Here’s a Quick Way to Connect RS232 Equipment

Most programmable controllers will come with a RS232 communication port. This recommended standard (RS) has voltage signals in the range between 3 to 15 volts DC with respect to the ground/common pin. RS232 devices are classed either DTE (data terminal equipment) or DCE (data communication equipment).
The maximum cable length for the communication cable is 15m, however depending on the environment I have seen this as much as 50m without an issue.
Most RS232 connectors are 9 pin like the diagram below, but they can also come in 25 pin or RJ45 connectors.

 

A minimum 3 wire RS232 connection consists of only the transmit data, receive data and ground. This is commonly used if full handshaking is not required.

Pin 2 RD ————————– Pin 3 TD
Pin 3 TD ————————– Pin 2 RD
Pin 5 Ground ———————- Pin 5 Ground
Pin 7 RTS                                       Pin 8 CTS
Pin 8 CTS                                       Pin 7 RTS
Cable Shield

Note: I always jump Pin 4 and 6 out together on each side.
The shield on the connection cable should only be connect to one housing when making the cable. I usually connect it on the PLC end.

5 wire RS232 connection consists of the  transmit data, receive data, ground, request to send (RTS), clear to send (CTS)

Pin 2 RD ————————– Pin 3 TD
Pin 3 TD ————————– Pin 2 RD
Pin 5 Ground ———————- Pin 5 Ground
Pin 7 RTS  ———————— Pin 8 CTS
Pin 8 CTS  ———————— Pin 7 RTS
Cable Shield

Note: The shield on the connection cable should only be connect to one housing when making the cable. I usually connect it on the PLC end.

RS232 is a one to one communication method. (1:1) This means it is designed to communicate to one device. If multiple devices are needed,(1:N) RS422 or RS485 should be used by way of converters.
RS232 must have the same settings on each end. (Port Settings)
These include the following parameters:
Bits per second:  9600 (Baud Rate)
Data Bits: 8
Parity: None
Stop Bits: 1
Flow Control: None

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.

The Secret Of Getting Rid Of Noise On Your Analog Signal

Allot of times in industrial environments we get noise on the analog signal input to PLC’s or other controllers. The noise can be generated by motors, bad wiring, etc.

Placing a 1- 100 uF capacitor on the input signal and ground (common to the cabinet)  will reduce the noise that the input is receiving.

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.

Who Else Wants To Lean PLC Programming For Free?

I have always been an old school programmer. Hardware in front of you hooked up to all of the I/O. I have recently looked at the automation direct do-more designer software solution. The Do-More Designer Software will allow you to build your ladder logic, download into a simulator (comes with the software) and run the code. The price of all of this… FREE

I will not get into allot of details because the documention available already will get you through the software step by step.
– Download the software
– Install the software
– Use the YouTube videos for help with getting around the software and making your first program.

The following are several links to help you discover the plc programmer in you:

Automaion Direct – Do-more Programming Software
http://www.automationdirect.com/adc/Overview/Catalog/Software_Products/Programmable_Controller_Software/Do-more_PLC_Programming_Software

http://www.aboutplcs.com/do-more/software/

http://www.aboutplcs.com/do-more/software/simulator.html

The simulator has allot of great features, including PID simulation.

Do-more PLC – How to videos on youtube
https://www.youtube.com/playlist?list=PLPdypWXY_ROoJx-HnK9gj2Z5a-i7th-UK

Update: Here is a video from YouTube about the simulator basic instructions:
http://www.youtube.com/watch?v=ZnRSw3ykW6k#t=274
https://www.youtube.com/watch?v=4JiMzBHPa7E

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.

