Liquid-level-monitor
This monitor utilizes a common 741 op-amp configured as a comparator along with a low-cost non-transistor output driver. In the absence of liquid, a voltage of approximately 2.92 V is present at the inverting input (pin 2) of the op-amp. The 100 kΩ resistors establish a reference voltage of +2.5 V at the non-inverting input (pin 3) of the op-amp. Under these conditions, the output of the op-amp is -3.56 V, which keeps the 2N2222 transistor turned off, resulting in a voltage of 0 V across its 1 kΩ output load resistor. When liquid reaches the probes, the 3.3 MΩ and 22 kΩ resistor circuit connects to ground. When sufficient current, approximately 1.4 µA, flows through the liquid, a small voltage drop of about 30 mV across the 22 kΩ resistor drives the op-amp to produce an output voltage of approximately 4.42 V. This output voltage then drives the 2N2222 transistor into saturation, generating a voltage drop of about 3.86 V across its 1 kΩ output load resistor.
The circuit operates as a liquid detection system, employing a 741 operational amplifier configured as a comparator to monitor the presence of liquid. The inverting input of the op-amp is connected to a voltage source that maintains a stable level of approximately 2.92 V. The non-inverting input is set to a reference voltage of +2.5 V using a voltage divider formed by two 100 kΩ resistors. This configuration ensures that when no liquid is detected, the output of the op-amp remains at -3.56 V, effectively keeping the transistor (2N2222) in an off state and preventing current from flowing through the output load resistor.
When liquid is introduced to the probes, the circuit formed by the 3.3 MΩ and 22 kΩ resistors creates a conductive path to ground. As the liquid conducts, it allows a small current of approximately 1.4 µA to flow. This current creates a voltage drop of about 30 mV across the 22 kΩ resistor, which is sufficient to raise the voltage at the non-inverting input above the inverting input threshold. Consequently, the op-amp output switches to approximately 4.42 V, signaling the presence of liquid.
The output from the op-amp drives the 2N2222 transistor into saturation, allowing a larger current to flow through the output load resistor. The voltage drop across this resistor is about 3.86 V, indicating that the transistor is fully on and providing a clear signal that liquid has been detected. This configuration is ideal for applications requiring reliable liquid level detection, leveraging the cost-effective components while ensuring operational efficiency. The use of a 741 op-amp and a 2N2222 transistor allows for a straightforward and effective design suitable for various electronic monitoring systems.This monitor uses a common 7 41 amp configured as a comparator and a low cost nontransistor as an output driver. With no liquid detected, a voltage of about 2. 92 V is present in the op amp"s inverting input at pin 2. The 100-KO resistors establish a reference voltage of +2. 5 V at the noninverting input at pin 3 of the op amp. Under those conditions, the op amp"s output is -3.56 V, which keeps the 2N2222 transistor turned off and the voltage across its 1-KO output load resistor at 0 V.
When liquid reaches the probes, the 3.3-MO and 22-KO resistor circuit conductively connects to ground. When enough current, about 1.4 p.A, flows through the liquid, the small 30 m V drop developed across the 22-KO resistor drives the op amp to deliver an output voltage of about 4.42 V.
This voltage then drives a 2N2222 transistor into saturation, which generates a voltage drop of about 3.86 V across its 1-KO output load resistor.
The circuit operates as a liquid detection system, employing a 741 operational amplifier configured as a comparator to monitor the presence of liquid. The inverting input of the op-amp is connected to a voltage source that maintains a stable level of approximately 2.92 V. The non-inverting input is set to a reference voltage of +2.5 V using a voltage divider formed by two 100 kΩ resistors. This configuration ensures that when no liquid is detected, the output of the op-amp remains at -3.56 V, effectively keeping the transistor (2N2222) in an off state and preventing current from flowing through the output load resistor.
When liquid is introduced to the probes, the circuit formed by the 3.3 MΩ and 22 kΩ resistors creates a conductive path to ground. As the liquid conducts, it allows a small current of approximately 1.4 µA to flow. This current creates a voltage drop of about 30 mV across the 22 kΩ resistor, which is sufficient to raise the voltage at the non-inverting input above the inverting input threshold. Consequently, the op-amp output switches to approximately 4.42 V, signaling the presence of liquid.
The output from the op-amp drives the 2N2222 transistor into saturation, allowing a larger current to flow through the output load resistor. The voltage drop across this resistor is about 3.86 V, indicating that the transistor is fully on and providing a clear signal that liquid has been detected. This configuration is ideal for applications requiring reliable liquid level detection, leveraging the cost-effective components while ensuring operational efficiency. The use of a 741 op-amp and a 2N2222 transistor allows for a straightforward and effective design suitable for various electronic monitoring systems.This monitor uses a common 7 41 amp configured as a comparator and a low cost nontransistor as an output driver. With no liquid detected, a voltage of about 2. 92 V is present in the op amp"s inverting input at pin 2. The 100-KO resistors establish a reference voltage of +2. 5 V at the noninverting input at pin 3 of the op amp. Under those conditions, the op amp"s output is -3.56 V, which keeps the 2N2222 transistor turned off and the voltage across its 1-KO output load resistor at 0 V.
When liquid reaches the probes, the 3.3-MO and 22-KO resistor circuit conductively connects to ground. When enough current, about 1.4 p.A, flows through the liquid, the small 30 m V drop developed across the 22-KO resistor drives the op amp to deliver an output voltage of about 4.42 V.
This voltage then drives a 2N2222 transistor into saturation, which generates a voltage drop of about 3.86 V across its 1-KO output load resistor.