Final Show and Tell May 3

My partner Cailey and I met earlier this week to work on the case for the final project. It is basically a larger (2.7'' x 2.5'' x 2'') rectangular version of my box design.

Case for final project.

We taped the battery holder to the lid. This way we would have better access to the batteries. When we folded the sides we noticed that the case was a bit too small for the lid with the battery holder to go in. We tried transforming the sketch by 10%, but after cutting it out, the case was way too big. It was frustrating to figure out a way to make our case design work since the project would be due during class. We decided to see our circuit the next day before making further adjustments to the case design.

On the last day of class we finally got to see our circuit (size and function). 

Oscar's sketch of the sound sensor/ volume detector.

Image of the circuit. The large op amp (black rectangle) is equivalent to 4 smaller op amps. When the circuit detects a loud noise the red LED will light up. The circuit must be reset by passing another magnet over the magnet on the circuit (turquoise wires on bottom of image).  The potentiometer (blue and white square on right) can be adjusted to make the circuit more or less sensitive to noise. 

We cut the breadboard making the circuit roughly about the same size as the battery holder, but still needed to make the case. We added stars along the hinges to allow the microphone detect noise volume, and to enable us to reset the circuit. With little time left, we cut out the new design but the hinge on the case broke. Therefore we went back to our first case cut out and tried enclosing the batteries and taping the breadboard to the lid. Cailey placed 2 pieces of metal inside the battery holder and soldered the wires (red and black)  from the breadboard to metal sheets.

Although our vision of having a streetlight with a red and green light (red for loud noise and green for indoor noise) changed as we progressed, in the end the circuit functioned perfectly and still needed a case. I learned how important it is to have the actual or drawing of the circuit to advance in the project design. By not having the circuit, we were not able to take into account the size of the case or foresee potential issues.

It was interesting to see the finished final projects of my other classmates. Essie and Frances made a dice that lights up red or green when you turn it. They designed their case by making 2 channels for the batteries to slide back and forth. The battery holders had metal sheets wrapped around the ends. As you turn it, the battery holder slides making the metal sheet touch the LED wires which causes it light up. The case design was quite amazing, especially since it was done with acrylic (acrylic breaks easily) and no screws.

Light up dice by Frances and Essie.

Hannah, Erin, and Kelsey made an interactive Harry Potter light-up pop-up book with multiple pages and a fun story line. I thought their project was very enjoyable and I could tell that they spent numerous hours working on coloring, cutting, typing, and pasting. On the first page (image below) the lights behind the candles flicker as you pull down the owl. This is due to the owl blocking the photo receptor above Ron's head. On the next page they used red LEDs to light up the cats eyes. The final light-up page used red and green LEDs which alternate depending on whether or not you turn the 2 switches off (this is directed in the story line). Their book had to be connect to the power source since the lights needed a high voltage to shine brightly. Most of their circuit was below the cardboard cover supporting the book.

The first and my favorite page of book.

This concludes the semester. I've enjoyed exploring engineering and believe all of us have acquired knowledge about circuits and the design process.

No Circuit and No Case... Yet April 30

Once again, Cailey and I decided to try out a new design for our final project since we are having trouble making our current case design which is an alteration of Cailey's first box design; the 1/8'' delrin melts with the wrong laser settings so the holes for the screws get ruined. We spoke with Oscar and he suggested that we should try Kelsey's lantern case which is sturdier and can be easily adjusted to fit our project. 

Kelsey's Lantern Case as an esp.

During class, we made the battery holder for 2 AA batteries (Kelsey's design was for 3 AAA batteries) and the bottom of the the case; Oscar will continue to work on the complex circuit in his office at Olin. We wanted to dedicate our time in figuring out the best way to increase battery contact which was a major problem for many of us in the lantern project. The way we were going to increase battery contact was by using Frances' and Essie's method of warping a piece of metal with a hammer into a small mound. This way the flat node of the battery would easily touch the metal piece.  The plan was to make a sandwich; bottom piece, metal sheet, and battery holder.

Before warping the metal sheet, Oscar realized that our sound sensor circuit would need 5V instead of 3V which would require at least 4 AA batteries. This meant that we would have to make further adjustments to Kelsey's lantern case (make it bigger) and that we would have to worry about contact between the four batteries and our complicated circuit. Thus we were back to square one, no case and no circuit to work with.

The good news was that Oscar allowed us to use a manufactured battery holder instead of designing one because there is only one class remaining. This eliminated issues with battery contact. We just need to create a new case design that would fit a 2.5''x 2.3'' battery holder and the invisible circuit. To keep things simple, we agreed to use my box design from the first project.

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.