Garage Distance Sensor Kicks Tennis Ball To Curb

Those with small garages might be familiar with the method of hanging a tennis ball from a ceiling to make sure they don’t hit the back wall with their car. If the car isn’t in the garage, though, the tennis ball dangling from a string tends to get in the way. To alleviate this problem, [asaucet] created a distance sensor that can tell him when his car is the perfect distance from the garage wall.

At the heart of the distance sensor is an HC-SR04 ultrasonic rangefinder and a PIC16F88 microcontroller. [asaucet] uses a set of four LEDs to alert the driver how close they are to the garage wall. [asaucet] also goes into great detail about how to use an LCD with this microcontroller for setting up the project, and the amount of detail should be enough to get anyone started on a similar project.

While this isn’t a new idea, the details that [asaucet] goes into in setting up the microcontroller, using the distance sensor, and using an LCD are definitely worth looking into. Even without this exact application in mind, you’re sure to find some helpful information on the project page.

24 thoughts on “Garage Distance Sensor Kicks Tennis Ball To Curb

  1. I first read about the tennis ball trick (I think it was a ping pong ball) on a book review. The author made the point that the ping pong ball was way cheaper and simpler than some electronic solution. Fifty years ago, it was just a few transistors. This is way more complicated.


  2. Who wants a ping pong ball hanging in their garage. You will get annoyed with it in a few months after you bump into it and get tangled walking around. Ultrasound sensor can be put anywhere and the lights at a convenient spot.

    1. Or you could adjust your mirrors and learn the size of your vehicle so you aren’t a hazard when you have to maneuver in a tight area outside your garage.

      But that doesn’t involve a breadboard. Fun project, but it enforces bad habits.

      1. [Name-calling edited out. Keep it civil, folks.]

        There are many reasons why even someone who can maneuver fine would find an aid useful. My garage is big enough for the vehicles, but I’d like to leave as much space in front as possible in order to leave space to walk across the front of the garage to access the side door. Would also like to ensure the garage door doesn’t hit the bumper or trailer hitch. Try adjusting your mirrors so you can see the top of the garage door and the trailer hitch that you couldn’t possibly see from your mirrors no matter how much you adjust them.

        Also other people may be using my cars and have to park them in the garage. I use tennis balls – it makes things easier for me and them. Have thought about a distance sensor, or small blocks on the ground or other solutions, but so far the hanging tennis balls haven’t annoyed me enough to do anything different.

      2. In the garage I’m using there is a mark on the side wall – my girlfriends father scratched his side mirror on that wall.
        Nowadays, I just line up my side mirrors to the mark, and voila – perfect position every time :D

        So yeah, just adjust your mirrors :D

  3. If you’d bothered to read the article you’d see that he explains why he gets rid of the LCD screen in the final version:

    “The second reason is simply that it is not needed in the final product. Being able to print text on a LCD display was helpful when writing the logic for distance measuring, but it will not be useful in the end.”

    Not useful in the end – kind of like your comment.

    1. Chivalry is dead, that we all know. But please don’t let humor be dead too.

      Keep ya hat on Jerry, here’s my olive branch. An Arduino Blood Pressure sketch. Don’t worry it doesn’t have an LCD. Instead when you get a reading above 140/90 it produces a 4Khz tone in an ear piece. This feature only deactivates when a high enough AC current is detected through the wearer.

      1. It sounded like your comment was an all too common(around here) useless negative comments and I apologize if it was truly in jest however anyone who read the article wouldn’t think it was funny because of the fact that the author specifically included that the LCD was for assistance in programming and not part of the final product.

        I’d have just used a laptop and serial debug to avoid having to attach the LCD but the author may have had perfectly good reasons not to do so…like not having a laptop.

  4. stuff on a string or distance sensors only tell you to stop…
    In my garage, I have a physical stop made out of a metal wedge that actually prevents me from driving into the pile of junk in the back of the garage :D

  5. A VERY simple solution to the “ball in the way when no car in the garage” was implemented by my dad. Simply hang a pulley from the ceiling or rafters, run the string/rope through the pull and connect to the door. When the door goes down it pulls the ball up. When the door goes up the ball comes down. For when the door is up and no car, put a cleat on the door and wrap the rope to raise the ball.

    1. I was thinking of something like this. Another idea is to have a padded board near the ground but within sideview mirror view and when the bumper hits the board, you’ll see the board move and then you can stop. Of course, it could be a hassle if the board is in the way of walking around the car.

  6. I tried doing this very same project several years back, but was unsuccessful. The issue I encountered was that the aerodynamic body design of my vehicle acted like a form of stealth. This is because the angles on my vehicle caused the ultrasonic range finder to have unreliable at best results since the sound waves bounced around my garage after hitting the windshield before getting back a reading. As result the distance readings were all over the place as I approached.

    I am curious to find out if there was any heuristics or fuzzy logic used in this project to help correct for these issues.

  7. Just an idea : A laser pointer mounted anywhere and positioned to fire a spot on to your dashboard when the car is at the right position. A microcontroller could be set to drive the laser for the few minutes you need it after opening the garage door.

    1. similarly, two pointers inside your car. when they converge to a single dot, you’re at your fixed distance. Like the old altitude systems for bombers once used. When I once parked in a garage, I used the pattern my taillights threw-when they were almost in focus, it was time to stop. If the lines and marks were easily seen, was way too close

  8. Here’s an old but effective idea out of WW2: In the war, Brits would drop bombs in the water to blow up dams. To know the right altitude, 2 spotlights shone down onto the water. When the spots meet, hold it right there until time to drop the backspin bomb.

    All you’d need to back the car into the garage perfect would be 2 flashlights in the back windows and a switch at the cockpit. When the spots meet, you’ll be at the right distance, though after a few experiments. 2 laser pointers would make it about PERFECT. Draw a vertical line on the wall and you could set up something to dock your car to – like the charger for an electric car.

    1. Or, use a flashlight and magnifying lens to focus it on the hood. You remove the minimal eye hazard. I was thinking of backing in, as I habitually back into parking spaces. (or at malls, just pull through) In that case, you back up until the light hits the back window. That’ll work unless someone does try to make a docking port for their electric car. Then, my one idea above would work.

      For some more WW2 history fun, they invented a way to make it less difficult to land planes onto carriers. To one side of that “runway” there was and still is, a thing with 3 bulbs behind a fresnel lens. Come in too high, you see one color light. Fly too low, another, fly just right, you get the desired color. Follow it in until the last couple seconds. If you’re good – or lucky – the tailhook catches and you land feeling like you’re going through the windshield.

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