Sunday, March 1, 2015

Multichannel Professional Data Logger on Raspberry Pi - Part 2

See the Part 1 for the overall description and Part 3 for the software implementation.

Hardware


The most interesting part to deal was the hardware. Below you can see an old prototype board, which includes a Raspberry Pi, two custom boards for ADC, sensor connectors and voltage dividers. In the middle - a small board to supply a power. It has real-time input voltage monitoring: on 7.5V - the Data Logger start making warning sounds, on 7.0 V - automatic shutdown. Two power supplies: AC-DC external, and internal pack batteries. Also the embedded ORing controller makes a smooth transition between battery and external power supply.



The boards has been designed and implemented by Boris Shogan, my old friend and awesome Electronics Engineer. It took a noticeable amount of collaborative work in our spare time and midnight oil burnt to make this happen. But it was a plenty of fun.

Since we need 16 ports total, the natural choice was to take two MCP3008 8-Channel 10-Bit ADC with SPI interface, and have it on two standalone boards (a compact 16-port single board which hosts both ADC is also available).

Originally we had it working on Raspberry Pi Model B (512 MB RAM), and later used the Model B+. We did not tried the Raspberry Pi 2, it was released just a few days ago.

Below is the IV-board for Currency and Voltage. The low-side external Shunt or Sense resistors are plugged to the blue connectors:


Currently this types of Shunt and Sense resistors are supported by default, other types can be easily added:
  • Shunt 500A 50mV
  • Shunt 300A 50mV
  • Shunt 100A 100mV
  • Shunt 100A 50mV
  • Shunt 10A 100mV
  • Shunt 2A 100mV
  • Sense R=0.1 15A
  • Sense R=0.1 20A
  • Sense R=0.25 14A
Below is T-board for Temperature measurements. The sensor is J-type thermocouples (also not shown, can be plugged to the connectors on the bottom).



See below the image of the complete product in the box. We have been given the enclosure, and this Customer asked us to make a table-top version, so here it is. Meantime we are working on a smaller "portable" version. Stay tuned.

Feel free to get back to me if you would like to get more details about the system, get a copy of software, or customized version for your needs. You can also purchase the assembled ADC boards or DIY kits.

6 comments:

  1. Great work ! I have been interested in using a rpi for data logging for a while , how would I go about purchasing the kits . I am interested in logging pressure transducers 2 or up to 4 temperature inputs , analog inputs 230v (for fault outputs) and current draws one or up to 4 . can it be configured for remote access via internet ? . Thanks

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  2. Thanks for your feedback. Yes, you can purchase the kits. We do not have a website to order yet, please send your contact info to email "andriy at rokhmanov.com" and I'll get back to you with all details.
    About your questions: the data logger web UI is accessible over the internet (as long as the data logger itself has an internet connection).
    Also let me know what kind of transducer you want to use, I don't think it will be difficult to implement.

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  3. Hi Andriy

    Great post i am currently working on a data logger very similar to yours. The ADC board is beautifully designed where can i buy. thanks

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  4. Hi, sorry for the delay. I've listed it on the eBay: http://www.ebay.com/itm/16-Channel-VIT-Data-Logger-for-Raspberry-Pi-expansion-kit-/191723945746

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  5. Hello, can you make a 16 channel temperature logger using K type thermocouples?

    Ship to UK?

    How much?

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    Replies
    1. Certainly. Please contact me by email in my profile for details.

      Thanks,
      Andriy

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