Tag Archives: Programmable Controller

Do-More, Do-More Designer, PLC, PLC Basics, PLC Learning

How to make a Start Stop Jog circuit in a PLC

January 3, 2015 garrys 9 Comments

Looking at a stop-start jog circuit in the PLC will help us in understanding the differences in hard-wiring the circuit and programming.

Basic Start Stop Circuit

Let’s start with the basic start stop circuit.
Here is what it looks like hard-wired. (Physical switches wired to outputs devices, such as motor contactors and relays.)

When the start pushbutton (NO) is pressed the power is passed through the stop pushbutton (NC) to the control relay (CR). The CR contact closes and ‘seals in’ the start pushbutton. The start pushbutton can now be released because the CR contacts allow the power to pass through to the CR.

NO NC Inputs

NO – Normally Open – This refers to the state of the input device if nothing acts upon it.
NC – Normally Closed – This refers to the state of the input device if nothing acts upon it.

Let’s take a look at the PLC program for the above wiring diagram.

The first thing that you will notice is that the input for Stop is NO contact and not NC. This is because the actual signal wired in the input is NC and we do not want to inverse this signal. You can see that the stop input is currently on in the program.
If we hit the start pushbutton then the circuit is complete and the output CR turns on.

Letting go of the start pushbutton, the output remains on because of the CR input seals in the start pushbutton.

Pressing the stop pushbutton will break the circuit and turn off CR.

Letting go of the stop pushbutton will return us back to the original state shown above.

Jog Hard Wire Diagram

Adding a jog input to the hard-wiring diagram will look something like this:

You can see that the diagram will work the exact same as the circuit above with the start and stop pushbuttons. The jog when pushed will break the sealing contact, and then make a bypass of the start pushbutton. This will keep the M coil on as long as the jog button is pressed. Letting go of the jog will stop the bypass of the start pushbutton which will stop the M coil. When the jog returns to the original state M input will already be off so it will not keep the M coil on.
The action on the jog is referred to as a Break before Make device. The jog pushbutton will break the circuit before making another connection.

PLC Jog Circuit

Sometimes in programming a PLC it can be beneficial to think of the inputs as Make before Break. Inputs are made before the previous ones are broken. The programmable controller will scan the program from left to right, top to bottom. The outputs from the rung above are available to the rungs below. Here is a previous article on PLC scanning.
Lets take a look at PLC program with a jog that will not work.

Even though this looks like it would work… Remember that the contacts in the PLC are making before breaking. You can jog the unit and it will turn on but as soon as you release your finger off of the pushbutton the not jog input will seal the CR in. The output will not be able to turn off.

We must consider the delay from on to off when looking at the PLC program for this circuit.
Here is a circuit that will work:

Notice that we create a delay from on to off by turning on an intermediate bit in the program.

Start Stop Jog using Set and Reset

Another way to do start-stop circuits in the PLC is to use the instructions Set (SET) and Reset (RST).
The set will have all of the conditions to turn on a bit in memory and the reset will have all of the conditions to turn off a bit in memory. These instructions are used to make the program easier to view and troubleshoot.
Here is the same logic above using the set and reset instructions.

Notice that X10 Jog2 is in parallel with the Start. We use a trailing edge one shot in parallel with the Stop. This sets our delay so the output will turn off.

Watch on YouTube: Learn PLC Programming – Free 4

If you have any questions or need further information please contact me.
Thank you,
Garry

If you’re like most of my readers, you’re committed to learning about technology. Numbering systems used in PLC’s are not difficult to learn and understand. We will walk through the numbering systems used in PLCs. This includes Bits, Decimal, Hexadecimal, ASCII and Floating Point.

To get this free article, subscribe to my free email newsletter.

Use the information to inform other people how numbering systems work. Sign up now.

The ‘Robust Data Logging for Free’ eBook is also available as a free download. The link is included when you subscribe to ACC Automation.

BRX Do-More, Communication, Do-More, Do-More Designer, HMI, Modbus TCP, PLC, PLC Basics, PLC Learning

Now You Can Have Robust Data Logging for Free – Part 12

December 19, 2014 garrys 5 Comments

Now You Can Have Robust Data Logging for Free – Part 12

HTML and Scripting Languages

We have the following accomplished:

PLC program
Visual Basic Program
Data collected in a Database
IIS web service established
ASP Script Written

Let’s take a closer look at the ASP Script ( AccRL.asp) that was written in part 11:

The <html> is at the start of the file and the </head> is at the end of the file. These tags all have to have a start and end. The ‘/’ indicates the end of the tag.

