my garage door is pretty narrow, about 10 cm (4") on each side of my car's rear mirrors. So every time I drive to garage, I need to go very slowly because I am afraid I might not be lined up correctly.

I am thinking about using Arduino and some sensors to help me. Output is pretty simple, just two leds, one for each side, showing me if I should turn little right or left to have perfect lineup to center. This I can handle with no problem

What I am asking for is idea how to measure the alignment of my car. I know how to use ultrasonic sensors for measuring distance. But I am not sure they are suitable for this project, because I want preferably to put arduino and sensors in my garage, not in my car.

Any idea how to work this out ?

3 Answers 3


It is very hard to determine position accurately there is a new project on kickstarter called Pozyx, you can look at that but that's expensive, to be honest this sounds like a job for hanging tennis balls or strings or something like that. But if you have a lot of money to blow and you just want a project go for it, you may be able to do this with ultrasonic sensors but I reckon that would be painful. Anyway good luck


It seems like an ultrasonic sensor on each door-post should do it. You need, I'm guessing, 30cm to the sides of your car as its nose enters the doorway. Smooth the sensor reading, compute a difference and display the sign of the differences as right/left lights. Keep a small dead-band around zero-difference or you'll drive the driver crazy!

Do Ultrasonic sensors have the range and accuracy you need for the job? Time for a feasibility study.

Update: Is 10cm plus the length of a mirror = a couple of feet? But even if so, you have to keep to +/- 10cm of the centerline to prevent striking the mirrors, so you could project your sensors out into the doorway by an amount the still keeps them > 10cm away from the car. You could mount them hinged (like the mirrors are) and padded to limit any damage from the occasional accidental touch.

  • I am little afraid, that general ultrasound sensor SR04 will not be useful, because of its wide angle. It might work when the car is pretty close to sensor but it will get false readings when the car is far from the sensors (couple of feet). So I would have to slow down or stop anyway, which is the problem I want to avoid with this project :-)
    – Frodik
    Jun 21, 2015 at 7:49

Try to place two distance ranging sensors like ultrasonic or active infrared at the sides of the driveway or garage door. Make sure that their readings are similar so that you know that you are in the center. If one has a higher reading(farther distance) light an led to your right so you know to go that direction and vice versa. Use communication through xbees, bluetooth, or something similar.

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