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LM Fluid Detector. The is a monolithic bipolar integrated circuit designed for use in fluid detection systems The circuit is ideal for detecting the presence. LM datasheet, LM circuit, LM data sheet: NSC – Fluid Detector, alldatasheet, datasheet, Datasheet search site for Electronic Components and. LM Datasheet, LM PDF, LM Data sheet, LM manual, LM pdf, LM, datenblatt, Electronics LM, alldatasheet, free, datasheet.

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The oscillators output is directly available at pin 5 and the Rx connects the oscillator output to the datasgeet through the blocking capacitor. Capacitor Cb couples the oscillator output to the probe and it ensures that no DC signal is applied to the probe. Level indicator using external reference resistor. With the give value of C1 the frequency will be around 6KHz.

Liquid level indicator admin October 12, 11 Comments. When the probe is not touching the water it equal to an open circuit situation and surely the probe resistance will be many M ohms and it is greater than the R ref 13K.

You may see the circuit if you are interested. How could I use this circuit to control the Digital input on a microcontroller? Resistor R3 limits the collector current of the internal transistor while resistor R4 provides protection to the IC from transients.

LM Datasheet, PDF – Alldatasheet

The internal transistor will be switched ON and Q1 whose base is connected to the collector of the internal transistor will be in OFF condition keeping the relay inactive. LM based liquid level indicator circuit.


Please refer to the second circuit above. A method for activating a relay when the liquid level exceeds a predetermined level is shown here. The tank must be made of metal and it should be properly grounded. Achei fantastico o site. When the reverse scenario occurs fluid level touches the probe the internal transistor is switched OFF and this in turn makes the transistor Q1 ON resulting in the activation.

Capacitor Ct sets the frequency of the internal oscillator.

LM 데이터시트(PDF) – National Semiconductor (TI)

Pin 9 of the IC can be used to solve this problem. Previous post Next post. Low liquid level indicator LED. Some time there may be situations when the fluid resistance probe to ground do not match with the 13K internal reference resistor.

Leave a Reply Cancel reply Your email address will not be published. A capacitor connected from this pin to ground will keep the internal output transistor steadily ON whenever the probe resistance goes higher than the reference resistor.

Your email address will not be published. There is no problem in driving the LED using AC signal and this method is very useful when it comes to use a loud speaker as the indicator. Usage of AC signal for detection prevents electrolysis and this dagasheet the probes long lasting.


Circuits based on this IC requires minimum number of external components and AC signal is passed through the sensing probe immersed in the fluid.

Hi Challa it is meant for normal water, hence can be used for our domestic use to control over head tank water level. In such cases there is option to avoid the internal reference resistor and an external reference resistor of your choice Rx in the circuit can be employed.

Low liquid level warning audio. You may also like: DC voltage is required for driving the relay and AC voltage cannot datasheft used here just like what we did daatasheet the case of LED and speaker.

LM1830 PDF Datasheet浏览和下载

Hai, Can it be used for Water level indicator in a Over head Tank. High liquid level activated switch. The circuit diagram of a liquid level indicator using loud speaker at its output is shown below.

Atenciosamente… Washington Souza Gomes. Manufactured by National Datashete, the LM can detect the presence or absence of polar fluids. Loud speakers can be driven only by using AC signals and a DC signal will not produce any sound out of the speaker.

The circuit detects the fluid level by comparing the probe to ground resistance with the internal reference resistor R ref.


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