Liquid

Simple humidity detector

The main (and only) job of this circuit is to activate a buzzer or a relay, each time the level of humidity takes a specific value. Main stage is a memory based on a flip-flop consisting of gates and IC1a IC1 b. The output of this step activates an oscillator (IC1c), which in turn leads to a piezoelectric speaker. At the start of operation of the circuit, the flip-flop is driven to logical '0' or through the C1 or through C2. From the moment you excited, the reintroduction of the peace achieved through the switch S1, which however is insufficient if the sensor 82 continues to be wet...

Fluid Sensor Limiter with MC14093B

A nice and small Fluid (water) sensor circuit that drives a relay for every use that comes to your head :)..

Water Detector with Buzzer

This is a simple circuit that can be used as a detector for water, such as a bath full detector. The terminals 'sensor' is connected to the probe. This may consist of two electrodes, or a PCB with surface adjacent tracks, the odd jobs with one socket, and the same with the other. If there is a noticeable drop, there is a running stream, so T1 and T2 are conducting. Bz1 gives a signal. The circuit must be powered for safety with a 9V battery, not with a power supply. The circuit can also be used for leaking washing machines...

Wet soil tester with LED

This is a very simple circuit that can be used to test whether a pot is dry or not. When the two probes are inserted in wet soil, then the resistance between the sensors are low. The base of T1 will therefore be more negative and the LED is not lit. However, when the soil is dry, its resistance will be high and will base more positive. ..

Moisture detector with pump controller

This moisture detector with pump controller is built around the special purpose LM1830 IC. The LM1830 is designed to detect moisture by passing an AC current through a set of probes. An internal comparator compares the resistance of the probes to an internal reference. When the resistance between the probes is low (indicating the presence of water or other conductive liquid) then the IC triggers it's output. An AC signal avoids electroplating and corrosion problems that are common when DC is used. To provide an adjustable delay hysteresis to avoid cycling the pump, a timer based around the 555 is used a range of about 5 seconds to two minutes. In this way the pump will stay active for a set amount of time even if the fluid level is below that of the probes...

Water level alarm

This circuit not only indicates the amount of water present in the overhead tank but also gives an alarm when the tank is full. The circuit uses the widely available CD4066, bilateral switch CMOS IC to indicate the water level through LEDs. When the water is empty the wires in the tank are open circuited and the 180K resistors pulls the switch low hence opening the switch and LEDs are OFF. As the water starts filling up, first the wire in the tank connected to S1 and the + supply are shorted by water. This closes the switch S1 and turns the LED1 ON...

Rain detector alarm

This circuit gives out an alarm when its sensor is wetted by water. A 555 astable multivibrator is used here which gives a tone of about 1kHz upon detecting water. The sensor when wetted by water completes the circuit and makes the 555 oscillate at about 1kHz. The sensor is also shown in the circuit diagram. It has to placed making an angle of about 30 - 45 degrees to the ground. This makes the rain water to flow through it to the ground and prevents the alarm from going on due to the stored water on the sensor...

Emergency Pump Control with 555

A simple Sump Pump Control Circuit using NE555...

Water Level control and monitor with PIC12F675

I found some similar circuits but aren't good enough for me. Some circuits measure the water's resistance to determine the level. That is dangerous for drinking water (contamination) or explosive liquids because electricity is in contact with water. The Pressure sensor have a tube. The tube end on the botton of the tank. When the liquid fill the tank, the pressure inside the tube increase. The 12F675 have A/D converters. The PIC measure the pressure and light up the led corresponding to the liquid level. Green LED = Full, Yellow = Half, Red = Almost Empty. When the tank is completely empty, It turn on the Water pump or activate the buzzer...

Simple Soil Moisture Meter with 741

Stick the metal probes into a freshly watered plant and adjust R5 for a mid-scale meter deflection. The meter will monitor the soil wetness and the meter will indicate whether it is to moist or to dry. This circuit uses a dual power supply which could be created by two 9 volt batteries...

Bedwetting (Enuresis) Alarm with 555 timer

A simple two tone water alarm that is light enough to be worn on the upper arm of a sleeper is described. It uses two LMC555 CMOS timer chips followed by a complimentary pair of emitter followers to drive an 8 ohm speaker. Power is supplied by a 9 volt transistor radio battery. An modification to produce a siren rather than two tone operation is discussed. A little experimentation with a signal generator showed that it would be very loud when driven with only 3 or 4 volts between 800 Hz and 3 kHz. I thought about ways to drive the speaker: use an LM324 quad op-amp followed by a pair of transistors, make a transistor multivibrator and have that drive a transistor buffer, make a couple of oscillators with a hex inverter. Just about the, the UPS delivery truck pulled up and I took delivery of a package from Mouser Electronics, which included among its contents, some LMC555N timer chips that I had ordered in anticipation of a very different project. ..

Plants Humidity Sensor

IC1D is a CMOS Schmitt trigger oscillator at about 2KHz. It starts and continues to oscillate with a supply down to 1.24V (the lowest output voltage of my LM317 variable power supply) or less. IC1A is an inverter. IC1B is a Schmitt trigger NAND gate. Its output is low only when both inputs are at, or higher than the upper Schmitt trigger threshold voltage. With 47 ohms or less between the probes, an input is always low, so the output is always high. With a resistance of only R8 between the probes, the voltage across C3 is high most of the time, so the gate?s output is low for ½ the oscillator?s period. With a resistance that is halfway, then C3 is charged high by that resistance when the oscillator?s output is high, then is discharged when the oscillator?s output is low. ..

Flood Sensor with 12F683

The water detection time is less than 10 seconds. Since the microcontroller enters a low consumption state between readings to preserve battery life, this state is always 10 seconds long. If water reaches the probes while being in the low power state it will have to wait until it finishes the sleep state before it can trigger the alarm. Also, the probes should be placed not to far apart from each other and they never should touch each other. The more probe area available for water sensing the better. After everything is checked ok the detector will enter it's normal state. Every 10 seconds it will check the probes and the battery's voltage...

It is a common problem you are in a bar or restaurant with your drink almost gone and you are desperately hoping that one of the staff will notice and offer you a refill. Sometimes they do, and sometimes they don`t. If they don`t, you leave a little less happy with your experience and are less likely to return, the waiter or waitress gets a lower tip, and the restaurant has lost the chance to sell you a drink. Meanwhile, thirsty customers may stand waiting at the door for lack of a table. Everyone loses. It is such a little thing; yet doing it right or wrong can easily make the difference between economic success or failure...

This circuit will emit an intermittent beep (or will flash a LED) when the water contained into a recipient has reached the desired level. It should be mounted on top of the recipient (e.g. a plastic tank) by means of two crocodile clips, acting also as probes. If a deeper sensing level is needed, the clips can be extended by means of two pieces of stiff wire...