Marble Material Sorter
Problem Statement: The National Recreation Park Association (NRPA) has asked your team to develop a solution to a growing problem in their parks. The association has placed dumpsters for recyclable material throughout the parks. They have a sorting facility; however, they need the device that will sort the recyclable material.
For this project, we needed to sort 15 marbles; the marbles would simply represent the recyclable materials. There are three different kinds of marbles (blue, green, and light blue or clear), and we needed to sort out five of each color. We could just grab a handful of marbles and throw it into our marble sorter and it would have to sort the marbles. For this project, we needed to come together as a group and find a solution for this engineering problem.
Constraints:
1. Separation process must be fully automated.
2. Must successfully separate commingled recyclable materials into individual holding bins.
3. Recyclable materials include 3 different ½ in. material spheres totaling 15.
4. Must be efficient – 2 minute max for completion of sorting process.
When we were brainstorming for this project, we wanted a gate that would be efficient. We had some ideas, but we researched to find a gate. Here is where we found our idea and decided to design our gate after:
For this project, we needed to sort 15 marbles; the marbles would simply represent the recyclable materials. There are three different kinds of marbles (blue, green, and light blue or clear), and we needed to sort out five of each color. We could just grab a handful of marbles and throw it into our marble sorter and it would have to sort the marbles. For this project, we needed to come together as a group and find a solution for this engineering problem.
Constraints:
1. Separation process must be fully automated.
2. Must successfully separate commingled recyclable materials into individual holding bins.
3. Recyclable materials include 3 different ½ in. material spheres totaling 15.
4. Must be efficient – 2 minute max for completion of sorting process.
When we were brainstorming for this project, we wanted a gate that would be efficient. We had some ideas, but we researched to find a gate. Here is where we found our idea and decided to design our gate after:
This is a good idea for the gate because it eliminates the conveyor belt system we would have to construct to separate the marbles. It serves two purposes; it keeps the marbles separated and it forces a marble to wait and let the photoreceptor sense the color.
After we found our gate, we thought of multiple things. The sorter in the video included two inclined planes that let the marbles simply roll down into the hoppers. We wanted a flashlight in our design to make it easier for our photoreceptor to distinguish the different materials. Our design also needed a hopper or bin system for our marbles. We had two main ideas for the bins. One of our ideas was to have the bins in a rectangular container that would lie on a chain and a sonar sensor would be on one the end to detect the distance of the bins and it would include two motors attached to a gear train to make the chains move (like the hopper system in the referenced video). The other idea was to have the bins attached to a rotating axle that would be attached to an encoder. We discovered that the conveyor belt system and feeders weren't needed so we tossed those ideas.
After we found our gate, we thought of multiple things. The sorter in the video included two inclined planes that let the marbles simply roll down into the hoppers. We wanted a flashlight in our design to make it easier for our photoreceptor to distinguish the different materials. Our design also needed a hopper or bin system for our marbles. We had two main ideas for the bins. One of our ideas was to have the bins in a rectangular container that would lie on a chain and a sonar sensor would be on one the end to detect the distance of the bins and it would include two motors attached to a gear train to make the chains move (like the hopper system in the referenced video). The other idea was to have the bins attached to a rotating axle that would be attached to an encoder. We discovered that the conveyor belt system and feeders weren't needed so we tossed those ideas.
We decided that the rotating idea would be simpler to code and construct, so we went with it. Here is our decision matrix:
Our design made it far, but sadly one of our partners couldn’t finish the project because he was a senior. In his portfolio he mentions a programming issue “that never was solved,” however, this was an issue that was recently solved. You see, the design of our marble material sorter was simple but it presented many issues because it included a VEX 269 motor and a quadrature encoder rather than a servo motor and quadrature encoder. This issue was solved when we realized that (1) the motor could be slowed down and (2) the code was set to keep the servo motor closed instead of opening it for the different marble values. So we changed the speed of the motor from 127 to 15, and the servo motor was changed from 30 to 127 in the code for it to open and release a marble.
