How to Build a HUD for your Car

Hello all, this is the Car Heads-Up Display (HUD) Version 1.0: Researched, constructed, and installed in approximately a month on a 2004 Toyota Highlander.  This is what it looks like in action:

Overview

HUDs are built-in on some modern luxury cars, but if you not lucky enough to have one, here's how to make your own, DIY-style. My model uses the car's OBD-II port to connect to an Arduino microcontroller, which is programmed to display the car's speed on a 7-segment display.  A fresnel lens is used to optically collimate the display, which is projected onto a piece of combiner glass. The difference between this and most third-party HUDs is:

• Optically Collimated - This means the display is focused at infinity, so the driver does not need to refocus his eyes from the road.  The display looks like it is floating in space right where the road is.  Most third-party HUDs are not collimated.
• Utilizes a Combiner Glass - This specially-coated piece of glass allows for virtually seamless viewing of the outside road simultaneous with the display, as opposed to cheap "reflective films."

Here is the full setup:

Overview of the setup

Shopping List

• Arduino Uno - $20
• OBD-II cable - $50 - This one comes with an Arduino library, so it's easy to program with
• 7-Segment Display - $13
• Arduino Protoshield - $10 - to easily mount the display on top of the Arduino (this is optional, you can just use perfboard instead)
• Power switch - $0.50 - really cheap and makes it easier to turn the power on/off instead of unplugging the wires every time
• Large Fresnel Lens - $1.80 - It really doesn't matter which one you buy as long as its at least ~220mm long
• Teleprompter Glass - $15 - Get the 7" by 4" custom size
• 4 Suction Cups - $3 ($1.50/pack of three) - You can use any suction cups you want, just make sure they can hold the glass safely (these are rated for 3lbs)
• Total Cost: $113.30

Supplies Needed

• Soldering Equipment
• Hookup Wire
• Lots of Cardboard
• Duct Tape
• Pliers

Prerequisites

• Some Soldering Experience
• Some Arduino Experience Suggested

Building

Step 1: Solder the Circuit

Connection labels on the protoshield

Solder these connections onto the protoshield to be mounted on the Arduino:

• OBD:
• Yellow wire to D0
• Blue wire to D1
• Red wire to 5V
• Black wire to GND (through the power switch if you have one)
• Display:
• VCC to 5V
• GND to GND
• RX to D6

Step 2: Upload the Code

Go here and download the code, then open it with the Arduino program, connect your Arduino to your computer, and upload the code.

Step 3: Build the Arduino Holder

Pick a place in your car to build the holder for your Arduino.  Keep in mind that it should be about 10 inches away from the lens, and it should be out of the way of your hands and legs when you drive.

I built my holder into an existing compartment below the steering wheel

Duct tape and cardboard are extremely cheap materials to use, and they hold up pretty well. Next, put the Arduino on top and connect it to the OBD wires.  I soldered headers onto my protoshield for easy connection with the OBD wires.

The fully-soldered protoshield mounted on top of the Arduino

Step 4: Mount the Combiner Glass

Bend the hooks of the suction cups to cradle the glass like this:

Angle the glass until you can see the reflection of the display, then tweak the suction cup hooks to hold the glass in that position.

If the suction cups hooks aren't long enough, just cut out a segment of a wire clothes hanger and bend it around the suction cup.

After you finish, you might want to pull on the glass a little bit to make sure the suction cups will hold.

Step 5: Mount the Lens

The fresnel lens is very flimsy by itself, so I recommend taping some support around the edge.  You can use cardboard, popsicle sticks, or anything you find around the house.  Wooden kabob sticks worked well for me.

Now that the lens is nice and sturdy, you need to figure out the exact position the lens should be in to collimate the display.  This can be tricky to get exactly, but you're looking for when the display is the most magnified without being blurry.  I found this the easiest way to do it:

Look through the combiner glass and through your windshield at an object far away (let's say a tree).  Notice how when you focus on that tree, the display splits into two images because your eyes are no longer focused on it.  Now place the lens right over the Arduino and then slowly move the lens up towards the combiner.  Still focusing on the tree, you should see the two images of the display gradually get closer to each other.  When the two images meet, stop moving the lens and mark its position.  That means that the display is now focused at the same location as the tree.

Light beams showing how collimation works

Now build a holder with cardboard and duct tape to hold the lens in that exact position.

When in doubt, more duct tape

The lens will probably be bigger than you need, so just use scissors to trim off some of the edges where it's not needed.

Congrats!

You now have a working heads-up display.  Go for a test drive to see how well it works, and email me at abnormalbill@gmail.com with questions or comments.