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Get where you need to go without taking your eyes off the road with a rooftop directional projection system. This conceptual technology project explores the idea of keeping your eyes on the road and forecasting directional changes at the same time.

This prototype uses a rooftop mounted projector wirelessly connected to your smartphone, sending the directions from your driving app over wi-fi to a Chromecast plugged into the projector which displays the images on the road immediately in front of your vehicle.

Here's a short video of it in action:


While not the most practical, this was a fun project to combine things we had laying around the shop and test the limits of what is possible with current technology.

Follow along as I show you how I made it!

Step 1: Supplies (and Some Notes About Screen Casting)

To accomplish this project we need to solve the power requirements of the projector, the wi-fi hotspot, and the Chromecast. Instead of tapping into the car's battery I dedicated a power supply just for the electronics and kept everything neatly stored on a lockable rooftop storage.

I used a Nexus 4 smartphone for this project, as it supports screen casting from your phone to the Chromecast. Screen casting allows you to mirror what your your smartphone displays to be sent to the Chromecast. Not all phones support screen casting with the Chromecast, allowing you only to cast certain apps, like YouTube and other Google properties.

Step 2: Rough Assembly + Testing Theory

The projector was plugged into the power inverter and the battery was connected to the inverter to power it up, then everything was placed on top of the car. The projector was powered up and tilted towards the ground to approximate the location and angle needed to successfully view the imagery from the drivers seat.

With the components on the roof and energized I could validate that this concept works, even in a well lit parking area. I took note of the angle the projector needed to be to project in front of the car and still be viewable from the drivers seat over the hood.

Step 3: Electronics Platform

To make a platform for the electronics to sit on, the inside of the cargo box was measured between the attachment rails.

I cut a sheet of 1/4" plywood to fill the front space of the cargo box, it fits between the attachment rails and flares out around the back end of the attachment screws to help hold it in place.

Step 4: Place and Secure Electronics

I arranged the projector to face forward, and the inverter and battery were placed behind the projector to minimize the cable distance.

To ensure the components wouldn't move around while the car is moving they were each secured to the platform with tension straps. The mobile wi-fi hotspot was secured with a small velcro pad.

Step 5: Measure Rooftop Box Opening

With the components secured and in the proper placement we can mark where the projector lens will interface with the cargo box. The component assembly was placed inside the cargo box, with the projector lens almost touching the front of the box. A marker was used to trace the location of the estimated projector beam.

Step 6: Cut Rooftop Box Opening

I used a 2" hole saw to cut through the cargo box at the marked location. The edges were cleaned up with fine grit sandpaper to make a nice smooth opening.

Step 7: Install Rooftop Box

With the opening for the projector beam made in the rooftop box, the entire unit can be installed on the roof of the car.

This model rooftop cargo box has claws that grip onto the roof rack which hold it in place. The claws are opened from the inside by unscrewing the four handles. With the claws open the rooftop box can be slid into place over the roof rack, then screwed tight again to secure the rooftop box in place.

Step 8: Test Assembly With Opening

With the hole cut the projector can be installed again and tested to see what adjustments need to be made.

The image projection was larger than my opening, you can see in the image above the light hitting the inside of the cargo box. The opening will need to be the enlarged to allow a clean projection.

Step 9: Realize Your Opening Is Too Small and Enlarge

Using a coping saw I enlarged the hole to allow the light from the projector to pass through without being obstructed.

Step 10: Window for Opening

To protect the lens of the projector while driving I made a small window from a scrap piece of clear acrylic. I cut an oval shape about 2" larger than the opening, then used waterproof industrial adhesive to secure the acrylic in place.

Step 11: Tidy Up Wires

Since these components are secured so close together we can tidy up the wiring. The long cables for the inverter and the projector were wrapped and secured with twist ties.

The leads from the inverter to the battery were pincher clamps, which is not suitable for this application. I cut the pincher ends off and made a screw eyelet from the leftover ends. These eyelets will be the new connection points that will be screwed into the battery terminals.

Step 12: Plug in Everything

With the components securely fastened to the platform and the cables managed everything can be plugged in.

The inverter leads were attached to the battery, then the projector, mobile hotspot, and Chromecast were plugged into the inverter. Lastly, the Chromecast HDMI was plugged into the projector.

Step 13: Install Electronics in Rooftop Box

The electronics platform can be installed into the rooftop box and securely fastened down with a few tensions straps.

Step 14: Get Chromecast App

For the smartphone to communicate with the Chromecast in the projector we'll need the Chomecast app. This free app allows you to beam media from your smartphone to the Chromecast dongle.

While the Chromecast app will cast loads of supported media from any smartphone (like YouTube, Twitch, Hulu, Songza) the Nexus smartphones offers screen mirroring, which will allow allowing you to cast whatever is viewed on your phone. Since we want to cast a directional app that is not supported by the Chromecast app we'll need to have direct screen mirroring.

