CLD Traffic Light Sample Exam.

I am posting my solution for the CLD Traffic
Light Sample Exam. Comments and input is appreciated. The main VI is
Traffic Lite.vi.
Thanks in advance.
Attachments:
TrafficLite_5.22.10.zip ‏47 KB

Nice work, VI Joe. I heve just a few comments. The first two will get you more points from the judges, the third is personal style preference.
Add descriptions and tip strips to your controls (and indicators).
You go to either Idle or Display from almost every state; poll the controls before your main Case Structure executes and update the indicators afterwards instead. You wouldn't need to use a State Queue any more if you did this.This would also get your Stop button to work as required. As VENKATESH.J mentioned, it needs to respond immediately.
This is a cleaner way to queue up multiple states:
Jim
You're entirely bonkers. But I'll tell you a secret. All the best people are. ~ Alice

Similar Messages

CLD Traffic light

Hi all,
I have a timing question on the sample CLD traffic light exam (see attachment). I am seeing a possible discrepency between the spec and the solution.
On the spec, it says that the duration for each type of light is as follow:
Red: 4sec
Yellow: 2sec
Green: 4sec
However, if you look at the sample solution provided, you will see that the red light will light for 6 second. Doesn't that exceed the spec? Anybody has a better (more accurate) solution than provided?
Thanks!
Yik
Kudos and Accepted as Solution are welcome!
Attachments:
2419.zip ‏426 KB

Hello Yik,
If you look at the specification, the sequence is listed as Green, Yellow, Red, Red. This second Red is necessary to prevent all lanes of traffic from proceeding at once.
If you only keep the Red light on for 4 seconds, the East and West bound traffic will recieve a Green light while the North and South bound lights have just changed from Green to Yellow, resulting a traffic light which does not operate correctly.
The "8" seconds of Red light on will also create a time period where all lights are Red, allowing any slow cars to exit the intersection.

Car Wash CLD Sample Exam Solution

Attached is my solution to the CLD Car Wash Sample Exam. Comments will be appreciated. The main VI is Main_6.15.10.
Thanks in advance.
Attachments:
CarWash_6.15.10.7z ‏60 KB

Here are my thoughts....
Your solution is functional, so there are points for that right away. Where I think there could be some more work is the architecture. The exam requirements state that the design must be "easily scalable". To me that means new states or cycles can be added without much messing about on the block diagram. If you notice, there are only certain... lets call them Properties of each cycle type. You could have an array of cycle properties such as cycle time, cycle position switches, cycle name, and flags for standard or deluxe. Then you could reduce your cycle handling to a single state that just indexes through the cycle array and executed the next appropriately flagged cycle.
I noticed a Select node in each of your cycle states with constant True and False wired to it. That is a total of three elements plus two wires that should have just been a Not right off of the Boolean palette.
You stop the program with a Stop button, yet you allow the user to close the window. You should consider a Panel Close? event in your event structure to handle a use trying to close the window so that you can execute a graceful stop.
There is no VI Description filled out for your main VI. You should also have an icon for the main VI. The suggested front panel shown in the exam has an icon.
When your VI is running, you have the scrollbars, toolbar, and menu bar shown. None of those serves any function for the application, so they should not be shown at runtime.
The Stop button that is used to stop your application is reset with a Property Node. Not that there is a performance issue here, but it is generally not good practice to do that unless you are forced to. Consider just using a Mechanical Action of Latch When Released instead of Switch When Released. That way you do not need to force the reset to the False state. Of course, I would rather see something like a Stop state writing to the While Loop conditional terminal. Also, you could have used a Local Variable to write the initial state of the Sim Switches instead of the Property Node.
The graders like to see code comments describing your algorithms. I would say that you need more of those.
A 10 msec timeout on the event structure is a bit hyper. Nothing in the system runs that fast, and the only thing you are waiting for is the user. You could actually have a -1 wired there if you add an event case for the Stop button and Panel Close. It will greatly reduce the CPU cycles (again not that there is a huge performance issue here).
Come to think of it, the 20 msec wait for next multiple timer is a bit hyper too. Your timing requirements are on the order of seconds. You do not need to loop that fast.
In general I prefer to have the Event Structure outside the State Machine. Either that, or I use the Event Structure as the State Machine (in place of the Case Structure). That way, if you need to respond to the user interface, you can do so without waiting to cycle back to the Idle state.
This one was not listed in the requirements, but it would be very helpful to see the clock. A cycle countdown timer or elapsed time indicator is so helpful to the user and the grader. It confirms that things are working properly and the the application has not sieved up. Users like to see something "alive" on the screen.
To end on a positive... good job remembering to Disable the Purchase Selection buttons once the user clicks one. I got ding'd for forgetting about that back when I took the CLD in 2003.

