Rotary volume led indicator circuit

Discussion in 'General Electronics Chat' started by ekremgusani, Oct 21, 2018.

  1. ekremgusani

    Thread Starter Senior Member

    Mar 20, 2011
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    I will appreciate if someone can help me with circuit without arduino and programming to build a circuit volume led indicator with leds that can go up wilth volume up and down with volume down.
    I want to connect that circuit to my actual radio or any knob volume device.
    I want it to be similar to this video on YouTube but without arduino programing.
    Will appreciate circuit or if i can buy the actual ready to use module.
    Thanks.
     
  2. Reloadron

    Distinguished Member

    Jan 15, 2015
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    If you can settle for something less all of the whistles and bells there are plenty of experimenter ready made boards out there based on the LM3914 Dot/Bar display analog-controlled LED driver or the LM3915. A simple Google of LM3914 board with LEDs should get you started. The LM3914 is basic so none of the features in the video but will give a dot / bar display of audio level.

    Ron
     
  3. crutschow

    Expert

    Mar 14, 2008
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    But how would you interface that to a volume control (while it's also controlling volume)?
    Offhand I don't see how that can be readily done. :confused:
     
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  4. ArakelTheDragon

    Well-Known Member

    Nov 18, 2016
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    A simple comparator will do. This circuit is normally done to indicate battery voltage, but you can use it for volume as well. If during the volume increase, the voltage increases, then all you have to do is compare the higher voltage to the other pin of the comparator and on the output you will get a high.

    If the circuit is current controlled, it becommes trickier, you need to convert the current to voltage, for which there are many ways. Lets leave this for after you tell us is your device voltage or current controlled?
     
  5. crutschow

    Expert

    Mar 14, 2008
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    That AC voltage will depend upon the audio source signal voltage as well as the volume control setting.
     
  6. ArakelTheDragon

    Well-Known Member

    Nov 18, 2016
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    Is it not a DC audio source?
     
  7. crutschow

    Expert

    Mar 14, 2008
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    What is a DC audio source? :confused:
    Audio signals are AC.
     
  8. ArakelTheDragon

    Well-Known Member

    Nov 18, 2016
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    I thought so too, but everytime I tought it, I was corrected by what I see posted on variour places, so I do not dare say it anymore.
     
  9. Reloadron

    Distinguished Member

    Jan 15, 2015
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    Uh Oh, I failed to read the question through.
    I should have read deeper into that. No, I don't see it readily done working from a volume control pot. My bad on that for not completely reading through the question.

    Ron
     
  10. Sensacell

    Moderator

    Jun 19, 2012
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    Dual- Gang Pot

    One pot makes DC for the lights, the other does the audio.


    Next idea...

    Incremental encoder and digital pot.
     
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  11. djsfantasi

    AAC Fanatic!

    Apr 11, 2010
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    How about a hybrid solution? Mechanical and electrical. This required a few design constraints. Is there sufficient space for a larger pot? Is there room for the LEDs? And is there room for an external driver board and wiring for the LEDs? If you think there is, read on.

    What is the description of the pot to which you’d like to add this feature? Shaft size, resistance and type (linear or logarithmic)?

    If it’s a single, linear pot, I’d look for a dual linear (stacked) pot to replace the existing one. (this is what sensacell is suggesting). Then use the second deck to drive a LM3914 circuit.

    I’ve had no luck funding a stacked pot with both linear and logarithmic decks. So, I thought why not make your own.

    If it’s a logarithmic pot, then I’d look for a dual logarithmic pot and a dual linear pot from the same manufacture.

    Pots from the same manufacturer often use the same mechanical casing. CAREFULLY disassemble the casings. Gently bend the metal clips so you can reuse them. Remove the bottom decks. Make sure you don’t lose the wiper. Then, reassemble the pots, switching the bottom decks.

    You should get two pots, each with a logarithmic deck and an linear deck. Rewrite the pot into its original location. Bring the linear leads out to an LM3914 circuit board.

    And you’ve hacked your solution!
     
  12. Reloadron

    Distinguished Member

    Jan 15, 2015
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    Do they still make the LM3915? If we want to get something along the lines of a VU (Volume Unit) maybe the LM3915 would be a better choice?

    Ron
     
  13. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    There are 3 versions.
    The LM3914 , a linear voltage display.
    The LM3915 , a logarithmic display in 3 dB steps.
    The LM3916 , a dedicated VU meter display.

    Bertus
     
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  14. DC_Kid

    AAC Fanatic!

    Feb 25, 2008
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    Is the ask a VU meter or light display with volume setting?

    I'd say easily done, but you need addressable LED elements, like neoPixels. You can do VU and volume setting display with below method. The point at which you sample the source will depend on if you want VU or just volume setting display. If VU then you need to find a pre-amp out setting because those have max voltage and will vary. For volume control display you need non varying voltage at dial point, etc.

    As example, using a neoPixel ring from Adafruit, and a Trinket 5v, you can monitor the voltage from the pot and then light up the correct amount of LED's accordingly, and you can do so in many ways. neoPixels allow you to send I/O to the pixel addressing color and brightness. So technically you can fade from green to yellow to red as the volume goes from low to high, or, you could have just one LED light up to follow the dial around, you could even blink the LED's when volume was pegged to max.

    Skies the limit when it comes to neoPixel LED's. Plenty of examples around for neoPixel and Trinket/Arduino platform.


    Without programming i'd say using op-amp to build steps is a good way. Just monitor the voltage from the pot and choose resistors accordingly to build a op-amp step/ladder.

    Simple bar graph, see https://www.allaboutcircuits.com/textbook/semiconductors/chpt-8/the-operational-amplifier/
     
    Last edited: Oct 22, 2018
  15. MisterBill2

    Distinguished Member

    Jan 23, 2018
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    I never heard of a "DC audio source." In fact, I can't even imagine one.
     
  16. Bernard

    Expert

    Aug 7, 2008
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    Post # 15, rectified & lightly filtered AC.
    We need input from OP to go further.
     
  17. MisterBill2

    Distinguished Member

    Jan 23, 2018
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    The simple way is to replace the regular volume control with a dual one, like for stereo, or, if it already is a dual, add a third pot and use that to control the LEDs. The much more complicated way would be to use one of those DC volume control ICs and use the same control voltage to also control the display.Quite complicated but it certainly will work.
     
  18. ArakelTheDragon

    Well-Known Member

    Nov 18, 2016
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    Why does it needs to be complicated, its better to use 4 comparators, wich will also amplify the signal and the circuit is simple.
     
  19. MisterBill2

    Distinguished Member

    Jan 23, 2018
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    The reason that it "needs to be complicated " is that the requirement is to light a long string of LEDs, adding one at a time, as the control is rotated. Using four comparators would only control 4 LEDs. And adding a circuit to get a steady control voltage without affecting the sound quality would be quite complicated.
     
  20. ArakelTheDragon

    Well-Known Member

    Nov 18, 2016
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    4 comparators can easily switch 4 strips of LEDs with a transistor on the output. And since comparators can be used for very small signals and medical equipment, they will not affect the sound quality.
     
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