Introduction: Parking Sensor : Introduction

About: I am currently doing B. Tech in Electronics and communication engineering.

This Car Parking Sensor Circuit using IR Transceiver and LM324 assistant can protect your car from any damage while reverse parking. It indicates the distance of car from any object and raise an alarm when it reaches close to the wall or the object and needs to be stopped. In this Instructable, I have created the PCB layout of sensor using CAD Soft EAGLE. I have also tested it's circuit on a breadboard. PCB design in EAGLE is a two-step process. First you design your schematic, then you lay out a PCB based on that schematic.


CAD Soft EAGLE- EAGLE is a scriptable electronic design automation (EDA) application with schematic capture, printed circuit board (PCB) layout, auto-router and computer-aided manufacturing (CAM) features.


Here is the link for free download:
Grab the most recent version that matches your operating system (the software is available for Windows, Mac and Linux). EAGLE installs just like any old program, it'll self extract and then present you with a series of dialogs to configure the installation. After installation, you will presented with a window, where you will have to license the eagle software. First time you open the EAGLE, you will presented with control panel. Here, there are a lot of icons, which can be used for creating a new project, managing Libraries, for adding new Libraries and many more.

Step 3: Downloading the Required Libraries

Now, you are all set to create projects in CAD Soft EAGLE.

For example: In this Instructable, we downloaded a library of LM324

(for free download of LM324)

Step 4: Create Project

Now, we will start creating a new project. first, go to the control panel, click on the projects icon. Now, right click on the directory where you want the project to live (by default EAGLE creates an "eagle" directory in your home folder), and select "New Project". Then, name the your newly created project folder. For this project, we are actually making a Parking sensor. Therefore, name will be "Parking_Sensor".

Step 5: Create a Schematic

Now, we will create a Schematic for our project named "Parking_Sensor". To add a schematic to a project folder, right-click the folder, the go to "New" and select "Schematic". Now, you will be presented with schematic editor.

Step 6: Adding Parts to a Schematic

Here, we will be adding the components using ADD tool, adding the frame , adding the power input, adding the connectors. Schematic design is a two step process. First you have to add all of the parts to the schematic sheet, then those parts need to be wired together.

Step 7: Using the ADD Tool

The ADD tool -- (on the left toolbar, or under the Edit menu) -- is what you'll use to place every single component on the schematic. The ADD tool opens up a library navigator, where you can expand specific libraries and look at the parts it holds. With a part selected on the left side, the view on the right half should update to show both the schematic symbol of the part and its package. Here, we will add given list of components:
Part Description | Library |

LM324P |Texas instruments|

LED | Adafruit |

10K Resistors | Adafruit |

1K Resistors | Adafruit |

330 ohm | Adafruit |

470 ohm | Adafruit |

15K | Adafruit |

4.7K | Adafruit |

Photo diode | Siemens |

Step 8: Add a Frame

The frame isn't a critical component for what will be the final PCB layout, but it keeps your schematic looking clean and organized. The frame which you want to add, it should be in SparkFun-Aesthetics library,and it's named FRAME-LETTER. Find that by either searching or navigating and add it to your schematic. After selecting the part you want to add, it'll "glow" and start hovering around following your mouse cursor. To place the part, left-click (once!). After placing a part, the add tool will assume you want to add another -- a new frame should start following your cursor. To get out of the add-mode either hit escape (ESC) twice or just select a different tool.

Step 9: Save and Save Often

To save either go to File > Save, or just click the blue floppy disk icon . For this project, "Parking_Sensor".

Step 10: Adding the Power Input

Next we'll add different parts all devoted to our voltage supply input. Use the add tool for these parts:
Part Description | Library |

3.5 mm Terminal block | Adafruit |

VCC | SparkFun-Aesthetics|

GND | SparkFun-Aesthetics|

Step 11: Wiring Up the Schematic

With all of the parts added to our schematic, it's time to wire them together. We will use net tool because it does a better job of connecting components.

Step 12: Using the NET Tool

To use the NET tool, hover over the very end of a pin (as close as possible, zoom in if you have to), and left-click once to start a wire. Now a green line should be following your mouse cursor around. To terminate the net, left-click on either another pin or a net. Start routing your whole circuit. Start back in the upper left, and route your circuit. Whenever a net splits in two directions a junction node is created. This signifies that all three intersecting nets are connected. If two nets cross, but there's not a junction, those nets are not connected. Then start routing your whole circuit.

Step 13: Names and Values

Every component on your schematic should have two editable text fields: a name and a value. A part's value allows you to define unique characteristics of that part. For example, you can set a resistor's resistance, or a capacitor's capacitance.

For example: In this Instructable, I have named and given values are:

LED1 -- IR Transmitter

D1 ---IR Receiver














Terminal Block-- Power_supply

Step 14: Turning Your Schematic Into a Board Layout

To convert your schematic to a PCB layout, do this:

1.Open your schematic project from the Autodesk EAGLE Control Panel.

2.At the top of your interface, select the SCH/BRD sch-brd-icon . This will begin the process of generating a PCB layout based on the components and wiring in your schematic.

