Meanwhile, in bar mode, all eight LEDs will be on. If 1 or no LEDs are lit, it can mean the battery is dead. How the Circuit Works The potentiometer is the mainstay of the circuit. We simply have to connect the 10 LEDs to the IC, set the reference voltages for input voltage and limit the current through the LED and we are all set. In dot mode the mode pin pin 9 has to be left floating, in this mode only one LED will be turned on based on the input voltage.

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Pin 5 is a very important pin. Pins 1 and are the output pins.

LM3914 Dot/Bar Display Driver IC

As you might have noticed we have connected all the 10 LEDs directly to the IC without any current limiting resistor this is because the IC has an internal current limiter and the value of current can be set by using the pin VRO pin 7. Since we are using LEDs with such long leads, we simply connect pin 4 to ground.

In this circuit, we will be using the same for both.

This is the signal pin. Since the reference voltage is 5V and there are 10 LEDs, each 0. The potentiometer we will use can really be of any value.


If 5 LEDs are lit, this could mean it’s at half strength. The LM is an pin chip. How to use a LM? Dot mode only lights up a single LED at a time. TL — Programmable Reference Voltage.

As we increase voltage, more LEDs turn on. We place a toggle switch on this pin so that we can switch between the 2. In this circuit, we’re going to use the LED bar graph to show the level of voltage that a potentiometer has.

This includes the pinout and all the details of how to connect the LED Bar graph. We do and show the math below so that there’s a exact relationship between the voltage and the LEDs lit on the bar graph.

How to Build an LM3914 Dot/Bar Display Driver Circuit

So you can use whatever you have. The formulae to calculate the current is given below, where I is the current through each LED and RL is the resistor connected to pin 7.

The same voltage that powers the chip can be used for V LED We do not have to connect current-limiting resistors to the LEDs because the R1 resistor functions as the current-limiting resistor.

Using 10mA, resistor R1 calculates out to be 1. We connect one end terminal to 5V and the other end terminal to ground, while connecting the wiper terminal to pin 5. Depending on the its resistance affects the voltage directly.


LM Dot/Bar Display Driver Pinout, Datasheet, Features & Equivalent

The IC can operate in two different modes, one is bae dot mode and the other is bar mode. If all 10 LEDs are lit, this could mean full strength. Since we are monitoring V here, the low reference voltage pin 4 is set at 0V and the high reference voltage pin 6 is set to 5V. This varies the voltage that is fed into the LM If 1 or no LEDs are lit, it can mean the battery is dead.

LM Dot/Bar Display Driver IC | NightFire Electronics LLC

This establishes power to the chip. According to the datasheet, a good current to flow through the LEDs is displlay. How we go about computing this is this: This circuit can be a building block to build a number of other circuits. In the above example we have used a ohm resistor as Rl and hence the current through each LED will be around 25mA, you can modify the value as required. Pin 4 is the R LO. The formulas and math elcetronic how this was calculated was shown above.

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