User manual

64l Robotics experiment with PIC microcontroller

GP2D120 Infrared Ranger module has 3 terminals: Power input (Vcc), Ground (GND)

and Voltage output (Vout). To read the voltage values from the GP2D120, you must wait

till after the acknowledgement period which is around 32 to 52.9 ms.

The output voltage of GP2D120 at a range of 30 cm and +5V power supply is be-

tween 0.25 to 0.55V, with the mean being 0.4V. At the range of 4 cm., the output voltage

will change at 2.25V± 0.3V.

5.6.2 How the IR Ranger Module works

Measuring range can be done in many ways. The easiest to understand is through

ultra sonic where sound waves are sent to the object and the time it takes to reflect back

is measured. This is because sounds waves do not travel fast, and can be measured by

present day equipment. However, in the case of infrared light, the time it takes to hit an

obstacle and reflect back can not be measured because infrared light travels fast. No

measurement equipment is available yet. Therefore, the following theory must be used.

The infrared light is sent out from a transmitter to the object in front, by passing

through a condense lens so that the light intensity is focused on a certain point. Refrac-

tion occurs once the light hits the surface of the object. Part of the refracted light will be

sent back to the receiver end, in which another lens will combine these lights and. deter-

mine the point of impact. The light will then be passed on to an array of photo-transistors.

The position in which the light falls can be used to calculate the distance (L) from the

transmitter to the obstacle using the following formula:

ect

GP2D120

Transmit LED Photo arra