Car Parking Guard Circuit Electronic
The Q1 photo detector picks-up the infrared beam generated by IR LED1 and IR LED2 and reflected by the surface placed in front of it.
IR LED1, IR LED2 and Q1 are placed facing the car on the same line, a couple of centimeters apart, on a short breadboard strip fastened to the wall. Q1 picks-up the infra-red beam which generated by IR LED1 and IR LED2, and reflected by the surface placed in front of it.
If there is a obstacle the IR beam will radiate back to the IR sensor and the 20KHz modulated signal is given to the pin3 of LM567 through photo Darlington transistor, at this point the pin8 of the LM567 is turned to low and also gets locked to detect the 20Khz signal. By this the LM555 is turned low and disabled by this the led will remain lighting and buzzer makes the continuous sound to alert the driver.
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