The <head> is used to place the information for the web page. The refresh will load the page after 300 seconds (5 minutes). This way the information will always be the latest. The title is used to label the page. This is the information at the top of the browser. The SHORTCUT ICON is used for the icon at the top of the browser near the page address.

<html>

<head>
<meta HTTP-EQUIV=”Refresh” CONTENT=”300″>
<title>ACC Automation – Robust Logger</title>
<LINK REL=”SHORTCUT ICON” HREF=”http://192.168.1.3/ACC_Do.ico”/></head>

The <% and %> symbols indicate the start and finish of VBScript in the page. We dimension our variables for StartTime and EndTime. These will be used to determine how long our script took to execute.
<%
Dim StartTime, EndTime
StartTime = Timer

We dimension the variables that are used for the connection to the database file.
Dim OBJdbConnection
Dim rs1
Dim objCmd

We set up the connection to the database and determine what information we need to retrieve.
Set OBJdbConnection = Server.CreateObject(“ADODB.Connection”)
OBJdbConnection.Open “Provider=Microsoft.ACE.OLEDB.12.0;DATA SOURCE=C:\AccRL\data\AccRL.accdb;Persist Security Info=False;”
set rs1 = Server.CreateObject(“ADODB.recordset”)
with rs1
.CursorType = adOpenForwardOnly
.LockType = adLockReadOnly
.CursorLocation = adUseServer
.ActiveConnection = OBJdbConnection
.Source = “SELECT * FROM Minute_Log;”
end with

Using getrows will allow us to execute the Select command and retrieve all of the information in one pass from the database. This is the quickest method to get the information out quickly.
rs1.Open
arraytime = rs1.getrows()
rs1.close

We now write the information from the database to the page.
Response.Write arraytime(0,0) & “ ”
Response.Write arraytime(1,0) & “ ”
Response.Write Year(arraytime(1,0))& “/” & Right(“0” & Month(arraytime(1,0)), 2) & “/” & Right(“0” & Day(arraytime(1,0)), 2) & “ ”
Response.Write arraytime(2,0)& “ ”
Response.Write arraytime(3,0)& “ ”
Response.Write arraytime(4,0)& “ ”

The EndTime is now set and the total time it took for the process is displayed.
EndTime = Timer
Response.write “Processing took “&(EndTime-StartTime)&” seconds ”
%>
</body>
</html>

ASP.Net Tutorial

Now that you have information into the database and IIS running, you can display the data in various ways.

Charts:

Graphs:

Gauges:

This ends our robust logger design. For the complete PLC program, VB source code and web page file please send me an email and ask for the ACC Robust Logger Program. I will be happy to email you the information.

If you have any questions or need further information, please contact me.
Regards,
Garry

If you’re like most of my readers, you’re committed to learning about technology. Numbering systems used in PLC’s are not difficult to learn and understand. We will walk through the numbering systems used in PLCs. This includes Bits, Decimal, Hexadecimal, ASCII and Floating Point.

To get this free article, subscribe to my free email newsletter.

Use the information to inform other people how numbering systems work. Sign up now.

The ‘Robust Data Logging for Free’ eBook is also available as a free download. The link is included when you subscribe to ACC Automation.

BRX Do-More, Communication, Do-More, Do-More Designer, HMI, Modbus TCP, PLC, PLC Basics, PLC Learning

Now You Can Have Robust Data Logging for Free – Part 11

December 14, 2014 garrys 9 Comments

Now You Can Have Robust Data Logging for Free – Part 11

HTML and Scripting Languages

We have the following accomplished:

PLC program
Visual Basic Program
Data collected in a Database
IIS web service established

The machine that has the IIS web service must have the Microsoft Access Database Engine 2010 installed. This can be obtained by the following link:

You can select the 32 bit or 64-bit version that matches your computer.

Microsoft Access Database Engine 2010 Redistributable
Note: If you have office installed on your machine already then you probably will already have this file.

