PT100 on Q50UDEH

[Andrei Blagaila]

Has anyone used a PT100 temperature sensor to control the temperature in a certain environment? I want to use it over CC-Link. Any suggestions for modules and for temperature control any ideas how to do them? I have never worked with PT100 on Mitsubishi and i'm clueless how it's done. 

[JRoss]

There are analog modules available for CC-Link both from Mitsubishi and from others. I've only used the Mitsubishi ones. I don't know if they have RTD inputs available, so you might need a transmitter to convert the RTD signal to 4-20mA.

Once you have the signal in the PLC, you'll use PID control (most likely) for the temperature control part. Look for the Analog Edition of the QPLC programming manual on Mitsubishi's website, it should have all the detail you care to read.

Why do you want to do the temp signal over CC-Link?

[Andrei Blagaila]

RTD signal? Sorry I'm new to analog signals. I know about 4-20 and 0-10 but i have never heard of RTD. I need to use over CC-Link because i need to measure the temp on the field near some remote I/O's where I plan to insert the new PT100 module. Do you have some examples of how to do a PID in ladder (SW is done in ladder) and how to read the analog signal?

[Luke.S]

RTD = Resistance Temperature Detector

There are various standard RTD types and PT100 is one of them ( 100 being 100Ω I believe) . You can take the readings remotely over CCL with this device station:

https://www.cc-link.org/sch/c020?CL=1&prodId=Prod46&menuSeqNo=2

Then you would have to use function blocks or code PID in the PLC to calculate commands to output to PWM or whatever method you are using to control your heater.

OR

You could just use a temperature controller which interfaces with the PLC over CCL. It handles the PID loop locally and will have an auto tuning function greatly reducing your development and tuning costs. Commands such as temp. SV and monitor data such as temp. PV can be sent over CCL.

https://www.cc-link.org/sch/c010List?bunruiNm1=CC-Link&catTemplateSeqNo=9&menuSeqNo=2

If your project is simple ladder (no variables) and you can't use function blocks then you are looking at a quite involved and risky software development if you do the PID on the PLC.

I'm assuming you are using CCL v1.1 or 2 with a Q here.

[Andrei Blagaila]

Q CPU with CCL but i'm not sure about the version. My Master CCL is a QJ61BT11N. 

I found the manual for the remote RTD reading module. The first step is to understand how to get the data that the PT100 reads and then how to manipulate it to have a value. 

All my program (many POUs ) is written in ladder. I don't think I can use one of the POU that's reserved to write a FB program or can I? I'm fairly new to Mitsubishi and don't have a lot of knowledge of what is possible and what not.

After I do this I need to figure out how to control the temperature. From my understanding they want to use solid state relays (semiconductor relays). I'm guessing PWM is the way to go in that case?

I will look over the manuals today and try to see how can I read from the module but if you can give me some examples how to get the info from the module and manipulate it, they would be extremely appreciated.

[Crossbow]

When you set up the master, you tell it where in memory to place the data for the slaves.  Each slave is assigned the same amount of memory, so some slaves occupy more than one address.

The manual for each slave explains how that slaves stores its data.  

There is no reason to write any function blocks.  The data will be transferred to the PLC automatically.

Don't recall if Q has a PWM command, but if it did, you would use it with a transistor output card to control pulses to external solid state relays.

[Andrei Blagaila]

I found the manual for the  AJ65BT-64RD3. Aftel a while reading I found the example program and understood how the I/O are assigned. I wrote a bit of software but i'll wait for the module and PT100 to test it out. If this solves the current issue of reading the temperature, I will need to find out how to use PWM and PID to control it using ladder diagram