• AVR Freaks

Hot!PIC16F876A 10 bit ADC replacement of TC7107

Author
karan123
Super Member
  • Total Posts : 912
  • Reward points : 0
  • Joined: 2009/02/02 11:11:21
  • Location: 0
  • Status: offline
2020/01/21 22:01:26 (permalink)
0

PIC16F876A 10 bit ADC replacement of TC7107

Hi,
 
Can I use PIC16F876A ADC 10-bit in replacement of  TC7107 3-1/2 Digit Analog-to-Digital Converters ?
TC7107 have full scale voltage 200mV . I can used TL431 as external ADC voltage reference Vref+.
 
--
Karan
 
 
#1

12 Replies Related Threads

    ric
    Super Member
    • Total Posts : 25592
    • Reward points : 0
    • Joined: 2003/11/07 12:41:26
    • Location: Australia, Melbourne
    • Status: online
    Re: PIC16F876A 10 bit ADC replacement of TC7107 2020/01/21 22:10:24 (permalink)
    0
    What do you mean "replacement" ?
    Do you just mean "can I get the same measurement range?" ?
    The answer is almost certainly "No", but you really need to properly describe your requirements.
     
    Do you really want to use such an ancient PIC to replace something else anyway?
     

    I also post at: PicForum
    Links to useful PIC information: http://picforum.ric323.co...opic.php?f=59&t=15
    NEW USERS: Posting images, links and code - workaround for restrictions.
    To get a useful answer, always state which PIC you are using!
    #2
    karan123
    Super Member
    • Total Posts : 912
    • Reward points : 0
    • Joined: 2009/02/02 11:11:21
    • Location: 0
    • Status: offline
    Re: PIC16F876A 10 bit ADC replacement of TC7107 2020/01/21 22:15:53 (permalink)
    0
    Thanks... ric for reply..
     
    TC7107 not needed yet, Want to use PIC16F876A  .
     
    I have to measure and process voltage in terms of mV with PIC16F876A 10-Bit ADC as
    with TC7107 3-1/2 Digit Analog-to-Digital Converters (Without Programming).
     
    I need to use serial port and 7-Segment that's why i need MCU Not TC7107.
     
    Thanks...
     
    --
    Karan
    post edited by karan123 - 2020/01/21 22:17:52
    #3
    ric
    Super Member
    • Total Posts : 25592
    • Reward points : 0
    • Joined: 2003/11/07 12:41:26
    • Location: Australia, Melbourne
    • Status: online
    Re: PIC16F876A 10 bit ADC replacement of TC7107 2020/01/21 22:28:19 (permalink)
    0
    karan123
    I have to measure and process voltage in terms of mV

    That's still too vague.
    The TC7107 has differential inputs that can measure plus and minus voltages.
    The PIC has several single ended inputs. You can use two of them to simulate a differential measurement, but it won't be as good.
    You have not revealed enough details of your requirements to say if the 16F876 will be good enough.
     
     

    I also post at: PicForum
    Links to useful PIC information: http://picforum.ric323.co...opic.php?f=59&t=15
    NEW USERS: Posting images, links and code - workaround for restrictions.
    To get a useful answer, always state which PIC you are using!
    #4
    karan123
    Super Member
    • Total Posts : 912
    • Reward points : 0
    • Joined: 2009/02/02 11:11:21
    • Location: 0
    • Status: offline
    Re: PIC16F876A 10 bit ADC replacement of TC7107 2020/01/21 22:36:18 (permalink)
    0
    Ok.. I need only Positive Signals (in milli Volts)
    .Negative Signals are not my requirements.
    I can Use TL431 as Voltage Reference for ADC.

    If I am using 5V Vref. My Step size is 5/1024 = 4.88mV approx. Which is not likely to be handled my requirements. So please advise..

    --
    Karan
    post edited by karan123 - 2020/01/21 22:40:33
    #5
    dan1138
    Super Member
    • Total Posts : 3343
    • Reward points : 0
    • Joined: 2007/02/21 23:04:16
    • Location: 0
    • Status: offline
    Re: PIC16F876A 10 bit ADC replacement of TC7107 2020/01/22 00:26:30 (permalink)
    0
    Your reply is ultra lame.
     
    You need to describe:
    • Range of the analog input voltage you need to measure
      from lowest (most negative) to highest (most positive).
    • Range of values to be displayed (in decimal perhaps?)
      from lowest (most negative) to highest (most positive).
    • Number of digits to be displayed (1,2 or 3).
    • Required resolution, how much does the input voltage
      change for a one count change in the displayed value.
    • What kind of 7-segment display, LED, LCD, other.
    Describe what you can and ask questions about what you do not understand.
    #6
    oliverb
    Super Member
    • Total Posts : 265
    • Reward points : 0
    • Joined: 2009/02/16 13:12:38
    • Location: 0
    • Status: offline
    Re: PIC16F876A 10 bit ADC replacement of TC7107 2020/01/22 01:55:32 (permalink)
    +1 (1)
    Quick observations:
    a "3-1/2 digit" converter would be expected to have a readout spanning from -1999 to +1999, so nearly 0-4000.
     