ActiveX Data Objects (ADO) is used to access databases from your web pages. ADOVBS.inc is a file that has all of the ADO constants defined. Be sure to add this file in your root web application directory. How to add this code to a web page is shown in the sample code below.
You can download ADOVBS.inc from this site in text format. (Just rename to ADOVBS.inc from ADOVBS.txt)
ADO Introduction:
http://www.w3schools.com/asp/ado_intro.asp

Lets set up ASP on IIS to display any error messages to our browser.
Call up Control Panel and then go to Administrative Tools. Call up Internet Information Services (IIS) Manager.

From IIS Manager, double click on ASP under IIS. Expand Debugging Properties and change the Send Errors To Browser to True.

Let’s also ensure that your browser is set to display the error messages in internet explorer (IE). Call up Internet options from the main settings.

Click the setting for ‘Show friendly HTTP error messages’. This will ensure that the error messages show up in your browser.

The last part of our project is to display the database information to the network. We do this by using a webpage. The HTML and VBScript can be writing in any editor. (Like Notepad)

There are also a great number of online editors that you can visually see what your page will look like while developing your code.

http://htmledit.squarefree.com/

http://www.onlinehtmleditor.net/

http://www.w3schools.com/html/tryit.asp?filename=tryhtml_basic

To learn more about VBScript following the link below:

http://www.w3schools.com/Asp/asp_ref_vbscript_functions.asp

Lets take a look at the AccRL.asp file:

<html>
<head>
<meta HTTP-EQUIV=”Refresh” CONTENT=”300″>
<title>ACC Automation – Robust Logger</title>
<LINK REL=”SHORTCUT ICON” HREF=”http://192.168.1.3/ACC_Do.ico”/></head>
<!– #include virtual=”/adovbs.inc” –>
<%
Dim StartTime, EndTime
StartTime = Timer

Dim OBJdbConnection
Dim rs1
Dim objCmd

Set OBJdbConnection = Server.CreateObject(“ADODB.Connection”)
OBJdbConnection.Open “Provider=Microsoft.ACE.OLEDB.12.0;DATA SOURCE=C:\AccRL\data\AccRL.accdb;Persist Security Info=False;”
set rs1 = Server.CreateObject(“ADODB.recordset”)
with rs1
.CursorType = adOpenForwardOnly
.LockType = adLockReadOnly
.CursorLocation = adUseServer
.ActiveConnection = OBJdbConnection
.Source = “SELECT * FROM Minute_Log;”
end with

rs1.Open
arraytime = rs1.getrows()
rs1.close

Response.Write arraytime(0,0) & “ ”
Response.Write arraytime(1,0) & “ ”
Response.Write Year(arraytime(1,0))& “/” & Right(“0” & Month(arraytime(1,0)), 2) & “/” & Right(“0” & Day(arraytime(1,0)), 2) & “ ”
Response.Write arraytime(2,0)& “ ”
Response.Write arraytime(3,0)& “ ”
Response.Write arraytime(4,0)& “ ”

EndTime = Timer
Response.write “Processing took “&(EndTime-StartTime)&” seconds ”
%>
</body>
</html>

Place this AccRL.asp file into the root directory of our web server. Call up the page though our browser (http:\\localhost\AccRL.asp) and the following output will be seen.

In part 12 we will break down the ASP code and modify. For the complete PLC program, VB source code and web page file please send me an email and ask for the ACC Robust Logger Program. I will be happy to email you the information.

ASP.Net Tutorial

If you have any questions or need further information, please contact me.
Regards,
Garry

To get this free article, subscribe to my free email newsletter.

Use the information to inform other people how numbering systems work. Sign up now.

The ‘Robust Data Logging for Free’ eBook is also available as a free download. The link is included when you subscribe to ACC Automation.

BRX Do-More, Communication, Do-More, Do-More Designer, HMI, Modbus TCP, PLC, PLC Basics, PLC Learning

Now You Can Have Robust Data Logging for Free – Part 10

December 14, 2014 garrys 11 Comments

Now You Can Have Robust Data Logging for Free – Part 10

Computer Web Server (IIS)

We have come a long way. The PLC program has been written. The visual basic program has been written. Information is now being collected from the Do-more PLC via Modbus TCP and stored in a database using visual basic.

