Bar graph display is series of LEDs connected either making cathode pins common or anode pins .These kind of display are very useful to display statistic data in the form of bar . They are eye catching because of their intensity . Long Bar graph display can be used in public areas ,stock exchange center or weather forecast data center . Each box in bar graph indicate perticular level of the data . They can are also used in musical system to display visualization and other
This is menual connection of bar graph display . here pin number 8,9,10 are connected to vcc and corresponding negative terminals are connected to ground and hence 3 boxes are only glow. what if you want to make a automatic system for example if you want to make a music equalizer ? Then you need a bar graph display driver IC . In this method you need to control only one pin ie SEG pin . The bar will be shown according to the input voltage .
How to connect bar graph display to microcontroller ?
Here according to the input voltage from potentiomete the LM3914 IC is decoding the value and the bar is showing that value. This concept is used in many devices and microcontroller . For example to some sensor sense something and equivelent voltage is sent to LM3914 IC and value displays on bar graph .