[Thu Apr 26] Screaming Dice We Are Coming!

As always, Essie gave me a surprise at the beginning of the class - our dice overall design and the battery case! Although the models were dissembled for different usages, and I didn't get to take a picture to the battery case.

This was our initial dice design. We were going to make the middle square hole bigger to fit our battery case in, but we ended up dropping this design because it gave us little space for inside circuit.

We will be using 1.5V button batteries. The flat side is positive and other side is negative. I tested the batteries with the bi-LEDs and two-pin white LEDs and decided that we would only need two button batteries and no resistors to make our life easier.

We divided up our work. Essie was concerned about being able to change batteries when the batteries die; therefore, she spent the majority of her time revising the battery case (although that idea was later dropped because we had to make our structure work first...) I decided to work on the circuit design - especially how to light up the top LED when it lands and makes contact at the bottom.

I decided that we are going to have two pieces of metals connecting the positive and negative end of the battery so that there is more space for the wires to make contact with the batteries. Then I would put a piece of metal on the bottom of the dice and connect that to one leg of the LED on top. The other leg of the LED connect to the top of the battery. When the metal at the bottom of the battery touches the metal on the bottom of the inside of the dice, it will complete the circuit and the LED on top will light up.

From the side, when the bottoms make contact.

From the side, when the bottoms don't make contact.

Sitting on table, when the bottoms don't make contact.

Sitting on table, when the bottoms make contact.

It didn't come that easy though because I was having trouble making good contacts. I thought that this was essential in our design because the dice will be tossed around so it's important to make sure that the design is flexible enough to have good connection even when the dice is getting thrown around. One problem was the metal plates that I cut were a little bent in some corners and that made making connections even harder. I asked Oscar for help. Oscar said a way to make sure the pieces make good contact is to make the an indentation on both contacting pieces. We took one part of Essie's design for the battery case which is a square with a circle taken out in the middle, then I made an indention with a hammer.

I couldn't find an extra piece of Essie's battery case design, but that should go under the metal plate.

Oscar also trained me to solder because taping is definitely not the best method to make good connection. I actually tried soldering earlier today but it didn't go well... After Oscar's demonstration, I realized that it was no wonder that I failed my previous attempts...

Several things about soldering:
1) Make sure the soldering head is wet
2) Make sure the head is in contact with both the wire and the metal or whatever you are soldering together
3) Try to make a good angle of the solder

During the weekend, Essie and I worked on the project a little more (another 8 hour late Friday night engineering party!) I experimented the beeper. I picked the CEM-1201(50) because that was the only beeper of suitable size. I looked it up online and realized that it needs 1.0 - 2.0V voltage, 20mA current and has coil resistance of 50 +/- 7.5 Ohms. I measured my battery; it was 1.33V. Therefore, the total resistance in the circuit should be around 100 Ohms.I started with connecting the beeper and the battery with a 48 Ohms resistor. It wouldn't beep but it made this interesting painful little buzz whenever I just connected or disconnected the wire with the beeper... But that was definitely not 2048 Hz as indicated by the instructions I found online.. I tried different resistors from 1 Ohms up to 150 om and none of them worked... I asked some engineering friends but none of them knew either... Then on Saturday I met someone who is a EE PhD on the bus so I asked him about it...   He said it might be because the beeper needs alternate voltage... I didn't think of that. But if that's the case, then our screaming idea needs to be trashed because it's too complicated...

But anyways, I put that aside for a while and started to build a second circuit for a LED on a different side. (It turned out that I never had the time to go back to the beeper.) It was difficult to do because without the case, I felt like what I was doing wouldn't be that helpful when we integrate everything together. Luckily, Essie was just about done with the box so I helped her cut the design and here it is:

Yes, no screws! Essie and I were set that we would avoid screws this time, but since we are supposed to toss it around, it needs to be strong as well. This design holds pretty strong, except for it's hard to dissemble without breaking anything.

It is a little different from our original six-face light up design. We thought that would make the inside too complicated to be done in such a small and dense box. Therefore, in order to make our life easier, we would make it roll on only four sides instead of six sides.

When we integrate our parts together, it looks something like this:

One problem I found was that since wires are relatively stiff, the battery case was not heavy enough to bend the wires to make connections. Therefore, we need some other ways to let it free fall...

