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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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 also like: Achei fantastico o site.

Low liquid level warning audio. The load that is the relay is connected at the collector of Q1. Previous post Next post. For non metal tanks fix a small metal contactor at its bottom level and ground it. The tank must be made of metal and it should be properly grounded.

The probe must be placed at the level you want to monitor. Your email address will not be published. Level indicator using external reference resistor. Some time there may be situations when the fluid resistance probe to ground do not match with the 13K internal reference resistor.

There l1m830 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. LM based liquid level indicator circuit. Hi Challa it is meant for normal water, hence can ratasheet used for our domestic use to control over head tank water level. You have to connect the tweeter between Pin No12 and Vcc through suitable resistance.


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

The circuit of a low liquid level indicator with LED is shown above. With the give value of C1 the frequency will be around 6KHz. Capacitor Ct sets the frequency of the internal oscillator.

Manufactured by National Semiconductors, the LM can detect the presence or absence of polar fluids. Usage of AC signal for detection prevents electrolysis and this makes the probes long lasting.

Hai, Can it be used for Water level indicator in a Over head Tank. Hi, can this sensor circuit be used to detect diesel fuel? In such cases there is option to avoid the internal reference datazheet and an external reference resistor of your choice Rx in the circuit can be employed.

Hi Rohit Pin No 5 is oscillator out put for external reference resistance. How could I use this circuit to control the Digital input on a microcontroller? When the probe to ground resistance goes above the R ref the oscillator output is coupled to the base of the internal output transistor making it conducting. The LED connected to the collector between pin 12 and Vcc is driven.

Pin lm180 of the IC can be used to solve this problem.

LM 데이터시트(PDF) – National Semiconductor (TI)

Low liquid level indicator LED. Atenciosamente… Washington Souza Gomes. The circuit diagram for the above said scheme is shown below. High liquid level activated switch. The circuit diagram of a liquid level indicator using loud speaker at its output is shown below. External transistor Q1 is connected to the collector of the internal transistor.

(PDF) LM1830 Datasheet download

DC voltage is required for driving the relay and AC voltage cannot be used here just like what we did in the case of LED and speaker. Please refer to the second circuit above. The oscillators output is directly available at pin 5 and the Rx connects the oscillator output to the probe through the blocking capacitor. Loud speakers can be driven only by using AC signals and a DC signal will not produce any sound out of the speaker.


You may see the circuit if you are interested. 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. The circuit is similar to the first circuit except that the LED is replaced by a loud speaker and the load current limiting resistor is changed from 1. The probe used here can be any metal rod with size and shape of your choice.

A method for activating a relay when the liquid level exceeds a predetermined level is shown here. Capacitor Cb couples the oscillator output to the probe and it ensures that no DC signal is applied to the probe. 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.

Resistor R3 limits the collector current of the internal transistor while resistor R4 provides protection to the IC from transients. Liquid level indicator admin October 12, 11 Comments. Leave a Reply Cancel reply Your email address will not be published. The load connected through the relay whether pump, lamp, alarm, solenoid valve or anything is driven. 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.