Wind Tunnel/Howard Community College/Fall 2011/550 Wizard Jr/Weekly Reports

Link to Wizard Jr team page.

Week 1

In the first week it was initially thought that the wind tunnel could have an array of computer case fans as the source of wind. As I had several of these lying around the house as spares, I linked them together to a PC power supply, and jump started the supply using the paperclip method. The power supply was able to run at least eight 12V@0.53A fans without any power faults for an extended time. I looked into and later found a fan controller that while not able to display the rotational speeds of the fans, did provide 30W per channel so that multiple fans could be controlled off a single header. In addition, early research was done into the design, function, and expectations of wind tunnels with several sites providing useful information and design schematics and step-by-step guides.

I was later informed that I should try and use an Arduino to connect the fans to the computer so that the speed could be entered on the PC, and the array of fans would immediately respond and alter the wind speed within the tunnel. Multiple Google/Bing web searches using various terms resulted in overly complex or insufficient design results.

Week 2

I was given an Arduino Uno and after locating the main site for Arduino, downloaded the programing software and drivers necessary to write software and load it onto the board. Installing the software took several steps but was otherwise straightforward. In addition, I was allowed to borrow a powerful R/C motor and ESC to use as the source of wind in the wind tunnel. Learning how to program the Arduino and interface it with the ESC was the task for the following week.

Week 3

R/C servos use PPM versus PWM for control which requires use of the servo library in the Arduino software. This in addition to a new search term, pwm esc arduino, led to better prospects for usable code. Connecting the ESC to the Arduino Uno board required using two wires. Several programs were tested with none producing any response from the servo although there was indication that the ESC and arduino were interacting, passing commands with responses from the ESC, but none of the commands were getting to the servo.

Week 4

After the failure of the searched code, I was given code used by a previous team but they still produced no results. With the possibility being that the ESC or servo was at fault, both were returned and I was given a less powerful combination to use with the previous group's code. This combination proved fruitful with only a minor change in one parameter of the esc_easy code resulted in the R/C servo immediately spinning and accepting commands sent via the Arduino to the ESC.