Tuesday, May 21, 2024

A STEM Project: Camera Obscura - A Pinhole Camera

This camera obscura allows light to go through a small 1 mm pinhole opening. The light is projected on the other side of the box on a piece of vellum. The projected image is upside down. Four boxes of 65 lb. black cardstock of varying depths...1, 1 1/2, 2 and 2 1/2 inches with a pinhole are to be made.  The lid of the box is made out of vellum.

Here is the PDF.  

Here is the .Studio file.

Please check to see if the pinhole is cut properly. There might be a hanging chad that needs to be removed by poking it with a pin.  All of the pinholes are the same size in each of the boxes.

 I used a six LED bulb clip-on light as the light source.  I colored two small squares of plastic wrap.  Each plastic square covered two of the six LED bulbs.  I used a dark pink and blue permanent marker.  I did try other colors but they were too faint.  I taped the blue square to the upper portion of the light and the pink square to the lower portion of the light.  I left the middle two LED bulbs clear.
Place the boxes in a straight line and a ruler parallel to the boxes as shown above. Moving the light so that it is parallel to the largest box, I observed that the image that is portrayed in the velum has the colors reversed.  I continued to do the same for the remaining boxes. Images shown below.
2 1/2 inch depth
2 inch depth
 1 1/2 inch depth
1 inch depth

Conclusion: 

If the distance between the pinhole and velum is reduced, the size of the image will decrease and the image will become brighter since the light spreads over a small area. If the distance between the pinhole and velum is increased, the image size will increase and the image however will get less bright since the light spreads over a large areaThere were six LED bulbs in the lamp.  Only four lights were clearly visible, the other two lights were faint as they were out of range.


A STEM Project: Making a Simple Paper Microscope Using a Glass Marble Coded in TurtleStitch



Simple Components of a Marble Microscope
Eyepiece tube, a specimen slide and a glass marble lens

Simple Microscope Assembly Using a Glass Marble

In a previous blog posting, I created a simple microscope using a clear glass marble from the Dollar store. I designed and coded parts of the microscope in TurtleStitch. https://papercraftetc.blogspot.com/2024/04/a-stem-project-making-simple-microscope.html 

In this posting, I coded the entire microscope design in TurtleStitch and I will explain the steps that were required to program the design. 

Coding a Three Dimensional Design in TurtleStitch To Be Cut and Joined in Paper

Coding a three dimensional object appears at first to be a daunting task because of the third dimension. It is easy to code a square in two dimensions but how do you code a square box with a top that slides into the  bottom? It is best to examine a square box like this and look at its structure. How was it made? Each side of the box needs to be coded.  Squares are easy to code and then the joining of the sides needs to be taken into account. 

To create a simple square box, all the side lengths will be the same. The square that is in the middle of the above figure needs to be dashed lines because solid lines are cut lines and dashed lines are fold lines.
When the inner square is changed to dashed lines, the image should look like this.

The only thing that is left to do is to make tabs for the box. The tabs are needed so that the corners of the box can be joined at this location with glue.  I like to make my tabs from .25 to .5 inches wide depending on how big the box will be.  


Two tabs are joined at the sides of the squares in the upper and lower squares. 

For the simple microscope box, the sides of the box need to be shorter. In the example above, the four outer squares were adjusted to the same height to make the box with a shorter height. 

The design is now ready to be coded in TurtleStitch. This design is called a net because it is a design which can be cut and folded to create a solid shape.

When designing in paper,  the size of the object must be taken into account because of the constraints of  the medium.  Paper comes in different sizes, usually 8 1/2 x 11 inches. The above photo shows another variation of a box. This box had to be made differently because the top of the box is bigger. The sides are cut separately and then are attached to the top of the box. 


Basic Building Blocks in TurtleStitch 

There are some basic building blocks that are needed to code a three dimensional design in paper. A 3D design requires tabs and folds to join the different paper parts together. They are an edgefold block, a dashed line block and a one inch block.


Edgefold Block

The edgefold block is used to create a tab strip for gluing parts together. The tabbed strip can be made with three variations of teeth - rectangular, trapezoidal or triangular teeth and a variable number of teeth.

https://www.turtlestitch.org/users/Elaine/projects/Edgefold%20Block


In the example shown above, a 2.5 inch x .5 inch strip is created with eight trapezoidal shaped teeth spanning the strip with the orientation of the teeth going downward.


