motor sequencing - ladder logic required

[lanky]

Im new to plc's and need some help on efficient motor sequence ladder logic:

Inputs(control) - motor 1
motor 2
motor 3
motor 4

Outputs - motor on 1
motor on 2
motor on 3
motor on 4

If only one motor is trying to start (one input high) then it should start instantly and then block the other motors from starting for a time period.
If two or more are trying to start together then one with higher priority should start instantly then the other(s) after the time delay and so on.

Can someone please provide the ladder logic for this design with description of operation.

Thankyou for any responses
Sean

 

[ctolbert]

lanky:

Check Phil's site out...it's pretty good for people new with ladder logic.

http://www.plcs.net/

Another great sight is

http://www.control.com/index_html

Our website

http://www.automationdirect.com

has programming examples if you are using Koyo plc's. It's not really applicable if using other types.

Hope this helps some.

Carl

 

[kgvijayakumar]

Dear Lanky,

From the posting, I assume that finally all the motors will get started sequentially after a prescribed time delay. Correct me If I am wrong.

Also how is the priority defined.

If it is a contact, priority can be ANDed with the Input to run one motor. Make such that when this motor starts, it initiates (starts)a time delay, say T1 for motor 1. If motor 2 is going to start, let that be T2. This TIMER T1 ON(RUN) contact can be used to disable the outputs of other motors 2,3,4.

again the priority contact / bit will enable the start of the next "suited" motor. Here another Timer T2, T3 T4 will start and will block the other pumps. A symbolic rep is given down:
(Sorry Lanky, I couldnot post the rungs. Your e-mail will be useful)

P1 is the priority Bit/ contact for Motor 1 (O/P 1)
If any other timers are running it will not allow the motor 1 to start.
If motor 1 got enabled thro this logic and starts, then T1_R in other logics
will be “1” and will not allow other pumps to run till 40 seconds delay
of T1, even if its priority bit is set.


Similarly for motor 2 (O/P 2)
I/P 2 P2 T1_R T3_R T4_R O/P 2

Everything can be put in AND ed logic. K.G.Vijaya Kumar

 

[melone]

Just to elaborate on kgvijayakumar's statements a little more. With regards to ladder logic, and AND function is a line with all of the required inputs that are to be ANDed together with the output being the desired output coil to be activated.

---||------||-------||---------------------------( )-
Input1 Input2 Input3 Output

Input1 & Input2 & Input3 = Output

Good Luck and keep us posted!

 

[TheDOG]

A more "elegant" solution would be to use a compare function with a timer (for timing purposes)and a move statement (for the priority)...a little more programming experience would be required. The logic is a lot less cluttered.
Good luck!!

 

[krunal]

there is a conveyor belt on which there r cages.there r in all six motor,s(induction motor)i.e these motors r running the conveyor belt. conveyor belt is divided into subloops according to the motors[speed], now when cage goes from one sub loop to another pushers r used also proximity sensors r used ,I want a ladder logic for synchronization of all subloops.

 

[Macbeth]

Without Knowing your plc best I can do.

-| |- N.O.
-|/|- N.C.
-|^|- Trans On or One shot
-(S) Set
-(R) Reset
-(TMR) Timer




Start1 Hold stop1 Motor1
-----| |-----|/|-----|/|--------( )
|
|
Motor1 |
-----| |-----------

Motor1 Hold
-----|^|--------(S)


Start2 Hold stop2 Motor2
-----| |-----|/|-----|/|--------( )
|
|
Motor2 |
-----| |-----------

Motor2 Hold
-----|^|--------(S)


Start3 Hold stop3 Motor3
-----| |-----|/|-----|/|--------( )
|
|
Motor3 |
-----| |-----------

Motor3 Hold
-----|^|--------(S)


Start4 Hold stop4 Motor4
-----| |-----|/|-----|/|--------( )
|
|
Motor4 |
-----| |-----------

Motor4 Hold
-----|^|--------(S)


Hold
-----| |---------(TMR1)

TMR1 Hold
-----| |----------(R)

 

[skills]

A neat way to do this would be to have a motor start event to trigger a start inhibit that precludes further starting for desired period. Since scan time is probably 8-10ms; it's unlikely that multiple start buttons can appear simultaneously pressed, which, according to Einstein, simultanity can never be demostrated; but, I digress. We can post a solution here; but, that would spoil your fun. The above suggestions are perfectly acceptable