The next step is to deliver the information on the network. We will do this by installing Internet Information Services. (IIS) This is a group of internet servers that include a Web or Hypertext Transfer Protocol server (HTTP) and a File Transfer Protocol server (FTP). IIS will allow us to connect the physical hardware to the data. This could be desktop computers, laptops, tablets, cell phones, watches, etc. The advantage of using HTTP is that we can share the information with all of these devices without having to be concerned over the operating system of each of them. As long as they can display a web page we are good to go.

Active Service Pages (ASP) will be installed at the same time. This is a program that will run scripts at the server before delivering the HTML code to the browser. It is similar to CGI and Perl but is simpler and faster.
ASP.Net Tutorial

We will install this on a Windows 8.1 machine.

Call up the Control Panel.

Swiping in from the right and searching for “control panel”.
Win + x will call a menu to select the control panel.

Select Programs and Features

Select Turn Windows features on or off

Select ASP after expanding Internet Information Services / World Wide Web Services / Application Development Features. This will select all of the other options.

Hit OK to install the services.

We now have IIS installed.

Under the following default directory, you will find the location to put your web pages.

C:\inetpub\wwwroot\

If you call up the iisstart.htm file in this directory it will call up a page from Microsoft to explain the IIS web service.

Installing IIS on windows 7 and XP is very similar to the above procedure. Windows 98 you had to install a personal web service (PWS) and then ASP separately.

Further information on ASP can be obtained from the following website:

http://www.w3schools.com/asp/

This site will walk you through ASP.

In part 11 we will look at HTML and scripting languages like JavaScript or VBScript.

If you have any questions or need further information, please contact me.
Regards,
Garry

To get this free article, subscribe to my free email newsletter.

Use the information to inform other people how numbering systems work. Sign up now.

The ‘Robust Data Logging for Free’ eBook is also available as a free download. The link is included when you subscribe to ACC Automation.

BRX Do-More, Communication, Do-More, Do-More Designer, HMI, Modbus TCP, PLC, PLC Basics, PLC Learning

Now You Can Have Robust Data Logging for Free – Part 9

December 6, 2014 garrys 7 Comments

Now You Can Have Robust Data Logging for Free – Part 9

Computer Program Visual Basic (VB6) Continue

The final code will be completed for the program. If you want a link to download the complete code then go to the contact page and put a Robust Logger Program in the description.

The actual code that will be seen will be in Italic. This way you can pick out the code from the commentary.

Private Sub Form_Load()
MbusStatus = 0
ProductionPointerNow = 10
MinutePointerNow = 660
End Sub

When our form loads, the MbusStatus will be set to 0. This will control all of the communications to the Do-More PLC. The ProductionPointerNow and the MinutePointerNow will be used to determine where we are in getting data.

Here are our declarations for the program.

Dim MbusQuery
Public MbusResponse As String
Dim MbusByteArray(255) As Byte
Public MbusStatus As Integer
Public ProductionPointer As Integer
Public ProductionPointerNow As Integer
Public MinutePointer As Integer
Public MinutePointerNow As Integer

Start Logging Button:

We will stop or ensure the timer between reads has been disabled.

We will then check the status of the Winsock. If it is not opened and ready to send then change the background colour to indicate to the operator what is going on.

Note: Winsock RemotePort = 502

Private Sub Command1_Click()
Timer1.Enabled = False ‘ Stop the interval between reads to the PLC
Dim StartTime
If Winsock1.State <> 7 Then
If (Winsock1.State <> sckClosed) Then
Winsock1.Close
End If
Winsock1.RemoteHost = Text1.Text ‘ Set IP Address
Winsock1.Connect
StartTime = Timer ‘ Use the timer to determine if a connection cannot be made
Do While ((Timer < StartTime + 2) And (Winsock1.State <> 7))
DoEvents
Loop
If (Winsock1.State = 7) Then
Text1.BackColor = &HFF00& ‘ Change background colour to green
Else
Text1.BackColor = &HFF ‘ Change background colour to red
Exit Sub
End If
End If

Check the status of the Winsock. If we are good to go then determine the MbusStatus (0 to 9) and either send a read or write string out to the PLC.

