Introduction: Garage Parking Assistant

About: I am a fictional game character. A mere figment of your imagination, a breeze in the wind, a drop in the lake, a KING among men.

Hi everyone, so......I have the tennis ball hanging from the roof in my garage to show where to stop when parking in the garage. (You know.....the one that constantly lobs you in the head when you walk around in your garage!) :o

This does not solve the entire problem though and it is a very old solution, so I thought I’d get rid of the ball and move into the 21st century with some led’s, ldr’s, sensors etc.

This does not only show you when you are close to the front, but monitors the sides as well, so you don’t hit stuff on the side and it even helps give you enough space to open your

The project requires no expert knowledge of electronics or anything, ANYONE CAN MAKE IT.

If you do not know how to Solder, for instance.........THERE's an INSTRUCTABLE for that :)

Step 1: Safety

This project involves the use of lasers....... BE CAREFUL!!!!

Lasers are dangerous and can affect your eyesight adversely or even cause blindness.

At certain strengths they can heat up and burn things as well.


Electronic components are also prone to getting hot or burning when incorrectly connected or handled and can cause a fire.

Depending on how you choose to power your project, there may also be the possibility of a shocking hazard.

Neither myself or this site or anyone (for that matter), but yourself will take any responsibility for any issues that may arise from the recreation of this project.

Step 2: Gather the Parts

You will need...... (In no particular order)

12 x 5mm Red LED’s

8 x 3mm Red LED’s

3 x BC547

3 x 1N1004 diode

3 x Light Dependant Resistor / LDR

3 x 10K ohm resistor, 5%, ½ watt (brown, black, orange, gold)

5 x 100 ohm resistors, 5%, ½ watt (brown, black, brown, gold)

3 x 10uf 25v electrolytic capacitor

3 x 47K potentiometer (“pot” for short)

3 x 12v Relay

1 x on/off switch (I used an IR transmitter and receiver switch......but, that’s a whole other instructable by itself, so use any on/off switch you wish)

3 x laser pointers

3 x round plastic encasement (I used a BIC ball point pen casing)

PVC pipe (the size and amount will depend on the size of your car and garage)

1 x 15mm by 15mm plywood (or whatever material you choose to make your octagon from)

2 x match sticks

2 x 3mm by 5mm plastic strips (I cut it out of the side of a ice cream tub, but can use any material you choose)

1 x stencil

Black paint or black permanent marker

White Paint

Single gauge project wire (copper wire is better when soldering than for instance “silver” wire)

Perfboard (about 30mm by 30mm)

Step 3: Gather the Tools

Soldering Iron


Solder paste

Nail Clippers

Hack saw

Wire strippers


8mm drill bit

5mm drill bit

3mm drill bit

Project knife

Hot Glue Gun

Glue sticks

Tester (test your components before using them and a continuity tester to check your connections after having soldered the project’s parts together).

I have added links that show how to test the components and which testers can be used.

I like to test all components before using them and the further test will be by bread boarding before soldering the project together. If you do not have a breadboard or even know what it is......don’t worry, it’s not a critical or essential step......I just do it because of my own paranoia lol

I absolutely HATE when I have put everything together just to find out that I have to go search for an issue due to a component not working. Also cause most of my components are salvaged and not bought, i tend to have more component failures.

Step 4: Making the Octagon and Arrows

Making an octagon is quite simple, but a perfect octagon is a tiny bit more complicated.

Here is a link that explains how to draw an octagon.

You can use any shape, I just chose the octagon because it most closely resembles the standard “STOP” sign.

Cut the S, T, O and P out of your stencil and put them next to each other in the centre of the front of your octagon. Now measure out a rectangle around them on the octagon and cut out the rectangle so that the letters can be affixed inside the octagon.

Colour the letters black with your black paint or permanent marker.

Drill 5mm holes about 4mm from the centre of each side of the octagon.

The arrows I cut out of plastic and can be any size you wish to make them. Mine are 50mm long with the widest point of the arrow 30mm and the “shaft” of the arrow 10mm.

Drill 4 x 3mm holes in the shaft of each arrow.

Paint the front of your octagon white (you can use any colour, I just chose white because it reflects light better.)

Attach a match stick (without the head) to the left and right side of your octagon.