Dashed line Block

The dashed line block is used to create a fold line for bending the paper at the tabs.

https://www.turtlestitch.org/run#cloud:Username=Elaine&ProjectName=Dashed%20Line%20Block

In the example shown above, a 1 inch dashed line is created with 5 dashes per inch.



One inch Block

A one inch block is necessary to convert the design to the correct size when it is cut using an electronic paper cutting machine as the size is not preserved in the export process. This file should be exported as a DXF file in TurtleStitch.  It should then be resized in the electronic paper cutting software using the one inch block as reference. 

https://www.turtlestitch.org/run#cloud:Username=Elaine&ProjectName=One%20Inch%20Block


The one inch block is used for reference once the file has been opened with the electronic paper cutting software to be cut. The one inch block needs to be moved away from the design by placing a value in steps to inches block.


Please Note: I have consolidated all of these blocks into one TurtleStitch program called "Basic Components of 3D Papercrafting". 

https://www.turtlestitch.org/users/Elaine/projects/Basic%20Components%20of%203D%20Papercrafting


Here are the three links to the TurtleStitch code for the Simple Microscope.

1). Simple Microscope Box 

https://www.turtlestitch.org/run#cloud:Username=Elaine&ProjectName=A%20Simple%20Microscope%20Box

2). Simple Microscope Components 


3). Specimen Slide   


Coding the Simple Microscope Box 

The microscope box is a square box with four sides that are attached with four tabs.

The top and bottom of the box are similar. The difference between them is that the bottom is 98 % smaller than the top of the box.  This allows for the box to slide into one another easily.


I created some custom blocks for the box because I wanted to simplify my code.

The blocks that I created are the Turn Left 90 Degrees and Turn Right 90 Degrees blocks. I combined a turn and move in each of these blocks. Using these blocks will cut coding down by 50% when these blocks are used. 



The two sided edgefold block creates the side of the box and two tabs.




I also created a Box block which contains the code which creates the top of the box. To create the bottom of the box. The 'side' value is set to 98% of the top's value. 

Calculate the center of the box to put a hole in it for the microscope light.


Once the box top is made, a hole is placed in the center by using the following calculations.

size of the side/2 = center point of square box

Once at the center of the box is determined, the radius of the circle needs to be subtracted to put the turtle in the correct position to construct the circle. The turtle needs to be pointing upward to construct the circle.



Image of the box top and bottom (one inch square not shown) that were created in TurtleStitch.


Coding the Simple Microscope Components

Eyepiece tube (red) and the lens holder strips (blue) are coded like the Simple Microscope Box with the same blocks - edgefold, dashed lines, turn right and turn left blocks 

The coding of the lens holder requires trigonometry to calculate the inner hexagon's side length.


The outer hexagon is made with the 'dash line' block and the 'edgefold' block using the hexagon length value of 0.555 inches.


To find the inner hexagon side length,
The side length of the inner hexagon is equal to the outer hexagon side length minus two times the opposite side of the triangle.

Find the hypotenuse.
And then the opposite side length of the triangle to move the turtle the inner side length distance.


Here is the code that calculates the hypotenuse and the inner side length of the hexagon.


The circle measurement for the lens circles were measured from the glass marble.  The outer circle is approximately 0.45 inches and the inner circle is half of that measurement. The coding of the placement of the circles inside of one another is the same concept of the circle placed in the center of the box.


Coding the Specimen Slide

The specimen slide looks complicated to code but it is easy to see that only half of the slide needs to be coded because the image is mirrored.

The next thing to look at before coding is the shapes that make up the design. The circular cutouts are semicircles which are easy to code using the Arcright or Arcleft blocks. The rest of the design is right angles which are simple to code.

I did add a special feature in my Specimen Slide block code.  I added a variable called 'scale'. I wanted to be able to vary the size of the specimen slide without changing my code. 

To scale a design, the scale variable needs to be multiplied by the value of the movement of the turtle. The scale value must be multiplied each time a move is made.  This is a tedious task if the scale value is added after the code has been made.  It is a good idea to think about scaling before any code is written.

The design can be scaled in the electronic paper cutting software but it is nice to have the ability to code it.  It is not always easy to get exact sizes in the electronic paper cutting software. 

 
Directions to Cut the Box with the Silhouette or other any other electronic paper cutting machine.

