There are times when it is difficult to judge the distance while reversing the car or while parking. If someone is there to help you that is great but in situations when you are driving alone then what will you do? Or you are a new driver and cannot judge the distance? This reverse parking sensor circuit will solve all these problems. You can easily install at the back side of your car. Operated at 5V power supply and can also recharge batteries. You can also use them as shadow alarm at doors to protect your car. When shadow of a intruder fall on it will also give you alarm. This alarm will provide you the musical sound that’s why it will not tease your ears.
Main components of this circuit are LM358 IC, LDR, UM66 IC, speaker and few more discrete components.
LM358 consist of two independent, high gain operational amplifier in one package. Important feature of this IC is we do not require independent power supply for working of each comparator for wide range of power supply. LM358 can be used as transducer amplifier, DC gain block etc. It has large dc voltage gain of 100dB. This IC can be operated on wide range of power supply from 3V to 32V for single power supply or from ±1.5V to ±16V for dual power supply and also supports large output voltage swing.
Pin configuration of IC is shown below-
From the above figure you can see that op amp has two inputs and one output in independent LM358. Input are pin 2 (negative pin) and 3 (positive pin), positive pin is used for positive feedback and negative pin is used for negative feedback. In ideal condition when no feedback is applied, gain of the op-amp should be infinite. When voltage at pin 2 is more than voltage at pin 3 it will raise the output towards the positive maximum voltage and a slight increase at negative pin compared to positive pin will lower the output towards the negative maximum. This feature of op-amp makes it suitable for the purpose of level detection.
LDR is a device whose sensitivity depends upon the intensity of light falling on it. The resistance of LDR decreases when intensity of light falling on it increases and vice versa (resistance increases when intensity of light falling on it decreases). In dark or in absence of light, LDR exhibits a resistance in the range of mega ohms, which decreases too few hundred ohms in presence of bright light. You can also use photodiode or phototransistor in place of LDR but in that case you have adjust the sensitivity with the help of variable resistor.
UM66 is a melody generator IC. Used in various application like in calling bell, in phones and toys. They have built in ROM programmed for playing different music.
Pin configuration of UM66 IC-
UM66 is capable of operating at the voltage range between 1.5 to 4.5V. So take care while powering power supply or for safety always use Zener diode with UM66.
Working of circuit
Working of circuits is very simple as we know LM358 compares the voltage applied at input pin and provide you the output. The voltage level which we want to detect is applied on either of the input pins (may be 2 or 3) and the voltage to be detected is applied on the other pin (may be 2 or 3). For dark sensor circuits we are applying voltage on negative pin (pin 2) and voltage to be detected is applied on positive pin (pin 3).
Whenever input voltage applied on positive pin because of light which falls on LDR, photodiode and phototransistor slightly rises above the voltage on negative pin. The output suddenly rises to the positive maximum and remains positive until the input voltage falls below the level to be detected. This causes the output pin 1 of IC1 to go high which provide power supply to IC2 that is UM66 pin 2 and we receive output at pin 1. The speaker connected at output gives you a alarm. We have used transistor T1 to amplify the weak signals from UM66.
Be care full in alignment of LDR.