    This makes it effectively 12 bits resolution give or take a few counts.
     
    Now many applications don't use the full range, and a range of 0-1000 can be covered by 10 bits.
     
    As several people have pointed out the input voltage range is different. It is not uncommon to see the -ve input tied to ground and the +ve input fed from a voltage divider. In this case it may be possible to just change the divider to yield a larger voltage swing.
     
    Another issue is noise. Most of the "3-1/2 digit" converters use a slow dual-slope conversion that averages the input over a relatively long period, typically >100ms. The PIC takes "snapshots" of the voltage at the time of conversion. For this reason a low-pass filter may be needed to clean up the signal.
    #7
    karan123
    Super Member
    • Total Posts : 912
    • Reward points : 0
    • Joined: 2009/02/02 11:11:21
    • Location: 0
    • Status: offline
    Re: PIC16F876A 10 bit ADC replacement of TC7107 2020/01/22 06:35:55 (permalink)
    +1 (1)
    @dan1138 . Please Check my reply as below in Bold
    • Range of the analog input voltage you need to measure
      from lowest (most negative) to highest (most positive).
               0mV to 200mV
    • Range of values to be displayed (in decimal perhaps?)
      from lowest (most negative) to highest (most positive).
               - .99  to  9.99  
    • Number of digits to be displayed (1,2 or 3).
             Two Digits with minus sign
    • Required resolution, how much does the input voltage
      change for a one count change in the displayed value.
             1mV or 2mV  
    • What kind of 7-segment display, LED, LCD, other.
                    7-segment display LED
     
     
    Thanks Karan
    #8
    karan123
    Super Member
    • Total Posts : 912
    • Reward points : 0
    • Joined: 2009/02/02 11:11:21
    • Location: 0
    • Status: offline
    Re: PIC16F876A 10 bit ADC replacement of TC7107 2020/01/22 06:41:37 (permalink)
    0
     
    oliverb Thanks ..
     
    Can I TL431 for Set Vref ?
    #9
    dan1138
    Super Member
    • Total Posts : 3343
    • Reward points : 0
    • Joined: 2007/02/21 23:04:16
    • Location: 0
    • Status: offline
    Re: PIC16F876A 10 bit ADC replacement of TC7107 2020/01/23 15:34:33 (permalink)
    0
    karan123

    @dan1138 . Please Check my reply as below in Bold
    • Range of the analog input voltage you need to measure
      from lowest (most negative) to highest (most positive).
               0mV to 200mV
    • Range of values to be displayed (in decimal perhaps?)
      from lowest (most negative) to highest (most positive).
               - .99  to  9.99  
    • Number of digits to be displayed (1,2 or 3).
             Two Digits with minus sign
    • Required resolution, how much does the input voltage
      change for a one count change in the displayed value.
             1mV or 2mV  
    • What kind of 7-segment display, LED, LCD, other.
             7-segment display LED

     
    One thing you have not described is what is to be displayed on the 7-segment LEDs over the input voltage range (0mV to 200mV).
     
    For example:
     
    When the input voltage is 0mV display -.99 on the LEDs, when the input voltage is 200mV display 9.99 on the LEDs. This is, using a linear scale, show the input voltage of 0mV to 200mV on the 7-segment LED displays as: -.99 to 9.99
     
    Is this how you need the input voltage to map to the displayed values?
    post edited by dan1138 - 2020/01/23 15:40:42
    #10
    NKurzman
    A Guy on the Net
    • Total Posts : 18266
    • Reward points : 0
    • Joined: 2008/01/16 19:33:48
    • Location: 0
    • Status: online
    Re: PIC16F876A 10 bit ADC replacement of TC7107 2020/01/23 16:24:25 (permalink)
    0
    karan123
     
    oliverb Thanks ..
     
    Can I TL431 for Set Vref ?


    Probably, But not set to 200 millivolts.  See the Data sheet. 
    #11
    1and0
    Access is Denied
    • Total Posts : 10346
    • Reward points : 0
    • Joined: 2007/05/06 12:03:20
    • Location: Harry's Gray Matter
    • Status: offline
    Re: PIC16F876A 10 bit ADC replacement of TC7107 2020/01/23 19:05:50 (permalink)
    0
    On the '876A, the minimum reference voltage range is 2 V yielding a resolution of ~2 mV.
    #12
    ric
    Super Member
    • Total Posts : 25592
    • Reward points : 0
    • Joined: 2003/11/07 12:41:26
    • Location: Australia, Melbourne
    • Status: online
    Re: PIC16F876A 10 bit ADC replacement of TC7107 2020/01/23 19:21:10 (permalink)
    0
    MAYBE you could fake an extra bit of resolution with some good averaging code.
    You'd certainly have a lot more than 1 mV of noise to provide the dithering.
     
     

    I also post at: PicForum
    Links to useful PIC information: http://picforum.ric323.co...opic.php?f=59&t=15
    NEW USERS: Posting images, links and code - workaround for restrictions.
    To get a useful answer, always state which PIC you are using!
    #13
    Jump to:
    © 2020 APG vNext Commercial Version 4.5