Attach your arrows (pointing towards the octagon) to the other ends of the match sticks. I used the glue gun to attach these to each other.

Colour the match sticks black, so that they are not as prominent and sink into the background, so that it looks as if the arrows are floating next to the octagon.

Step 5: Adding the LED's

I arranged the led’s into pairs of 4 connected in series. To connect electronic or electric components in series simply means connecting them in a row with the one component’s positive lead connected to the other components negative lead. (On led’s we call these the anode and cathode, but let’s leave all that to the experts)

Here is how it’s done..... (Even with no electronic knowledge)

The led has a short lead and a long lead.

Take your first led and connect the short lead to the long lead of your second led,

Now take the short lead of your second led and connect that to the long lead of your third led,

Then connect the short lead of your third led to the long lead of your fourth led.

Now your first and fourth led will each have one “loose” lead.

Just to drive the experts crazy......let’s go ahead and call the “loose” lead of the first led the “positive” lead and the “loose” lead on the fourth led we’ll call the “negative” lead.

Now, led’s need a resistor to limit the current flowing through them. There are a wide variety of calculators on the internet that shows you what type of resistor you will need for your led arrangement whether it be series or parallel, 4 led’s or 10 led or whatever.

In this case I am using a 9 volt power source, so the online calculator says I need a 56 ohm resistor however, I like to use a bit higher resistor so that the led is not constantly working at its maximum output. So I am using am 100ohm resistor. Do not use a lower value because that will cause your led’s to fail and if you choose to use a higher or lower power source, use the calculator to show you which type of resistor to use.

Too high value resistor and your led will light up weak or not at all.

Too low value resistor and your led will heat up and fail.

Here is a link to a resistor calculator.

Connect 1 x 100ohm resistor to the short “loose” / “negative” lead of the fourth led in your series arrangement. (Remember, the value of the resistor needs to be adjusted if your power source and led arrangement is not the same as mine)

Now....make two arrangements of 3mm led’s as described above and three arrangements of 5mm led’s as described.

Insert one of the 3mm x 4 led arrangements through the holes on your one arrow and the other arrangement of 3mm led through your other arrow.

Take two of the 5mm arrangements and put them through the 8 holes in your octagon.

Place the last arrangement of 5mm x 4 led’s behind the “STOP” sign you put inside the rectangle of the octagon earlier so that they will shine through the sign and give them a white backing to make them reflect better.

Step 6: Making the Sensors

Each of the sensors is made exactly the same and uses the same components.

Again, if you are not clued up on electronics......don’t stress........I’m not either, so I’ll make it as simple as possible so that anyone can duplicate the result.

If you are an electronics expert......I apologise in advance for some of my terminology that might not be technically correct, but the point of this instructable is not to teach anyone electronics or electronics principles.

Let’s start.....

The capacitor will have a line down the one side, which is the “negative” side of your capacitor.

Solder your 10uf 25v electrolytic capacitor to the bottom right corner of your perfboard with the “negative” lead to the bottom and “positive” lead to the top leaving one row of holes open on both sides of the perfboard.

Solder one red and one black wire at the bottom of the perfboard on the right side row that you left open with the red wire next to the “positive” of the capacitor and the black wire next to the “negative” of the capacitor.

Your LDR should have a red dot on the side, this indicates the “positive” lead.

To the left of your capacitor, solder your LDR with the “positive” lead to the top and “negative” lead to the bottom. LDR’s are notorious for failing when they get too hot, so when you solder careful not to hold the heat to them too long.

Your BC547 has three leads, with the flat side of the BC547 facing towards you, the left lead is the collector, the middle lead is the base and the right lead is the emitter.

Solder the base of the BC547 above the “positive” of the LDR.

Your “pot” has three leads. We will only be using two. Looking at the “pot” you will see two leads on the one side and one on the other side. The one standing alone is the “base arm” and the other two are “sweeper arms”

Solder the “base arm” above the base of the BC547 and the “sweeper arm” above that.

Resistors technically do not have a “positive” or “negative” side, so it can be soldered in any way round.

Solder the one side of your 10K ohm resistor above the “sweeper” side of your “pot” and the other end of the resistor above that.

Now move another line over to the left on your perfboard and solder the emitter of your BC547 next to the “negative” side of your LDR.

