Sequence starting motors 2

[vitzwaters]

Need to start packhouse motors driving conveyor belts of Fruits. Want to use equal flip flop timer to run about 15 motors (0.37 -0.75kw).The last Belt must run first and the first(At Fruit entrance) must run last otherwise fruits will pille at the next consecutive belt. Must operate manually or Auto. Trip of either of the motor must set trip pilot light, and stop all motors. I did attach circuit drawing. Now got a condition from the packhouse manager that occassionally might want to run different belts independently manually, how can i modify my circuit to manually achieve the condition. Please note i have not to use any PLC in my control circuit.

Vitzwaters

 

[Skogsgurra]

Your best choice is to use a PLC. If the specs keep changing, you will be sorry you didn't.

Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[Skogsgurra]

It's cheaper, too.

Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[itsmoked]

Agreed.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[LionelHutz]

It really isn't that difficult to do what you describe with hard logic. However, the requirements need to be nailed down first so what you create will work.

A PLC has tons more flexibility but the downside is that it's likely the people who will operate and maintain this system im the future will likely not be able to follow the PLC logic and definately not want to modify the PLC logic. This means that any PLC issue will likely become yours. Not a bad prospect if you can make money but definately a bad bad if the customer expects free support (and a customer can come up with many reasons why you should do it for free).

From my view, you should have known that each motor is required to run individually from the start. This is how the conveyers and motors are each tested during maintenance.

 

[waross]

In the control scheme for each individual motor there will be a set of permissive of interlock contacts that prevent operation unlessl the prevoius motor in the sequence is running. Connect your manual bypass contacts across this set of contacts. You may consider using "Hand/Off/Auto" selector switches.

Bill
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"Why not the best?"
Jimmy Carter

 

[vitzwaters]

Thanx for all contributions. I modified the design so that it could do the job. I considered all your contribution. In the future, i think i would need to use PLC but have no starting point for PLC development. Any references so that i can learn hw to do automatic processes using siemens s7?

 

[panelman]

As others have said a PLC give lots of flexibility but if you want to stay away from software then the way to go is Hand/Off/Auto switches for each motor.

The last motor is the first to start and a NO aux on that is the Auto signal for the next one and so on.

Overloads are kept specific to motors so if a motor stops then everything upstream also stops but everything down stream carries on thus clearing as much product as possible from the belts.

 

[waross]

A compromise between hardwired interlocks and a PLC may be a smart relay with timing functions. You will probably find that you need some logic. Timed stops are useful to unload the belts. You still need Emergency stops.

Bill
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"Why not the best?"
Jimmy Carter

 

[Skogsgurra]

If you do not want to jump into deep waters (the S7 can be tricky for a beginner) then use the Siemens LOGO! (yes the "!" is part of the name). It has a very low threshold for beginners, you will be testing programs in one or two hours - and you can simulate and test very realistically within the development system. Dirt cheap, too. You need to add one or two expansion modules to the basic units. But still dirt cheap.

Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...