Pseudocode
Start Program
Turn the flashlight on at all times
When a ‘start’ button is pressed
Set the servo in the proper position so the line follower or photoreceptor can read marble
Wait for the sensor to sense what type of material it is
If the value is less than or equal to 3023 for the line follower,
Don’t turn the motor and don’t move the encoder
Now set the servo to the proper position so that the blue marble can fall when gate opens
Wait slightly
Now open the gate so a marble can fall
Wait slightly to release the marble
Set the servo back to catch another marble in the gate
If the value is greater than or equal to 3024 and less than or equal to 3040
Turn the motor slowly
Turn the axle until the encoder is in the proper location
Now stop the motor
Now set the servo to the proper position so that the light blue or clear marble can fall when gate opens
Wait slightly for the marble to move into position
Open the gate
Wait slightly so the marble can fall into its proper hopper
Set the servo back so it can catch another marble
Wait for a moment
Start the motor slowly in the opposite direction
Turn until the hopper is in the normal position
Stop the motor
If the value is anything greater than 3041
Start the motor slowly
Turn the axle until it is in the proper position to catch a green marble
Stop the motor
Set the servo in position to properly let a marble fall when the gate is opened
Wait so that the marble is in the right position
Open the gate
Wait slightly for the marble to fall
Set the servo in the proper position to catch another marble
Wait for the hopper to return to its original position
Start the motor in the opposite direction
Spin the hopper until it is in proper position
Stop motor
When a ‘stop’ button is pressed
Stop all tasks
Turn the flashlight on at all times
When a ‘start’ button is pressed
Set the servo in the proper position so the line follower or photoreceptor can read marble
Wait for the sensor to sense what type of material it is
If the value is less than or equal to 3023 for the line follower,
Don’t turn the motor and don’t move the encoder
Now set the servo to the proper position so that the blue marble can fall when gate opens
Wait slightly
Now open the gate so a marble can fall
Wait slightly to release the marble
Set the servo back to catch another marble in the gate
If the value is greater than or equal to 3024 and less than or equal to 3040
Turn the motor slowly
Turn the axle until the encoder is in the proper location
Now stop the motor
Now set the servo to the proper position so that the light blue or clear marble can fall when gate opens
Wait slightly for the marble to move into position
Open the gate
Wait slightly so the marble can fall into its proper hopper
Set the servo back so it can catch another marble
Wait for a moment
Start the motor slowly in the opposite direction
Turn until the hopper is in the normal position
Stop the motor
If the value is anything greater than 3041
Start the motor slowly
Turn the axle until it is in the proper position to catch a green marble
Stop the motor
Set the servo in position to properly let a marble fall when the gate is opened
Wait so that the marble is in the right position
Open the gate
Wait slightly for the marble to fall
Set the servo in the proper position to catch another marble
Wait for the hopper to return to its original position
Start the motor in the opposite direction
Spin the hopper until it is in proper position
Stop motor
When a ‘stop’ button is pressed
Stop all tasks
Design Process
The pictures below are the "old" marble sorter before it was later dissassembled and improved. As you can see, we included a flashlight, three hoppers, and a small gear train that acted as our hopper system.
All of these pictures and more can be found on our partner's engineering webpage:
http://vaartstraengineering.weebly.com/marble-sorting-machine.html
http://vaartstraengineering.weebly.com/marble-sorting-machine.html
The design of the gate wasn't working, so I decided to simply dissassemble it and change the design. The new gate consisted of the same two metal parts, but the orientation was different. We made the axle of the servo motor pass through the corner of the sector-shaped VEX piece and inverted the piece so the circular edge would be facing downwards, instead of upwards.This made it easier for the marbles to go through and onto the line follower without getting jammed or projected at us. Below are two photographs that show the sector-shaped metal piece before and after.
This was an attempt to sort marbles by our old marble material sorter. As you can see from the video below, it failed because the servo was set to close the gate (at 30) instead of opening it (at 127) when the hopper for the correct color of the marble was in proper position. This was later changed and adjusted.
Our motor rested on the base plate with a gear going through the axle, and this gear turned another gear that would cause the quadrature encoder to read the revolutions of its axle. The two axles wouldn’t be close enough for the gears to touch sometimes, so what we did is we simply placed two washers on them, attached to a rubber band. This made the two gears spin more efficiently and it improved our design. The hoppers themselves were the VEX battery charging packages, and they were the perfect hoppers for the job. The entire marble material sorter rested on two base plates so that when we worked on the mechanical model, everyobdy in our group could help modify either the gate section or the hopper system.
Here are some pictures of our new marble material sorter:
Here are some pictures of our new marble material sorter:
So now the real question was whether the marble sorter would work or not. We tested it many times, and most of the time 13-15 of the 15 marbles made it into their hopper. Here is our marble sorter sorting all 15 marbles:
In the photograph above, you can see that the marble material sorter correctly sorted the 15 marbles into their three hoppers.
Reflection
After many errors and many mistakes, our design finally worked. The gate worked effortlessly and the hoppers did the job that they were supposed to do. The encoder read just the right values and the motor turned at just the right speed. This project was a success, and it definitely was a challenge for being the last and final project of the year.
Everyday there are people who need engineers to program and design real world applications for robotics, and The National Recreation Park Association was just one of the many examples.
This year was a blast, and hopefully other people will find this class as fun as I did. As for me, I will hopefully publish more portfolios in the near future.
Everyday there are people who need engineers to program and design real world applications for robotics, and The National Recreation Park Association was just one of the many examples.
This year was a blast, and hopefully other people will find this class as fun as I did. As for me, I will hopefully publish more portfolios in the near future.