Design for Final Project April 26

Unfortunately, the circuit we built in the previous class was not working today. Therefore while Oscar debugs our circuit, Cailey and I began designing the case for the sound sensor. We decided to make a streetlight since a green LED will light up for indoor noise and a red LED will light up for outdoor noise. To save time, we will use Cailey's box idea from project 1 which was two identical pieces with three squares screwed together. In this design, the bottom piece will be the battery holder which will hopefully keep the 2 AA batteries in place by pressure. A metal piece will be glued onto the sides to allow the current to flow. The top piece will have the microphone and the 2 LEDs sticking out and the circuit will be soldered and placed properly inside the cover.

Streetlight design for the final project.

 Because the case design is simple we were able to sketch it out quickly on inkscape and cut out multiple prototypes. We used 1/8'' white delrin and 1/8'' wood.

Problems we need to address are how to keep the screws in place and what material (delrin, wood, 1/4'', 1/8'') will work best. I would like to continue our design in 1/8'' delrin  instead of wood because I think it will be sturdier. In the following class session we will cut out our design in thicker delrin to see if it works better.

Battery holder on 1/8'' wood. Velocity: 0.7 Power: 100%

The hole for the nail needs to be centered since the nail moves out of place.

Sound Sensor April 23

The sound sensor we will attempt to make will detect the volume of sound. When one speaks loud or if there is a loud noise the red LED will light up. On the other hand, if the sound is not lough enough or if one is using their indoor voice, the green LED will light up. Making the circuit for the sensor will be challenging, therefore Oscar will help us build the circuit. Today he drew out our potential circuit and explained its function to us.

Circuit drawing.

The circuit will have a voltage between 0V and 5V which makes the middle ground 2.5V; the capacitor charges and discharges evenly. Our circuit will have negative feedback meaning that the output is connected back to the input voltage. In addition, the circuit will oscillate between 0V and 5V.

Hysteresis with negative feedback.

Basically, the sound coming into the microphone will be amplified by the capacitor. The comparator will enable the lights to turn on whether the red or green LED when the sound passes a threshold.

Once my partner and I built the circuit, according to the drawing, we were able to see in the oscilloscope how the circuit detected sound. Our circuit was very sensitive to any noise in the room and did not have a comparator or LEDs. It was fun seeing the voltage oscillate as the sound entered the microphone.

Finished Lantern & Evaluations April 20

The two pieces to our lantern.

 Off position.

On position. Pictures taken by Cailey.

Since today was the deadline for this lantern project, that meant evaluations. My personal evaluation on our lantern was that we could have thought of a better way to improve the battery contact with the LED. The reason is because the correct amount of pressure must be applied to the lid for the light to stay on. Our circuit was the simplest out of all the lanterns since it only involved batteries and an LED (no switch). The problem that the other groups had with their lantern was finding a way to have good contact between the batteries and the rest of the circuit. Essie's and Frances's lantern was a small rectangular box made out of acrylic and screws. Their circuit included a switch to turn the white LED on and off, and had a cool light bulb image on the cover. Erin's, Kelsey's, and Hannah's lantern had the most complex circuit but did not work due to a lack of proper battery contact. Their lantern was in the shape of an octagon for a better grip and had three LEDs (red, green, and orange) with a designated on and off switch. A lesson everyone learned from their lantern was to pay attention to the circuit components; this will help you foresee any potential problems in the actual case design.

Our final group project will be designing something that interacts with humans. In class we looked at a cool light up book with touch and pressure sensors. This gave us all great ideas in ways we can make our project interact with humans. My partner Cailey and I decided to make something that will light up a certain color when you are speaking loud and another color when you are speaking low. We will concentrate in making the circuit first before designing the case.

Contact Problems & Adjustments April 19

Throughout the class period Cailey and I continuously made adjustments to our lantern.

  Adjustment 1: We decided to change our LED from a red light to a white light because the white LED shines brighter.

Circuit with a red LED.

Circuit with a white LED.

 Adjustment 2: Since we switched our LED to a larger light, we need to make the hole on the case bigger. 

