Tag Archives: pid controller example

Implementing the Solo Process Temperature Controller

The SOLO Temperature Controller is a single loop dual output process temperature controller that can control both heating and cooling simultaneously. It is available in 1/32, 1/16, 1/8 and 1/4 DIN panel sizes and is UL, CUL and CE approved. The name of temperature controller is deceiving. This unit will also accept voltage and current into them, which is great for process control.

Recently I was asked: How you can change the pressure value from PSI to Bar?

They were bringing into the controller a voltage signal. This can be scaled using the tP-H (High level signal) and tP-L (Low level signal). The units on the display scaled for you. The default is -999 to 999. See section 11-2 of the following information guide that comes with the controller. Continue Reading!

Solo Process Temperature Controller

The SOLO Temperature Controller is a single loop dual-output process temperature controller that can control both heating and cooling simultaneously. It is available in 1/32, 1/16, 1/8 and 1/4 DIN panel sizes and is UL, CUL and CE approved.



There are four types of control modes:
PID (Auto Tuning (AT) function)
P stands for proportional and accounts for present values of the error – It reacts to the amount of error which is the difference between the SP (Set Point) and the PV (Present Value)
I stands for integral and accounts for past values of the error – It uses math to basically find the approximation of the area under the curve.
D stands for derivative and accounts for possible future values of the error, based upon the rate of change – It uses math to determine the slope of the error over time and multiply this by the derivative gain.
AT – Auto-Tuning as the name implies will automatically cycle your control system through two cycles and set the PID parameters.

ON / OFF
On/Off control is the simplest form of control. In the case of temperature, the output will be on when the temperature is below-set point. When the temperature gets above the set point of the controller the output will be off. When this cycling occurs frequently, you can add hysteresis to the output. This will limit the time the output goes on and off by a number of degrees.

Manual
Manual mode is when you need to control the output directly. By entering manual mode the operator can adjust the values of the output(s).

Ramp / Soak control
The Ramp / Soak control mode is used to control the outputs according to the pre-programmed SP patterns with the PID control method. The Solo can have eight programs with eight steps each. Note: This can be increased with the additional use of hardware and software via HMI or PLC.

The available outputs include relay, voltage pulse, current, and linear voltage. There are up to three alarm outputs available to allow seventeen alarm types in the initial setting mode. SOLO can accept various types of thermocouple, RTD, or analog input. This means that cascade control is possible with these controllers.

Cascade (Application)
When you use the output of one of the Solo process controllers as the input to another, this would be cascade control.

It has a built-in RS-485 interface using Modbus slave (ASCII or RTU) communication protocol.
The Solo Process Temperature Controller can be configured through the buttons on the front of the unit or by the configuration software. Monitoring of up to four controllers at once can be done through the same configuration software.

The following is the wiring of the Modbus Serial communication. We will use a USB to RS485 converter from Automation Direct. (USB-485M)
Installation and operation instructions can be found at the following link: USB to RS485 PC Adapter Installation

Solo Process Temp Controller 010 Communication Diagram-min

The solo process temperature controller needs to be setup before we can communicate to it. The default setting is ‘Off’ for the On-Line Configuration. Here is the way to change into the different modes in the Solo.

Solo Process Temp Controller 015 Solo Parameters-min

In the Initial Setting Mode we will change the online configuration and make the changes to the Modbus settings as follows: 9600 Baud, Even, 7 Data Bits, 1 Stop Bit, Modbus ASCII Format. We will leave the default unit number as 1.
Solo Process Temp Controller 011 Solo Parameters-min
Solo Process Temp Controller 012 Solo Parameters-min

Our controller is now set to communicate.

Download the documentation and/or configuration and monitoring software at the following URL link:
http://support.automationdirect.com/products/solo.html

The configuration and monitoring software does not have to be installed. You just need to download the file “slsoft.zip”.
Once downloaded right click on the file and select “Extract All…”. The file ADC1105.exe can now be run.
Solo Process Temp Controller 020 Software Install-min

The recommended screen resolution is 1024 x 768. If you do not have this resolution then there is another program that will allow us to create a shortcut to this program and change our default resolution. After we exit the program, our screen resolution will return to its original state.



Reso is a free application that works well. It can be downloaded at the following URL link:
http://www.bcheck.net/apps/reso.htm

Download the exe file (reso.exe) into the same extracted folder that you have the ADC1105.exe file.
Solo Process Temp Controller 021 Software Install-min

Click on the reso.exe file in the folder to run the application.
Click the Browse… button and select the ADC1105.exe solo configuration software.
Under the Graphics Mode: Resolution: select 1024×768
We can leave the rest to the defaults as shown below. Now Click Create Shortcut.
Solo Process Temp Controller 022 Software Install-min
Put the shortcut in the same directory as the software that was downloaded.

