What is the functionality of the LM3914V driver?

  • Thread starter GUOJINMIAO
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In summary: 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.Maybe parallel comparators referenced to the next reference voltage up or something?
  • #1
GUOJINMIAO
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TL;DR 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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  • #2
GUOJINMIAO said:
Summary:: LM3914V is a chip that drives 10 LED-based on linear input voltage values.

Hi , all!
Thehttps://www.utmel.com/components/lm3914v-driver-alternatives-pinout-datasheet?id=328 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.
 
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Likes DaveE
  • #3
GUOJINMIAO said:
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

Related to What is the functionality of the LM3914V driver?

1. How does the LM3914V driver work?

The LM3914V driver is a monolithic integrated circuit that is designed to sense analog voltage levels and drive a display of 10 LED bars in a linear manner. It uses a voltage divider network and a comparator to compare the input voltage to a reference voltage and turn on or off the corresponding LED bar based on the result of the comparison.

2. What is the maximum voltage that can be applied to the LM3914V driver?

The maximum supply voltage for the LM3914V driver is 25V. This means that the input voltage should not exceed 25V, otherwise it can damage the driver.

3. How many LEDs can be driven by the LM3914V driver?

The LM3914V driver can drive up to 10 LEDs. Each LED bar represents one step of the input voltage, so if the input voltage range is divided into 10 steps, then each LED bar will correspond to one step.

4. Can the LM3914V driver be used with different types of LEDs?

Yes, the LM3914V driver can be used with a variety of LEDs, including standard LEDs, high-brightness LEDs, and even incandescent bulbs. However, it is important to make sure that the maximum current rating of the LEDs does not exceed the current output of the driver.

5. How can I adjust the brightness of the LEDs driven by the LM3914V driver?

The brightness of the LEDs can be adjusted by changing the value of the current-limiting resistor connected in series with each LED. Increasing the resistance will decrease the current and therefore decrease the brightness, while decreasing the resistance will increase the current and brightness. It is recommended to use a potentiometer in place of the resistor to have a variable brightness control.

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