- PID SIEMENS STEP 7 SERIAL
- PID SIEMENS STEP 7 MANUAL
- PID SIEMENS STEP 7 CODE
- PID SIEMENS STEP 7 DOWNLOAD
Thankfully there are manual tuning options as well. In my case, the temperature response of the furnace was incredibly slow and the lag between output and response was great enough that auto-tuning wasn't a viable option. Unfortunately, the process I was trying to control did not lend itself well to auto-tuning. Once the tuning process is complete, the PID loop will be activated and you're ready to go. Once pre-tuning is complete, you can do further finetuning. I think this is fairly straightforward and doesn't need much comment, but do remember to be careful before starting auto-tune as the controller will take over and measure the response to different outputs. From here, you can start the auto-tuning process. While the program is running on the PLC and you are online, you can use this icon to launch the tuning window. This is how we enter the auto-tuning process. Right next to that icon is an icon with what looks like a pair of pliers and a yellow warning sign.
We'll get to manual tuning in a moment, so let's look at the auto-tune process first.Įarlier, we used the " Toolbox" icon on the block to configure the block. You will need to either manually start it, or walk through the tuning procedure.
PID SIEMENS STEP 7 DOWNLOAD
Now you've set up your block and have provided inputs/outputs, how do you get started? If you download your program to your PLC you will quickly see that the PID loop is not currently active. So basically, this block is a one-stop shop for any kind of PID control. And you can use any or all of them simultaneously. It's worth noting here that the output options for the block are plentiful - engineering value, Output_PER, and PWM. As I chose to use the input option (not Input_PER), I had nothing to do here.įinally, there are " Advanced Settings." This is where you can take advantage of the built-in warnings for process value monitoring, set minimum on/off times for a PWM output, output value limit values, and manually enter PID gains. Next, if using Inper Per, you will need to define your " Process Value Settings." These options will define the scaling used to convert your percentage input to engineering units (for comparison to your setpoint). In my case, I wanted to control temperature using a setpoint and input in degrees F, and an output in % that I could feed directly to an analog output to my valve. The first set of choices you have are " Basic Settings." This is where you define what kind of inputs/outputs you're using. Just click on the 'toolbox' icon in the upper right-hand corner of the block to open up the configuration window. Luckily, there's a very handy configuration tool provided.
Choose how often your cyclic OB executes based on how fast your process is.Īfter you've added your block, it up to you to configure it. You don't want the PID block to execute every scan (it needs time to respond to changes in the control value), therefore, add it to a cyclic OB. But before you add it, be careful where you're going to drop it.
PID SIEMENS STEP 7 CODE
You can click and drag a block from here directly to your code to add it to your project. Under the basic instructions, there's another group called "Technology." Expand this and you should see a group of instructions called PID Control. This is the tab that contains all of your tools (timers, counters, math, etc).
One of the first questions I had after discovering that there were native PID blocks provided in STEP 7 was "Where are they?" If you're looking, expand the instructions tab on the right side of the development screen in STEP 7. So, if you're looking into using PID on your S7-1200, I hope the following tips may be useful in getting you up to speed. In my case, I was controlling the temperature in a furnace by actuating a proportional valve - so PID_Compact fit the bill. For most purposes, I would think PID_Compact (for use with continuous input/output variables) would be sufficient, but if you're trying to control motor-actuated devices, such as valves that require digital open/close signals, the PID_3Step block could be very useful. If you've thought about PID on an S7-1200, you probably know that Siemens is kind enough to provide two PID function blocks in STEP 7: PID_Compact and PID_3Step. But there were a few things I picked up along the way that may be helpful for the next person looking to close the loop.
PID SIEMENS STEP 7 SERIAL
Like serial communications, PID was also fairly straightforward. Recently I had another chance to be DMC's S7-1200 pioneer - this time using the S7-1200's PID blocks, and luckily, not involving death by dysentery, cholera, or snakebite. And while it was very straightforward, it was still a learning experience. Due to the limited number of projects we've had using the 1200 line of PLCs, this was an office first. A few weeks ago I had the chance to experiment with serial communications using a Siemens S7-1200 PLC outfitted with a CM1241 (RS-485 module).