Solder the collector of your BC547 above that.

Your 1N1004 diode will have a line on the one side, the side with the line is the “positive” side.

Solder the “negative” side of the diode above the collector of your BC547 and the “positive” above that.

Take a black wire and solder it in the next row over to the left next to the collector of the BC547.

Take a red wire and solder it in the next row over to the left next to the “positive” of the diode.

Up to this point, we have not connected any of the components to each other, we have just affixed/soldered them to the perfboard therefore none of the solder of one component should touch or “run into” the solder of any other components.

We will now connect the components to each other and the board’s “positive” and “negative” sources as follows.

Start with creating a “negative rail”. A “negative rail” is one long solder/wire line from the one side of the perfboard to the other side where we can connect some of the components “negative leads”.

I use a solder line rather than wire, so solder a solid solder line from the black wire at the bottom right to the emitter of your BC547 connecting the “negative” leads of your black wire, capacitor, LDR and emitter of the BC547.

We are going to do the same in creating a “positive rail” at the top of the board connecting the “positive leads of the capacitor, 10K ohm resistor and diode.

Now connect the “positive” of the LDR to the base of the BC547 and the base of the “pot” with solder.

Solder the red and black wire we added next to the 1N1004 diode to the positive and negative of the diode.

We need to connect the relay. We will connect the relay to the black and red wires we added on the far left.

There are various different relays out there, so it will be impossible to explain the exact way of connecting yours, but the basics of all of them are the same.

I used a 4 pole relay (i.e. 4 connecting points)

Two of those points act as a switch and the other two allow power to run through the relay when the switch is activated. Here is a link to how a relay works and which points are which.

Connect the wires on the far left, the red one to the “feed” of the switch part of the relay and the black lead to the other point of the switch part.

If you are using an automotive relay, connect red to 86 and black to 85.

Take a piece of the pen casing, about 30mm long and place it over the LDR and affix it to the board with the glue gun.....again making sure not to heat up the LDR too much. Colour the entire outside of this piece of pen casing black.

This point is critical to the operation of our sensor, so I will elaborate on the working of it a bit.

(Experts....look away now lol) The LDR is like a switch that goes on or off depending on the amount of light it receives. In our project, we will be shining a laser directly at the LDR which essentially turns the circuit “off” and as soon as the laser is interrupted, we want the circuit to come “on”, but there is a problem......

LDR’s react to all different kinds of light, so sunlight, for instance can create a false “off” in our circuit.

The piece of pen casing around the LDR is to prevent any other light than that of the laser we shine on it to fall on the LDR at any time.

Now we have some cleaning up to do. If you use the same kind of perfboard I have then there are silver strips running from one end to another which connect components. I said to solder components together because I have little to no trust in those strips, they can sometimes give “bad connection”. But in having ignored them, we now actually have some unintended connections that we need to go and get rid of.

The one end of the resistor is connected to the “pot” and the other end to “positive rail”, but between the two leads of the resistor, there is still a piece of silver strip. Now, we want the power to run from the “pot” through our resistor to the “positive rail” (or actually visa versa), but it now runs through the metal strip too, so we simply need to take off the metal strip between the legs of the resistor.

Take an 8mm drill bit and place it against one of the holes of the unwanted strip and roll it back and forth between your fingers whilst applying a bit of pressure. That will easily remove the metal film exposing the perfboard material and “breaking” the unwanted connection. Don’t use a drill for this, only the bit. The material is soft and a drill will create a hole right through the perfboard.

Repeat this step everywhere where there are “silver strip” connections which are not mentioned in the steps and also do the same between rows of components

Take your nail clipper and remove any excess wire of the components.

Now take the continuity tester and ensure that all your connections are good.

Recreate this another two times, so that you have three sensors.

Step 7: Bringing It All Together

At this point, we should have a “display” (your octagon with arrows) and three sensors. Right?

Take one of the sensors and connect the “positive” and “negative” (red and black) wires on the bottom right side of your sensor to the power source that you will be using.

We still have two points on our relay that are not connected, let’s connect them.....

On the octagon, we have three LED arrangements consisting of four LED’s each and on each of the arrows we have one led arrangement each.

Connect all of the “negative” wires of the three arrangements on the octagon to each other and the “positive” of the same three arrangements to each other.

