LM393: the multipurpose differential comparator


There is a very interesting integrated circuit such as the LM393, which we added to our list of electronic components already described. This chip or IC has infinite possibilities, as you will see, which makes it very versatile for a wide variety of electronic projects and, although it is also sold as a separate chip, you can also find it in a module, to integrate it with Arduino or other boards. development in the simplest way.

Well, here we are going to see in depth what this circuit is, how it works and what it can be used for...

What is LM393?


El LM393 is a voltage comparator integrated circuit widely used in electronics. It is characterized by its low cost, ease of use and versatility. It works by comparing two input voltages: one at the non-inverting input (pin 2) and one at the inverting input (pin 1). If the voltage at the non-inverting input is greater than the voltage at the inverting input, the output (pin 3) is driven to a high level (5V). If the voltage at the inverting input is greater than the voltage at the non-inverting input, the output is activated at a low level (0V).

This circuit is low power consumption, consumes little current and dissipates little power, making it ideal for cases where need to consume little, such as equipment that depends on a battery. And, although I said that it works at 5V, you can really find a range between 3v and 18v of power, as you need.

The LM393 can work in two modes Main:

  • Comparator with hysteresis- In this mode, the LM393 incorporates a small voltage threshold that prevents the output from oscillating between high and low levels when the input voltages are close to their comparison point. This provides greater stability and prevents "bounce" of the output.
  • Comparator without hysteresis- The output responds directly to changes in input voltages, without the hysteresis effect. This can be useful for applications where a quick response to voltage changes is required.

Said like this, you may only think that it can be used to compare voltages and nothing more, but the truth is that thanks to that characteristic, depending on what other elements it is combined with, it can be used for other purposes. many applications:

  • Voltage comparators: Simply take advantage of this property to compare two reference or sensor voltages.
  • Zero crossing detectors: Detect the moment when an AC signal crosses the reference voltage (0V).
  • Voltage alarms: indicate when a voltage exceeds a predefined threshold.
  • Oscillators: Generate square wave signals using positive feedback.
  • Interfaces with sensors: convert analog signals from sensors into digital signals for processing by microcontrollers.
  • OthersIn addition, if it is used to compare outputs from various sensors, we can see very varied applications as we will see in the next section...

Module types

LM393 modules

The LM393 is the basis of various electronic modules that offer specific functions, as I mentioned before, can be used for many things. Here are just a few of them:

  • rotation speed sensor: In this type of module, the LM393 is integrated along with other elements to measure the rotation speed of a moving object. A slotted disc or gear wheel passes in front of an infrared light emitter and an IR light receiver. Each passing slit interrupts the light beam, generating electrical pulses. The LM393 compares the frequency of these pulses with a time reference, calculating the rotation speed. Even other elements could be used to calculate the distance traveled by a wheel, for an odometer.
  • Photoelectric optical sensor: This other is used to detect the presence or absence of an object. An infrared light emitter emits a beam of light toward a light receiver. If an object interrupts the beam, the LM393 detects the decrease in light signal and activates the output.
  • sound detector- If a transducer such as a microphone is used, the presence of sound or vibrations can also be detected. A microphone converts sound waves into electrical signals, the LM393 compares the amplitude of these signals with a predefined threshold, and if the amplitude exceeds the threshold, the LM393 activates the output, indicating the presence of sound.
  • Linear speed measurement: Another function is to measure the speed of an object in linear motion. A magnetic tape with magnetic patterns passes in front of a reading head. The reading head generates electrical pulses that represent the speed of the object. The LM393 compares the frequency of these pulses to a time reference, calculating linear velocity.
  • infrared sensor- With IR, you can detect the presence of an object that emits or reflects infrared radiation. An infrared receiver detects infrared radiation emitted or reflected by an object. The LM393 compares the intensity of the infrared signal with a predefined threshold. If the intensity exceeds the threshold, the LM393 activates the output, indicating the presence of the object.
  • Temperature sensor module: with a thermistor, we can also measure the ambient temperature, or any other element in contact with the temperature sensor. A thermistor changes its electrical resistance as a function of temperature. The LM393 forms a voltage divider circuit with the thermistor, the output voltage of the voltage divider depends on the resistance of the thermistor, which reflects the temperature.

As you can see, the LM393 serves as a base for reading the sensors, and thus has an output that can be used by other elements such as Arduino to generate actions by programming the microcontroller or MCU.

Where to buy and prices

The LM393 can be found as an independent chip to integrate it into your own electronic systems with the components you need, but also in modules such as those described in the previous section, with everything necessary, for greater convenience and to be able to easily integrate them with Arduino. It is cheap, and you can find it in electronics stores or also on platforms like Amazon or Aliexpress. Here I make some recommendations:

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