This circuit teaches how to construct a sensor that measures the level of liquid in a tank or other container.
By delivering a small electrical signal it uses specific probes to detect whether liquid has touched them.
This circuit design uses no harsh chemicals which helps avoid corrosion.
Circuit Working:
Parts List:
| Component | Quantity |
|---|---|
| Resistors (All resistors are 1/4 watt unless specified) | |
| 470k | 2 |
| 10M | 2 |
| Capacitors | |
| Ceramic 2.2nF | 4 |
| Semiconductors | |
| IC 4093 | 1 |
| Transistors BC557 | 1 |
| Diodes 1N4148 | 3 |
| Relay 12V | 1 |
A single IC 4093 is easily used to construct a pair of CMOS gates.
With its Schmitt trigger features and four NAND gates the IC 4093 provides the ability to build two units for both detection and control of two liquid levels.
These gates can work with hysteresis due to the Schmitt trigger characteristic which improves system control and accuracy.
By shorting their input pins two NAND gates which basically act as NOT gates with Schmitt trigger capability are used as inverters in this liquid level sensor application.
An oscillator is set up at the first gate N1 to apply a frequency across the sensing probes.
This oscillating electrical pulse ensures the probes strength by avoiding corrosion especially in applications like water level monitoring where the probes can get immersed for long periods of time.
When the liquid reaches the right level the second gate N2 acts as a buffer stage creating a conductive route across the probes.
When a little pulsing current is detected a high logic level is set at N2s input.
A PNP BJT bipolar junction transistor is activated by this high logic output which results in an inverted low logic at the N2 output.
By deactivating the correct pump through its contact wire the BJT activation in turn sets off a relay which instantly stops the rising liquid.
Depending on whether the container stores water or another fluid the relay and fluid pump motor need to be wired correctly.
Please feel free to leave a remark below for quick answers if have any questions or need any explanations about this simple liquid level sensing circuit which can also be used as a corrosion free water level controller circuit.
Formulas:
A NAND gate oscillator circuit can even be used as a liquid level sensor to stop corrosion among other possible uses.
A NAND gate oscillator circuits oscillation frequency (f) can possibly be estimated using the below mentioned formula:
f = 1 / 2.2 × R × C
where:
- R is the resistance in ohms.
- C is the capacitance in farads.
This calculation provides an estimated frequency based on the values of the oscillator circuits resistor R and capacitor C.
How to Build:
To build a Simple Anti Corrosion Free Liquid Level Sensor Circuit following steps can be followed for the connection:
Connections for Power:
- The power supplies positive and negative terminals should be connected to the right terminals on the breadboard.
IC 4093 Configuration:
- The IC 4093 should be placed on the breadboard.
- Connect pins 7 and 14 of IC 4093 to the positive and negative supplies respectively.
Circuit N1 of the oscillator:
- Connect the pin 2 N1A output to the pin 1 N1A input.
- A resistor should be connected between pins 2 and 6 of IC.
- A capacitor should be connected between pin 2 and the negative.
- Connect the liquid level detecting probe to both pin 1 and the negative.
Buffer Stage N2:
- Connect pin 12 N2A input to pin 11 N2A output.
- Connect the probe for liquid level sensing to pin 12.
- Connect pin 8 N2B input to pin 9 N2B output.
- Connect a diode between pin 9 and pin 6.
- Connect the base of the PNP transistor to pin 9 via a resistor.
- Connect the collector of the PNP transistor to the positive supply.
- Connect the emitter of the PNP transistor to one side of the relay coil.
- Connect the other side of the relay coil to the negative supply.
Relay Switching:
- Connect the common contact of the relay to the pump motor.
- Connect the normally open NO contact of the relay to the power supply.
- Connect the normally closed NC contact of the relay to the pump motor.
- Turn on the circuit and watch how it works.
- If required modify the oscillator circuits resistor and capacitor values to get the required frequency for liquid level sensing.
Conclusion:
Please keep in mind that this is only a starting point and depending on specific requirements and the qualities of the liquid that is being detected the exact resistor and capacitor values as well as the overall circuit design needs to be adjusted.
When working with electronic circuits and components take proper precaution.
References:
Preventing corrosion to sensor by eliminating all voltage on pin?