My Solution for CLD Sample Exam (Traffic Light)

Hi there folks,
I was just preparing for my CLD exam and was going through the sample exam provided on ni.com.
I wanted to get any feedback for my solution. I looked at the solution and it seemed way to complex
to achieve a simple task! Then again, I am still learning.
ThanX in advance.
Attachments:
Traffic Light1.zip ‏81 KB
Traffic Light2.zip ‏81 KB

About queues vs shift registers. Queues allow you the ability to insert elements into either end of the queue. You can also write code to insert several elements at one time. With shift registers, only one new element can be carried over to the next loop at one time.
Lets say you have a state machine that always executes in the same order, no matter what the outcome, like State1 then State 2 then State 3. A shift register works fine for this simple example. However with queues, you can use a loop to insert the 3 states before the main state machine loop, then dequeue in the state machine. This is really a matter of preference.
Next example. Lets say you had a situation where you want to run 3 states, but if the second one fails, you want to run 2 other states before going to the third one. You could use a shift register, and you would have to look at each state to see which is next. A queue would allow you to insert the 2 extra states in between states 2 and 3. Of if you want to exit on some failure during a state. You can use the queue to insert the exit state at the opposite end so that it is the next to be dequeued.
Another situation is if you allow the user to call certain actions that require running several states. When the user presses button A, you enqueue states 1,2,3. If the user presses button C you enqueue states 7,8,9. So now you have a state machine in which states are defined by some user action. This would be more difficult to do with a shift register.
There are many other situations where a queued state machine is better than just a simple shift register. For the simplest of situations, I might use a shift register only. But I like to make it a habit to always use queues because of their versatility, and for the fact that I can go back and upgrade a simple state machine to a more complex one easily if it is done with queues. Be sure to use shift registers on the queue error in and error out so that errors can be propogated from one state to the next. On each state, check the error status. If one occures, enqueue a state at the other end to jump to your error handling state (or exit).
- tbob
Inventor of the WORM Global

Does NI post solutions to CLD sample exams?

Does NI post solutions to CLD sample exams?
Thanks in advance.

There's solutions in the CLD sample exams zip file found here and there's a sample solution for the CLA exam.
There are only two ways to tell somebody thanks: Kudos and Marked Solutions
Unofficial Forum Rules and Guidelines

CLD Sample Exams: How to deal with references ?

Hi@all:
I reviewed the sample exams solution for the CLD provided by NI and noticed, that they trifle with references. As shown in the Security System and the ATM Machine, references were opened, but not closed at the end.
What do you think, will this cost Style points?
The exams can be grabbed on the NI site searching for CLD.
Solved!
Go to Solution.

I would ding them for a lot of points but it is not my test but NI's so play to their rules get the cert and then do it right.
When you get to that part of the exam just add a note saying those refs do not need t be closed because they are static and maybe you can get some bonus points for knowing the differnence.
How to know the difference?
See here.
Ben
Ben Rayner
I am currently active on.. MainStream Preppers
Rayner's Ridge is under construction

Security CLD sample exam

This is my answer to the CLD sample exam "security system" Does anyone have any suggestions or comments?
Attachments:
Alarm4.vi ‏35 KB
File.vi ‏16 KB