If (Winsock1.State = 7) Then
Select Case MbusStatus
Case 0, 2
‘Read all the Daily Production Values
MbusQuery = Chr(0) + Chr(0) + Chr(0) + Chr(0) + Chr(0) + Chr(6) + Chr(0) + Chr(3) + Chr((Val(ProductionPointerNow) \ 256)) + Chr(((Val(ProductionPointerNow) Mod 256) – 1)) + Chr(0) + Chr(20)
Case 3
‘Reset Daily Production Pointer to 30 (Write)
MbusQuery = Chr(0) + Chr(0) + Chr(0) + Chr(0) + Chr(0) + Chr(9) + Chr(1) + Chr(16) + Chr(0) + Chr(0) + Chr(0) + Chr(1) + Chr(2) + Chr(0) + Chr(30)
Winsock1.SendData MbusQuery
Case 4, 6
‘Read the Minute Log Pointer
MbusQuery = Chr(0) + Chr(0) + Chr(0) + Chr(0) + Chr(0) + Chr(6) + Chr(0) + Chr(3) + Chr(0) + Chr(1) + Chr(0) + Chr(1)
Case 5
‘Read all the Minute Log Values
MbusQuery = Chr(0) + Chr(0) + Chr(0) + Chr(0) + Chr(0) + Chr(6) + Chr(0) + Chr(3) + Chr((Val(MinutePointerNow) \ 256)) + Chr(((Val(MinutePointerNow) Mod 256) – 1)) + Chr(0) + Chr(20)
Case 7
‘Reset Minute Log Pointer to 670 (Write)
MbusQuery = Chr(0) + Chr(0) + Chr(0) + Chr(0) + Chr(0) + Chr(9) + Chr(1) + Chr(16) + Chr(0) + Chr(1) + Chr(0) + Chr(1) + Chr(2) + Chr(2) + Chr(158)
Winsock1.SendData MbusQuery
Case 8
‘Read the current Daily Production Values
MbusQuery = Chr(0) + Chr(0) + Chr(0) + Chr(0) + Chr(0) + Chr(6) + Chr(0) + Chr(3) + Chr(0) + Chr(9) + Chr(0) + Chr(20)
Case 9
‘Read the current Minute Log Values
MbusQuery = Chr(0) + Chr(0) + Chr(0) + Chr(0) + Chr(0) + Chr(6) + Chr(0) + Chr(3) + Chr(2) + Chr(147) + Chr(0) + Chr(10) End Select
Winsock1.SendData MbusQuery ‘Send out the Modbus Information
Timer2.Enabled = True ‘Set the timeout timer for communications
Else
MsgBox (“Device not connected via TCP/IP”)
Exit Sub
End If
End Sub

Retrieving the information from Winsock

We first get all of the bytes of data from winsock. Then we determine the MbusStatus and then handle the data appropriately.

