Having won the Young Novice category for the international Piwars competition, we figured we should update and showcase what we have done in the last few months, since it has been a while since we have properly posted.
We have completely overhauled the old body design, going for a more functional system and a more aesthetic look with a fire engine
This design was made by Calvin in QCAD. The finger joints were generated in makercase, which sped up the design process a huge ton. Our laser cutter also has the handy tool of making less deep cuts - engravings - if the engravings are put in a separate layer, as seen above with the blue lines.
The front cabin is less wide compared to the back: this holds our Pi, battery and blinky lights for easy access to the most needed components. Putting the Pi there allows us to easily switch out Dupont connectors for different attachments for each challenge.
[its a stock photo cus I couldnt be bothered to take a picture]
The little rectangle sticking out of the front cabin is where our attachment dovetail bracket is held. We have 2 JGA25-370 motors, quite powerful and gave us the speed and power for the competition.
Our line follower contraption was made of 3 IR sensors, as well as a bracket made in Fusion 360 by one of the guys.
These worked absolutely excellently, until we met the speed bump, at which point our lack of ground clearance sealed our fate, but it is another thing to consider for our next bot.
Then comes the ace up our sleeve that helped us secure the win. Our nerf gun.
To complete the challenge of Zombie Apocalypse, the objective is to shoot zombies. A maximum of 15. However, without a gun, the points you can get are significantly decreased since you are only allowed to roll a ball toward the targets on the ground. The high value targets are up top on the platforms, and the only possible way to shoot them was to use servos and a nerf gun to shoot the targets.
So, we thoughts that the easiest solution would be to use an off-the-shelf nerf gun to save us time designing the mechanism. We would put a solenoid near the trigger of the gun and attach a small steel rod perpendicular to it, so that when current is supplied to the solenoid, the steel rod presses the trigger of the gun.
[nerf darts not loaded for safety :) ]
As you can just about the see, we also attached a rubber band to the solenoid so that it would rebound to its original position without firing the gun constantly.
There are some raw electronics on the side whose function I will explain briefly. A buck converter brings the 15V from the 4S LiPo battery down to 8V, the operating voltage of the gun. The gun's VCC and GND are directly connected to its output, whilst it is also connected to a BJT transistor, MOSFET and diode. The solenoid is connected directly to our Raspberry Pi 3b+ via Dupont connectors as a signal wire.
The components are connected so that when the RPi GPIO pin gets pulled LOW, we trigger the solenoid. When the GPIO pin is HIGH, the transistor stops giving voltage to the solenoid, meaning it does not trigger.
To control the gun's positioning, we have an excellent bracket that rotates along a ball bearing horizontally, and an M6 bolt vertically. We have two servos connected to both axes, and we use the DPAD keys on the PS4 controller to move them. A laser pointer was also mounted on the gun to allow easy aiming.
We also had our blinky lights for the fire engine, that looked absolutely great, especially when we won Pi Noon.
That's all for today.
This has been a great learning experience for all of the team members and I would like to extend my thanks to all those who organised, judged and marshalled the event.
See you next year! (hopefully)