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FDC1004EVM: Liquid Level Sensing Sensor with TIDA-00317

Part Number: FDC1004EVM
Other Parts Discussed in Thread: TIDA-00317, FDC2214EVM, FDC2214

I want to know if the towel is wet or dry . Is it possible?

using FDC1004EVM and TIDA-00317.

The distance between TIDA-00317 and towel  is about 5cm.

towel size  10cm x 10cm ,towel thickness 1cm.

Can i get the water content .

  • Hey Hyungbae,

    I have significant doubts that you will be able to do this accurately using the capacitive sensing technique. The reason for this is firstly, you want to go 5cm. I have seen 125 mils or fewer done fairly effectively. I've also seen systems that reach out to 500 mils with limited accuracy careful circuit design. So I think your desire to use 1970mils is highly unlikely seeing as how 500 was already hard enough to extract data from the noise.

    Let's say you do somehow get a signal that indicates that there is a "level" there, you will have to contend with the irregular moisture content of a towel and the fact that it won't be the same amount of wet everywhere. Your best chance of having this sensor work would be to have a soaking wet towel which I think is unlikely in most instances. To compensate, you will have to design a sensor that can interpret the whole length of the towel since you want to get any wet area meaning a large plate sensor. A perfect design to pick up noise, even with careful design and filtering .

    In closing, yes, if you put very nice kit (read expensive) and lots of design time in, you could get a system that may work a good portion of the time accurately. I would look for alternative ideas. Sorry this is not what you'd want to hear I'd bet but you should know the realities of the situation since this could be a hard process.

    If this answered your question please verify below by hitting the green button! If you have additional questions, just send them along my way and I'll be happy to answer them for you.

    Best Regards,
    Nick
  • Thanks Nick

    now i changed mind. chang to FDC2214EVM.
    can i get the towel is wet or dry.
    I thingk FDC2214 is more power full.
  • Hey Hyungbae,

    I think this part could do the trick for you. Below is a plot of the plate size characterization for different distances; the source document can be found here:

    Unfortunately, I do still have some reservations on the resolution of dampness to which you will be able to measure but I would bet you could detect a difference between wet and dry. The reasons for my concern are as follows:

    1. What is Wet?

    You will need to characterize the capacitance associated with the towel at every step from soaked to bone dry to really give a user a sense of the towel's moisture content. Think bone dry, semi damp, damp, very damp, etc... This is certainly doable and if it solves your problem then by all means try. 

    2. Towel Position

    For this to work you will need to ensure that the towel stays in the same spot at all times. If only half of it is in front of the sensor you will need to be able to detect this and adjust the sensor values or your info will be incorrect

    All in all, I would say go ahead and give the eval board a shot to see if your idea works, it's only 30 bucks or there abouts. 

    If this answered your question then please verify this answer below by hitting the green button below! If not, feel free to send along any additional questions that you may have and I'll do my best to answer them quickly and accurately. 

    Best Regards,

    Nick

  • Hi Nick.

    today morning  one FDC2214EVM arrived .

     my finished job like this.

    Questions 1)  is how to design electrodes sizes and single or double side  and FR4 or FPCB?

    Questions 2 ) where i connected electrodes terminal A and Bin FDC2214EVM board?

    Questions 3 ) i need change firmware or not?

    Questions 4 ) do you have library for ARM, if you have can i get it?

    if i get the  this answer ,  I'm handling can do it.

    Sorry for making tired for a long time.

    Best Regards,

    Hyungbae Kim

  • Hey Hyungbae, 

    No worries about asking all of the questions, that's what I'm here for after all! Anyway, let's see if we can answer that list for you:

    hyungbae Kim said:
    Questions 1)  is how to design electrodes sizes and single or double side  and FR4 or FPCB?

    Designing one of these sensors is the same as designing a regular capacitor essentially. If you have a good understanding of electormagnetic theory you'll be golden. However, since it is always nice to have a guide, you can find a very detailed one located here. It sounds like your design will use parallel fingers model seen below:

    hyungbae Kim said:
    Questions 2 ) where i connected electrodes terminal A and Bin FDC2214EVM board?

    I'm not sure which terminals you're referencing, however all of the information you should need including the schematic and board layout can be found in the EVM user guide.

    hyungbae Kim said:
    Questions 3 ) i need change firmware or not?

    You shouldn't need to change any firmware if you are following the user manual and using the GUI provided by TI. Just like all other software out there, there may be firmware updates that are written and you should check periodically to make sure that you are using the most up to date version. Once you decide that this part is complete and you've fully evaluated it, you will need to write your own firmware to use with the part since the TI source code isn't available to customers.

    hyungbae Kim said:
    Questions 4 ) do you have library for ARM, if you have can i get it?

    Unfortunately, I don't know the best place to go to for this information. There is such an abundance of information out there it would be hard to give you a rock solid document about it. I suggest looking through the ARM section of our website and googling to get the best answers. I truly think this will yield the best results for you.

    If this answered your question, please hit the green answer verification answer below, I really appreciate it! If you have anymore questions don't hesitate to send them along and I will answer them to the best of my ability for you.

    Best Regards,

    Nick

  • Hi Nick.

    thanks lot. i do my best.

    Best Regards,

    Hyungbae Kim