Simple Water Level Indicator Circuit using IC ULN2004

This Simple Water Level Indicator Circuit using IC ULN2004 work like small helpers for our water tank.

It uses one special chip named as ULN2004 to control many things together.

This chip can work with big electricity but here it only control lights.

The lights show how much water is inside the tank.

So with this circuit we can see easily if tank need more water or if water is too much.

Circuit Working:

Parts List:

This water level indicator circuit shows easily signaling for how much water is in overhead tank.

Circuit is simple as it uses one IC and some small parts.

Main part is one IC called ULN2004 and it have 7 channel Darlington array.

Each input of this IC connects to one metal probe to check water and output connects to LEDs with resistors.

One common probe is connected to positive wire.

When water touches the probe it makes connection and light LED turns ON.

We can make this on normal PCB board and put it in small box which is easy to keep.

Use brass or chrome pins for probes and connect with 3 core shielded wire.

Fix probes in a tank from side and put one low, one middle and one high.

When there is no water then there will be no light.

When water goes up then green lights turn ON slowly.

When tank is full red light turns ON.

So if all green and red lights are ON then tank is full.

Formula:

From this circuit diagram, we can use formula for Power Dissipation and Heatsink for IC ULN2004:

Power Dissipation and Heatsink:

ULN2004 have maximum power limit.

If we use big current on output then maybe it may need heatsink and so it is better to check power use.

Use this formula:

Pd = Vout × Iout

where:

• Vout is the voltage at output in volts
• Iout is the current at output in amps

Important Info:

To know max current, voltage and more details then see ULN2004 datasheet.

Datasheet also show power curve to help us choose the heatsink.

ULN2004 design is strong for normal use and mostly no extra math needed.

But above idea still helps in some cases.

How to Build:

To build a Simple Water Level Indicator circuit using IC ULN2004 we need to follow the below mentioned connection steps:

Prepare the PCB:

• Design or get one PCB layout that fit ULN2004 IC, resistors, LEDs and wire for probes.
• Put all parts on PCB like in above circuit diagram.

Assemble the parts:

• Solder ULN2004 IC on PCB and be sure to put it correct way.
• Solder resistors to LED anode side and then connect LED cathode to output pin of ULN2004.

Connect the probes:

• Connect 7 probes to input pins of ULN2004 IC.
• One probe is common probe and connect this one to positive wire.

Put in box:

• Place PCB inside small box and fix it so it may not move.
• Make small holes in box for probe wires to come out.
• Close and seal box so no water go inside.

Fix probes in tank:

• Put probes from side of a tank.
• Low probe go bottom, middle probe in center, and high probe on top.
• Use 3 core shield wire to connect probes to PCB.

Testing:

• Turn ON power and fill tank with water.
• Check if LEDs turn ON step by step as water goes up.
• Be careful and always follow safety rules when working with electric and water.

Conclusion:

To conclude this Simple Water Level Indicator Circuit using IC ULN2004 is easy and good way to check water level in overhead tank.

It uses Darlington transistor array inside the IC and some small parts to show water level using LEDs.

This project is not too hard to make and can help in water saving and control system.

References:

Water level indicator using ULN2803

Datasheet IC ULN2004