Connecting hum. & temp. sensor to the internet

Discussion in 'General Electronics Chat' started by 555, Aug 7, 2014.

  1. 555

    Thread Starter New Member

    Aug 7, 2014
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    Dear Reader

    Task:
    temperature and humidity readings should be time stamped and recorded locally, then sent to a server where the data is visualised and provided to internet browsers.
    The thermometer and hygrometer is a WS-9400.

    Plan:
    sniff data (temp. & hum.) sent to the LCD screen, send them to a raspberry pi, which locally records the data on its SD card and uploads them to a server.

    Questions:
    1) how can the signals to the LCD screen be sniffed? Would you use tools such as the bus-pirate?
    2) most probably the signals have to be amplified. How can this be done?

    Thank you very much for your help!
     
  2. sirch2

    Well-Known Member

    Jan 21, 2013
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    I wanted to do something similar in terms of reading an LCD on a consumer product but failed to successfully hack the LCD. So I thought outside the box and used a mobile phone and Optical Character Recognition. You can pick up a secondhand Android smart phone for cheap (you or your kids may have one sitting in a drawer). You point the phone camera at the LCD, capture an image and identify the LCD segments of interest. I didn't need to connect to a server but all smart phones have WiFi so it is easy to send data.

    This approach has the advantage that it can be used with any LCD, with just a bit of re-programming so if your temp sensor dies and you buy a different model, you don't have to start again with the protocol analysis.

    I am happy to send you my Android code if you are interested.
     
  3. Sensacell

    Well-Known Member

    Jun 19, 2012
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    Sounds nightmarishly over complicated for the task at hand.

    I would suggest getting sensors that already have a digital output, or get a data acquisition board for your computer and read in the analog voltages from the sensors.
     
  4. sirch2

    Well-Known Member

    Jan 21, 2013
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    "nightmarishly over complicated"

    really?

    Write a bit of pretty simple code to process an image or write a bit of pretty simple code to read some digital sensors or build something with A to D and write some code, all sounds fairly similar

    In the application I used it for the sensor was not commercially available as a component.
     
  5. 555

    Thread Starter New Member

    Aug 7, 2014
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    0
    Dear readers

    Thank you for your inputs

    @ Sensacell
    I agree getting the right sensors is the way to go for temperature and humidity tracking. However there are a couple of LCD screens on machines around here and the informations displayed have to be accessible online. The WS-9400 is to get first hands on sniffing LCDs.

    @ sirch2
    Good idea! As answered to Sensacell, information from several LCDs have to be provided online.
    Could you describe in more detail how you tried to hack the LCD?

    Thank you for help,

    555
     
  6. sirch2

    Well-Known Member

    Jan 21, 2013
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    it's several years ago and I didn't really keep notes but pretty much what you would expect. Look at what is on each line with a scope as the display is updated then pick the "interesting" signals and try to make sense of them. What I tried was hooking them up to the inputs of an Arduino and then wrote a bit of code to buffer and dump pin status when ever a pin changed. I have to say I didn't try too hard and I'm sure with enough time and effort it could be done. However the issue was that the display showed several pieces of information at a time, life would have been a lot simpler if I could have got it to show individual characters or segments one at a time.

    Just getting the thing hooked up was a pain and basically meant the device was pretty compromised afterwards. The imaging idea is completely non invasive, violates no warranties and is portable across a number of different devices.

    Just as an aside, my original imaging idea was to use an array of photo-transistors, but that only works with a back lit LED ans is bulky. I also tried an optical mouse sensor but sorting out the optics on that was too hard.

    In a way I agree with Sensacell that it feels a bit wrong to use a mobile phone but once you get over the natural engineering squeamishness about it, it really is the way to go.
     
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  7. 555

    Thread Starter New Member

    Aug 7, 2014
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    Dear sirch2

    thank you very much for your insights.

    Based on your experience, the LCD's used in the WS-9400 does it receive analog or digital input?
    Would the bus-pirate be the right tool to find out the communication protocol?

    Thank's again for your help and with my best regards,

    555
     
  8. ErnieM

    AAC Fanatic!

    Apr 24, 2011
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    QFT. Do you really expect sniffing visual data via a call phone ios somehow easier and less costly then just buying a new pair of sensors?

    The signals doing to the LCD are a series of square waves. If an individual segment is off the segment drive will be in phase with the backplane square wave; if on (dark) it will be out of phase. OR those phases may be reversed, it depends on what liquid crystal fluid is contained.

    So for the 5 digits to capture you only need 35 inputs, plus one or more for the backplane signal(s).

    However, a sensor for this may be found for even less cost then the display you want to snif.
     
  9. sirch2

    Well-Known Member

    Jan 21, 2013
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    555 - sorry, I really can't comment as I have no experience of either.

    ErnieM - I agree that if individual sensors are an option then it is better but in my case that was not an option, neither was accessing the individual LCD segments. I was faced with a tiny ribbon cable (something like 20 way) that communicated with a bespoke LCD which displayed up to 4 readings plus battery status and other status details.
     
  10. NorthGuy

    Active Member

    Jun 28, 2014
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    And if you want to sniff, it'll be easier to sniff the sensors that your device uses, not the LCD.
     
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