What is a Simple Voltage Level Indicator?
A voltage level indicator is a simple electronic circuit that allows you to measure the immediate voltage between two nodes of any live circuit. It is very easy to design and maintain, but at the same time is one of the most important and frequently utilized electronic configuration seen in everyday consumer electronics. A few examples would be laptop and smartphone batteries, power banks, etc. So, in today’s tutorial, we are going to design a simple Voltage-Level Indicator Using LM3914 Dot/Bar Display LED Driver IC.
The heart of this circuit is an LM3914 IC. LM3914 is an analog controlled LED driver IC. It eliminates the need for programming a microcontroller and also reduces the hardware required to drive the 10 LEDs. The input voltage for LM3914 can vary from 3V to 18V. The IC has two operating modes DOT mode and BAR mode, also more than one IC can be cascaded to control up to 100 LEDs. Since the LEDs can be controlled without any flickering and perform flawlessly with equal brightness these IC’s are commonly used in visual alarms and other metering or monitoring applications.
Hardware Component
You will need the following parts to build this project:
| S.No | Component | Value | Qty |
|---|---|---|---|
| 1) | LED Driver IC | LM3914 | 1 |
| 2) | Piezo Buzzer | 3V | 1 |
| 3) | LEDs | 5mm, 3.5V | 9 |
| 4) | Diode | 1N4007 | 1 |
| 5) | Potentiometer | 10K | 1 |
| 6) | Resistors | 56K, 18K, 4.7K | 1 |
| 7) | Variable Power Supply | DC, 12V | 1 |
| 8) | Soldering Iron | 45W – 65W | 1 |
| 9) | Soldering Wire with Flux | – | 1 |
| 10) | Terminal Block Connector | – | 1 |
| 11) | AVO meter | – | 1 |
| 12) | Veroboard | – | 1 |
| 13) | Jumper Wires | – | As Per need |
LM3914 Pinout
Useful Steps
1) Solder the LM3914 IC on the Veroboard. After that, Solder the -ve terminals of the nine LEDs with pin 1, 18, 17, 16, 15, 14, 13, 12, and pin 11 of the LM3914 IC
2) Solder the -ve terminal of the 3V piezo buzzer with pin 10 of the IC.
3) After that, Solder the variable end of the 10KOhm pot with Pin 4 & fixed ends with pin 3 & pin 2 of the IC.
4) Solder a 56K resistance between pin 3 of the IC and the 10K preset pot.
5) After that, solder an 18K resistor between pin 4 & pin 2 of the IC.
6) Solder a 4.7K resistor between pin 6, 7 and pin 2, 8 of the IC.
7) After that, Solder the +ve of the 1N4007 with Pin 3 & 9 of the IC & the -ve of the diode with the +ve terminals of all the LEDs & the buzzer.
8) After that, Solder the -ve terminal of the block connector with Pin 2 & 8 of the IC & the +ve terminal with pin 9 & 3 of the IC.
9) Power up and test the circuit using an AVO meter
Circuit Diagram For Voltage Level Indicator
Working Explanation
The working of this circuit is pretty simple. A DC input enters the SIGNAL pin of the LM3914 IC. The LM3914 glows the LED triggers the 9 LEDs to glow with respect to the increasing/decreasing level of the input supply voltage. Here we have also connected a 5V buzzer to indicate when the input DC supply has reached the max threshold of the LM3914 IC. Here, the reference voltage at Pin 7 is set by a 4.7K resistor.
The IC has two different mode of LED driving operations, one is the mode and the bar mode. In Dot mode, the MODE pin (pin 9) is open by using a toggle switch, in this mode, only one LED will turn on depending on the input voltage from the DC source. In Bar mode, the mode pin (pin 9) connects to the V+ pin and the LED will turn on or turn off sequentially based on the input voltage.
Applications
- Most commonly used in devices such as power bank and laptops to indicate the immediate charge level of the battery.
See Also: Ding Dong Sound Generator Circuit | How to setup WiFi on Raspberry Pi 3? | LC Meter Circuit using 555 Timer
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