Now we have 3 series arrangement connected to each other in parallel.

Take that “positive” and connect it to the one “open”(not connected) pin of your relay and the other “open” “feed” pin of the relay to the “positive” of your power source.

Now connect the “negative” of you parallel arrangement to the “negative” of your power source.

Now do the same with the other two sensors on each of the arrow LED arrangements.

Voilla, the whole project is now connected!

Now we can set it up and then we’re done J

Step 8: Powering the Project

The project can be powered on 9 or 12v, we are using 12v relays, so technically 12v is better, but 9v should be enough for most or all relays to “pull up”. I recommend using a constant power supply rather than cells or batteries. I am using a 9v wall wart. Connect an on/off switch between the wall wart and your project to turn it on and off. Lasers are very fidgety and if left on constantly it might affect their life span.

My lasers use 4 x 1.5v cells. I replaced them with a constant power supply which you can find at this link, so that I don’t have to replace batteries. This constant power supply is linked to my 9v wall wart, so that I can turn everything on or off at the same time.

Step 9: The Garage Layout and Set Up

I used pvc pipe and connected it in a “T” shape as follows....

Measure the width of your car’s wheel base and cut a piece of pvc pipe to that length, now cut it in half and connect the two pieces with a pvc “T connection” creating the top of the “T”.

Now measure the height that you want the display to stand from the ground, so you can comfortably see it from inside the car when you pull into the garage and cut a piece of pvc pipe to that length.

Connect that pipe to the “leg” end of the “T connection”.

Turn the pvc “T” upside down and connect the display to the top of the leg part and two of the sensors to each side of the top of the “T”, so that the LDR points towards the entrance of the garage. Connect two more pieces of pvc pipe to the ends of the top of the “T” to act as a base for the whole thing to stand on.

For the placement of the third sensor, we need to pull the car into the garage, so that the nose of the car is close to your pvc stand but not touching it. Now place the third sensor next to the car so it points across the front of the front wheels to where the wheels would just begin to interrupt the laser beam falling on the LDR of that sensor. Pull the car out.

Now place two of the lasers at the entrance of the garage pointing onto the sensors at the ends of your pvc stand running parallel to your garage walls and the third one pointing towards the sensor pointing over the front wheels.

Put the whole structure closest to the opposite side of where you get in and out of the car i.e. I have a right hand drive car, so mine is placed closest to the left wall which makes me pull the car in closer to the left making more space on the right for me to get out.

Ensure that the sensor that is connected to the left arrow is on the left and the one connected to the right is connected to the right.

Once everything is set up, we can fine tune the sensors as follows......

With the circuit on and the laser pointing at the sensor, turn the adjusting screw on the "pot" until the relay makes a "click" and that sensors display led's come on, then turn the adjusting screw back a tiny bit until the relay clicks again and the display led's go off.

Do the same for all sensors.

Step 10: The Last Word.......

This is how it works........

When the project is switched on, there will be lasers shining parallel to the left, right and front of your car. If you go too close to the left, your wheel will break the connection of the laser to the LDR which will light up the LED’s on the left arrow indicating that you are too close to the left and the same happens on the right hand side. When you get close to the front where you need to stop, your front wheels will break the connection on that LDR which will illuminate your stop sign.

The reason for this instructable is because I am a complete novice myself and by sharing, maybe some will improve on my concept and also share. Also, one friend saw mine and now everyone i know wants you guys can build your own :p

I want to reiterate, I am at best a novice when it comes to electronics, so if you have technical questions, they are better directed at the awesome and always very helpful experts within the instructables community.

This instructable is made with my fellow novices in mind too, so I over explained everything in an attempt to be as clear as possible, but if anything is not clear please let me know, so that I can edit and improve this instructable to better assist you and others.

Also, this is my very first instructable, so any constructive comments to better any future instructables I might write will be greatly appreciated.

I stated earlier that this instructable is not to teach electronics etc., but if you accidentally learned something during the course of this instructable......i apologize lol. Hopefully this at least sparked a bug in you to go and learn electronics....HAVE FUN! :)

I also want to take this opportunity to thank the instructables community for this awesome site that helps so many people.

Again, if you made it, SHARE IT! If you have a better solution or shortcut, SHARE IT!

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