Private Sub Winsock1_DataArrival(ByVal datalength As Long)
Timer2.Enabled = False ‘Stop communications timeout timer
‘Get all the inforamtion from the data arriving
Dim B As Byte
Dim j As Byte
returnInfo = “”
For i = 1 To datalength
Winsock1.GetData B
MbusByteArray(i) = B
returnInfo = returnInfo & B
Next
j = 0
On Error Resume Next
Select Case MbusStatus
Case 0
‘Read the Daily Production Pointer
ProductionPointer = Val(Str((MbusByteArray(10) * 256) + MbusByteArray(11)))
If ProductionPointer <> 30 Then
ProductionPointerNow = ProductionPointerNow + 20
MbusStatus = 1
Else
MbusStatus = 4
End If
Case 1
With Adodc1
.CommandType = adCmdTable
.RecordSource = “Production_Log”
.Refresh
.Recordset.AddNew
End With
‘Read all the Daily Production Values
Label18.Caption = Format$((Str((MbusByteArray(10) * 256) + MbusByteArray(11)) & “/” & Str((MbusByteArray(12) * 256) + MbusByteArray(13)) & “/” & Str((MbusByteArray(14) * 256) + MbusByteArray(15))), “yyyy/mm/dd”)
Label19.Caption = Val(Str((MbusByteArray(16) * 256) + MbusByteArray(17)) & Str((MbusByteArray(18) * 256) + MbusByteArray(19)))
Label20.Caption = Val(Str((MbusByteArray(20) * 256) + MbusByteArray(21)) & Str((MbusByteArray(22) * 256) + MbusByteArray(23)))
Label21.Caption = Val(Str((MbusByteArray(24) * 256) + MbusByteArray(25)) & Str((MbusByteArray(26) * 256) + MbusByteArray(27)))
Label22.Caption = Val(Str((MbusByteArray(28) * 256) + MbusByteArray(29)) & Str((MbusByteArray(30) * 256) + MbusByteArray(31)))
Label23.Caption = Val(Str((MbusByteArray(32) * 256) + MbusByteArray(33)) & Str((MbusByteArray(34) * 256) + MbusByteArray(35)))
Label24.Caption = Val(Str((MbusByteArray(36) * 256) + MbusByteArray(37))) / 10
Label25.Caption = Val(Str((MbusByteArray(38) * 256) + MbusByteArray(39))) / 10
Label26.Caption = Val(Str((MbusByteArray(40) * 256) + MbusByteArray(41))) / 10
Label27.Caption = Val(Str((MbusByteArray(42) * 256) + MbusByteArray(43))) / 10
Label28.Caption = Val(Str((MbusByteArray(44) * 256) + MbusByteArray(45))) / 10
With Adodc1
.Recordset.Update
.Recordset.MoveLast
.Refresh
End With ProductionPointerNow = ProductionPointerNow + 20
If ProductionPointer = ProductionPointerNow Then
MbusStatus = 2
End If
Case 2
‘Read the Daily Production Pointer
ProductionPointer = Val(Str((MbusByteArray(10) * 256) + MbusByteArray(11)))
If ProductionPointer = ProductionPointerNow Then
MbusStatus = 3
Else
ProductionPointerNow = ProductionPointerNow + 20
MbusStatus = 1
End If
Case 3
‘Reset Daily Production Pointer to 30 (Write)
If (MbusByteArray(8) = 16) And (MbusByteArray(12) = 1) Then
MbusStatus = 4
ProductionPointerNow = 10
Else
Text1.BackColor = &HFF
End If
With Adodc1
.CommandType = adCmdTable
.RecordSource = “Production_Log”
.Refresh
.Recordset.AddNew
End With
Case 4
‘Read the Minute Log Pointer
MinutePointer = Val(Str((MbusByteArray(10) * 256) + MbusByteArray(11)))
If MinutePointer <> 670 Then
MinutePointerNow = MinutePointerNow + 10
MbusStatus = 5
Else
MbusStatus = 8
End If
Case 5
With Adodc2
.CommandType = adCmdTable
.RecordSource = “Minute_Log”
.Refresh
.Recordset.AddNew
End With
‘Read all the Minute Values
Label29.Caption = Format$((Str((MbusByteArray(10) * 256) + MbusByteArray(11)) & “/” & Str((MbusByteArray(12) * 256) + MbusByteArray(13)) & “/” & Str((MbusByteArray(14) * 256) + MbusByteArray(15))), “yyyy/mm/dd”)