Here’s a Quick Way to Understand PLC Inputs and Outputs

The term I/O means Input/Output. I/O can come in two different types; Discrete or Analog Most people starting out leaning about programmable logic controls (PLC) are taught all about discrete input and outputs. Data is received from devices such as push-buttons, limit-switches etc. and devices are turned on such as motor contactor, lights, etc. Discrete input and output bits are either on or off. (1 or 0) The following program will show a motor control circuit stop start. Motor off:

Motor on:

Analog inputs Common input variables for analog are temperature, flow, pressure, etc. They are converted to an electrical signal into a PLC analog input. Standard electrical signals are 0 – 20 mA, 4 – 20 mA, 0 – 10 volts DC, -10 – 10 volts DC. Note: It is recommended that a 4 – 20 mA signal is best. If voltage is required, a resistor can be added to get a voltage input. Analog outputs Common output variables for analog are speed, flow, pressure, etc. They are converted from a word in the PLC to the output of the analog. The range of signal is then outputted to the device to control the position, rate, etc. Standard electrical signals to the device are 4 – 20 mA, 0 – 10 volts DC, -10 – 10 volts DC. Both Analog Inputs and Outputs use words to determine the signal going to or from the device. Example: 4 – 20 mA current Input – 8 bit resolution 4 mA = 000000002 = 0016 20 mA = 11111111= FF16 Example: 4 – 20 mA current Output – 8 bit resolution 0016 = 000000002 = 4 mA FF16 = 111111112 =20 mA For a review of numbering systems, follow the link below: What everyone should know about PLC numbering systems

 

Let me know if you have any questions or need further information.
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.

Here’s a Quick Way to Convert Grey Code into Binary for PLC

Grey Code
Grey Code is used because only one bit of data will change at a time. The following chart shows the conversion of Grey Code to Binary.

Number Binary Code Grey Code Number Binary Code Grey Code
0 0000 0000 8 1000 1100
1 0001 0001 9 1001 1101
2 0010 0011 10 1010 1111
3 0011 0010 11 1011 1110
4 0100 0110 12 1100 1010
5 0101 0111 13 1101 1011
6 0110 0101 14 1110 1001
7 0111 0100 15 1111 1000

It is important for absolute encoders because if the power is interrupted the encoder will know where it is within the one bit.

Example:
Power is interrupted when the encoder is between 7 and 8. If we are looking at Binary Code all of the bits would be effected and we would not be sure as to what number we are looking at for the encoder. Therefore we have lost position. In Grey Code only one bit changes so we will still be able to tell if we were on 7 or 8 if the power was interrupted.

The following sample PLC program will convert 4 bit grey code into binary code.
This code was written in an Automation Direct PLC software called Do-more Designer.

Do-more Designer Software
How to use video’s for Do-more Designer Software

Contact me for the above program. I will be happy to email it to you.
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.

What Everybody Ought to Know About PLC (Programmable Logic Controller) Numbering Systems

Programmable Logic Controllers (PLC) are the same as computers. They only understand two conditions; on and off. (1 or 0 / Hi or Low/ etc.) This is known as binary. The PLC will only understand binary but we need to display, understand and use other numbering systems to make things work. Let’s look at the following common numbering systems.

Binary has a base of two (2). Base means the number of symbols used. In binary the symbols are 1 or 0. Each binary symbol can be referred to as a bit. Putting multiple bits together will give you something that looks like this: 100101112. The 2 represents the number of symbols/binary notation. Locations of the bits will indicate weight of the number. The weight of the number is just the number to the power of the position. Positions always start at 0. The right hand bit is the ‘least significant bit’ and the left hand bit is the ‘most significant bit’.

Let’s look back at our example to determine what the value of the binary number is:
100101112 =
We start with the least significant bit and work our way to the most significant bit.
1 x 2= 1 x 1 = 1
1 x 2= 1 x 2 = 2

1 x 2= 1 x 2 x 2 = 4
0 x 2= 0 x 2 x 2 x 2 = 0
1 x 2= 1 x 2 x 2 x 2 x 2 = 16
0 x 2= 0 x 2 x 2 x 2 x 2 x 2 = 0
0 x 2= 0 x 2 x 2 x 2 x 2 x 2 x 2 = 0
1 x 2= 1 x 2 x 2 x 2 x 2 x 2 x 2 x 2 = 128
 100101112  = 1 + 2  + 4 + 16 + 128
 100101112  = 151
Note that the we just converted the binary number to our decimal numbering system. The decimal numbering system is not written with a base value of 10 because this is universally understood.
To be sure we have the concept down, let’s take a look at our decimal numbering system the same way as we did the binary.
Decimal has a base of ten (10). The symbols are 0, 1, 2, 3, 4, 5, 6, 7, 8 and 9.
15110 =
1 x 10= 1 x 1 = 1

