Plant water gauge
To calibrate the gauge, connect the battery and press the probes gently into a pot containing a plant that is just on the verge of needing water (stick it in so...
Single chip pump controller
This circuit controls the level of a tank using a bang-bang controlled electrical pump. The actual level of liquid is measured by a capacitive level-meter. The ...
Water-level sensing and control
The operation of the circuit is based on the difference in the primary impedance of a transformer when its secondary is loaded and when it is open-circuit. The ...
Plant-water monitor
When the soil is moist, the LED glows. If the moisture falls below a certain predetermined level, the LED begins to flash. If there is still less moisture, the ...
Acid rain monitor
A bridge rectifier and 12-volt regulator powers the MOSFET sensing circuit. The unregulated output of the bridge rectifier operates the drain solenoid via switc...
Water-level indicator
In this a warning device WD1 is in series with SCR1. When the liquid level causes a conductive path between the probes, the SCR conducts sounding WD1. The warni...
Thermally based anemometer
This design used to measure air or gas flow works by measuring the energy required to maintain a heated resistance wire at constant temperature. The positive te...
Frequency limit detector
Simple frequency limit detectors providing a GO/NO-GO output for use with varying amplitude input signals may be conveniently implemented with the ICL8211/8212....
Power loss detector
A positive going input charges C through the IN4148 and R. The diode keeps the scs off.
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Window comparator
This circuit provides independently adjustable upper and lower threshold settings, and has sign, in window range, in upper window, and in lower window digital o...
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...
Infrared approach detector / sensor
Basic operation of the monitor attached to the circuit is to detect objects (obstacles), at distances ranging from a few millimeters to and a few centimeters. D...
Temperature measurement using two cables
In those cases we want to measure the temperature in an area far from where it is. The imaging unit installed, you should find some way to connect the latter wi...
2 Axis Solar Tracker Circuit
The sun trucker uses a combination of three photoresistors R7, R8 and R9, to ensure that the circuit will follow the sun during the day, but stop working at nig...
Static charge-electricity detector
The detector will sense static charges and free ions in the air. It can be used to indicate the presence of ion emission, high voltage, static electricity, and ...
Heartbeat monitor
? simple heart-beat transducer can be made from an infrared LED and an infrared phototransistor. ?t works because skin acts as a ref1ecti?e surface for infrared...
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 :)...
Car Exhaust Meter
Bridge circuit contains two resistors lOO-ohm (R3 and R4), and two thermistors (Tl and T2). At room temperature, the resistance of T1 and 1'2 is about 2000 ohms...
Light to Frequency Converter TSL220
A large area photodiode and current to frequency converter combined in a clear plastic 8-pin DIL package. The output is a pulse train whose frequency is directl...
Humidity Sensor with the H14DL
A humidity sensor with temperature compensation built-in. Never apply a DC voltage to the sensor, even measuring the sensor with an ohmmeter will damage the dev...