Display for a reference signal

Discussion in 'Test & Measurement Forum' started by Rennieaj, May 6, 2018.

  1. Rennieaj

    Thread Starter Member

    May 6, 2018
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    hello,
    This is my first post on here so bear with me please.
    I play the bagpipes in a band and we use a meter to tune our pipes. We take a reading from the master set and tune the rest to that value. I calibrate and look after our meters and have a bit of electronics knowhow. I want to add some functionality to the meter so that when we take a reading we can hit a button which stores a reference value, this will be displayed via 3 leds, if the left one is lit it is too low (flat) middle is the target and right is too high (sharp). This value can be reset so I assume it will need some kind of memory function. Can anyone please please help.
    Thanks
     
  2. crutschow

    Expert

    Mar 14, 2008
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    Hos is the meter output reading displayed now?
     
  3. Rennieaj

    Thread Starter Member

    May 6, 2018
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    4
    On a analogue needle display, can I take the inputs from that as my inputs for the additional circuitry?
     
  4. BR-549

    AAC Fanatic!

    Sep 22, 2013
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    Does the needle move to the left on flat and right on sharp? Show us your meter.
     
  5. Rennieaj

    Thread Starter Member

    May 6, 2018
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    4
    Left flat right sharp
    The added functionality is to reduce human error/eyesight/perspective etc.
    Something along the lines of the attached YouTube link
     
  6. BR-549

    AAC Fanatic!

    Sep 22, 2013
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    Have you looked for a smartphone audio spectrum app?
     
  7. Rennieaj

    Thread Starter Member

    May 6, 2018
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    I want to add it to that meter, I already have a smartphone app
     
  8. BR-549

    AAC Fanatic!

    Sep 22, 2013
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    Adding the youtube has confused me. You want a 3 LED output, right?
     
  9. Rennieaj

    Thread Starter Member

    May 6, 2018
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    4
    Yes, similar to the one on the video in a previous thread, one for target reached, one for flat and one for sharp. Hit a button to take a reference and probably another to reset
     
  10. crutschow

    Expert

    Mar 14, 2008
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    Yes, likely.
    You would need to measure the meter voltage (both across the meter and to circuit common) to determine where you want the LEDs to light

    A comparator circuit could be configured to light the left and right LEDs at the desired voltages with a window comparator for the center LED.

    The comparators could likely be configured as latches to save the reading or a separate FF latch circuit used.
     
  11. Rennieaj

    Thread Starter Member

    May 6, 2018
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  12. Rennieaj

    Thread Starter Member

    May 6, 2018
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    That all sounds great, thanks,
    Would you happen to have any diagrams and what components I would need to purchase to achieve?
     
  13. crutschow

    Expert

    Mar 14, 2008
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    Yes.
    But I need the voltage measurements I mentioned to give you a proper design.
    What is the battery voltage for the device?
     
  14. BR-549

    AAC Fanatic!

    Sep 22, 2013
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    One could also use an arduino. It can measure the period of a mic input. That period count can be stored and used as a reference for the next mic input. That second input.....will be less than, equal too, or higher than that first count. That result will light one of three LEDs.
     
  15. Rennieaj

    Thread Starter Member

    May 6, 2018
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    The meter is powered off a single 9v battery
     
  16. crutschow

    Expert

    Mar 14, 2008
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    Okay, if you can post those meter measurements, I'll try to gin up a circuit for you.
    Measure the voltage across the meter for the desired points for the LEDs to light, along with the voltage measurements for each of those desired meter deflections from each terminal of the meter to the minus terminal of the 9V battery.
     
  17. Rennieaj

    Thread Starter Member

    May 6, 2018
    35
    4
    I welcome all suggestions, Im not familiar with ardunio, what does it involve?
    I’m not sure I understand, the result can be different from time to time, there won’t be a set value
     
  18. Rennieaj

    Thread Starter Member

    May 6, 2018
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    4
    I’ll hopefully get those measurements tonight, thankyou so much
     
  19. BR-549

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    Sep 22, 2013
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    Arduino is a company that produces various microprocessor configuration boards.

    There are several other companies that do the same thing.......but arduino is real popular with hobbyist. It has a simple free software interface for beginners.

    Some of the small boards might fit inside your existing equipment.

    It was just an alternative suggestion. You would have to learn to program.

    It might be worth a read. Unless your purpose is singular.

    One could record, store or add as many references as you want.
     
  20. crutschow

    Expert

    Mar 14, 2008
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    You need a set (fixed) value where the LEDs light.
    I need to know what the voltage value is.
     
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