This Sensor circuit was designed as an aid in parking the car near the garage wall when backing up. LED D7 illuminates when bumper-wall distance is about 20 cm., D7+D6 illuminate at about 10 cm. and D7+D6+D5 at about 6 cm. In this manner you are alerted when approaching too close to the wall. All distances of the sensor mentioned before can vary in this operation , depending on infra-red transmitting and receiving LEDs used and are mostly affected by the color of the reflecting surface [...]
This circuit was designed as an aid in parking the car near the garage wall when backing up. LED D7 illuminates when bumper-wall distance is about 20 cm., D7+D6 illuminate at about 10 cm. and D7+D6+D5 at about 6 cm. In this manner you are alerted when approaching too close to the wall. All distances mentioned before can vary, depending on infra-red transmitting and receiving LEDs used and are mostly affected by the color of the reflecting surface. Black surfaces lower greatly the devic [...]
This circuit gives out an alarm when its sensor is wetted by water. A 555 astable multivibrator is used here which gives a tone of about 1kHz upon detecting water. The sensor when wetted by water completes the circuit and makes the 555 oscillate at about 1kHz.The sensor is also shown in the circuit diagram. It has to placed making an angle of about 30 - 45 degrees to the ground. This makes the rain water to flow through it to the ground and prevents the alarm from going on due to the s [...]
This LED thermometer is designed for in home use, to read temperatures between about 60 and 78 degrees Fahrenheit. It is based around a precision temperature sensor IC, the LM34DZ. This sensor require no calibration and can measure temperatures of between -50F and +300F. While the circuit shown here does not use the full range of that sensor, it can be modified to do so by simply changing the voltage reference to U2 at the sacrifice of precision.Part Lists:C1 - 1uF 25V Electrolytic Cap [...]
The transmitter circuit consists of WZ-X01 RF module, Holtek HT-640 encoder and 8 bit A/D converter. U1 ADC0804 converts the analog voltage to digital data, U2 encodes that data (D0~D6) along with D6, D7 and transmitting through the RF transmitter module.The potentiometer VR1 varies the voltage to the A/D U1 pin6, since only the lower 6 bits are used; the trim pot VR2 has to adjust so that the maximum input to the U1 will not exceed 1.25V. The S2 (D6) and S3 (D7) are used for controlli [...]
This is a small circuit fm transmitter using transistor BF494 . The reach of the transmitter will depend a lot on this antenna, of the feeding of the circuit and of the place where will happen your operation. With a feeding of 6 V (4 piles AA) and an antenna of about 40 cm of length, we can arrive to the 200 meters. With a smaller antenna, or in place with many structures of iron (flagstones) the reach will be sensibly reduced. A common wall without metallic structure is not obstacle f [...]
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