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low power ADC IC interface with Arduino

Manh Huynh
Prodigy 55 points
Other Parts Discussed in Thread: ADS8634

Hi, 

I am looking for a low power ADC IC, sampling 1MSPS. bipolar input range -3V -> 3V

especially, I dont know how to connect ADC IC with arduino.

Could you help me find the ADC IC I want, and the way to connect with Arduino ?


Thank you

  • 0
    TI__Mastermind 43830 points

    Hi Manh

    Here is a search of ADCs that align with your criteria.

    http://www.ti.com/lsds/ti/data-converters/precision-adc-less-10msps-products.page#p3093min=-12;-5&p3093max=3;12&p1089=1000000;12500000

    One of the devices in the list is the ADS8634 which is probably the best fit. Since it is a Precision ADC I am going to move this thread into that forum so that the appropriate experts can help you with any other questions you have.

    Best regards,

    Jim B

  • 0
    TI__Guru* 92655 points
    Manh,


    Before you go too far with this device, how many bits do you need from the ADC? Can you use an 8 bit ADC? With the ADS8634 running at 1MSPS, you'd still need to clock out 16 bits per data.

    I could be wrong, but I believe that the Arduino uses an 8MHz clock and the Mega uses a 16MHz clock. I don't think either would be able to handle the data rate at all.

    Regardless, I think you need to use a slower data rate from the ADC.


    Joseph Wu
  • 0 in reply to Joseph Wu
    Prodigy 55 points

    Hi Joseph,

    Thank you for your help.

    I could slow down  data rate, it is not much important in my project..

    Since I need the high precision, I want highest bit ADC that I can, so I preferred 16bits more than 8 bits. 

    So what is required clocks for ADC 16 bits to achieve 1MSPS. Can you reccomend some processors ?

  • 0 in reply to Manh Huynh
    TI__Guru* 92655 points
    Manh,


    First, let's start with your system. What is it you're trying to measure? How fast do you need to sample it? Typically, I work with devices that have a max rate of 2000 samples per second. If you need something faster, I can still point you in the right direction.

    Second, what kind of resolution are you looking for? Do you need 16 bits or higher resolution? What is the max signal level you expect to read, and what sort of noise will there be in the measurement?

    Do you need to amplify the signal? Do you need multiple input channels? What sort of communications will you want to use? (SPI or I2C are two popular communications schemes) Are there any other special features that you need in the system.

    Note that with the Arduino, the data rates are likely going to be very slow. I'm not sure you're going to be able to communicate with anything that runs near 1MSPS. I think it'll be difficult to get anything within 2 orders of magnitude of that.

    I'm not familiar what to use to communicate with a device that fast. In general, I can help with the ADC, but not the master side of the system. Let's start with what specs and features you need first.


    Joseph Wu
  • 0 in reply to Joseph Wu
    Prodigy 55 points
    The signal I want to read is signal emitted from the screen of mobile devices. These signals are low voltage -0.3V to 0.3V as I measured using Oscilloscope. Now, I want to make a low power wearable devices, that can act like oscilloscope. As I calculated, the sampling rate 66KHz is enough for this project. The problem is
    - When I try to use arduino, it can not read the negative voltage.

    I am really want to get help on this project.
    Joseph Wu, could you help me on the design ? If yes, can I talk with you through email, since in emails I can send some figure, and reports so that you can understand more.

    Give me your contact email if you can.

    Thank you very much
  • 0 in reply to Manh Huynh
    TI__Guru* 92655 points
    Manh,


    I've friended you and you should be able to message me through the e2e site. You'll also be able to send me files if you need to.

    As for the problems that you are having now, what device are you using? How is your system set up? You mention that you can't read negative voltages, so what are you getting when you do try to read negative voltages.

    I might not be able to help you much. I generally help with specific ADCs and I'm not an expert on the microcontoller side.

    Regardless, send me a few more details through the forum and I may be able to find some help for you.


    Joseph Wu
  • 0 in reply to Joseph Wu
    Prodigy 55 points
    Hi,

    I am not talking about Mircocontroller,

    What i want is that way to convert a unipolar ADC to a bipolar ADC since most of microcontrollers have unipolar.
    I am using Arduinio mini pro 3.3v with unipolar inside.

    Do you know some devices are circuit to do that ?

    Thank you
  • 0 in reply to Manh Huynh
    TI__Guru* 92655 points
    Manh,


    Are you asking how to convert the +/-300mV signal to something that is unipolar?

    I would try using some sort of op-amp to build something that adds a DC offset and some gain. You could also use an instrumentation amplifier to do the same thing. Just search google for "arduino" and "bipolar ADC measurment". There are plenty of example circuits that you can build. I'd be sure that the circuit fits with the bandwidth and offset error that you need in your measurement.


    Joseph Wu
  • 0 in reply to Joseph Wu
    Prodigy 55 points
    Thanks Joseph Wy tooooo much !

    I have found a way to convert it. It is more difficult than I think because there is coupling capacitive on Ground. Though the signal is still weak but I am now can move them to positive region :).

    Again, I am really appreciated your help.