Islandman wrote:
... but I'm not sure what to do about the file reference. I use this to close the file at the end (that's why I circulate it). Since I log an event every time there is a change, I access the file many times, but I want to close the file at the end, only once.
No, you're not understanding. You are using "write to spreadsheet file", which is a high-level function. You can open it like a plain subVI and see what's inside. You will notice that it opens the file, writes (or appends) the data, then closes the file, all inside the function. Thus there is no need to open or close the file externally. At all! Ever! You have a useless and redundant mix of high-level and low-level file functions.
Sure, if performance is an issues, that constant file opening and closing could be a bottleneck. So an alternative would be to use all low-level file function. You would open/create the file before the loop, keep the file open during the loop and write using plain low-level functions, then close the file after (outside) the main loop once the program finishes.
ALSO: Your subVI needs a makeover anyway. Use intuitive control labels (not "numeric"!). Arrange the FP nicely. Add some documentation. You should also do something about the icon. It is surrounded by blank space, making the wires seem to hang off in thin air. It is also a bit disconcerting that you are not doing much error handling. The main program would never know if the file program encounters an error. Then you are abusing the file open error to determine if the file exists or not. There is a function for that! You don't need to get the date/time in the error case, so this function belong inside the other case.
LabVIEW Champion . Do more with less code and in less time .

Traffic Light CLD Critique please

Have at it. Go ahead be harsh. There may be some extra junk in the project I didn't clean up like some subVIs I ended up not using or elements in my cluster I didn't use, so feel free to ignore those
CLA, LabVIEW Versions 2010-2013
Attachments:
traffic light.zip ‏111 KB

Yes you definitly missed some documentation points (maincluster.vi), the traffic lights on the FP (look at the context help), your typedefs.
Second your timer.vi and lightcluster indicators have no customized icons.
Third, you let the user close the window, but you don't handle the close event, that's bad.
Ton
Message Edited by TCPlomp on 22-05-2010 02:19 PM
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CLD-R sample exam #2, question #11

Answer A is the stated correct answer according to the sample exam answers section.
Correct me if I am wrong but Merge Errors ONLY reports the FIRST error. If multiple errors occur with those four error lines,
ONLY one will be reported by error out, not ALL errors.
Where I am going wrong with this one...is it because only one input to Merge Errors is used?
(the error out line looks like a non-array input (thus how could all errors be reported without and array of error outs???)
Thanks,
Ryan

1984 wrote:
In the past 12 years I have developped and deployed unreliable codes like this in about 10 different countries.
If this is unreliable then NI should start reviewing its own VIs as there are numerous VIs shipped with LabVIEW has solutions like this.
Hey, lets assume this is a control system for (Why not?) a 250kWatt weather radar
Stop the pulse modulator
shut down the RF Source
Remove power to the Klystron's magnet
Trust me, you want them to happen in that order. with code shown as drawn above, there is a possibility to remove the magnetic field first. That would dump a 60kV 12A pulse through the klystron with no field to focus the beam. At which point a 70 pound klystron is going to impolitely install a new hole in the building's roof.
Frankly, I despise that question as none of the distractors takes into account a failure in a predicated step of shutdown.

CLD-R sample exam question #37

Hi all,
I've been looking over the most recent CLDR sample exams and I'd like clarification on the answer to one of the questions. I figure that since the question is publically available, it's ok for me to refer to it here.
The question is from sample exam #1. The specific question is #37. Code is shown in which "This VI's path" is stripped twice and a path to a subVI is built using "build path" and a subVI name (i.e. therefore using a relative path to refer to the subVI). The resulting path is then used to open a reference to a subVI. The subVI is run dynamically using a Call by Reference Node. The reference is then closed.
The question states: "Which of the following steps must be taken if you decide to build the block diagram shown into an executable?"
The possible answers are:
a. The file path needs to be stripped one more time because the build process will add another layer to the file structure, causing problems
b. The VI that is being called dynamically needs to be manually added to the build specification
c. The application window will not close when the executable has been stopped.
d. One or more functions will not work outside of the development environment.
The correct answer is given as "b".
I think "a" is an equally valid answer. The build process DOES add another layer to the file structure, thus goofing up all the relative paths, and that needs to be accounted for when building executables.
Why on earth would you offer two correct answers to a question and only accept one as the "right" answer? That makes no sense to me.

a. The file path needs to be stripped one more time because the build process will add another layer to the file structure, causing problems
\ The source file settings Set destination can be configured " the same heirarchy so this is not absolutly needed (And Diane, the paths are stripped from the other end so a folder in front is no problem)
C & D are not actions this is the worst sort of distractor. Random statements that don't fall into the rule of the question.
E.G.
What questions will you find posted to the NI Forums
A.I have a problem with communicating to a device on a serial COM port.
B.Why on earth would you offer two correct answers to a question and only accept one as the "right" answer?
C.You should use an Express vi for that!
D.Here is a link to a KB article.
B is the only correct answer but many examinees will choose the bad distrators.
Jeff

