Introduction: Direction Projection

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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!