Unipi HW Questions



  • Hello,

    My company is thinking about changing from a PLC control to UniPi to control for one of their smaller bench top machines as a prtotype for future development of an new upgraded product.

    I have a couple of questions regarding UniPi before we can start thinking about if Unipi is suitable for this project.

    1. Is it possible to connect a K-type thermocouple to the UniPi directly?

    2. Is it possible to connect a touchscreen directly without using any IO?

    3. if (1) is not possible) Is it possible to connect a “PiFace Rack” to the UniPi board so that a seperate K-type sensor board can be mounted together with the Unipi?

    Thanks in advance.

    Shaun.



  • Hello,

    My company is thinking about changing from a PLC control to UniPi to control for one of their smaller bench top machines as a prtotype for future development of an new upgraded product.

    I have a couple of questions regarding UniPi before we can start thinking about if Unipi is suitable for this project.

    1. Is it possible to connect a K-type thermocouple to the UniPi directly?

    2. Is it possible to connect a touchscreen directly without using any IO?

    3. if (1) is not possible) Is it possible to connect a “PiFace Rack” to the UniPi board so that a seperate K-type sensor board can be mounted together with the Unipi?

    Thanks in advance.

    Shaun.



  • Hello,

    1. I will do a research on this and let you know

    2. This week RPi foundation released 7inch display especially for the RPi so now there is exactly what you need https://www.raspberrypi.org/products/ra ... h-display/

    3. It might be possible but I did not find any documentation of their boards... But if it would be possible it would definitely need modifying the ribbon cable



  • @Shaun:vjye8oay:

    1. Is it possible to connect a K-type thermocouple to the UniPi directly?

    No it is not. You need specialized ADC for thermocouples, see e.g. MAX31855 http://www.maximintegrated.com/en/products/analog/sensors-and-sensor-interface/MAX31855.html



  • @jaroslav_sobota:3ty58xxb:

    @Shaun:3ty58xxb:

    1. Is it possible to connect a K-type thermocouple to the UniPi directly?

    No it is not. You need specialized ADC for thermocouples, see e.g. MAX31855 http://www.maximintegrated.com/en/products/analog/sensors-and-sensor-interface/MAX31855.html

    OK I understand that K-Type thermocouples cannot easily be used, thank you for answering.

    I thought that maybe the 1 wire system would be an option but unfortunatly the temperature range is too low, I need a minimum of +250C.
    I do not need a negative temperature value, just from "room temperature" to 250C, do you have any alternative to the 125C standard DS18B20s please?



  • @Shaun:d18gtyy7:

    I thought that maybe the 1 wire system would be an option but unfortunatly the temperature range is too low, I need a minimum of +250C.
    I do not need a negative temperature value, just from "room temperature" to 250C, do you have any alternative to the 125C standard DS18B20s please?

    I'm not aware of any other solution. You might be interested in the RIO-2018 Modbus module, which you can use to read thermocouple data.
    http://www.artila.com/en/news/news-2015-05-15.html

    How many thermocouples and other I/O are you using in your machine?



  • For prototyping or proof-of-concept phase you could also use the MAX31855 breakout board from Adafruit.
    https://www.adafruit.com/products/269

    But you would need to modify the ribbon cable between UniPi and the RPi, because UniPi uses GPIO pins 9, 10 and 11 for inputs. These pins are the hardware SPI bus of the RPi which the MAX31855 breakout board connects to.



  • @jaroslav_sobota:3ruvvmme:

    I'm not aware of any other solution. You might be interested in the RIO-2018 Modbus module, which you can use to read thermocouple data.
    http://www.artila.com/en/news/news-2015-05-15.html

    How many thermocouples and other I/O are you using in your machine?

    This project is as much about driving costs down and increasing flexibility of the machine as much as possible, for example displaying and printing the machines production cycle information and operating parameters, network connectivity etc.

    As the machine stands at the moment I have 2 switches(start & stop), one thermocouple (K-Type), one pressure transducer (0 to 10v) and 2 inputs from micro switches, and 4 outputs to SSR's & 1 HMI, at the moment we are looking into replacing the Omron PLC & HMI, replacing these with Raspberry could save up to 60% of the electrical components costs per machine.

    ideally I would like to have everything except the touchscreen mounted together and in a modular format, Having the odd printed circuit board floating around and pieces of breadboard will not be acceptable.

    My role is software engineer, and I would like to use the Rex control system for programming but electronics is not in my or our service engineers skill set, if a part fails we need to replace the defective module, not get the soldering iron out.

    If I can get this small project started I have no doubt that is will lead onto other projects as soon as I can demonstrate the increased flexibility and cost effectiveness of using Raspberry instead of PLC's in our smaller machines, BUT…... at the end of the day it must be easy to support both on site (world wide) and by our customers own engineers.



  • @Shaun:2mztr7ba:

    As the machine stands at the moment I have 2 switches(start & stop), one thermocouple (K-Type), one pressure transducer (0 to 10v) and 2 inputs from micro switches, and 4 outputs to SSR's & 1 HMI, at the moment we are looking into replacing the Omron PLC & HMI, replacing these with Raspberry could save up to 60% of the electrical components costs per machine.

    Can you put here a link to the datasheet of the Omron PLC and I/O modules you are trying to replace?
    What load are you switching with the SSRs? AC or DC current?
    What sampling frequency and precision do you need for the analog input (pressure transducer)?
    What is the price of the current solution with Omron PLC and HMI?



  • @jaroslav_sobota:1j6te3ge:

    Can you put here a link to the datasheet of the Omron PLC and I/O modules you are trying to replace?
    What load are you switching with the SSRs? AC or DC current?
    What sampling frequency and precision do you need for the analog input (pressure transducer)?
    What is the price of the current solution with Omron PLC and HMI?