How we can drill-down, sorting, traffic lights, in ALV report

hi gurus ,
how we can drill-down, sorting, traffic lights, in ALV report .
please any one suggest that...
regards,
praveen

Check the sample code for drill-down, sorting, traffic lights, in ALV report.
REPORT YMS_COLOURALV NO STANDARD PAGE HEADING.
TYPE-POOLS: SLIS, ICON.
DATA: FIELDCAT TYPE SLIS_T_FIELDCAT_ALV.
DATA: BEGIN OF IMARA OCCURS 0,
LIGHT(4) TYPE C,
MATNR TYPE MARA-MATNR,
MTART TYPE MARA-MTART,
MAKTX TYPE MAKT-MAKTX,
COLOR_LINE(4) TYPE C,
TCOLOR TYPE SLIS_T_SPECIALCOL_ALV, "cell
END OF IMARA.
DATA: XCOLOR TYPE SLIS_SPECIALCOL_ALV.
START-OF-SELECTION.
PERFORM GET_DATA.
PERFORM WRITE_REPORT.
FORM GET_DATA.
WRITE ICON_GREEN_LIGHT AS ICON TO IMARA-LIGHT.
IMARA-MATNR = 'ABC'.
IMARA-MTART = 'ZCFG'.
IMARA-MAKTX = 'This is description for ABC'.
APPEND IMARA.
WRITE ICON_YELLOW_LIGHT AS ICON TO IMARA-LIGHT.
IMARA-MATNR = 'DEF'.
IMARA-MTART = 'ZCFG'.
IMARA-MAKTX = 'This is description for DEF'.
APPEND IMARA.
WRITE ICON_RED_LIGHT AS ICON TO IMARA-LIGHT.
IMARA-MATNR = 'GHI'.
IMARA-MTART = 'ZCFG'.
IMARA-MAKTX = 'This is description for GHI'.
APPEND IMARA.
LOOP AT IMARA.
IF SY-TABIX = 1.
IMARA-COLOR_LINE = 'C410'. " color line
ENDIF.
IF SY-TABIX = 2. " color CELL
CLEAR XCOLOR.
XCOLOR-FIELDNAME = 'MTART'.
XCOLOR-COLOR-COL = '3'.
XCOLOR-COLOR-INT = '1'. " Intensified on/off
XCOLOR-COLOR-INV = '0'.
APPEND XCOLOR TO IMARA-TCOLOR.
ENDIF.
MODIFY IMARA.
ENDLOOP.
ENDFORM. "get_data
FORM WRITE_REPORT.
DATA: LAYOUT TYPE SLIS_LAYOUT_ALV.
LAYOUT-COLTAB_FIELDNAME = 'TCOLOR'.
LAYOUT-INFO_FIELDNAME = 'COLOR_LINE'.
PERFORM BUILD_FIELD_CATALOG.
CALL FUNCTION 'REUSE_ALV_GRID_DISPLAY'
EXPORTING
IS_LAYOUT = LAYOUT
IT_FIELDCAT = FIELDCAT
TABLES
T_OUTTAB = IMARA.
ENDFORM. "write_report
FORM BUILD_FIELD_CATALOG.
DATA: FC_TMP TYPE SLIS_T_FIELDCAT_ALV WITH HEADER LINE.
CLEAR: FIELDCAT. REFRESH: FIELDCAT.
CLEAR: FC_TMP.
FC_TMP-REPTEXT_DDIC = 'Status'.
FC_TMP-FIELDNAME = 'LIGHT'.
FC_TMP-TABNAME = 'IMARA'.
FC_TMP-OUTPUTLEN = '4'.
FC_TMP-ICON = 'X'.
APPEND FC_TMP TO FIELDCAT.
CLEAR: FC_TMP.
FC_TMP-REPTEXT_DDIC = 'Material Number'.
FC_TMP-FIELDNAME = 'MATNR'.
FC_TMP-TABNAME = 'IMARA'.
FC_TMP-OUTPUTLEN = '18'.
APPEND FC_TMP TO FIELDCAT.
CLEAR: FC_TMP.
FC_TMP-REPTEXT_DDIC = 'Material Type'.
FC_TMP-FIELDNAME = 'MTART'.
FC_TMP-TABNAME = 'IMARA'.
FC_TMP-OUTPUTLEN = '10'.
APPEND FC_TMP TO FIELDCAT.
CLEAR: FC_TMP.
FC_TMP-REPTEXT_DDIC = 'Material'.
FC_TMP-FIELDNAME = 'MAKTX'.
FC_TMP-TABNAME = 'IMARA'.
FC_TMP-OUTPUTLEN = '40'.
APPEND FC_TMP TO FIELDCAT.
ENDFORM. "build_field_catalog

