Trying to use LM3914V Driver

  • #1
Summary:
LM3914V is a chip that drives 10 LED-based on linear input voltage values.
Hi , all!
The LM3914 can light all LEDs/activate all outputs on a rising input similar to a VU meter kind of thing or function more like a set of window comparators and only light one LED/activate one output at a time, e.g. 1V to 2V input is only output 1 on, 2V to 3V input is output 2 on but 1 off, 3V to 4V input is output 3 on but 1 and 2 off, and so on. Is it right?
But I tried to think about it, Maybe parallel comparators referenced to the next reference voltage up or something? An enable/high Z pin on the comparators in the simplified schematic? Bar mode is easy to simulate, it's the same circuit as the simplified schematic.
Do any amazing people know about this? Thanks

[Moderator Note: Post has been edited to delete a questionable link. Here is a more generic link to the datasheet]

https://www.ti.com/product/LM3914?keyMatch=LM3914
 
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Answers and Replies

  • #2
tech99
Gold Member
2,204
844
Summary:: LM3914V is a chip that drives 10 LED-based on linear input voltage values.

Hi , all!
The LM3914V can light all LEDs/activate all outputs on a rising input similar to a VU meter kind of thing or function more like a set of window comparators and only light one LED/activate one output at a time, e.g. 1V to 2V input is only output 1 on, 2V to 3V input is output 2 on but 1 off, 3V to 4V input is output 3 on but 1 and 2 off, and so on. Is it right?
But I tried to think about it, Maybe parallel comparators referenced to the next reference voltage up or something? An enable/high Z pin on the comparators in the simplified schematic? Bar mode is easy to simulate, it's the same circuit as the simplified schematic.
Do any amazing people know about this? Thanks
I think the chip has a string of comparators and the reference for each is taken from a string of resistors forming a potential divider across the supply. I think the data sheet gives the schematic. I found the bar graph display a bit power hungry and also tended to be unstable. I have used both the linear version and the log version, and I have also used the chip as an A to D converter to demonstrate pulse code modulation using 4 bit coding.
 
  • #3
Baluncore
Science Advisor
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4,176
Maybe parallel comparators referenced to the next reference voltage up or something?
A column of series resistors provide reference voltages spaced between Rhi and Rlo.
Comparators check the input voltage Vin, against all the reference voltages.

In one LED only mode, the digital outputs of adjacent comparators go to XOR gates that turn on the LED where the comparator outputs are different. Rather than a bar, that will show only one LED on.
 
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Likes Tom.G and dlgoff

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