Export the TurtleStich design as a DXF file.

The DXF file is then opened in the Silhouette software. The size of the one inch square is observed. The size of the entire file needs to be resized as the size is not preserved from one application to the other.  Divide 1 by the size of the observed one inch square and then multiply by 100. Transform the entire file with the calculated percentage amount.  Check the one inch square to see if it is now one inch.  (The one inch square is no longer needed, and it can now be deleted.)

Simple Microscope Cutting Files

Here are the files to make the simple paper microscope.  I have three versions of the files.  The first is a PDF where you can cut out the pieces with scissors.  The second file is for the Silhouette and the third file is all other electronic paper cutting machines. 

Materials needed. - Glue Dots, Glass Marble and a Tea Light

Here is the PDF. I used 65 lb cardstock.

Here is the .Studio file for the Silhouette.

Here is the SVG. The file goes beyond the viewable area.  Zoom out to see the entire file.
Make the Box 
Crease the box top as shown above and apply glue to the two tabs on the sides. Repeat for the other side of the box. Insert the tea light into the box and affix it with a Glue Dot (not shown).

Apply Glue Dots to the two tabs of the specimen slide.

Make the Eyepiece Tube

Crease the tube and apply glue to the side tab.  Shape into a hexagonal tube. 
Apply glue to the lens holder on the six tabs. 

Insert the lens holder into the eyepiece tube.

Make the Lens Holder

Crease the two lens holder strips into a circle.
Apply glue to the two tabs and adhere.

Glue the lens holder strip onto the lens circle. Repeat for the second one.

Insert the glass marble into the smaller side. Apply glue to the top edge of the larger side.

Adhere the two sides together.

Assemble the Viewing Platform


Insert the specimen into the specimen slide.

Assemble the simple microscope by placing the specimen slide on top of the lite box and then align the eyepiece tube in the center of the specimen slide to view the specimen.


Saturday, May 4, 2024

A STEM Project: 3D Printing a Galton Board To Demonstrate The Concept of a Binomial Distribution

3D Printing a Galton Board To Demonstrate The Concept of a Binomial Distribution

Here is a video of the Galton Board in action.
There are a lot of outside forces that prevent the candy balls from falling accurately - such as friction, the inconsistent size of the candy balls, the acetate is flexible and causes the flat surface to buckle. Even with these inconsistencies the concept of the binomial distribution is still shown. 

The mathematical concept of a binomial distribution can be visually displayed using a Galton Board. A Galton Board was invented by Sir Francis Galton (1822-1911).  It is a rectangular board with evenly spaced pegs.  A small opening at the top of the pegs funnels the small balls.  The small balls bounce from peg to peg.  The ball can either fall to the left or to the right once it hits a particular peg. Each movement has the probability of fifty percent. The small balls continue bouncing from one peg to the other and then are funneled into rectangular slots.  Once in these slots, the small balls are observed. with a sufficient sample size, the observed formation demonstrates the shape of a binomial distribution.

I will now explain how I made the Galton Board.


Using the Silhouette software, I created a copy of the Galton Board from an image that I observed in Wikipedia https://en.wikipedia.org/wiki/Galton_board#/media/File:Galton_box.jpg  I saved this image as an SVG file.

I then created the outside border of the box by deleting the interior design and saving this image as an SVG file.

I imported the base layer and made the base 2 mm thick.

I imported the pegged layer and made this layer 4 mm thick. When copying the image from Silhouette software, the image must be at the same exact location.  This ensures that the two images will stack on top of one another.  Once they are stacked, the pegged layer must be moved upwards 2 mm to account for the base layer.


The layers are then grouped together to complete the design for exporting to the 3D printer.
Here is my design in Tinkercad


Once the Galton Board has been 3D printed, make the paper and acetate cover for it using an electronic paper cutter machine.

Here is the PDF. I used 65 lb cardstock and acetate for the cover of the Galton Board.

Here is the SVG for all other cutting machines. The file goes beyond the viewable area.  Zoom out to see the entire file.

Make the paper frame by creasing the sides and gluing the corners. 

Use a 1/4 tsp. of Snow Cap candy balls.  The white candy balls are the residue at the bottom of the Snow Caps candy.  Attach the acetate and then the paper cover. I used Scotch tape to fix the paper cover to the Galton Board.