Liquid level indicator
LM1830 based liquid level indicator circuit. LM1830 is a monolithic integrated circuit that can be used in liquid level indicator / control systems. Manufactured by National Semiconductors, the LM1830 can detect the presence or absence of polar fluids . Circuits based on this IC requires minimum number of external components and AC signal is passed through the sensing probe immersed in the fluid. Usage of AC signal for detection prevents electrolysis and this makes the probes long lasting. The... read moreDigital compass circuit
Description. Here is the circuit diagram of a very simple and accurate electronic compass using the 1490 digital compass from Dinsmore. The 1490 digital compass is a solid state Hall Effect device which is sensitive to detect the Earth’s magnetic field. The sensor is internally damped to simulate the performance of an ordinary compass. The circuit shown here is the simplest one that can be built around this sensor. The sensor has 12 pins at the bottom which are... read moreTemperature controlled LEDs
Description. The circuit is nothing but two LEDs (D1 and D2), whose status are controlled by the temperature of the surroundings. The famous IC LM35 is used as the temperature sensor here. Output of LM35 increases by 10mV per degree rise in temperature. Output of LM35 is connected to the non inverting input of the opamp CA3130.The inverting input of the same opamp can be given with the required reference voltage using POT R2. If the reference voltage is... read moreZero degree Celsius alarm
Description. This simple circuit will produce an alarm whenever the temperature falls below zero degree. A thermistor is used here to sense temperature. The op-amp LM7215 is used to compare the reference voltage and voltage from the thermistor network. Reference voltage is given to the non inverting input (pin3) of the IC and voltage from thermistor network is given to the inverting input (pin4).When temperature becomes less than zero degree the voltage at the non inverting input becomes larger... read moreVHF field strength meter
Description. This is a simple and low cost wide band VHF field strength meter. The field strength is measured by converting the radio signal to DC and measuring it. The RF signal will be picked up by the coil and rectified by the diode D1.Even a very small DC voltage is sufficient to alter the biasing of FET and it will be reflected in the meter as an indication of the presence of a radio signal. The meter can... read moreElectromagnetic field sensor circuit
Notes. This is a very simple circuit that can be used to sense electromagnetic radiations. The circuit can even detect hidden wrings. A 1mH inductor is used for sensing the electric field. The electric field will induce a small voltage in the sensor inductor and this induced voltage is amplified by the opamp.The headphone connect at the output of the opamp will give an audio indication of the electric field. For example, the electric field around a mains transformer... read moreSingle chip metal detector circuit
Description. This is a simple single chip metal detector circuit based on IC CS209A from the Cherry Semiconductors. A 100uH coil is used to sense the presence of metal. The IC CS209A has a built in oscillator circuit and the coil L1 forms a part of its external LC circuit which determines the frequency of oscillation. The inductance of the coil change in the presence of metals and the resultant change in oscillation is demodulated to create an alarm.... read moreTouch switch using CD4011.
Description. A simple touch switch circuit using CD4011 is given here. The IC CD4011 is wires as a flip flop here. The 9, 13 pins of the IC works as the set and reset contacts respectively.CMOS ICs like 4011 require requires a very low current for controlling its gates. Since the pins 9 and 13 are connected to the positive via resistors R1 and R2, the logic gates of the ICs will be in high state. When we touch... read moreWater Sensor Circuit with Alarm
If you are looking for a Water level indicator or a Water level controller, there are pretty good circuits we have developed. This one is just a fun project made for hobby purpose! You can call this a water sensor circuit for sure! Description. This is a simple musical alarm circuit which produces a musical tone when water or some conducting liquid comes in contact with the two sensor wires provided. The circuit is based on four transistors and... read more