We tried drilling the case we had for the red LED but ended up ruining the wood (case on left). Therefore, we made a new case with a hole (3/16'' diameter) that is 1/8'' from the top of the case for the white LED (case on right).

 Adjustment 3: We initially thought that gluing a piece of metal to the bottom of the battery holder would be sufficient in transferring the current from the 2 AA batteries to the rest of the circuit. However, since the batteries have different nodes at the ends, the flat node didn't not have good contact with the metal sheet.

Picture taken by Cailey Stevens. A flat sheet of metal allows limited contact for the batteries.

 To increase the contact for the flat battery node, we folded one side of the metal sheet. This method worked. 

Picture taken by Cailey.

 Adjustment 4: The bottom of the battery holder was glued using a hot glue gun since it kept moving out of place.

The bottom of the battery holder was suppose to stay in place with the help of the tabs but this was not the case, as shown above.

Now that we had solved the battery contact problems in the battery holder, we needed to add the LED and the resistor, which would require soldering pieces or gluing metal sheets on the top lid for contact. Since we wanted our lantern to turn on when you push the case down, we needed to find a way to make a spring that would touch the batteries and ultimately complete the circuit (turns on the LED). We thought about and made small metal sheets to glue onto the lid to connect the LED wires and the resistor. Connecting the wires to the metal sheets would require us to solder them together. This method would be difficult and we anticipated that it might not work. We also tried coiling wire to glue onto the lid but this method would also require us to use the soldering gun to connect the LED, resistor, and coil. The main reason the coil did not work was because it did not provide a good contact with the batteries and the coil eventually stopped being a spring.

Different ways we tried making the spring/ battery contact for the LED and the resistor.

We finally came to the conclusion that if the LED wires simply touch the battery nodes, there would be no need of using a resistor to light up the lantern. Thus we removed the resistor from our circuit. We came up with the idea of rolling up the metal sheet to increase the contact with the batteries.

The LED was hot glued onto the case and the wires were soldered to the metal sheets.

And at last there is light!

Picture taken by Cailey.

Lantern Case April 12

Now that Cailey and I have completed the battery holder, we moved onto our next task (the lantern case). Since Cailey was absent, my professor was my temporary partner for the project. Making the case was simple. All we did was use the transform key on Inkscape to resize a copy of the battery holder to make the case.

Outside view of the lantern with the hole for the light to shine. The hole needs to be higher in this model though.

The biggest problem that we had with the outside of the lantern was making the top cover. The idea was to make it look the same as the bottom cover of the battery holder but with more tabs to go in between the hinges. In order to get the dimensions for the lid, we manually traced the battery holder with the batteries inside. The tabs on our first lid as shown below were too close together so the lid would not go in.

The tab on the right side slides in but the tab on the left is not far enough to slide in.

In our next attempt we added 2 dovetails to the lid to keep the case from opening.

The case is marked with the holes for the dovetails to go in.

Making the dovetails on the lid required a lot of free hand drawing; Oscar told me that it would be best not to waste time trying to calculate exactly where the holes should be or how narrow the dovetails should be. After a few attempts we decided to have only 2 tabs on the front of the lantern and the 2 dovetails to hold the case together.

Back view of the lantern. The dovetails and the tabs hold the shape the lantern. I will make the lid wider because it does not completely cover the lantern. In addition to making it wider I will fix the holes on the case for the dovetails because the hole on the left is too pointy.  

Top view of the lantern.

This is a photo of our nearly finished lantern. The hole was slightly drilled to allow the LED to slide in. When it is in this position the light will not turn on.

    

Battery Holder April 9

 After finishing the sketch of the battery holder with the dovetail edges and the hinges, my partner and I tested out the battery holder design on 1/8'' delrin.

The bottom broke off and these sides are nearly impossible to snap together at the corner.

 We identified a major problem with our idea; sides with dovetail edges and a bottom with hinges do not work well together. The hinges that make the sides bend from the bottom kept breaking because the dovetail edges do not connect at right angles. You must connect the sides like a puzzle first and then fold them to make a corner. Hence, we needed a new idea. I came up with a new way to make the lantern that incorporated both the hinges and dovetails (image shown below).

