LASCR - Light Activated Silicon Controlled Rectifier

In the realm of electronics, the Light Activated Silicon Controlled Rectifier (LASCR) holds a prominent position as a specialized semiconductor device. With its unique ability to be triggered by light, the LASCR finds numerous applications across various industries. In this blog post, we will delve into the working and construction of LASCR, explore its uses, and highlight its ratings. Let's dive into the world of LASCR with the power of AI technology.

What is the use of LASCR?

LASCR, or Light Activated Silicon Controlled Rectifier, serves as a vital component in electronic circuits where light control is required. Essentially, it acts as a switch that can be turned on or off using light. The use of light as the triggering mechanism provides precision and control in a wide range of applications.

What is a LASCR in basic electronics?

In basic electronics, a LASCR is a semiconductor device that exhibits characteristics of both a diode and a thyristor. It comprises four layers of alternating N and P-type materials, forming a PNPN structure. The device remains in a non-conducting state until a light source of sufficient intensity illuminates the device's gate. This illumination allows a small control current to flow, turning the LASCR into its conducting state.

What are the applications of light-activated Silicon Controlled Rectifier LASCR?

The applications of LASCR span across several industries, each benefiting from its unique light-controlled properties. Some prominent applications include:

  1. Light Sensors: LASCRs are used in light-sensitive applications, such as dusk-to-dawn lighting systems, where they act as light sensors and automatically turn lights on or off based on ambient light levels.
  2. Laser Triggering: In laser-based systems, LASCRs act as effective triggers for the generation of precisely timed pulses in laser technology, enabling accurate measurements and precise control.
  3. Security Systems: LASCRs are employed in security systems to detect unauthorized access or motion, triggering alarms or surveillance devices when the beam of light is interrupted.
  4. Photoelectric Controls: Photoelectric sensors utilizing LASCRs are used in industrial automation for detecting the presence or absence of objects on conveyor belts or assembly lines.

What are the ratings of LASCR?

LASCRs come in various ratings to cater to different application requirements. The key ratings to consider while using LASCRs are:

  1. Voltage Rating: The maximum voltage that the LASCR can withstand without breakdown.
  2. Current Rating: The maximum current that the LASCR can carry without overheating.
  3. Power Dissipation: The maximum amount of power that the LASCR can dissipate without damage.
  4. Triggering Current: The minimum current required at the gate to switch the LASCR into its conducting state.

What is the practical use of SCR?

The Silicon Controlled Rectifier (SCR) is a closely related device to LASCR, and its practical use is as a controlled switch in various applications. SCRs find applications in motor control, heating elements, power regulation, and electronic switching circuits. They are widely used in industry and automation, where precise control over power flow is required.

The LASCR is triggered into the Conduction state when the light falls on it, the operation of LASCR is similar to the ordinary SCR except that its gate can be triggered by light.

LASCR Circuit Symbol, Construction

LASCR Construction

The LASCR (Light Activated Silicon Controlled Rectifier) consists of four layers of semiconductor which form a PNPN or NPNP structure, it has three junctions J1, J2, and J3, and also three terminals, the anode terminal of LASCR is connected to the P-Type of material of PNPN structure and the cathode terminal is connected to the N-Type layer of the Silicon Control Rectifies while the gate of the LASCR is connected to the P-Type of material near to the cathode, as shown in the given Figure.

Operation / Working of LASCR

The LASCR (Light Activated Silicon Controlled Rectifier) starts conduction when it is forward-biased. For this purpose, the cathode is kept at negative positional and the anode is at positive positional. We apply a positive clock at the gate terminal and so the Silicon Controlled Rectifier turns ON.

When forward bias voltage is applied to the LASCR (Light Activated Silicon Controlled Rectifier), or applied light of a required level the junction J1 and J3 become forward bias while the junction J2 becomes reverse bias. When we apply a clock pulse at the gate terminal, the junction J2 becomes forward biased and the LASCR (Light Activated Silicon Controlled Rectifier) starts conduction.

The LASCR (Light Activated Silicon Control Rectifier) turns ON and OFF very quickly, At the OFF state the LASCR (Light Activated Silicon Control Rectifier) provides infinity resistance and in the ON state, it offers very low resistance, which is in the range of 0.01Ω to 1Ω