We were trying to investigate a simple way to make a representative LED output from a given input voltage. Basically this was intended to be a quick checker for the Battery we use in the Offline Inverters.
We found that LM3914 was a low part count Bar Graph display with Analog inputs available. And it was already in our dusty component drawer waiting for some one to use it.
This chip has a Direct Drive for the LED and contains a FLASH ADC kind of Structure for Analog Voltage to Bar Graph representation.
|Internal Block Diagram (Sources: National Semi)|
|Pin Out Detail for the DIP Package (Source: National Semi)|
|Basic Circuit for LM3914|
So we modified the circuit by adding a 10k POT (BOURNS) in place of the R1 and R2.
|Our Modified Design for Variable Voltage|
We also added a small filter 10K + 0.1uF to make sure we have clean input to the chip.
This is one handy circuit from our creations, hope that this would help you to develop your own application.