Traffic lights on push button

Hi all,
          In my requirement i have a field as push button , now i require to put traffic lights on this push button.I am displaying alv grid through
class cl_gui_alv_grid
please help me with a sample code.
regards,
kushagra

Hi,
Pass below codes as texts for the push buttons:
@0A@ - Red
@09@ - Orange
@08@ - Green
Below code can help you understanding handling normally without pushbuttons:
DATA: ok_code TYPE syucomm.
TYPES: BEGIN OF ty_data,
         num TYPE i,
         icon TYPE icon_d,
       END OF ty_data.
DATA: wa_data TYPE ty_data,
      i_data TYPE TABLE OF ty_data.
DATA: i_fieldcat TYPE lvc_t_fcat,
      wa_fieldcat TYPE lvc_s_fcat.
DATA: g_cust_cont   TYPE REF TO cl_gui_custom_container,
      g_container   TYPE scrfname VALUE 'GRID1',
      g_grid        TYPE REF TO cl_gui_alv_grid.
START-OF-SELECTION.
DO 10 TIMES.
    wa_data-num = sy-index.
    IF sy-tabix < 4.
      wa_data-icon = '@0A@'.
    ELSEIF sy-tabix < 7.
      wa_data-icon = '@09@'.
    ELSE.
      wa_data-icon = '@08@'.
    ENDIF.
    APPEND wa_data TO i_data.
ENDDO.
END-OF-SELECTION.
CALL SCREEN 100.
*&      Module STATUS_0100 OUTPUT
*       text
MODULE status_0100 OUTPUT.
SET PF-STATUS 'MAIN100'.
SET TITLEBAR 'MAINTITLE'.
IF g_grid IS INITIAL.
    PERFORM display_list.
ENDIF.
CALL METHOD cl_gui_cfw=>flush.
ENDMODULE.                 " STATUS_0100 OUTPUT
*&      Module USER_COMMAND_0100 INPUT
*       text
MODULE user_command_0100 INPUT.
DATA: l_event TYPE REF TO cl_gui_event.
CASE ok_code.
    WHEN 'EXIT' OR 'BACK' OR 'CANC'.
      PERFORM exit_program.
ENDCASE.
CLEAR: ok_code.
CALL METHOD cl_gui_cfw=>flush.
ENDMODULE.                 " USER_COMMAND_0100 INPUT
*&      Form DISPLAY_LIST
*       text
* --> p1        text
* <-- p2        text
FORM display_list .
IF g_cust_cont IS INITIAL.
* Create Custom Container
    CREATE OBJECT g_cust_cont
           EXPORTING container_name = g_container.
* Create Ojbect for Grid Display
    CREATE OBJECT g_grid
           EXPORTING i_parent = g_cust_cont.
* Build Field Catalog
    PERFORM build_catalog.
* Display Output in Grid Form
    CALL METHOD g_grid->set_table_for_first_display
      CHANGING
        it_fieldcatalog = i_fieldcat
        it_outtab       = i_data[].
ELSE.
* Refresh Display
    CALL METHOD g_grid->refresh_table_display.
ENDIF.
ENDFORM.                    " DISPLAY_LIST
*&      Form BUILD_CATALOG
*       text
* --> p1        text
* <-- p2        text
FORM build_catalog .
PERFORM build_fld_catalog USING:
     1 'NUM'   'I_DATA'   space     'Number'   10,
     2 'ICON'   'I_DATA'   'X'     'Icon'      10.
ENDFORM.                    " BUILD_CATALOG
*&      Form BUILD_FLD_CATALOG
*       text
*      -->P_1      text
*      -->P_0182   text
*      -->P_0183   text
*      -->P_C_X text
*      -->P_0185   text
*      -->P_12     text
FORM build_fld_catalog USING    p_col
                                 p_fld
                                 p_tab
                                 p_icon
                                 p_text
                                 p_len.
CLEAR: wa_fieldcat.
wa_fieldcat-col_pos = p_col.
wa_fieldcat-fieldname = p_fld.
wa_fieldcat-tabname = p_tab.
wa_fieldcat-icon = p_icon.
wa_fieldcat-scrtext_l = p_text.
wa_fieldcat-outputlen = p_len.
APPEND wa_fieldcat TO i_fieldcat.
ENDFORM.                    " BUILD_FLD_CATALOG
*&      Form EXIT_PROGRAM
*       text
* --> p1        text
* <-- p2        text
FORM exit_program .
CALL METHOD g_grid->free.
LEAVE TO SCREEN 0.
ENDFORM.                    " EXIT_PROGRAM

