How I can measure remaining battery Volts and "transform" to Ohms?

Hello everybody,

we are developing a new product and we want to add some extra features as battery level indication.

For this reason I plan to add to our board a device (digital potentiometer?) that is going to "transform" the measured voltage from the battery to Ohms. I need the Ohms as input in order to set battery alarm indication. 

So we need a device that it will measure voltage from 3 - 5,5  volts and transform it to some KΩ. Is digital potentiometer suitable for our application? How about AD5116?
Are there any other products (preferable not SMDs) that are suitable for our  application? Thank you very much in advance. I am looking forward for your  response.

  • 0
    •  Analog Employees 
    on Nov 15, 2015 6:01 PM

    Moved to more appropriate community.

  • 0
    •  Analog Employees 
    on Nov 15, 2015 10:45 PM

    Hi,

    First, let me explain how a digipot(digital potentiometer) works. A digipot is a digital-to-analog converter that would accept digital data, translate that digital data, and finally set the output (which is the potentiometer) to the preferred value.

    Now, my understanding to your post is that you would need a part that would accept 3V to 5.5V as input and you want that part to have an output in the form of a resistor. Is this correct?

    If so, I think I can offer you a basic solution. I believe that you would first need and ADC for your 3V-5.5V input. Recently, most microcontrollers have built in ADC like the ADuCM360. But if you are looking for high performance ADC's, you may want to look at this page to see ADI's portfolio of ADC's. Depending on your speed and resolution requirement, we can do some recommendations of parts. You would need to do some coding. Afterwards, translate the codes from the ADC using the microcontroller as inputs to the digipot. The digipot will set the output to its appropriate value.

    I hope this answers your question. If you have other concerns, please do not hesitate to ask.

    Regards,

    Mark

  • 0
    •  Analog Employees 
    on Nov 16, 2015 6:19 AM

    If you consider ADuCM360, you also can take in account ADuC706x, ADuC703x and ADuCM33x.

  • Thank you very much for your reply!

    Unfortunately we don't have much available space in our board for a second micro controller. Our application is really simple and we just want to have a notification when the battery is below 10-20%, so most probably we will just use an extra resistor as voltage divider for this purpose.

    However, thank you very much for your replies.

    Regards

    Nikos