The Switch Doc rebuilds his cat toy launcher with 3D printing

Mouse Firing Base and Motor

The MouseAir firing base is built as a separate module in its own file. It is added as a module call in the main MouseAir Bottom code. The base consists of a servomotor stand, the "mouse containment box," and a slot for the ramp to be inserted. Why do I have the ramp inserted rather than built in one piece? Turns out that it is very difficult to install the rack and pinion gear and the servomotor with the ramp in place, so I build the ramp separately and then just slide it in (Figure 15).

Figure 15: MouseAir V2 firing ramp.

Without the ramp in place, you can see the underlying rack and pinion gear (Figure 16), whose OpenSCAD file I found on Thingiverse and just modified to make the pushing ramp that pushes the mouse up into the spinning motors then into the air.

Figure 16: Rack and pinion gear for the firing ramp.

There is also a stand for the second servomotor that powers the mouse loading conveyor belt on the MouseAir top (Figure 17). The top has the mounting hole for the DC launching motors and the tower for the pan and tilt mechanism for the Pi Camera.

Figure 17: Completed MouseAir V2 ready to fire!

Mouse Loading Conveyor Belt

The mouse loading mechanism proved to be the most difficult mechanical design aspect of the entire project. The goal was to be able to load and launch up to five mice reliably using the loading mechanism. In MouseAir Version 1, I used a PVC pipe and two servomotors to dump a mouse into the firing slot. It was just not reliable enough; although the pipe was big enough to load eight mice, the mice would get stuck and land badly in the firing slot, making the whole contraption noisy and slow. In MouseAir V2, I first used a ramp with one servomotor controlling a two-rack-and-pinion slot dropping one mouse at a time. It worked better, but it still wasn't good enough.

Finally, I decided to try using a flexible timing belt to build a small conveyor belt that would load the mice one at a time into the firing slot. It took me less than one day to convert the MouseAir top and bottom to use this scheme. My use of modules and debugging techniques had improved dramatically. Figure 18 shows the debug print for the conveyor belt.

Figure 18: Debug print for conveyor belt prototype.

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