Traffic light project for Multisim

Hello, I am trying to design a working traffic light for both N/S and E/W sides of traffic (i.e., six lights). I will build it later, for real, using the Elvis II breadboard. I have been looking around at other schematics on the web, I have drawn many of these on Multisim and none of them work. It also needs to be a U.S. traffic light, as the ones in the U.K. are different. I have tried many different combinations, with the 555 timer and the 4017 decade counter, but I don't know how these components actually work. I need help. The simplest circuit would be better, I know, like some kind of RS flip-flop or JK flip-flop (?). I don't know how these components really hook up together or how I am supposed to get the timing right, where the red and green on opposite times will stay on for a required time, like 15 seconds for demo purposes, and then go to yellow on the side the green was on for 3 seconds ( after the green goes out and the red stays on with the yellow) and then it flip-flops to green and red on the other side for 15 seconds. I don't know how to go about this. A good example would be very helpful. Thank you, brett1405
Solved!
Go to Solution.

Hi -
I am trying to build the same type of circuit in Multisim and am unable to get any simulation to run. The error keeps saying my "timestep is too short", which I have no idea what that means... Do you have any suggestions? I wasn't able to find the sample circuit in my Multisim version for the traffic light either.
I have what looks like a mess of a circuit and I don't even know where to begin to trouble shoot it...
Attachments:
Final Circuit2.ms10 ‏266 KB

CLDR Sample Exam Question

I was going through the CLD recertification sample exam (here), and one of the questions has me stumped. For question 39, I understand what the code is doing and the right answer, but I can't seem to find how to place this code on a block diagram. I'm referring to the function with the -3->, ?, and i on the icon. Can anyone tell me where on the function pallete to find this (LV2009 or 8.6)?
Thanks ahead!
==============================================
David Kaufman
LabVIEW Certified Developer
==============================================
Solved!
Go to Solution.

Well it's the same like this:
Allthough it is quite unclear to me why I had to reverse the first part of the array.
But a very advanced functionality, I like the way to initialize with an array.
Ton
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Sample Exam Solutions for Review

Good afternoon,
I am taking the CLD exam tomorrow morning and wanted to submit my sample exam for review. I was able to finish it in just about 4 hours.
Here is my solution, please provide feedback.
Thanks.
Steven

Manushak wrote:
Hello all
I have solution for "sprinkler controller".
I would be glad if someone could take a look and give me a feedback.
I want to write more comments, but my english is poor and there are many mistakes in my texts. Do you know, can i have any translater with me in time of exam. Or can i use online translators. It will help my very much.
Overall a C- job Some things you did well. Please excuse me for only pointing out the flaws as my time is limited.
You have some bad habits that you need to break;
Icons. They need to convey information to the next maintainer of your code. Is that a flame under a teakettle? Like GUIs the color usage in icons should avoid garashness and help aid clairity. Your file read vi icon uses a glyph I would associate with a error dialog.
Use a project
Tip Strips on every object the user can see on the GUI!
Timing- you have failed to meet spec on preserving the elapsed time if rain occurs durring the servicing of a zone. You need an elapsed timer with a pause feature.
Wire bends. Enough said?

CLD Traffic Light Sample Exam.

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