27-07-2012, 04:45 PM
Wind speed meter with ultrasonic technique
Wind speed meter with ultrasonic technique.pptx (Size: 734.28 KB / Downloads: 57)
Introduction
wind speed meter (anemometer) is intended for use in a variety of sports type activities, such as track events, sailing, hang-gliding, kite and model aircraft flying, to name but a few.
It can even be used to monitor the conditions in your garden.
A probe is pointed in the direction from which the wind is blowing and a screen displays the rate at which the wind is moving between two ultrasonic sensors.
The eadout is shown on an alphanumeric liquid crystal display (l.c.d.), with readings in metres per second, feet per second, kilometres per hour and miles per hour.
The resolution is to the nearest tenth of a metre per second, from zero up to around 50mph, and possibly higher.
Description of Ultrasonic Circuit
The circuit diagram for the ultrasonic transmission and reception functions is shown in Fig. The two transducers are shown as X3 and X4. As just said, they are both used interchangeably as transmitter and receiver. Analogue multiplexer IC3 selects the mode in which the transducers are used. The transducers operate at the usual ultrasonic frequency of 40kHz. The transmission pulses are generated by a PI microcontroller, which is described presently in relation to Fig in control circuit. The route that the pulses take through IC3 is selected by the logic level applied to its pin 10, also controlled by the PIC. When pin 10 is held low, the pulses are routed from IC3 pin 3 to pin 1, and out to transducer X3.
The final gain stage is provided by transistor TR1. Its base (b) is biased normally low by resistor R9.
Description of control circuit
As shown in the control circuit diagram of fig. the PIC16F628 microcontroller (IC1) is responsible for generating and sending pulses to the ultrasonic transducers, and for timing the return of the received signal. The results of its calculations are output to the 2-line 16-characteralphanumeric l.c.d., X2. This is operated in 4-bit control mode, with its screen contrast adjustable by preset VR1. The PIC is operated at 20MHz as set by crystal X1 in conjunction with capacitorsC3 and C4. It can be programmed in situ via connector TB1, whose pins are in the author’s standard order suited toprogramming by Toolkit TK3. Note, however,the comment later about programming brand new PIC16F628 devices.