LCD-LED DisplayLights and Display Board Circuits

Laser Level Detector Schematic Circuit Diagram

Rotating Laser Level Enhancements

Rotating laser level, invaluable for aligning objects indoors or outdoors, are readily available at affordable prices. However, the visibility of the rotating laser beam diminishes at large distances, especially outdoors. In such scenarios, the laser beam detector presented here serves as a practical solution. This detector functions effectively within a range of up to 50 meters (150 feet) and is crafted entirely from standard components. Encased in a plastic housing, it can be securely affixed to an object, such as a post or a beam. Equipped with three LEDs and a beeper, the detector provides clear indications whether the object needs to be elevated or lowered.

Laser Level Detector Schematic Circuit Diagram 1


Sensing and Indicating with Integrated LEDs

Utilizing LEDs with transparent packages and integrated lenses (having a round surface) as sensors, this system employs a total of five LEDs for both the top and bottom detection zones, alongside two op-amps (IC1a & IC1b or IC1c & IC1d) responsible for driving the ‘Move Up’ and ‘Move Down’ indicator LEDs. Additionally, the middle sensor LED controls the ‘OK’ indicator LED, functioning through two op-amps (IC2a & IC2b).

Signal Processing and Timing Control

To initiate action, the rising edges of the op-amp output signals serve as triggers for three distinct monostable multivibrators, each implemented with the CD4047 IC. Alternatively, the circuit enclosed within the dashed outline (utilizing one gate of a CD4044 quad RS latch) can be used instead of the monostable multivibrators. However, in this configuration, the output signal features an opposite polarity, necessitating the replacement of the BS170 N-channel MOSFET with a P-channel type.

Laser Level Detector Schematic Circuit Diagram 2

Setting Monostable Times for Laser Detection

For effective laser detection, the monostable time of the middle retriggerable Monostable Multivibrator (MMV) should exceed the laser’s rotation period (e.g., for a 2 rpm laser, it should be over 500 ms). This ensures that the beeper produces a continuous tone. Adjustments can also be made to the laser’s speed, especially in cases where rotating laser levels come with variable speeds. The monostable times of the upper and lower MMVs are calibrated to create distinguishable short and long beeps, respectively.

MOSFET Configuration for Beeper and LED

To drive the shared beeper, three MOSFETs (T1, T2, and T3) are set up as a wired-OR gate. The fourth MOSFET (T4) is dedicated to powering the ‘OK’ LED. This configuration guarantees efficient control over both the audio and visual indicators. The entire circuit can be conveniently enclosed within a housing, accommodating three penlight cells, making it a compact and portable laser detection system.


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