This circuit shows you how to build a sensor to check the liquid level in a tank or container.
It uses special probes that can tell if there is liquid touching them by sending a tiny electrical signal.
This circuit design helps prevent corrosion because it does not use any harsh chemicals.
Circuit Working:
Parts List:
| Component | Value | Quantity | Notes |
|---|---|---|---|
| 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 | ||
| Others | |||
| Relay | 12V | 1 |
Specifically, a pair of CMOS gates is utilized which can be implemented using a single IC 4093.
The IC 4093 containing four NAND gates with Schmitt trigger characteristics provides, the flexibility to construct two units for simultaneous detection and control of two liquid levels.
The Schmitt trigger property allows these gates to operate with hysteresis enhancing accuracy and control in the system.
In this liquid level sensor application two NAND gates are employed as inverters by shorting their input pins, essentially functioning as NOT gates with schmitt trigger capability.
The first gate N1 is configured as an oscillator to apply a frequency across the sensing probes.
This oscillating electrical pulse helps prevent corrosion of the probes ensuring their durability particularly in applications like water level sensing where the probes may be immersed for extended periods.
The second gate N2 serves as a buffer stage establishing a conductive path across the probes when the liquid reaches the desired level.
Upon detection a slight pulsating current triggers a high logic level at the input of N2.
This high logic output causes an inverted low logic at the output of N2 activating a PNP BJT bipolar junction transistor.
The BJT activation, in turn triggers a relay, leading to an immediate cut off of the rising liquid by deactivating the relevant pump through its contact wiring.
Appropriate wiring of the relay with the fluid pump motor is essential depending on whether the container holds water or another fluid.
For any queries or clarifications regarding this basic fluid level detection circuit which can also function as a corrosion free water level controller circuit please feel free to comment below for prompt responses.
Formulas:
One of the many uses for a NAND gate oscillator circuit is as a liquid level sensor to prevent corrosion.
The following formula may be used to estimate the oscillation frequency (f) of a NAND gate oscillator circuit:
f = 1 / 2.2 × R × C
Where:
- R: is the resistance in ohms.
- C: is the capacitance in farads.
Based on the values of the resistor R and capacitor C in the oscillator circuit, this calculation yields an estimated frequency.
How to Build:
To build the anti corrosion free liquid level sensor circuit described you can follow the connection steps:
Power Connections:
- Connect the positive and negative terminals of the power supply to the appropriate terminals on the breadboard.
IC 4093 Setup:
- Place the IC 4093 on the breadboard.
- Connect pin 7 to the positive supply and pin 14 to the negative supply.
Oscillator Circuit N1:
- Connect pin 1 N1A input to pin 2 N1A output.
- Connect a resistor between pin 2 and pin 6.
- Connect a capacitor between pin 2 and the negative.
- Connect the probe for liquid level sensing to 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.
- Apply power to the circuit and observe its behavior.
- Adjust resistor and capacitor values for the oscillator circuit if necessary to achieve the desired frequency for liquid level sensing.
Conclusion:
Please note that this is a basic guide and the specific resistor and capacitor values, as well as the overall circuit configuration may need adjustment based on your specific requirements and the characteristics of the liquid being sensed.
Always exercise caution when working with electronic components and circuits.
References:
Preventing corrosion to sensor by eliminating all voltage on pin?