Help Please - LM3914 Problems

Discussion in 'The Projects Forum' started by markodaguy, Mar 24, 2015.

  1. markodaguy

    Thread Starter New Member

    Mar 24, 2015
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    I'm doing an assignment for school and I found a circuit that I would like to build for this assignment (see circuit attached http://www.edutek.ltd.uk/Binaries/Circuits/Survival_Game.pdf ). However, when I connect the the LM3914 on a breadboard, LED 9 from pin 11 lights up straight away and stays lit. Changing the signal doesn't affect LED 9 at all and stays lit. When I disconnect the signal from ground, all the LEDs from the output of the LM3914 light up and stay lit. When I connect the signal back to ground all the LEDs switch off except for LED 9 from pin 11.

    The circuit is supposed to work in a way when the switch is pressed when the output of 555 timer is high the capacitor charges up. This then should increase the voltage supplied to pin 5 of the LM3914 and light up the bottom LED. When switch is pressed again at output high, LED2 from the output of the LM3914 should light up while the driver works in DOT display.

    I've tested in circuit in simulation programmes such as livewire and the circuit works perfectly fine.

    Any advice would be greatly appreciated.
     
  2. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    It looks like there is some kind of short on pin 11.
    Looking at the schematic of an LM3914, pin 11 goes only to the led:

    [​IMG]

    Can you post a photo of the breadboard?

    Bertus
     
  3. Dodgydave

    Distinguished Member

    Jun 22, 2012
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    lets have a look at your built circuit, pictures please...
     
  4. Alec_t

    AAC Fanatic!

    Sep 17, 2013
    5,779
    1,103
    Sounds like you have a wiring error on your breadboard. Double-check all connections against the LM3914 datasheet.
     
  5. markodaguy

    Thread Starter New Member

    Mar 24, 2015
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    0
    All yellow wires are ground and all red are are live.
    I didn't capture the right side of the board as that is the "sound section" which requires the LM3914 to function for it to function.
    I am also didn't put the 330k resistor (R7) which is next to C3.
     
  6. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    Look at the jumper between pin 8 and 9.
    Then at the following schematic for dot/bar selection:

    [​IMG]

    Bertus
     
  7. Dodgydave

    Distinguished Member

    Jun 22, 2012
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    you have the Adj pin 8, connected to the Dot pin 9, your not using the ref Hi and ref Lo pins to set the upper/lower limits.
     
  8. markodaguy

    Thread Starter New Member

    Mar 24, 2015
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    0
    Even when I disconnected the mode from the adjust, the LED still remains turned on.

    When I disconnect the mode from ground all the LEDs turn off. The last led, led 10 turns on when I press the button when the astable is on high and the capacitor ccapacitor. It's supposed to go up Led by led every time the button is pressed. when mode is connected to live all LEDs turn on as in bar mode.
     
  9. Dodgydave

    Distinguished Member

    Jun 22, 2012
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    Pin 4 is going to ground with a diode REVERSED , and pin 6 is going to ground with a 10K, Why?
     
  10. markodaguy

    Thread Starter New Member

    Mar 24, 2015
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    Damn I made a noob mistake with the diode my bad.
    I followed the first diagram that bertus sent where pin 6 and 7 are connected together with a resistor going to ground, this is supposed to control the brightness of the LEDs.
     
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