Introduction: Water Level Indicator Using ULN 2003 IC

Water overflow from the overhead tank is a issue for everyone and in every household. It, along with wastage of electricity also causes lots of water wastage and with new laws being passed water wastage even on tank overflow could be penalised.

Thus here I am presenting a easy and simple DIY project for all enthusiasts and students that will have a environmental impact also.

To keep it with zero noise pollution project I have not included a buzzer in this.

It requires easily available and cheap components.

This instructable is sponsored by


ULN2003 IC

330 Ohm Resistors (0.4W) - 7

LEDs - RED, Green,Yellow/blue

Wires - sufficient length from the water tank to the suitable position of the level monitor ( 7 wires)

Step 1: Circuit

Few things to know about ULN2003A IC

The ULN2003A is an array of seven NPN Darlington transistors capable of 500 mA, 50 V output.

It features common-cathode flyback diodes for switching inductive loads.

The seven Darlington pairs in ULN2003 can operate independently except the common cathode diodes that connect to their respective collectors.

The ULN2003 is known for its high-current, high-voltage capacity. The drivers can be paralleled for even higher current output.

Main specifications:

500 mA rated collector current (single output)

50 V output

Includes output flyback diodes

Inputs compatible with TTL and 5-V CMOS logic

Water Level Circuit

It works on the same principle as the NPN transistors work but in a more compact design outline. The ULN2003A is 7 NPN transistors in one package.

Step 2: PCB Design

I have used EasyEda to design the 2-layer PCB.

Gerber Files Link

EasyEDA Project link

Step 3: Step 3 : Ordering the PCBs

Now we have got the PCB design and it’s time to order the PCB’s. For that, you just have to go to , and click on “QUOTE NOW” button.

JLCPCB are also sponsor of this project. JLCPCB (Shenzhen JLC Electronics Co., Ltd.), is the largest PCB prototype enterprise in China and a high-tech manufacturer specializing in quick PCB prototype and small-batch PCB production. You can order a minimum of 5 PCBs for just $2. To get the PCB manufactured, upload the gerber file you downloaded in the last step. Upload the .zip file or you can also drag and drop the gerber files. After uploading the zip file, you’ll see a success message at the bottom if the file is successfully uploaded. You can review the PCB in the Gerber viewer to make sure everything is good. You can view both top and bottom of the PCB. After making sure the PCB looks good, you can now place the order at a reasonable price. You can order 5 PCBs for just $2 plus shipping. To place the order, click on “SAVE TO CART” button. My PCBs took 2 days to get manufactured and arrived within 20 days using standard registered post delivery option. There are fast delivery options also available.PCBs were well packed and the quality was really good.

Step 4: Assembling and Working

The R8 resistor is optional based on the input current, in testing a lipo battery (4.2V) does not require the resistor for the circuit to work safely.

Also the jumper is optional, it will act a on/off switch if required.

The wire connected to the tank terminal is placed at the bottom of the tank. Then all the other wires from 0 to overflow are placed at respective levels in the tank preferably attached to a non conductive pole of sorts that can be placed in the water.

As the water level of the overhead tank rises the LEDs starts to light up in sequence like a bar graph.

After assembling everything and connecting the wires, it looks as shown in images.

NOTE: there will be salt deposits on the open wire ends in the tank if the water in your locality is hard water, then you need to clean the salt deposits on a regular basis.