Label30.Caption = Format$((Str((MbusByteArray(16) * 256) + MbusByteArray(17)) & “:” & Str((MbusByteArray(18) * 256) + MbusByteArray(19)) & “:” & Str((MbusByteArray(20) * 256) + MbusByteArray(21))), “hh:nn:ss”)
Label31.Caption = Val(Str((MbusByteArray(22) * 256) + MbusByteArray(23)) & Str((MbusByteArray(24) * 256) + MbusByteArray(25)))
Label32.Caption = Val(Str((MbusByteArray(26) * 256) + MbusByteArray(27)))
With Adodc2
.Recordset.Update
.Recordset.MoveLast
.Refresh
End With MinutePointerNow = MinutePointerNow + 10
If MinutePointer <= MinutePointerNow Then
MbusStatus = 6
End If
Case 6
‘Read the Minute Log Pointer
MinutePointer = Val(Str((MbusByteArray(10) * 256) + MbusByteArray(11)))
If MinutePointer = MinutePointerNow Then
MbusStatus = 7
Else
MinutePointerNow = MinutePointerNow + 10
MbusStatus = 5
End If
Case 7
‘Reset Minute Log Pointer to 670 (Write)
If (MbusByteArray(8) = 16) And (MbusByteArray(12) = 1) Then
MbusStatus = 8
MinutePointerNow = 660
Else
Text1.BackColor = &HFF
End If
With Adodc2
.CommandType = adCmdTable
.RecordSource = “Minute_Log”
.Refresh
.Recordset.AddNew
.Refresh
End With
Case 8
‘Read the current Daily Production Values
Label18.Caption = Format$((Str((MbusByteArray(10) * 256) + MbusByteArray(11)) & “/” & Str((MbusByteArray(12) * 256) + MbusByteArray(13)) & “/” & Str((MbusByteArray(14) * 256) + MbusByteArray(15))), “yyyy/mm/dd”)
Label19.Caption = Val(Str((MbusByteArray(16) * 256) + MbusByteArray(17)) & Str((MbusByteArray(18) * 256) + MbusByteArray(19)))
Label20.Caption = Val(Str((MbusByteArray(20) * 256) + MbusByteArray(21)) & Str((MbusByteArray(22) * 256) + MbusByteArray(23)))
Label21.Caption = Val(Str((MbusByteArray(24) * 256) + MbusByteArray(25)) & Str((MbusByteArray(26) * 256) + MbusByteArray(27)))
Label22.Caption = Val(Str((MbusByteArray(28) * 256) + MbusByteArray(29)) & Str((MbusByteArray(30) * 256) + MbusByteArray(31)))
Label23.Caption = Val(Str((MbusByteArray(32) * 256) + MbusByteArray(33)) & Str((MbusByteArray(34) * 256) + MbusByteArray(35)))
Label24.Caption = Val(Str((MbusByteArray(36) * 256) + MbusByteArray(37))) / 10
Label25.Caption = Val(Str((MbusByteArray(38) * 256) + MbusByteArray(39))) / 10
Label26.Caption = Val(Str((MbusByteArray(40) * 256) + MbusByteArray(41))) / 10
Label27.Caption = Val(Str((MbusByteArray(42) * 256) + MbusByteArray(43))) / 10
Label28.Caption = Val(Str((MbusByteArray(44) * 256) + MbusByteArray(45))) / 10
With Adodc1
.Recordset.Update
.Recordset.MoveLast
End With MbusStatus = 9
Case 9
‘Read the current Minute Log Values
Label29.Caption = Format$((Str((MbusByteArray(10) * 256) + MbusByteArray(11)) & “/” & Str((MbusByteArray(12) * 256) + MbusByteArray(13)) & “/” & Str((MbusByteArray(14) * 256) + MbusByteArray(15))), “yyyy/mm/dd”)
Label30.Caption = Format$((Str((MbusByteArray(16) * 256) + MbusByteArray(17)) & “:” & Str((MbusByteArray(18) * 256) + MbusByteArray(19)) & “:” & Str((MbusByteArray(20) * 256) + MbusByteArray(21))), “hh:nn:ss”)
Label31.Caption = Val(Str((MbusByteArray(22) * 256) + MbusByteArray(23)) & Str((MbusByteArray(24) * 256) + MbusByteArray(25)))
Label32.Caption = Val(Str((MbusByteArray(26) * 256) + MbusByteArray(27)))
With Adodc2
.Recordset.Update
.Recordset.MoveLast
End With
MbusStatus = 0
End Select
Timer1.Enabled = True ‘Set the interval between the next communication
End Sub

