1. Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.
    Dismiss Notice

Using 8051 as a multimeter with 7seg LED display?

Discussion in '8051/8951' started by Learner, Sep 21, 2004.

  1. Learner

    Learner New Member

    Joined:
    Aug 27, 2004
    Messages:
    51
    Likes:
    0
    Location:
    Area 621.xxx
    Hi guys,
    I am looking to build a multi meter using 8051, I know that I can use an AD converter to display the voltage but what can I do to measure the resistance and the current?

    Can anyone refer a link or suggest the easiest way to do this?

    So far, I have figured that I can put the AD on the bus but would I need a HEX to decimal decoder on the bus to display the voltage? or shouldn't it be a binary to decimal decoder?

    Thanks!
     
  2. williB

    williB New Member

    Joined:
    Aug 30, 2004
    Messages:
    2,217
    Likes:
    3
    Location:
    New Jersey
    to measure current use a one ohm resistor in series with the circuit you want to measure
    since I = V/R
    if R = 1 you are measuring current directly :)
     
  3. williB

    williB New Member

    Joined:
    Aug 30, 2004
    Messages:
    2,217
    Likes:
    3
    Location:
    New Jersey
    what a/d converter are u using ? some output strait binary others compliment the output .
    u may or may not have to do some convertion in your 8051 program to get the output to straight binary , then u can use a binary to seven segment decoder..or you could do it all in the program by connecting the outputs of the 8051 directly to the segments of the display.
     
  4. dave

    Dave New Member

    Joined:
    Jan 12, 1997
    Messages:
    -
    Likes:
    0


     
  5. Learner

    Learner New Member

    Joined:
    Aug 27, 2004
    Messages:
    51
    Likes:
    0
    Location:
    Area 621.xxx


    Hi williB,
    That's an AWSOME idea!!!!! Thanks a million for that!!!! :D

    no wonder I ain't getting straight As at college....... :(
    why didn't I think of that! :?
     
  6. Learner

    Learner New Member

    Joined:
    Aug 27, 2004
    Messages:
    51
    Likes:
    0
    Location:
    Area 621.xxx

    Well, I am still trying to think my idea through and come up with a schematic.....

    My goal is to make the 7 seg led be as spontaneous as possible with minimal circuit required, so I would not want to use an 8051 if it is not necessary.

    So far, I am thinking of just using a 8 bit AD since I will be measuring less than 100V and then connect the 8 bit output straight to the binary to decimal decoder to the 3 digit 7 seg display. Any AD you would like to recommand, I think I will just pick some 8 bit AD from TI since they offer free samples :D :D
     
  7. Oznog

    Oznog Active Member

    Joined:
    Apr 21, 2004
    Messages:
    2,879
    Likes:
    11
    Location:
    Austin, Tx
    You'll find an alphanumeric LCD display quite easy to drive, more visible in bright light, lower power, and far simpler to wire up. You sure you want an LED?
     
  8. williB

    williB New Member

    Joined:
    Aug 30, 2004
    Messages:
    2,217
    Likes:
    3
    Location:
    New Jersey
    well the TI TLV 1571 has ten bits resolution , parallel output
    one lsb is 4.8 mV (nice) Vref is your supply voltage on this part(5V)
     
  9. williB

    williB New Member

    Joined:
    Aug 30, 2004
    Messages:
    2,217
    Likes:
    3
    Location:
    New Jersey
    Is there any in particular that u have used?
     
  10. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

    Joined:
    Nov 17, 2003
    Messages:
    39,228
    Likes:
    641
    Location:
    Derbyshire, UK
    Almost all LCD text modules use the Hitachi chip set, so as long as it's one of those it doesn't matter much one you use - I've used various different makes and models, you simple connnect it up and it works with the existing software (as it's written for the same chip set). The only difference I have found is in the contrast setting, you usually have to adjust that for different ones.
     
  11. williB

    williB New Member

    Joined:
    Aug 30, 2004
    Messages:
    2,217
    Likes:
    3
    Location:
    New Jersey
    so all i have to do is desolder the LCD from the other board and use it like that?
    in the top photo is the 14 connections ? right?
     

    Attached Files:

    • lcd1.jpg
      lcd1.jpg
      File size:
      17.7 KB
      Views:
      1,091
    • lcd2.jpg
      lcd2.jpg
      File size:
      22.2 KB
      Views:
      1,004
  12. williB

    williB New Member

    Joined:
    Aug 30, 2004
    Messages:
    2,217
    Likes:
    3
    Location:
    New Jersey
    i just noticed that your photo (on you site ) of the LCD has 16 contacts??
     
  13. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

    Joined:
    Nov 17, 2003
    Messages:
    39,228
    Likes:
    641
    Location:
    Derbyshire, UK
    Yes, that should be fine, I've used many LCD modules removed from other equipment.

    The one in the photo in my tutorials has 16 connections because the other two are used for back lighting - which isn't actually fitted on the board in the picture, but some LCD's have the unused connections there anyway.
     
  14. williB

    williB New Member

    Joined:
    Aug 30, 2004
    Messages:
    2,217
    Likes:
    3
    Location:
    New Jersey
    thanks i 'll try it :)
     

Share This Page