LM3914 IC: Pin Configuration, Circuit Working and Applications

In the year 1980, National Semiconductor was launched the IC LM3914 and is still obtainable from Texas Instruments. The IC LM3914 is one kind of integrated circuit, mainly used to activate displays that visually display an analog signal’s magnitude. A single IC can drive many displays like 10 LCDs, vacuum fluorescent otherwise LED displays. A single LM3914 can drive up to 10 LEDs, LCDs, or vacuum fluorescent displays on its outputs. The output threshold linear scaling will make the apparatus functional like a voltmeter. In the basic pattern, it gives a 10 step scale which is flexible to over hundred sections with additional LM series integrated circuits in series. Two alternatives to this IC are the LM3915 and LM3916.

LM3914 IC Pin Configuration

The LM3914 IC pin configuration is discussed below. The DIP version (Dual-inline Package) of this IC includes 18-pins, where the polarity can be specified with both a notch as well as a dot. Half of the pins of this IC can be in charge of driving the light emitting diodes, and the remaining pins are used for controlling the IC, reference voltages and power.

LM3914 IC Pin Configuration
LM3914 IC Pin Configuration
    • Pin1: (LED1, LED2, LED3,..LED10): The LED which has to be operated is allied to these pins
    • Pin2: (V- or Ground): GND pin of the integrated circuit
    • Pin3: (V+ or Vcc): Supply voltage ranges from 3V to 18V
    • Pin4: (RLO): Low-level voltage used for potential divider
    • Pin5: (Signal): Input pin analog signal based on which the LED is controlled.
    • Pin6: (RHI): High-level voltage used for potential divider
    • Pin7: (Ref Out): Reference voltage of Output for limiting the LED current
    • Pin8: (Ref Adj): Adjust pin used for voltage reference
    • Pin9: (Mode): Choose among Dot or Bar Mode

LM3914 IC Features

The features of the LM3914 IC include the following

  • It can drive LCDs, LEDs otherwise vacuum fluorescents. The dot otherwise bot display mode can be selected by the user externally.
  • It can be expandable upto100 displays.
  • The internal voltage ranges from 1.2V-12V
  • The operating voltage will be less than 3V
  • The programmable output current ranges from 2 mA-30 mA
  • Multiplex switching is not necessary or communication among outputs.
  • The outputs of LED drivers are open collectors and current regulated.
  • The outputs interfacing can be done by CMOS logic otherwise TTL

IC LM3914 Based Alarm Driver Circuit

The circuit configuration of an IC LM3914 is shown below. The circuit can be built with basic electrical as well as electronic components. The essential component of this circuit is IC Lm3914. In the following circuit, an alarm driving switch for over range can be connected to a bar type LM series LED driving display circuit. This circuit can be used for bar type displays.

IC LM3914 based an Alarm Driver Circuit
IC LM3914 based an Alarm Driver Circuit

Here the circuit uses a PNP transistor which is specified with Q1. The connection of this transistor can be done among the LED positive terminal as well as the negative terminal, and the base terminal of the transistor is connected to the pin-10 of the IC to make the LED10 drive. An alarm unit is connected to the collector terminal of the transistor in series.

Usually, Q1 transistor, LED10 and alarm unit will turn off, however, if LED10 is activated, then it pulls Q1 transistor through resistor R2 & therefore activates the alarm unit, that specifies the condition of over range.

In the above circuit, an alarm unit uses the piezo siren unit form for generating an acoustic alarm sound otherwise a gated astable switch unit that continuously activates the LED brightness among high as well as low levels beneath the over-range state or combination of both. If preferred, the unit can be switched with any one of the LED display, the alarm will trigger when that otherwise any high LED will be energized.

Applications of LM3914 IC

The LM3914 IC can be used to build electronic projects that include the following.

  • Battery Meter for Robot
  • Monitoring of 12V Car Battery
  • Tester Circuit for Soil Moisture
  • Monitoring of Lead Acid Battery Charger
  • Charge Monitoring Circuit for Atmospheric
  • Kitchen Exhaust Fan for Controlling Temperature
  • Meter Circuit for Temperature
  • Digital gauges
  • Electronic displays
  • Low-cost monitor devices
  • Crude Battery level indicators
  • Fade bars

Thus, this is all about LM series IC pin configuration, circuit working with applications. From the above information, finally, we can conclude that LM3914 is a monolithic IC that detects analog voltage levels as well as drives all the LEDs by offering a linear analog display. A solitary pin can change the display from a traveling dot toward a bar graph. The drive of current toward the light emitting diodes is regulated as well as programmable, removing the necessitate for resistors. This characteristic is one that permits the whole system’s operation from less than 3V. Here is a question for you, what is the function of the LM3914 IC?



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