Step 15: Sync Chromecast

With the assembly energized we can sync the Chromecast to the app on your smartphone. Connect your smartphone to the mobile hostspot wi-fi.

When the projector is on and the Chromecast dongle is inserted and powered, a startup screen should appear letting you know the Chromecast is present. This screen will appear even when there is no wi-fi signal and there is no phone tethered to the Chromecast.

Open the Chromecast app and start the sync with the Chromecast dongle. The process is automated, so as long as your dongle is powered and in the projector the app will sync with the projector. The projector screen will change to show progress, and after a few moments the projector will be paired with the smartphone. You can now cast your screen.

Step 16: Get Navigation App

Since we're able to cast anything that's on the Nexus smartphone screen, you can use the driving app of your choice.

Step 17: Keystone Correction

Projecting from the roof of the car to the road will result in the image being skewed into a trapezoid shape, like the keystone in a stone arch. Almost all projectors can correct for this effect through an option in a menu, or as a button on the projector itself.

Step 18: Close Up Box and Wait for Night

With everything installed and working we just need to have a need for directions at night, since even the brightest projectors can't overcome the sun - even on cloudy days.

Step 19: Direction Projection

Night time, lost, and in need of directions? Engage the rooftop direction projection system!

Pull over and turn on the projection system, then hop back inside your car and sync your smartphone.

Step 20: Light Will Guide You

With your smartphone synced you can load up the directional driving app of your choice and have it cast in front of your car. Let the direction projection guide your way, without taking your eyes off the road.

Even with the headlights on, the projection beam lands just in front of the hood and in between the headlights, so there's no interference to reading the projection directions.

Step 21: Take Me Home

This Direction Projection explores the idea of using a high-powered projector as a directional aid while driving. This project has the added benefit that if the driving directions ever steer you wrong you've got the ultimate high beams to clear the road ahead.

Be safe out there!

