Live Fire I

Objective:

The purpose of this test was to demonstrate the firing sequence. The motors were spun up and the loader actuated so that one shot was fired every two seconds for nine shots.

Procedure:

Two pins on Port A were set to output. They were turned on and off in one second intervals. Simultaneously the loader servo was actuated to load a dart. This process was put into a loop that ran nine times. The launcher motors were given 3.6 V each. The test was run twice.

Outcome:

The test was somewhat successful. Several problems were encountered. Vibration was the major cause. Small asymmetries in the launcher wheels create violent vibrations at high angular velocities. Several failures were encountered:

• Because the Nerf darts are very lightweight they are easy to knock out of position. The vibration from the motors shook the darts enough to cause two blanks to be fired out of the nine shots in each trial.
• The CMU board consists of a processor board and a CMOS camera board connected by pins. The connection is not particularly secure so the vibration from the motors was enough to shake the CMOS board loose.
• The velocity of the wheels is enough to wear significantly on the dart bodies. Streaks of the dart foam were visible on the wheels after the test.
• The launcher is not accurate. A spread of approximately 1.5 to 2 feet was observed at a range of about 10 feet.

A simple change can be made that will improve all of these problems. By lessening the voltage to the motors from 3.6 V each to 2.4 V each the vibration will be significantly less. This will help keep the darts settled in the hopper and will generally be better for the wellbeing of the structure. By using a lower velocity the darts will not wear as fast and the accuracy should be improved.

Other improvements will be implemented. The loader servo arm will be modified to have a more suitable shape. The CMOS board will be glued to the CMU processor board. Depending on the performance of the hopper while running the launcher motors at 2.4 V, a mechanism may be constructed to hold the darts in place.

Video:

Live Fire I