    This is the PLC http://uk.rs-online.com/web/p/plc-cpus/0401589/

    We are switching a 220V ac load on all four SSR's

    A sampling time of .5 seconds will be ok and precision of 1 integer (no decimal places)

    The aporoximate cost, for these components can be calculated here

    http://uk.rs-online.com/web/p/product/7 ... wwod3h4IGg

    http://uk.rs-online.com/web/p/plc-cpus/0401589/

    http://uk.rs-online.com/web/p/plc-expan ... s/0401438/



  • First of all, for temperature range 0..250°C I recommend using Pt100 or Pt1000 sensors (see e.g. http://www.thermibel.be/documents/pt100 ... ml?lang=en)

    For the hardware I would go for Raspberry Pi 2 with the 7" official display and Modbus TCP remote I/O unit:
    RPi2 complete set (micro SD card, power supply) 45 GBP
    RPi official display 42 GBP

    Turck BL20 Modbus TCP gateway (BL20-E-GW-EN)
    BL20 8x DI (BL20-E-8DI-24VDC-P)
    BL20 8x DO (BL20-E-8DO-24VDC-0,5A-P)
    BL20 8xAI/4xRTD (BL20-E-8AI-U/I-4PT/NI)
    Approximate total is 335 GBP

    The Raspberry Pi will serve as both the HMI and the PLC (or the "brain" of the system). The DO module allows you to control the SSRs and you have 4 spare signals. The DI module reads the pushbuttons and microswitches and you have 4 spare signals. The AI/RTD module reads the pressure transducer and the PT100/Pt1000 temperature sensor and you have 4 voltage inputs or 2 temperature inputs remaining to expand your system.

    The licence of the REX Control System with Modbus I/O driver is 84 USD (~57 GBP).

    So for approx 479 GBP you have a solution which I believe completely replaces the Omron PLC and gives you much more potential.

    As soon as UniPi with SSR is available, it might be possible to reduce the price even more, but at the moment I see this solution as the best way to go.



  • @jaroslav_sobota:5etmpkxr:

    So for approx 479 GBP you have a solution which I believe completely replaces the Omron PLC and gives you much more potential.

    Firstly let me thank you for your research into my thermocouple problem, however 479 GBP is only slightly less than the Omron equipment cost after our discount has been applied. I agree that Pi would give much greater flexibilty but i still have to reduce costs as much as possible to help off set the development costs of the project.

    As i mentioned the only real problem was the use of a thermocouple and i think i have found an alternative solution that i would like to show you.

    http://www.yoctopuce.com/EN/products/us ... ermocouple

    This unit supports Pi via the USB interface and looks to be exactly what I need to progress this project with Pi & UniPi.

    Jaroslav, I would greatly appreciate any feed back about this that you may have.



  • I did not know the Yocto-Thermocouple device. It seems applicable. Nice!

    If you run the VirtualHub on the Raspberry Pi, you will be able to read the thermocouple data into REX. Namely the section "18.2. VirtualHub and HTTP GET" will apply.

    Let me know when you have the device. Together we'll make it work…



  • I have just one more question before I can proceed with a proposal to present to the directors.

    I understand that the UniPi industrial system is supplied with standard REX for Raspberry Pi, however I would need to use the PIDAT function that is only supplied with the REX Advanced for Raspberry Pi.

    What is the total cost for UniPi Industrial if it is supplied with REX Advanced instead of REX Standard please?



  • Hello,
    as you easily can see here - it cost's less more money (35$ => 84$).
    https://www.rexcontrols.com/products/re ... spberry-pi
    Don't forget to tell your directors they 'll get a new level of machine Unfortunately it costs time to develop a safe one, which looks like it's your part.

    btw: For industrial usage I strongly recommend:
    1. use an HDD or better SSD for your Linux-OS (SDCard's are not suitable for permanent writing! (even SLC-SDCards)) - we tested this
    http://www.voelkner.de/products/796282/ ... wwody_EBTQ
    with 120GB mSATA SSD. The new PiDrive on Kickstarter is also an option.
    2. check for an UPS/USV to avoid damaging of OS after power blackout crash (at the moment we test a small easyacc powerbank - looks successful)
    iot



  • @iot:28op1ppj:

    Hello,

    as you easily can see here - it cost's less more money (35$ => 84$).

    So is the total cost of UniPi Industrial set €229.00 + $84?



  • If you are not afraid of the Linux command line, you can order the UniPi development set
    http://unipi.technology/product/unipi-development-set/ with Open source software (i.e. blank SD card) and you can obtain the Advanced licence of the REX Control System separately for $84, just like iot mentioned. So with RPi2 and EU power supply the price would be €186.65 + $84 (VAT excluded).

    If you wish to receive a complete package with REX installed, you have to wait for the official reply from the UniPi guys.



  • @jaroslav_sobota:1x8mbc8a:

    If you wish to receive a complete package with REX installed, you have to wait for the official reply from the UniPi guys.

    Yes I think this is the way to go, The UniPi Industrial kit + REX advanced installed ready to start working on & programming.



  • I have one final question please.

    Will I require an additional modified ribbon cable to allow a Raspberry Pi Touchscreen to be connected to UniPi?



  • AFAIK you can use a separate micro USB cable to power the RPi official touchscreen display so it does not consume any of the pins of the 40-pin header on the Raspberry Pi.
    But the cable to the DSI port of the Raspberry Pi is quite short so you need to place your Raspberry Pi close to the display, so you might need a longer cable to connect the Raspberry Pi to the UniPi board.