This is our model for the battery holder and the lantern case on 1/8'' wood.

Instead of making a lantern in the shape of a box, it will be an oval. The wooden hinges will stretch when we place the batteries inside. The pressure from the batteries on the hinges will make the dovetail pieces stay closed.

Our professor gave us the idea of making a simple oval with tabs sticking out to make the bottom of the battery holder.

Using the battery dimensions, we sketched out an oval that would fit properly.

Completed battery holder!

Project 2: A Lantern April 5

Our new goal is to create a small lantern that switches on and off and uses 2 or 3 AA batteries. The main challenges for this project is creating a switch and battery holder. Our objective is to make it as small as possible. With a partner we must decide on what color light to use, the number of batteries, and materials. We must keep in mind that light intensity depends on the voltage and different colored light need different voltages. A red LED uses about 2V. A green, yellow, blue and white light needs a voltage of about 3.6 to 4.  Resistors also depend on the voltage. 

There are many ways in approaching this project. Do you want to be able to dim the light. make it stand on its own, have an irregular shape, etc. My partner Cailey and I have decided to make a lantern with a red light since red light is better for your eyes in dark places and use 2 AA batteries. Our idea for the design is a combination of my first box with hinges and Kelsey's dovetail corners.

This is the layout for the battery holder and lantern.

We want the box the look similar to a shoe box. The bottom will be the battery holder and the top will have the light. We are still not sure how to incorporate a switch into the design. An idea for the switch is pushing down on the top half for the light to turn on. We will work on the battery holder first and then worry about the rest of the parts.

2 similar boxes will be put together to make the lantern. The blue lines will act like springs to make the lantern light up when they touch the batteries.

Outside view of the lantern.

"Judgement" Day April 2

Initial class discussion was on the steps we took in designing our boxes. It was a trial and error process for many, if not for all of us. My design process was a cycle of sketching, cutting, testing, resketching. Many of us realized that designing a box that meets all the requirements is more difficult and time consuming than anticipated. Every student had to come to the engineering lab to work on their box outside of class time.

In addition, everyone but Hannah changed their initial ideas for how they wanted their final boxes to look. The first idea I had in mind was a box with interlocking sides and a slideable lid. This idea made me block out other ideas and as a result made me spend a lot of class time drawing out the sides so that they will fit together properly with the right amount of friction. Yet, my final box consisted of no interlocking sides and a somewhat slideable lid. My box design was further shaped the more I tested my ideas and, most importantly, by incorporating the new ways my classsmates found for connecting their sides together. At first I was hesitant in using other's ideas because I wanted my box to be unique and complex but later I realized that screws and hinges were more efficient ways of connecting the sides than interlocking corners. Another reason why my box design changed was because each design I made showed me the things I needed to changed or keep in the next model. My final vision of what my box should look like came together when I added tabs to the sides instead of screws.

It was interesting to see everyone's final/ current box. Erin's box was held together by contact paper and would easily open. Hannah's box was an octahedron with a magnet keeping the lid closed. Cailey's box was made of 2 similar pieces of 3 sides attached with screws at right angles. Frances's box were 3 equal pieces with a living hinge and screws to make it into a box. Kelsey's box had dovetail joints to connect the sides and the movable sides were hinges. Essie's box was made of wood and held together by screws. The lid was locked with an extra piece and the lid had hinges to make it curved.

We evaluated each other's box based on performance (how durable is the box, are the requirements met), manufacturing (how easy is it for other people replicate your box), and aesthetic. Each box was rated on a scale from 1 to 5 (one as horrible and five as excellent) for the three categories. The ratings varied for each category and as each student evaluated the box. Some of the critics I can recall were on appearance (burnt, tape showing, sides were not straight), requirements not fulfilled (one movable joint), and the difficulty of others to assemble the box (screws are too difficult to use or designs are to complex to make).  Material choice was also criticized. Some students thought Erin's box can be made easily if you are good with contact paper but can fall apart as the tape wears off. Others disliked screws or thick sides.  A problem with my box was that the lid does not slide on and off nicely (it needs a path for the lid to slide straight into place). Positive comments about my box design were appearance, easy to assemble and customize.

