Homemade Laser Rangefinder

The featured rangefinder is a homemade type which can be used in building robots by the use of sensors with the technology of lasers.

An oscilloscope has been used to test the sensor side where the pulse width varies by the movement of a hand in front of it. The laser is directed around the room through the spinning mirror which utilizes a small piece of blank CD which is attached to the underside of the CPU fan. A phototransistor attached to a heatsink, located at the upper right, detects only the light in front of it. When the beam hits the phototransistor, the signal is amplified by the transistors and mixed with tacho output from the fan.

The distance between the phototransistor and the spinning mirror can be increased to improve the resolution. The device gives the advantage of being able to detect chair & table legs more accurately with the limitation on the range.

The sections that divide this circuit consist of power supply which depends on the type of laser, an amplifier with sensor, and the mixer with two variations comprising of flip flops in option and for spinning mirrors.

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