23-12-2009, 08:00 PM
help me for "ULTRASONIC MOTION DETECTOR".
23-12-2009, 08:00 PM
help me for "ULTRASONIC MOTION DETECTOR".
24-12-2009, 07:17 PM
Ultrasonic motion detectors emit and receive ultrasonic sound energy in a region of interest.Object motion within the region of interest and in the range of the ultrasonic motion sensor is detected and an alarm signal is produced.The range of these detectors differs from the designed range whenever the actual atmospheric sound propogation conditions vary from the atmospheric conditions assumed in the design .Ultrasonic motion detectors are commonly used for automatic door openers and security alarms. ultrasonic beams are easily blocked by thin materials, including paper and as a result False triggering is easly caused by reflections from blowing curtains, pets, and flying insects.
Circuit description The circuit uses a matched pair of 40 kHz transducer elements to detect movement up to 22 feet away. Crystal locked circuit for maximum stability. An LED is switched on for movement indication. The transmitter sends out a steady ultrasonic signal at 40kHz( wavelength ~= 6 mm). The reflected sound is detected by ultrasonic receiver. The signal is then amplified by amplifiers.An amplifier is selfbiasing. The time constant of the first amplifier is set to let the 40kHz signal through. Between the first & second amplifier there is a negative peak detector consisting two diodes which follows the envelope of the 40kHz signal. If there is no movement the envelope is just a straight line. The time constant ofsecond amplifier is much slower so that it will follow this envelope. When there is no movement neither diodes can conduct. If the signal falls or rises the diodes conducts which the output to go high. A low pass filter screens out unwanted spurious signals. Specific details about the circuit are available in this link: http://www.electronickitskit/complete/surv/k49.pdf
28-08-2012, 01:00 PM
Ultrasonic Motion Detector
ultrasonicdetector.pdf (Size: 168 KB / Downloads: 202) Something's out there—on the porch, in the driveway, or behind the shed. Or maybe it's inside—in the garage, basement, or den. Whatever it is, human or beast, it is moving. Perhaps it's just your teenager sneaking in from a late night out. Possibly it is only the neighborhood cat. Or, more ominously, it could be a prowler bent on theft or physical harm. Whatever is going on, you know something is up because you just installed the Ultrasonic Motion Detector described in this article. Depending on what parts you have available, or if you buy the complete kit from the source mentioned in the Parts List, the Ultrasonic Motion Detector can be built for less than $30. It contains a complete ultrasonic (40-kHz) crystalcontrolled transmitter and a supersensitive receiver on a printed-circuit board . Circuit Description The schematic for the Ultrasonic Motion Detector is shown in Fig. 1. A 9-volt battery, B1, directly provides power for some sections of the circuit. The battery is also connected to a 78L05 regulator, IC3. which provides a 5-volt-DC power source for other sections of the circuit. The transmitter section of the Detector is basically a crystal-controlled relaxation oscillator built around a 4049 hex inverter, IC2. One of the 4049 sections, IC2-c, along with resistors R21 and R22, and capacitors C11 and C12, "pings" the 40-kHz crystal into sustained oscillation. The remaining 4049 sections act as linear buffers to drive a 40-kHz ultrasonic transmitting transducer, BZ2. Construction The author built the Ultrasonic Motion Detector from a complete kit of parts, which includes a pre-etched and drilled PC board. That kit is available from the source mentioned in the Parts List. If you choose to round up your own components, it is still recommended that you use a PC board. You can use the foil pattern shown in Fig. 2 to make your own. Refer to the parts-placement diagram shown in Fig. 3 while assembling your circuit. Begin by soldering all resistors flush to the PC board. Then install the five diodes, making sure to orient them properly. Next, install the capacitors. Be sure to double check the polarity of C9. Go on to install crystal XTAL1. Bend the crystal's leads so that the part rests flat on the board. Note the two unused holes next to the two for the crystal. You can bend a resistor lead around the crystal in a "U" shape and solder the lead ends to the unused holes. That should hold the crystal in place. Some Applications Referring back to Fig. 1, note that transistor Q1 turns on and delivers a continuous unregulated 9 volts to a suitable load as long as something is moving within the Detector's range. If the load is a 9-volt relay, virtually any electronic device can be turned on in response to motion. That might be good enough for many applications˜lights can be made to flash, horns to blare, etc. (If you have trouble driving the coil of a 9-volt relay, you might need to reduce the value of R19 in Ql's base circuit.) However, there are times when you will want an output device to remain activated after motion has stopped. For example, if a prowler quickly crosses the field of "view," you wouldn't want a speaker to sound or a light to flash for just an instant. Continuous signaling, perhaps for many minutes, would be desirable. The alarm circuit shown in Fig. 4 will provide such a warning. It consists of three 555 timer ICs, IC1-IC3, where IC1 is operated in a monostable mode, and IC2 and IC3 are in astable configurations. |
|