Description
The card accelerator gets the cards to the players. All of the fabrication for the card accelerator was 1/4" MDF and 1/8" hardboard that was lasercut in Olin's machine shop assemblied with off-the-shelf items. The card accelerator was experimental in our third iteration and was finalized in our latest iteration and spray painted.
It is a wheel directly driven by a DC motor at the bottom of the ramp. The motor is attached to a motor controller that keeps the wheel turning at a constant speed. We mounted the motor on a linear slide and a screw lets us adjust it up and down while two springs keep the holder on the screw. This lets us tune the distance between the ramp and the wheel, adjusting the grip the wheel gets on the cards.
The accelerator is controlled using a proportional controller. The DC motor is attached to a current driver. A signal from the output is then sent through a non-inverting amplifier. The amplifier is essentially a proportional gain across the motor. In the third iteration we were running into issues with grounding the operational amplifier we were using in that we were getting -6V to +6V instead of 0V to 12V and was resolved in our latest iteration.
There was originally going to be an IR distance sensor on the motor mount. The idea was that the speed of the motor would change based on the distance the sensor detected. The main point being to adjust the speed of the card depending on the distance the players were from the card player. We realized toward the end of the third iteration that it was going to be more challenging than we thought. It we were going to have to redesign the motor controller and give it input from the Arduino. We decided that implementing the IR sensor was going to take too much time, and we were better off working on other things.
Things to keep in mind
- It's okay to kill your darlings
- Make sure that the material you are lasercutting is flat to avoid warped pieces