hall effect signal on to 7seg display

Discussion in 'The Projects Forum' started by ralphh85, Aug 29, 2007.

  1. ralphh85

    Thread Starter New Member

    Aug 29, 2007
    3
    0
    hello im new here! hopefully someone on here can help me!

    basically im tryign to bring up a number on a few 7 segment led displays dependent on the amount of pulses per min which come from a hall effect sensor.

    i believe i will have to convert the hall effect signal to an analog dc voltage then put this in tot he LED display.

    but where do i start? i have little electronics knowledge and dont have time to go back an do my A level!!

    any ideas?


    Ralph
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    You can get Hall effect sensors that have a digital output level. Apply the pulses to a counter chain, with a display showing the accumulated number.
     
  3. mrmeval

    Distinguished Member

    Jun 30, 2006
    833
    2
    A digital output can be done with a "hall effect switch"
    http://www.melexis.com/ProdMain.aspx?nID=148

    If you are not constrained as to how you count them or output them look at something like a pic, atmega, picaxe or other microcontroller solution.

    I like this http://www.arduino.cc but there will be an investment in learning it and then having it read the sensor and then output to a display of some sort.
     
  4. ralphh85

    Thread Starter New Member

    Aug 29, 2007
    3
    0
    well what im actually doing is...

    i have an old metro which has real fast engine (143bhp vvc engine) and also a carPC. windows based small mini itx pc used for playing music mostly.

    i want to remove my instrument cluster (speedo/rev counter/water temp/ etc etc) and replace it with a set of digi dials which i would really like to make myself as would be a good project!

    the speedo sensor which i can put in (from a rover 200 or similar) is just a hall effect sensor and it gives out 4 pulses per revolution.

    so i have the output i just need to bring it in and show up XXXmph.

    i am totally open to ways of doing it with no restrictions, most of what was said/the pages i just viewed kinda went over my head!

    whats the easiest way? i can wright basic software so must be able to pick it up somehow!


    cheers for help
    Ralph
     
  5. ralphh85

    Thread Starter New Member

    Aug 29, 2007
    3
    0
    i now know that obviously 0hz = 0mph

    and not so obviously 120hz = 129mph!! on my car this may be closer to 120hz = 122mph due to different gearbox tho but i would like it to have adjustament anyway!



    Ralph
     
  6. kender

    Senior Member

    Jan 17, 2007
    263
    0
    You could use a panel meter. It’s an OEM device that takes an analog voltage and displays it on 7LED or LCD (depending on a model, of which there are hundreds).

    Now, you need to convert pulses per minute to analog voltage. There are 2 possibilities:

    - If the pulses have constant width, then the duty cycle is proportional to the frequency. Then you can simply low-pass filter pulsed signal to convert it to DC voltage level.
    - If the pulses have a constant duty cycle, you could use a frequency to voltage converter (F/V). You can make one out of a 555 timer. Or you can get an F/V IC such as LM2917.

    Of course, you can do all this with a microcontroller too.
     
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