3.Select Yes if you get a warning dialog saying that the .brd file doesn’t exist and that you want to create it from your schematic. To switch from the schematic editor to the related board, simply click the Generate/Switch to Board command -- (on the top toolbar, or under the File menu) -- which should prompt a new, board editor window to open. All of the parts you added from the schematic should be there, stacked on top of each other, ready to be placed and routed.

Step 15: Arranging the Board

If you haven't already, click the Generate/Switch to Board icon in the schematic editor to
create a new PCB design based on your schematic:

The new board file should show all of the parts from your schematic. The gold lines, called Airwires, connect between pins and reflect the net connections you made on the schematic. There should also be a faint, light-gray outline of a board dimension to the right of all of the parts. Our first job in this PCB layout will be arranging the parts, and then minimizing the area of our PCB dimension outline. PCB costs are usually related to the board size, so a smaller board is a cheaper board.

Step 16: Moving Parts

Using the MOVE tool you can start to move parts within the dimension box. While you're moving
parts, you can rotate them by either right-clicking or changing the angle in the drop-down box near the top. The way you arrange your parts has a huge impact on how easy or hard the next step will be. As you're moving, rotating, and placing parts, there are some factors you should take into consideration. Don't overlap parts: All of your components need some space to breathe. The green via holes need a good amount of clearance between them too. Remember those green rings are exposed copper on both sides of the board, if copper overlaps, streams will cross and short circuits will happen. Minimize intersecting Airwires : While you move parts, notice how the Airwires move with them. Limiting criss-crossing Airwires as much as you can will make routing much easier in the long run. While you're relocating parts, hit the RATSNEST button -- to get the Airwires to recalculate. Part placement requirements: Some parts may require special consideration during placement. Tighter placement means a smaller and cheaper board, but it also makes routing harder.

Step 17: Routing the Board

Open up the Autorouter, don't worry about these other tabs for now, click Auto for 1 top. and N/A for 16 bottom, just click OK.

The autorouter won't always be able to finish the job, so it's still important to understand how to manually route pads (plus manual routes look much better). After running the autorouter, check the bottom-left status box to see how it did. If it says anything other than "Optimized: 100% finished", you've still got some work to do. Go to Display icon and click for layers top, bottom, pads, vias, unrouted and dimensions, now click apply and then OK Now, try turning Routing Grid down from 50mil 10mil. Now, you will presented with the window as shown in the pictures.

There are tons of optimizations and settings to be made in the autorouter. If you want to dig deeper into the subject, consider checking out EAGLE's manual where an entire chapter is devoted to it. After all optimizations are done. Go to the display icon again and hit ALL and then Apply and then OK. All your components will be visible to you.

Step 18: Adjusting the Dimension Layer

Now that the parts are placed, we're starting to get a better idea of how the board will look. Now we just
need to fix our dimension outline. You can either move the dimensions lines that are already there, or just start from scratch. Use the DELETE tool to erase all four of the dimension lines. Then use the WIRE tool to draw a new outline. Before you draw anything though, go up to the options bar and set the layer to 20 Dimension. Also up there, you may want to turn down the width a bit.

Step 19: Finishing Touches

There are a lot of ways of Finishing your project like:

  • Adding Copper pours
  • Adding Silkscreen

But here, I haven't used any of these. After this, I directly moved to the Export step.

Step 20: Export Schematic and Layout

Launch Eagle and open the board view of your project.

Turn the grid off via the View->Grid menu or using the command: “grid off”.

Turn off all layers except the ones that you want to print. I like to see layers 1, 17, 18 and 20. That’s top, pads, vias and dimension. If your board is two sided you only want to print one side at a time.

If the background is black we need to make it white. Do this via the Options->User Interface dialog or use the command: “set palette white; window;”.


Select a destination file. I prefer to use the .png format.

Check the Monochrome checkbox.

Change the resolution to a multiple of your screen dpi. The default screen resolution in Windows is 96 dpi so I normally use 555.

Click Ok to export the image.

Step 21: Working

The received by the IR receiver is amplified the by the operational amplifier U2:A. Resistor R4 and C4 forms peak detector to detect peak of the amplified signal.
Op – amp as Comparator: Op-amp has two inputs (non-inverting and inverting) and one output. The output of operational amplifier is high when non-inverting voltage is greater than inverting voltage. The output voltage is low, when inverting voltage is greater than non-inverting voltage. In the above circuit the voltages at non inverting pins of comparators acts as a reference voltage and inverting input voltages at comparators are compared with reference voltages to produce the output. Here resistors R8 to R11 are used to set different reference voltages at their non inverting pins. Resistors R12, R13 and R14 are used to protect the LED’s from high voltages.

Step 22: Enjoy!

After all this, you are all set. Now, you can send your layouts to the vender for fabrication.

Step 23: Applications

This circuit can be used in auto mobiles to park the vehicle safely.

We can use this circuit to measure the distance.

We can also use this circuit as IR Liquid Level Detector by making few modifications.

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