Box Complete March 29

After cutting out sketch 3 as a 1'' x 1'' box I realized that screwing on the screws takes patients and skill to properly make the screw go into the designated hole. The dimensions of the current holes as .1'' which are just about right.

Sketch 3 requires 4 screws. The top and left sides are 1/4'' shorter in length since the width of the lid would add to the length of the side (sides need to be 2'').

The knowledge I gained from sketch 3 was that I need to make my design easier to assemble (screws are a pain). Thus I revised sketch 3 and decided to add tabs on the sides. I had to resize the dimensions of the holes for the tabs to lock in (the length of the holes must be equal to the width of the material).

Revised version of sketch 3 without screw holes. The tabs are longer than the width of the material because I want to see how well it will hold the sides together.

Cut out of revised version of Sketch 3

In this prototype there are 2 holes for the lid to connect and these sides are taller.

Tabs worked quite well.

 I tried to make the holes for the tabs as close as possible to the edges to reduce how far the sides with the tabs will have to bend. This meant that the sides will not connect at 90 degree angles (you would have to use a different method for attaching the sides at right angles) and small gaps between the sides will be unavoidable.

The last changes I made to my design were making the tabs the same length as the material and having one tab and hole for the lid. Making changes to the lid also made it necessary for there to be only one side shorter than the rest (the shorter side had to be across the side with the hole for the lid to slide in).

The final lesson I learned from cutting out my design in acrylic and wood was that material is important. Delrin allowed the living hinge to bend without breaking; acrylic and wood would break.

Here is my final box! I customized it with stars and a moon that is not visible in the picture. 1/8'' Delrin velocity: 0.7 power: 100%

Resketching My Box March 26

Today in class I cut out the simple box design that I made before spring break. From this prototype I identified new problems that need to be address.

Design cut out on 1/4'' delrin of Sketch 1

Problems with my current box:

• The incisions for the hinges are not all the same (some lines are closers to each other than others).

• When the design was cut out, there were not enough line incisions for the sides to fold so this made it more prone to snapping. In the image above, you can see that the lack of lines for the hinge increased the tension causing it to break.

• Since I did not account for difference in the lengths of the side when the box folds the sides of the box do not touch at 90 degree angles. Instead the sides must bend further to make them connect so there are gaps between the sides in this design. In order to close the box without bending the sides too far in I would need to make two sides longer than the other.

• The dimensions of the rectangular hole for the screw to go into the side are too wide. 

• There is no circular hole for the screw to go in. The hole should be in on the bottom flap in the extra area sticking out.

I sketched out design 2 making the lines for the hinges symmetrical. In addition, I added more lines to decrease the pressure on the hinge when the sides fold. Sketch 2, however, has incorrect dimensions for the screws. The radius for the screws is still too big and the holes for the screw to go through are still too wide. I want to make the sides bend first before addressing issues with the screws. After cutting out sketch 2, I tested out how bendable the sides were and they did bend at right angles without breaking.

Sketch 2 of box. The dimensions for the screws and sides are off. A screw would attach the fixed sides. 

Although the sides bend, my professor told me that 4 lines (instead of 7) would be sufficient as long as I make them longer. Therefore I decided to resketch the design. With the help of my professor, I drew out the lines for the hinges with the correct dimensions on paper and drew the outline of how the top view of the box would look. Two sides would be longer and the other shorter. Calculating the dimensions and drawing out the design helped me visualize and account for previous problems.


Incisions for shorter sides.

Incisions for longer sides



In the drawing I took into consideration the thickness of the material (1/4'') which is part of the 2'' side length requirement. To calculate the length of the holes for the screws I subtracted the thickness of the material (1/4'') from the height of the screw (3/4''). My previous dimensions for the width of the hole and diameter for the circular hole was .2'' so I reduced it to about .1''.

Inkscape layout of box.

Design with correct dimensions of the holes for the screws. The square on the bottom right will be the lid which will slide on in the rectangular holes on the two sides.

For next class I will cut out this design and test it.