either of the machines
b) only one machien can be switched onat a time, a 10 second delay being required before the second machine can be started. The machines may be started in any order.
c) from the time that the last machine is turned off a 20 second delay is required before the exhaust fan may be stopped.
d) in the event of the fan motor overload protection operating, both the machines and the fan must stop immediately.
e) operating of the overload protection of a machine motor will only stop that machine as the workshop processes are independent of each other.
f) each machine is covered by a guard. The position of the guard is indicated by a changeover switch which changes position as soon as the guard starts to open but before any access can be obtained to the blades. The machien must not start until the guard is fully closed and must stop immediately if any attempt is made to open the guard.
Summary of inputs and outputs.
Inputs Contact type
Machine A
ON pushbutton NO
OFF pushbutton NC
overload NC
guardswitch terminal 1 NC
gaurdswitch terminal 0 NO
Machine B
ON pushbutton NO
OFF pushbutton NC
overload NC
guardswitch terminal 1 NC
guardswitch terminal 0 NO
Fan overload NC
Outputs
M/C A motor contact
M/C B motor contact
Fan motor contact
I know this is a lot to ask but help would be great.