Laser rangefinder

This device, which is still considered unique, could find application in almost all spheres of human life. Today, the laser range finder can be seen in the hands of geologists and surveyors. In other words, in those areas of human activity where it is necessary to measure the distance with particular accuracy. Therefore, laser roulettes, which are distinguished by high accuracy, increased reliability and an affordable price, have won high popularity. It is quite natural to ask the question whether it is possible to make a laser range finder with your own hands.

The group of devices that measure the distance electronically include: laser rangefinder, ultrasonic rangefinder.

Measurements with a laser rangefinder are made on the basis of light fluxes, the carrier of the signal is electromagnetic radiation, painted in the appropriate shade. In most cases, the red light is taken as the basis.

According to the laws of physics, the speed of light is much higher than the speed of sound, so the measurement time of the same distance will differ.

The main reasons for installing a laser rangefinder

The scheme of the laser rangefinder.

Using a mechanical tape measure is not always convenient. Sometimes it does not give a positive effect. In the past 10 years, an increasing preference is given to electronic rangefinders. This group of devices that measure distance electronically include:

• laser rangefinder;
• ultrasonic rangefinder.

All of these devices operate on the principle of the contactless method. Such a rangefinder with their own hands today create domestic masters. Devices work no worse than those that were released in the factory.

A hand-made laser rangefinder consists of several parts:

• pay;
• microcontroller;
• laser signal booster;
• laser;
• photodetector;
• filter.

Basically, the laser radiation occurs with a sinusoidal signal.

It is quite difficult to receive such a signal having a frequency of 10 MHz. A simple controller does not fit here. For this it is better to use the meander, which has the desired frequency. When the signal coming from the photodetector is amplified, unnecessary harmonics are removed by a special band-pass filter that operates at a frequency of 10 MHz. The output signal appears, strongly reminiscent of a sinusoidal.

Build: practical recommendations

Block diagram of a pulse laser rangefinder.

To make a range finder with your own hands, you can use a laser communication scheme as a basis. In this case, the data transfer is very fast, the speed is 10 Mbit. This value corresponds to the available modulation frequency.

For such a laser device, the simplest power amplifier is taken. It consists of a single 74HC04 chip, which is assembled from six inverters. The current supply is limited by special resistors. However, craftsmen can replace resistors with more reliable parts.

The commissioning board becomes a source of 5 volts. Thus, the amplifier receives power. To remove signal leads to another part of the electrical circuit, the amplifier body is made of steel, each wire is shielded.

Acting as a laser drive installed in the DVD-top boxes. Such a device has ample power to operate at a frequency reaching 10 MHz.

The receiver includes:

• photodiode;
• amplifier.

The composition of the amplifier includes a field-effect transistor, a special chip. When the distance increases, the photodiode's light falls. Therefore it is necessary to have a powerful gain. Collected scheme allows to reach 4000 units.

When the frequency increases, the signals from the photodiode begin to decrease. An amplifier of a similar design is the main and highly vulnerable part. Its setup requires very high accuracy. It is desirable to adjust the gain in such a way as to obtain maximum values. The easiest way would be to feed a 3V transistor. You can install an ordinary battery.

In order for the receiver to start working, it is necessary to supply 12 V. For this, a special power supply unit is installed.

Such an amplifier has a high sensitivity to any pickups, so it must be shielded. You can use the body of the optical sensor. Photodiode shielding can be made from ordinary foil.

The system described above will allow you to create a homemade laser range finder in a domestic environment.