Augmented reality sandbox control using Arduino Feather

It’s been a while since I completed this project. I promised the Augmented reality sandbox community to write something in details so someone can replicate it. Here is the gist of it:

The Augmented reality sandbox (ARsandbox) is an awesome simulator that blends sand landscaping with augmented reality. A projector casts color-coded elevation, contours, and simulated water flow over regular sand. A 3D sensor measures the sand landscape in real time so the computer knows where sand is high and how it slopes down and renders color and contours according the the 3D data. You can rain over the landscape by pressing a button or hold out your palm over a certain area.

Here is a video of one of my builds:

This is where the control box comes in. The sand box is a 40″ by 30″ box with up to 200lb of sand. The function to rain over the augmented terrain is to press the “1” key on a keyboard. Sand and keyboard shouldn’t mix, not to mention if the system is deployed in a museum, the keyboard probably should be hidden from patrons. So a box with rain and dry buttons will be most convenient. You can make these buttons by following this forum post. You buy and assemble a USB gamepad kit and doing some scripting but it’s not that easy to follow if you are a Linux beginner. I want a plug-n-play solution so that anyone that wants to add a button box can add it without any knowledge of Linux and minimal skills in circuit assembly. In order to achieve my goals, the electronics inside the box has to emulate keyboard keys “1” and “2” for rain and dry. This ensures that the control box requires no software setup on the Linux system. As a bonus, the buttons should flash blue and orange so it would invite patrons to press and is color-coded for rain (blue) or sun (orange). Enter the ARsandbox control box:

Here is a short video of the box in action:

Features of the box:

1. Two buttons. Blue button on the left emulates the “1” key. It starts the rain in the main simulation, and is used in the projector calibration program to enter tie points, and can be assigned other functions in other programs such as extracting plane. Orange button on the right emulates the “2” key. It drys the rain in the main simulator, and can be assigned functions in other programs.

2. Both buttons have LEDs that flash to invite patrons to press. My 5-yr old son figured out what they do simply by the colors they flash because he knew the rain and dry features already but wasn’t told what these buttons would do.

3. No software setup is needed. This box works like another keyboard, with only 2 keys though.

Here are the parts I used, in case you want to build your own:

1. Adafruit Arduino feather 32u4 basic board (1)
2. LED push buttons 16mm from adafruit (2)
3. USB-micro cable (1)
4. USB extension cable (1)
5. P-channel MOSEFT BS250 from mouser (2)
6. 330 ohm resistors (2)
7. 1K ohm resistors (2)
8. DuPont 30cm female-female jumper wires (4)
9. Prototype board or my printed circuit board. Click here to download (1)
10. Enclosure SK-15 and flange kit SK-99 from polycase (1)
11. Cable gland M3198GBH from Heiland for pre-assembled cables with USB connectors (1)
12. Arduino sketch. Click here to download

Here is the schematic of the circuit:

Since the ATMEGA32u4 microcontroller on Adafruit Feather 32u4 is operating at 3.3V, I had to use two transistors to ensure that the LEDs inside the buttons light up with sufficient brightness. Currently the code only blinks both button LEDs at the same rate. In the future, I may update the code to blink more rapidly on the button that is depressed.

The following is a prototype that I built with the parts on a perfboard. It’s a bit messy and also took almost 2 hours to complete. I had to solder 16 wire leads and a bunch of jumper wires on the back side of the perfboard. I wouldn’t recommend this to a beginner.

Here is the printed circuit board that I designed (3 boards, two on the right showing the top, 1 on the left showing bottom):

The board is fairly simple and straightforward to solder. Only 8 wire leads and soldering the rest on the printed board, which is very easy. I also cut in half 4 30cm female-female Dupont jumper wires so I can just use the female side with male pins on the board to cut wire leads in half.

Here is a photo of the assembled guts including the microcontroller soldered to the button box board. Notice the black female Dupont connectors :

Here is the assembled board placed inside the enclosure. This enclosure is not cheap but nice and easy to use. It has various knock-outs so I didn’t have to drill a single hole.

Here is the completed box:

Although I am not aiming to sell a lot of these boxes, I think that designing the printed circuit board was the right way to go. I probably spent a few hours designing and proofing my design but I saved about one hour for each subsequent box I made. Plus, if YOU are interested in making this box, it will save YOU at least that much time.