We will receive notification that the shortcut was created. Click OK.Solo Process Temp Controller 023 Software Install-min

Our folder will now look like this.
Solo Process Temp Controller 024 Software Install-min

Click on our shortcut (ADC1105 (at 1024×768)) to start the Automation Direct Solo Series Configuration Software.

There are six icons on the main menu. Follow these in order from left to right to set up or troubleshoot your system.
Solo Process Temp Controller 030 Software-min

Solo Process Temp Controller 031 Software-min

Under the Com port setup, we configure the serial port of the computer to communicate to the Solo. In our case we will use COM5, 9600, Even, 7 Data Bits, 1 Stop Bit, Modbus ASCII Format.Solo Process Temp Controller 040 Software-min

In the Configuration menu, we will select the address of the controller that we will be communicating. This will be the default of the Solo which is 1.Solo Process Temp Controller 035 Software-min

Selecting Connect will then communicate to the Solo process temperature controller and you will see on the screen a picture of the controller with the PV, SV and indicator lights active. Solo Process Temp Controller 050 Software-min

This screen will now allow you to set up all of the parameters in the Solo. Once you enter a value it will be red on the screen. After hitting enter on the keyboard and the value will then be sent to the controller and be displayed in black again.

Solo Process Temp Controller 060 Software-min

The recorder screen is used to monitor the temperature over time. You can monitor up to ten Solo Controllers at once.

Command Test is used to send individual Modbus command out. This is done in Hexadecimal.

The software for the Solo Process Temperature Controllers is very functional. Using the Reso software, you will be able to put the Solo Software in the 1024 x 768 that it was created for without manually changing the screen every time.

Watch on YouTube: Solo Process Temperature Controller

Watch on YouTube: Analog Input to a Solo Process Temperature Controller
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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Who Else Wants to Learn About On Off and PID Control?

Process control can be a bit intimidating. We will try and break down both On/Off and PID control in a fun way. This is a simple analogy without any math.


On/Off control can be used effectively with temperature control. Everyone’s house usually has a temperature controller that uses an On/Off control. When the temperature is below the set value (SV) the output switches on. The output will remain on heating the house until the present value (PV) is above the set value. At this point, the output will then go off. The house will constantly be doing this in a cyclic way. This means that the temperature of the house will vary a few degrees.
sine_wave

We can plot this out like the sign wave above. The setpoint is in the middle. By the time the output is turned off the thermal mass continues to heat the house, before starting to cool down. The same is true when the output is turned back on. It will cool down a little more then start to heat up again. This is called hunting. We can not get exactly on the set point value and stay there.

Let’s look at another way to explain:
Control On Off

You are in a car and can only use full gas or a full brake. Racing toward the stop sign at full gas, you use the full brake at the stop sign line. Naturally, you go past the stop sign and eventually come to a full stop. Putting the car in reverse, you again use full gas back toward the stop sign line. When you hit the line you apply the full brake. Missing the mark again.  This is like On/Off control action.

If we wanted to control the method a little closer then we could program in a hysteresis. (Dead band) This is just a range in which nothing would happen. It would take into consideration the amount that we went over the line in both directions.
Control On Off with Deadband

If we need to hit the stop sign target a little more accurately then we can now introduce another control method.

PID is a time-based control logic. It will look at a control period (CP) and determine what to do for the next. In a temperature control application, the control period would be 20 seconds. In a servo valve application, it can be 1 second. Let’s look at each of the control methods in the PID with respect to our car analogy.

Proportional Control (P) – This will increase in the amount based upon the error. The closer we get to the set point, the control period will be on for a longer period of time. (Reference to the output percentage  of control period time.)

Control Proportional

In our example, the car can be seen applying the brakes proportionally longer and longer times before the stop sign line is reached. If it goes over the stop sign line the car will apply the brakes even longer depending on the amount over the line. This is proportional control.

Integral (I) – Using just proportional control would always leave us below the set point. We need a method to reset us to the actual set point. This is where integration comes into play. It is interesting to note that PI control is one of the most commonly used in the industry.

Control Intregral

The car above is traveling along the road, following the dashed lines. If we used just proportional control we would find ourselves riding in the ditch. The integral control will move us into our lane and keep us close to the dashed line.

Derivative (D) – This mode of control will look at the rate of change and adapt our control to get us back to the set point. Remember that everything is based upon a control period which is time. PI relies on the fact that everything remains constant in your control. D will take into account the differences over time.

Control Differential

In our car analogy, the derivative function of the control will continually adjust as we move up the hill and down the other side. It will not do much as we drive along the straight road way.

We have looked at a very basic analogy of control logic without all of the details of math. This can aid in understanding what your process is doing and methods to correct. Further information can be obtained by the following references:

PID without a Ph.D. By Tim Wescott
Understanding PID in 4 minutes
PID Control – A brief introduction
PID Controllers Explained

Nice project using PID:
Desktop Line Following Robot

Watch on YouTube: Who Else Wants to Learn About On / Off and PID Control?
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.