I Like This. Thanks<br>
<p>how about projecting it onto the hood of your car? We all can see the hood when we are driving and it doesn't disturb us. How about converting one of those bug guards into a mini screen so it can project onto that? If the guard isn't dark enough you could add window tint and if it isn't long enough you could cut off the ends and epoxy it to the middle so you could see the arrows and map screen. If I have time to make a drawing of the idea I'll add it. </p>
Possibility of glare, on top of that most of the time those are only a few inches high.<br>And in my car I can only see the hood at a very steep angle because of its slope.
<p>Very good.</p>
Forget about the map part, now you can watch a movie in the car AND keep your eyes on the road!
Is this legal (as in being a visual distraction on the road)?
<p>best idea ever and sorry youre wrong it is very practical</p>
<p>This Photo has to be fake. I know not any navigation app that can out of the box ONLY project a direction like on the Photo.</p><p>I looked in to this because i liked the idea to use as a HID on the dashboard, for that you need (like this) a way to get the directional screen part from your navigation app.</p><p>Like copying the right or left hand corner of the nav screen.</p><p>Otherwise nice project :-) </p>
<p>There are tons of apps around. This is definitly no fake.</p>
name ONE app who can project ONLY the direction arrow?
<p>Just put it into a night and /or easy mode. I don't use any navigation software at all, so I can't help you there.</p>
<p>Put the projector under the front fender...</p>
<p>One word: EPIC</p>
<p>wow!</p><p>has anybody said anything to you while you were driving?</p>
<p>interesting... =D</p>
<p>is so original</p>
<p>How do you keep the very hot projector from overheating in a closed chamber?</p>
<p>Really cool idea. I hate to be a party pooper though. You might be careful if there are police officers around. I think in the US projecting beams of lights from anything other than your head lights is illegal. The fear is you could blind an oncoming driver. This is why in many states the spots on role bars must be covered. In case of accidental powering of the lights.</p><p>I think the idea is great. Might try to minimize it a bit and do a heads up display. Maybe predictive turn signals. So you never have to hit that switch again!</p>
<p>you could always integrate with information from Waze to shut the system off when cops are around :-)</p>
<p>Use Waze as your nav app and you get both! Directions and cop notification...</p>
<p>Nice idea,,, you covered the practicalities of it for real use but it is imaginative and food for thought. I read somewhere about a flexible polymere than can be used as a screen. Maybe cover your bonnet in it and have the arrows showing up on the bonnet and thus get around any problems of projecting light... </p>
<p>Hey, what driving app did you use?</p>
<p>Cool! No of such damn problems of head-up-displays! </p><p>How does it work in bright daylight? </p><p>How does it look when you're stopped behind another car at the traffic lights?</p>
<p>Cool project.</p><p>I thiiink I'll just turn of screen rotation and place my phone 180&deg; on my dash though.</p>
Great job, Mike.<br>To make it more simple, I suggest you to use mini led projector which is more tiny (as big as your palm) such as PICO, and it powered by 12V DC, so can skip the power converter thomas. Also you can put it behind the grill of your car.
<p>@Danang JKT</p><p>4 topics: Lumens, projection angle, accesibility, water protection</p>
<p>Awesome stuff, you should also check &quot;car HUD&quot; in google... works also in full sunlight!</p><p>Keep it up :-)</p>
<p>As cool of an idea as this is, the fact someone found a need for it disturbs me greatly. I have traveled, by road, all over the United States. I've gone long distances, and short distances when I got there. I've been through big cities, small towns and through farm land for as far as the eye can see. I've never needed any kind of device to tell me where I am going. The fact more and more people are losing the basic ability to navigate well defined roads is a bad sign. It honestly scares me that people rely so heavily on technology to go from point A to point B. <br><br>It's still a cool concept. I just hope that humanity does not become so mentally delapidated as to require the use of GPS and HUDs to go to the corner store for milk. :(</p>
<p>I agree with everything you said about navigating around. I enjoy getting around with a map. That said, I occasionally drive in the most illogical city (Boston) and appreciate being able to keep my eyes on the road and still making my turns to get where I want to go.</p>
Now I can watch movies like a dive-end on the backs of similar trucks im tailgating.
<p>You mean <em>drive-in</em> ? Brilliant idea ! And because everyone passing can watch your movies for free, this will make you extremely popular with your entire community !</p>
<p>Drive-end sounds more like it. the &quot;end&quot; is from the vehicle in front of you.</p>
<p>Maybe use a different color for daytime, depending on the strength of the light. I love the idea. And it's a good indicator for those who tend to tailgate / hug bumpers to stay back. </p><p>[You can also tell of those who keep asking if it works in the daytime hadn't read the whole instructible.]</p>
<p>I can see a marketable product here. This could easily be reduced to a smaller package that could be secured under the hood with projection through the grill. And, a Kickstarter campaign could provided the funding to pursue development. I would happily contribute to a Kickstarter campaign for this concept.</p>
<p>Very nice idea. </p><p>I just saw this feed on G+ and this made me join Instructables community earlier than I planned. Thanks for sharing :)</p><p>I would like to suggest an upgrade, to disable the projection as soon as you will be closer to following car. </p>
<p>The only problem I see with this is that if you have to stay really far back from other vehicles when stopped. Other wise the light from the projector will shine right in the drivers eyes in front of you. Other wise it is a neat idea. </p><p>The only other thing I would add is it may violate some state vehicle codes depending on your location</p>
<p>you shouldn't be driving any closer that one car length anyway, which is how far ahead of his car the image is being projected.</p>
<p>The photo for Step 21 shows the beam beginning about a car length away, not projecting a car length away, and ending about three car lengths away.</p>
<p>May be useful to you, but would it perhaps cause great distraction and confusion for other drivers ? Just the over-bright driving lights on some cars are a nuisance by themselves.</p><p>Imagine what the roads would look like if <em>everyone</em> used this ! Bendy arrows criss-crossing at junctions and moving all over the place ! A nightmare of confusion !</p>
<p>I don't think it works very well, look:<br>&quot;Step 21, You are on the wrong way!&quot;</p><p>Just kidding! </p><p>Man, amazing! Congrats for your idea and for your good job!</p>
<p>awesome! If only it could be packed under the hood...<br></p>
<p>Is it bright enough for daytime use? Great concept. </p>
<p>Wow, I thought everything was developed 2015, but no. This is a great idea and i will bet it will be standard om all cars within some hers. Really great work!</p>
<p>I really like the concept - first thought was day/ night projection, then the new BMW answer to GPS that displays info on the windshield/windscreen. The technology you merged is enticing and I appreciate what you've done as it can lead to other applications. Kudo's</p>
<p>There would be fewer issue using HUD technology than projecting on the road. Laws limit what kind/color of lights can be displayed from a vehicle and in the daytime it wouldn't work very well. I can even imagine a municipal signage law coming into play as you project images onto public roads. A HUD would use a lot less power also. Interesting idea though and of possible use for other purposes, like communicating with other drivers, marking safe following distances at highway speeds, etc.</p>
<p>that's actually pretty fecken ace!</p>
<p>This has merit. It's almost like showing other drivers your next planned move. I would agree with others though, a HUD would be more cost effective. Still hats off to you bringing a novel concept to reality.</p>
<p>Great idea, probably best as a heads up display. Issue I foresee, it projects everything on your phone including incoming phone calls, text messages, searching for a nearby restaurant. Just let everyone know about your distractions.</p>
<p>Some site, maybe banggood or cndirect was selling something that projects something on the road behind the car when you hit the brakes, uses a laser and either makes a straight line or writes the word &quot;stop&quot; on the pavement or something. Might have also helped with fog.</p>
<p>What would you do during the day? Heads up display on the windshield is much more practical.</p>

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