Car Parking Sensor schematic

This circuit can be used for an assist in parking the car near the garage wall backing up Pls. LED D7 illuminates Pls 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 Pls 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. Obviously, you can use this circuit in other applications like liquids level detection, proximity devices etc.

Note:
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.
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.
It is wiser to place all the circuitry near the infra-red LEDs in a small box. The 3 signaling LEDs can be placed far from the main box at an height making them well visible by the car driver.
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.

part list:
R1 : 10K R2,R5,R6,R9 : 1K R3 : 33R R4,R11 : 1M R7 : 4K7 R8 : 1K5 R10,R12-R14 : 1K C1,C4 : 1µF/63V C2 : 47pF C3,C5 : 100µF D1 : Infra-red LED D2 : Infra-red Photo Diode (see Notes) D3,D4 : 1N4148 D5-7 : LEDs (Any color and size) IC1 : NE555 IC2 : LM324 IC3 : LM7812

Low Voltage Monitor schematic

Low Voltage Monitor circuit is highly desirable for security and protection against everyday damage your equipment, especially for your favorite car. This circuit may be very simple / very simple to make because only by using ic LM339. The workings of this circuit is Buzzer will sound and lights Led will light up when your car battery in a state of tension is very minimal. Although the circuit is very simple but can protect your car from damage that would be very detrimental. This voltage monitor circuit may be beneficial to you.

Component List:

R1, R3 2 1K 1/4W Resistor
R2 1 5K Pot
U1 1 LM339 Voltage comparator IC
D1 1 1N5233B Zener Diode
D2 1 LED
BZ1 1 Piezo Buzzer
MISC 1 Board, wire, socket for IC

Notes
1. The circuit will operate from 9V to 12V.
2. Adjust R2 until the alarm goes off at the correct voltage.

Refrigerator Alarm schematic

Refrigerator Alarm circuit, so that we know whether the fridge is closed or not. Refrigerator sometimes likes to play or open the lid by the children, and this resulted in a refrigerator at room temperature decreases and will increase the electrical load, so that the electricity to be extravagant. Therefore it is necessary alarm circuit.

Alarm circuit schematic drawings Refrigerator

Circuit placement and How it Works: This circuit is stored into a small box, placed in the fridge near the lamp (if any) or the opening. With the door closed in the refrigerator in the dark, the photo resistor R2 presents a high resistance (> 200K) thus clamping IC1 by holding pin 12 high. When a beam of light came when opening, or a refrigerator light bulbs, photo resistor lowers resistance (<2K), pin 12 so low, IC1 starts counting after a predetermined delay (20 seconds) piezo sounder beeps sound for 20 seconds. then stopped during the same time interval and the cycle repeats until the fridge door closed. D2 is connected to pin 6 of IC1 allows the piezo sounder beeps sound 3 times per second.

List of Components:

R1 10K 1/4W Resistor
R2 Photo resistor (any type)
R3 R4 100K 1/4W Resistors
C1 10nF 63V Polyester Capacitor
C2 100µF 25V Electrolytic Capacitor
D1,D2 1N4148 75V 150mA Diodes
IC1 4060 14 stage ripple counter and oscillator IC
Q1 BC337 45V 800mA NPN Transistor
BZ1 Piezo sounder (incorporating 3KHz oscillator)
SW1_________Miniature SPST slide Switch
B1   _________3V Battery (2 AA 1.5V Cells in series)

Car Speed Alarm Schematic

When we are driving sometimes we do not know the speed of our car, especially when we are in the course of the highway so nice and straight, if the car's speed is too fast or faster than anyone could lead to accidents that do not want to happen. The circuit then requires the Car Speed ​​Alarm is to alert the driver who did not notice the speed because the roads are nice and straight. Even this series can be set speed, for example, we set when exceeded 100km/h the alarm should sound.

The workings of the circuit:A piezo buzzer will sound. Speed ​​pulse is inserted into the base of Q1 and the resulting waveform at the collector is fed through a RC network to the input of an LM2917 frequency to voltage converter, IC1. The resulting voltage is fed to three comparators (IC2d-IC2b) which has a reference voltage at the inverting input they are set by the 10-turn trimpots VR1, VR2 and VR3. The output of each comparator is applied through another RC network to the gate of an SCR. Anode of the three SCRs are commoned comparator inverting input connected to the left, IC2a.Non-inverting input is set to 2.3 V with a trimpot VR4. In use, once you exceed the speed setting for the comparator in particular, relating SCR to briefly pull the pin 2 of IC2a ​​low and short beep is emitted by a piezo buzzer. Then, if you exceed the speed setting that followed, another beep will be heard. The idea is to make each setting speed of several km / h higher than it actually is, so if you are driving at the correct speed in a particular zone, the buzzer will not sound. But as you increase speed, the buzzer will beep once because you exceed the speed settings for each zone. In this way, there is no need to constantly switch setting the pace as you pass through different zones and you can choose to ignore the beep is not "illegal".