Everything has been finalized and is working as intended.
The 3D parts were put on and the wiring were tidied up.
The controls were mounted onto the baseboard itself due to the control panel acrylic sheets not being available. All functions were retained.
A higher resolution video was taken to show the LCD panel working as intended.
When all the short length, solid, low-resistance wires were put on the assembly, the servos made enough power to change the spring attach point back towards the end of the tension control arm, which made the catapult a bit more powerful than during testing.
This has been a fun project and we are excited to bring our project to the presentation.
There were some problems with the requested parts.
- Only one of the hooks was printed instead of two. This may have been because the files for the two hooks requested, even though named hook1 and hook2, were identical parts and mistaken as duplicates when printing.
-For laser-cut parts, only the Arduino cover was available and the sheets to construct the control panel were either stolen or not printed.
Therefore, we will replace one of the spring hooks with a screw and put the controls (button and potentiometer) on the board at the intended place without any mounts.
These changes will make the catapult a bit less appealing visually, but will not affect any functionality.
This video shows the LCD successfully incorporated into our project.
The LCD component needed a lot of troubleshooting. To set the contrast, we had to use a diode from the Arduino kit instead of a potentiometer as suggested on the Arduino website. Luckily the contrast came out perfect with our diode. The LCD display now displays the current angle the release arm is set to in real time.
The LCD display fades a little bit while the servos are drawing power, but regains perfect contrast once the servo positions are set.
There was a bit of error near the top end range of angle (70-90 degrees) as the actual release angle control arm will not move much in that range while the potentiometer and the displayed angle will change normally. We were able to fix this problem by changing the scaling of the potentiometer input and servo output in the coding. The lower limit of the angle control arm has also been set so that the arm does not hit the base any more.
After this video was taken, the coding was updated so that the display also shows "Team Catapult!" when first being turned on and initializing. Then, when the angle is done being changed, the phrase "Ready to Fire" will also be displayed along with the current angle of the release control arm.
Also, the issue of inconsistent max pull of the spring has been fixed by using shorter solid wires with lower resistance instead of the braided ones in the Arduino kit. It seemed that the lowered resistance in the circuit allowed the servo the little bit of extra juice to consistently give maximum spring pull travel. There are still some kit wires on the board for the LCD display function, but they will be replaced in the future.
Once we get the 3D printed parts and acrylic sheets, the button and potentiometer will be put on the acrylic sheet control panel and the temporary nails in place of the spring hooks will be replaced. The catapult arm will also have a bowl for the shots to sit in.
The spring tenstion control arm still occasionally has trouble going to the max position due to the lack of torque in the servo. We are considering changing springs or further lightening the components in order to get more consistent object travel range upon firing.
The Arduino board placement and wires are still temporary for testing purposes and will be tidied up once we have all the functions we want.
We are contemplating putting an LCD display or LED lights to show the status/readiness of the catapult.
In this video, we explain the major design changes we had to make due to the lack of torque on the two control servos. The servo wasn't strong enough to lift and hold the release angle control arm in the original design. The spring tension control servo was also too weak to stretch the spring in varying ranges to give different tensions as we had envisioned. Because buying stronger servos were out of our project budget, we decided to make the following design changes to overcome the problems.
-The long catapult arm had to be shortened in order to downscale the catapult.
-The release angle control arm had to change to a lighter, one-arm design.
-The spring tension control arm had to change to a thinner and smaller design.
-The spring attachement point on the spring tension arm had to be moved closer to the axis of rotation
-The control scheme had to be changed to a firing button and a release angle control, foregoing the spring tension control due to the tension needing to be set to max to get any decent range when fired.
-The tension control arm will be automated for every shot as there is no need to control it any more. Pushing the firing button will pull the spring tension control arm to maximum angle, release the catapult long arm, lower the spring tension control arm, and return the release latch with enough delays between actions to make a smooth, automated fire and ready state.
So the coding will need to be changed and the wires will be tidied up when all functions are complete.
A video was taken for the very first firing test after initial assembly.
This post is mostly for laughs and giggles. Actual information to follow in upcoming posts.
This is a quick video testing the initial Arduino coding and the components.
Components include the Arduiono kit button, potentiometer, servo, and two 1/10 scale R/C stadium truck steering servos manufactured by Traxxas.
The coding and components work as intended and the next step of the projects is to buy supplies from Lowes to construct and assemble the catapult and install components onto it.
The coding used in this video is the file "Catapult 1" uploaded on Google Drive here.
The solidworks part files for 3D printing and Laser-cut acrylic sheets have been sent via email.
The 3D printed parts will include the bowl on the catapult arm for putting objects to fire in, and the two hooks for the spring to attach to. (pictured below)
The acrylic sheets will be cut to make the control panel to put the button and potentiometers on, as well as a clear cover for the arduino board for general protection.
All parts files are also uploaded on Google Drive as public files and linked here.
The assembly and the motion study of the catapult were completed. During the creation of the assembly some problems were detected. Spencer Crane has made the assembly, and Gabriella Mastrogiuseppe added parts and did the motion study. The problem was with contacting bodies. In fact, the lever of the catapult would go over the bar even if in the contact group they were both inserted. Also we were uncertain if there should be a servo motor in the assembly. For the study motion I utilized a motor rotating counterclockwise.
We had a small team discussion about acquiring the parts needed for the project.
The wooden components will be bought last, after the entire assembly has been completed and tested. This will give us more flexibility in getting the electrical and coding side of the project done.
Of the 3 servos required for this project, 2 will likely need more strength than the small ones included in our
Arduino kits. The catapult release servo will not need as much torque, and can be supplied by the Arduino kit. The 2 stronger servos in the design can come from my old RC stadium truck. Since this truck is a 1/10th scale stadium truck requiring relatively strong servos for steering, these servos will provide us with enough size and torque for the project.
We also bounced around the idea of adding LED lights and an LCD panel to indicate the control setting of the catapult, but decided to put this off until we can get the catapult working properly. Once the coding is done and controls are tested with the Arduino board, we will start working on adding these features in.
Here is a rough sketch of what the catapult will look like.
The baseboard and large arms will be made of construction wood bought from Lowes.
Laser-cut acrylic sheets and 3D-printed parts will make up the mounts for the servos and hinges used in the assembly.
The controls for the 3 servos will come from the potentiometers and push button switch included in our Arduino kits.
The catapult will be utilizing 3 servo motors to achieve what we want. Servo 1 will control the tension in the springs setting the tension point. Servo 2 will be potentiometer controlled and will control the bar that stops the catapult arm for controling launch distance of the object. Servo 3 will be a simple button controlled servo to hold the arm down while it is under tension from the springs, when the button is pushed the servo arm will rotate 90-degrees letting go of the catapult arm and launching the projectile.
For our group project, we have decided to design and build an Arduino-controlled catapult. The catapult will be made out of construction-grade wood, small springs, 3D-printed plastic parts (for mounting and assembling), and various parts out of our Arduino kits. We will be able to control the release angle and velocity using the Arduino-controlled servos. Team members on this project will be Spencer Crane, Brian Ahn and Gabriella Mastrogiuseppe.
