Need guidance on next project

So, my job is pretty much giving me a PLC lab to train with. I just finished up some basic analog signaling and processing using a process meter as source. You guys have any suggestions on where I should go next, or what project I might want to attempt. I have access to all kinds of devices, switches, scales, contactors, VFDs and any older PLC (mostly SLCs and Micrologix) components I want to use.

What kind of equipment do you normally work with?

Working with the VFD would be a good place to start. Not knowing the model of the PLC and VFD it is hard to give advise. Maybe enlighten us on that and we can help more.

I have AB and Emerson VFDs, and ControlNet, Ethernet/IP and DeviceNet cards for the SLC. I work in a packing plant so think scale/conveyors systems, and other packaging/fluid power machinery.

sparkie said:

I have AB and Emerson VFDs, and ControlNet, Ethernet/IP and DeviceNet cards for the SLC. I work in a packing plant so think scale/conveyors systems, and other packaging/fluid power machinery.

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I guess my last project I used an SCP instruction to scale a VFD's voltage. I'm trying to think of some other cool projects to challenge me a bit more

Try using message instructions to communicate with the drive and send the start command, speed reference and stop command. I know it is pretty easy to do with a Control or Compact Logix processor but using a SLC it will be more challenging.

1. Make a combination lock that requires 4 numbers to be entered in the right order. Don't need a lot of hardware for this. Packaging machines require knowing how to implement state machines. ( state machines )
2. Get the Ethernet/IP devices connected to the PLC. ( communications )
3. Synchronize two motors. ( motion control )

Peter Nachtwey said:

1. Make a combination lock that requires 4 numbers to be entered in the right order. Don't need a lot of hardware for this. Packaging machines require knowing how to implement state machines. ( state machines )
2. Get the Ethernet/IP devices connected to the PLC. ( communications )
3. Synchronize two motors. ( motion control )

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I have sort of synced two motors. I have used two starters with a safety. I have also utilized prox switches and photo eyes to start and stop motors. What do you mean by "state machines" ?

sparkie said:

What do you mean by "state machines" ?

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...shamelessly plagiarized from wikipedia...

A finite-state machine (FSM) or finite-state automaton (plural: automata), or simply a state machine, is a mathematical model of computation used to design both computer programs and sequential logic circuits. It is conceived as an abstract machine that can be in one of a finite number of states. The machine is in only one state at a time; the state it is in at any given time is called the current state. It can change from one state to another when initiated by a triggering event or condition; this is called a transition. A particular FSM is defined by a list of its states, and the triggering condition for each transition.

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Essentially a sequence of discrete steps with transitional logic to index the step and the associated action(s) of the step.

I see, so it would be like utilizing a truth table to determine a set number of states and how said machine is to behave, so say, if power is lost or it is stopped mid-cycle i can read a state and pick up where it left off.

sparkie said:

I see, so it would be like utilizing a truth table to determine a set number of states and how said machine is to behave, so say, if power is lost or it is stopped mid-cycle i can read a state and pick up where it left off.

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I think it would be a bit off to compare a fsm to a truth table, unless your truth table is a table of states.
One problem that I see with a truth table comparison is that several states can have the same TRUTH LOGIC, but depending in the specific state condition/transition logic, a totally different *target* state may be required.

A state machine is more like a *sequence* of states and transitions(conditional logic) that allows the machine *sequencer* to index to another step.
The term *sequence* is not exactly correct in that any valid state can be transitioned to from any other state -- depending on the origin STATE, target state and transition logic.
In the image, you can see that state 1 can transition to state 2 OR state 6 depending on the transition logic (IN = 'n').
State 2 can transition to state 3 OR state 6 (IN = 'i').


(if the picture does not show- see link http://upload.wikimedia.org/wikipedia/commons/a/a8/Fsm_parsing_word_nice.svg)

Now imagine that we are looking for the series of characters t r o t.
States 1 and 4 are looking for the same character (transition logic) but will have different target states - since states 1 and 4 have different state conditions.

State 1 condition - "START"
State 1 transition logic (= 't')
-true : goto to state 2
-false : goto state 6

State 2 condition - "found initial t"
State 2 transition logic (= 'r')
-true : goto to state 3
-false : goto state 6

State 3 condition - "found 'r'"
State 3 transition logic (= 'o')
-true : goto to state 4
-false : goto state 6

State 4 condition - "found 'o'"
State 4 transition logic (= 't')
-true : goto to state 7
-false : goto state 6

Whether you could use it as a *resume from power off* would depend on your process. The mid-cycle stop may be a good candidate where the stopping is just an inhibit of a transition from one state to another state.

Thank you, that actually clarifies a lot. I decided to start working on a keypad combination lock as a next project, it seems a bit tricky to do, so I've been working out some logic for it (remember I'm pretty new at this sort of stuff). I'll definitely keep you guys updated on how it progresses, but no work on it today. I called in sick, not feeling very well .

A Sequential Function Chart pdf

http://controlmanuals.com/files/Automation/PLC-%28Programmable-Logic-Controller%29/Programming-of-PLCs:-Sequential-Function-Charts~pdf446.html

Even if your hardware doesn't support SFCs it may help to work out the logic in SFC form then convert it to ladder.

sparkie said:

Thank you, that actually clarifies a lot. I decided to start working on a keypad combination lock as a next project, it seems a bit tricky to do, so I've been working out some logic for it (remember I'm pretty new at this sort of stuff). I'll definitely keep you guys updated on how it progresses, but no work on it today. I called in sick, not feeling very well .

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Just do not fail out on an incorrect keypress - that would make it too easy to guess the password. Let user enter whatever keypresses and then pass or fail.

visualization and reporting

Do you have any HMIs (PanelViews, etc) or visualization software (WonderWare) in the lab? The touch-screen UI on car radios is usually pretty bad--could try and build your own.
Business types like to see reports. What about something that spits out a nightly report with performance data on it? widgets/hour by shift or something like that

dan_bob said:

Do you have any HMIs (PanelViews, etc) or visualization software (WonderWare) in the lab? The touch-screen UI on car radios is usually pretty bad--could try and build your own.
Business types like to see reports. What about something that spits out a nightly report with performance data on it? widgets/hour by shift or something like that

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I'll get more into panelview programming once I'm better at PLC programming.