Build Your Hot Water Level Indicator Circuit

Description:

A straightforward device for indicating various temperature levels within a vessel.

Circuit Diagram

Notes:

Reduce energy expenditure and contribute to environmental sustainability with this circuit. SW1 is a normally open push button switch enabling the observation of the temperature of the vessel. When activated, the voltage difference at the junction of the thermistor and preset is compared to the fixed voltage on the op-amps non-inverting input. Depending on the temperature of the contents, the thermistors resistance will trigger the op-amp output to swing towards almost full supply voltage and illuminate the appropriate LED.

Construction:

Masking tape was employed to affix the bead thermistors to the vessel. Wires were soldered and insulated at the thermistors' ends. A plastic enclosure was utilized for housing the circuit. Battery lifespan is anticipated to be approximately 4 to 5 years, contingent on the frequency of operation of the push switch, SW1.

Sensor Placement:

Thermistors NTC1-4 should be distributed evenly across the height of the vessel. I positioned NTC1 roughly 4 inches from the top of my vessel and the others were spaced uniformly along the height of the vessel. As temperature increases, the sensor at the bottom of the vessel indicates the maximum level of temperature and should be situated about 8 to 10 inches from the base of the vessel.

Calibration:

With a full vessel of hot contents, adjust P1-4 so that all LEDs are illuminated. As temperature rises, the sensor at the bottom of the vessel will represent the peak temperature level. "Hot" can be defined as 50°C to 80°C, and the presets P1-4 facilitate adjustment of this range.

Parts: