LM3914 Schematic Help!

Discussion in 'The Projects Forum' started by deadlyzxcv, Jul 10, 2015.

  1. deadlyzxcv

    Thread Starter New Member

    Jul 8, 2015
    6
    0




    I need these circuit diagram so that i can build it for my project.
    Can someone post the circuit diagram for the two circuit in the two videos.

    For the first video at 0:45, what is that component the guy is trying to turn using a screwdriver?
    Is it a different kind of variable resistor?

    Thanks :)
     
  2. JohnInTX

    Moderator

    Jun 26, 2012
    2,341
    1,022
    Yes. Its called a trimpot. They are like the potentiometer he is using to vary the input voltage to change the LED readout. Trimpots are normally used for adjustment or calibration that is done once then left alone.

    All you need to know about the LM3914, including the schematic for this demo is in the datasheet available at TI. Check out the application notes as well.

    Good luck!
     
    Last edited: Jul 10, 2015
  3. ScottWang

    Moderator

    Aug 23, 2012
    4,853
    767
    You can see the internal structure in page 5 of datasheet, the schematic in page 12 for 20 LEDs, you can also choose dot mode or bar mode, the variable resistor that you are asked for is trimpot.

    What you watched in the videos that it was just used trimpot for a voltage level testing, the practical application as VU meter.


    LM3914 datasheet.
     
  4. deadlyzxcv

    Thread Starter New Member

    Jul 8, 2015
    6
    0
    Hi,
    In the datasheet, what page is the first video's circuit at? (10 LEDs with variable resistor and is in bar mode)
     
  5. ScottWang

    Moderator

    Aug 23, 2012
    4,853
    767
    Check the first page, using a 5K or 10K pot to connecting to pin 5, the pot connection as :
    pin 1 -- ground,
    pin 2 -- LM3914 pin 5,
    pin 3 -- +5V.
    If you have wiring error then you just exchange the pin 1 and pin 3 of pot.
     
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