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 plus D6 illuminate at about 10 cm. and D7 plus D6 plus 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 device sensitivity
Power supply must be regulated (hence the use of IC3) for precise reference voltages. The circuit can be fed by a commercial wall plug-in adapter, having a DC output voltage in the range 12-24V
The infra-red Photo Diode D2, should be of the type incorporating an optical sunlight filter: these components appear in black plastic cases. Some of them resemble TO92 transistors: in this case, please note that the sensitive surface is the curved, not the flat one
The best setup is obtained bringing D2 nearer to D1 (without a reflecting object) until D5 illuminates; then moving it a bit until D5 is clearly off. Usually D1-D2 optimum distance lies in the range 1.5-3 cm.
Avoid sun or artificial light hitting directly D1 & D2. If your car has black bumpers, you can line-up the infra-red diodes with the (mostly white) license or number plate
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