The last thing that we do is save and compile the VB program. I will be happy to send the complete program to you. Please go to the contact page and put a Robust Logger Program in the description.

In part 10 we will display the information on a web server. We will use IIS and ASP to actively connect and display the information in the database.

If you have any questions or need further information, please contact me.
Regards,
Garry

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BRX Do-More, Communication, Do-More, Do-More Designer, HMI, Modbus TCP, PLC, PLC Basics, PLC Learning

Now You Can Have Robust Data Logging for Free – Part 8

November 30, 2014 garrys 6 Comments

Computer Program Visual Basic (VB6) Continue

The display part of the program is done and we have reviewed the Modbus TCP protocol. It is now time to start the VB6 code. Let’s discuss how the logic will work.

1. The user selects ‘Start Logging’
2. The timer for the interval between communications is stopped.
3. The IP address is used to open the winsock connection. If the connection is made then the background colour of the IP Address will turn green and we will continue to step 4. If the connection already exists then continue to step 4. If the connection cannot be made then the background colour is red, further execution is stopped. The program will continue at step 1.
4. The following sequence of commands are made: Determine what command to send.

Read the Daily Production Log and Minute Log Pointers (MHR1 and MHR2 )
If MHR2 (Minute Log Pointer ) > 670 then
- Request the Minute Log starting at MHR670 and keep incrementing by 10 until the last location is requested.
- Write the value of 670 into MHR2 (Reset the pointer)
If MHR1 (Daily Production Log Pointer > 30 then
- Request the Daily Production Log starting at MHR30 and keep incrementing by 20 until the last location is requested.
- Write the value of 30 into MHR1 (Reset the pointer)
Read the current Minute Log information starting at MHR660
Read the current Daily Production Log information starting at MHR10

Once the command is sent a timer is set to determine if communications have been lost.

5. If the timer for communications is lost, go to step 3. Repeat the last command.

6. Turn off the timer to determine if communications have been lost. Read the information from the Winsock tool. If the data needs to be stored, then update the database. Set the timer for the interval between communications.

The above is the general program flow for the program.

Here are our variables:

Dim MbusQuery
Public MbusResponse As String
Dim MbusByteArray(255) As Byte
Public MbusStatus As Integer
Public ProductionPointer As Integer
Public MinutePointer As Integer

Private Sub Command1_Click()
Timer1.Enabled = False ‘ Stop the interval between reads to the PLC

Timer1 is used to control the amount of time between intervals of communication to the PLC.

Dim StartTime
If Winsock1.State <> 7 Then
If (Winsock1.State <> sckClosed) Then
Winsock1.Close
End If
Winsock1.RemoteHost = Text1.Text ‘ Set IP Address
Winsock1.Connect

StartTime = Timer ‘ Use the timer to determine if a connection cannot be made

Do While ((Timer < StartTime + 2) And (Winsock1.State <> 7))
DoEvents
Loop
If (Winsock1.State = 7) Then
Text1.BackColor = &HFF00& ‘ Change background colour to green
Else
Text1.BackColor = &HFF ‘ Change background colour to red
Exit Sub
End If
End If

Here is the code to control Winsock1. The IP address entered in Text1 is used to set the RemoteHost. We then check for the state of the Winsock1. The following are the different states that Winsock1 can be:

Constant	Value	Description
sckClosed	0	Default. Closed
sckOpen	1	Open
sckListening	2	Listening
sckConnectionPending	3	Connection pending
sckResolvingHost	4	Resolving host
sckHostResolved	5	Host resolved
sckConnecting	6	Connecting
sckConnected	7	Connected
sckClosing	8	Peer is closing the connection
sckError	9	Error

Here is the information that we will need to read and write to the MHR registers in the Do-More PLC.

‘ Read the information

‘0000: Transaction Identifier

‘0000: Protocol Identifier

‘0006: Message Length (6 bytes to follow)

’00: The Unit Identifier

’03: The Function Code (read MHR Read Holding Registers)

‘0000: The Data Address of the first register

‘0002: The number of registers to write

‘ Write the information

‘0000: Transaction Identifier

‘0000: Protocol Identifier

‘0009: Message Length (6 bytes to follow)

’01: The Unit Identifier

’16: The Function Code (read Analog Output Holding Registers)

‘0000: The Data Address of the first register

‘0001: The number of registers to write

’02: The number of data bytes to follow

‘0030 The number to put into the register

All of the information will be bytes of data. The maximum value in a byte is 256. If we need to send a value of 600 then the two bytes of data will be:
600/256 = 2.34
The most significant byte is 02
600 – (256*2) = 88
The least significant byte is 88
So the information that we need to send through Winsock1 would be Chr(2) and Chr(88) to represent the value of 600.

In part 9 we will continue with writing the VB6 program. We will start reading and writing the information to the PLC.
If you have any questions or need further information please contact me.
Thank you,
Garry

If you’re like most of my readers, you’re committed to learning about technology. Numbering systems used in PLC’s are not difficult to learn and understand. We will walk through the numbering systems used in PLCs. This includes Bits, Decimal, Hexadecimal, ASCII and Floating Point.

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