5 x 10= 5 x 10 = 50
1 x 10= 1 x 10 x 10 = 100
15110 = 1 + 50 + 100
151 = 151

Hexadecimal has a base of sixteen (16). The symbols are  0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E and F. Hexadecimal is used to represent binary numbers. F16 = 1111
Every for bits of binary represent one hexadecimal digit.
In our original binary number we now can convert this to hexadecimal.
100101112
The least significant four bits are:
01112 =
1 x 2= 1 x 1 = 1
1 x 2= 1 x 2 = 2

1 x 2= 1 x 2 x 2 = 4

0 x 2= 0 x 2 x 2 x 2 = 0

0111= 1 + 2 + 4 + 0 = 716
The most significant four bits are:
1001=
1 x 2= 1 x 1 = 1
0 x 2= 0 x 2 = 0
0 x 2= 0 x 2 x 2 = 0

1 x 2= 1 x 2 x 2 x 2 = 8

1001= 1 + 0 + 0 + 8 = 916
Therefore:
100101112 = 9716 
We can now convert this hexadecimal number back into decimal
9716 =

7 x 16= 7 x 1 = 7
9 x 16= 9 x 16 = 144
9716 = 7 + 144 = 151

The following chart will show all of the combinations for 4 bits (nibble) of binary. Its shows the Binary, Decimal and Hexadecimal (Hex) values. It is interesting to not that Hex is used because you still have only one digit (Place Holder) to represent the nibble of information.

Binary Decimal Hexadecimal Binary Decimal Hexadecimal
0000 00 0 1000 08 8
0001 01 1 1001 09 9
0010 02 2 1010 10 A
0011 03 3 1011 11 B
0100 04 4 1100 12 C
0101 05 5 1101 13 D
0110 06 6 1110 14 E
0111 07 7 1111 15 F
ASCII (American Standard Code for Information Interchange)
Two nibbles (8 bits of data) together form a byte. A byte is what computers (PLC) use to store and use individual information. So it will take one unique byte to represent each individual numbers, letters (upper and lower case), punctuation etc. www.AsciiTable.com
Example:
Chr ‘A’ = 4116 = 010000012
Chr ‘a’ = 6116 = 011000012
Chr ‘5’ = 3516 = 001101012
Each time you hit a key on your keyboard, the following 8 bits of data get sent.
A word is made up of two bytes, or 4 nibbles, or 16 bits of data. Words are used in the PLC for holding information. The word can also be referred to as an integer.
Long word / Double word is made up of 4 bytes, or 8 nibbles, or 32 bits of data. Long words are used for instructions in the PLC like math.
Hey what about negative numbers?
So far we have talked about unsigned words. (Positive numbers)
Signed words can hold negative numbers. Bit 15 (most significant bit) of a word is used to determine if the word is negative or not.
The following table shows you the signed vs unsigned numbers that can be represented in the PLC.
HEX
8000
BFFF
FFFE
FFFF
0000
3FFF
7FFE
7FFF
Signed
-32768
-16385
-0002
-0001
00000
16383
32766
32767
Unsigned
32768
49151
65534
65535
00000
16383
32766
32767
Memory retentiveness:
When working with PLC’s look at the memory tables to determine what will happen if power is removed from the device. Will the bits go all off or retain their prior state?
Usually there will be areas that can be used in the PLC for both conditions.
As you can see PLC numbering systems and computers are very much related and it all boils down to individual bits turning on and off. The interpretation of these bits will determine what the value will be.

Reference:
Let me know your thoughts, or questions that you have on PLC numbering systems.

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.