[Mon Apr 23] Final Project Second Thought

Before class, Oscar, Essie and I had a discussion about how to divide our work so Essie and I can work more efficiently and I can contribute more to our project. Oscar explained that we should first finalize our concept. Then we should think about what are the many things that we need to do. We should write them down and assign each task to one person so two people are constantly working on different parts of the project. We need to communicate with each other all the time so if one task takes longer or shorter than we expected, we need to reassign the tasks so that both of us have things to work on all the time instead of one person having to wait until the other one finishes. Integration is a very important process because things can go wrong and we might need to go back and revise pieces of our design.

With that in mind, we went back to our dice design. Essie and I were a little skeptical about it since last class because we were not sure how the gravity thing is going to work. I wanted to think more about it before we gave up but it did seem to have many issues, such as it would have to be very durable since it will be tossed around. I was also having a hard time convincing myself that the inside circuit is going to work because given our work from last class, it was hard to jam in wires going to different direction in a small space. The wires tend to touch each other and create a mess.

Therefore we decided to think about more options and eventually we thought we could do a theme park. We could make two boards perpendicular to each other. The one on the bottom will be the "ground" while the other one will be the background wall. It is going to have a merry-go-round, ferris wheel and a few human figures on the ground and fireworks in the background wall. We would have some LEDs on the ferris wheel that can be turned on and off and bi-LEDs on the top of the merry-go-round and as fireworks. We will also integrate motors into our design so the ferris wheel and the merry-go-round could spin. Our interaction will be turn the switch on and off for the motors and LEDs and we were going to integrate the potentiometer into our circuit so we can also change the speed of the motors and the brightness of the LEDs.

We tested out all the LEDs and circuit designs that we think we might run into and had a problem about the potentiometer. It can change the brightness of the lights okay, but at a particular point, it would suddenly become very bright. In other words, the brightness does not change evenly. Same problem with the motor. We waited for a long time before we could talk to Oscar but he didn't like the idea... because it was not interactive enough...

But he did help us to rethink about our dice idea. I told him that I was worried that putting a mass in the middle of the dice would make it hard to place the batteries. He said we could use the batteries themselves as the mass. Then I was worried that it is not going to be heavy enough or the connections might be bad. He said that we could somehow make the battery have a negative end at one side and have several positive ends coming out of the batteries to be connected to the LEDs. Therefore we don't need to use push buttons; we just need to make sure the wires connect well when the dice lands. We thought that would be hard but it could work. Essie and I also decided that we need to connect the bottom of the dice to the top so that when it lands on the bottom, the light on top would light up.

We left with a general idea that the dice is going to have a smaller box inside with the battery.

[Fri Apr 20] More Lantern + Evaluation

Everyone was finishing up their lantern project at the beginning of the class. Essie and I decided to make a wooden lantern. Essie had to redraw the whole battery case design because the material changed...

We wanted to have a more complicated circuit with three lights in parallel, using switches and touch buttons to control them. Therefore, after assembling the battery case, we started to solder the legs of switches and touch buttons because they were too short and impossible to coil with. That took a while but it finally worked. Then we started to connect the devices on the top layer with wires coming from the bottom layer like we did with our acrylic model. However, there were too many devices and it was so messy that all the wires started to touch each other...

That didn't work out well... We were just going to stick with our acrylic model.

At 3pm, we started to present our projects and evaluate others' projects. Here are my own evaluation and feedback from others for our design:

Pros of our project:

1. It works consistently. Compared to one group who hasn't got the chance to figure out the battery connection and the other group whose lantern sometimes have trouble staying lit up, our lantern performs well consistently.

2. Durable. Our lantern is the strongest among all. I think that's partially due to the fact that it's hard core nailed in together and no moving hinges.

3. No hot glue. This is not necessarily a pro, but we were very set on having our design like puzzle pieces all fitting together instead of having to use glue.

Cons of our project:

1. We focused too much on the structure, which is not the most important thing for this project. Oscar said that many designs need flexibility and we focused too much on building the perfect case for the two AAA batteries that we lost the flexibility of the project because the structure here is not the most important thing.

2. We thought that our design is the smallest among all but it makes sense to say that because we used nails, we used up more space than necessary.

3. We used so many nails in such a small thing which some people might not like.

A couple things to take away from the evaluation process:

1. Try to be creative and don't stuck with old techniques. Essie and I both used nails in our box designs and we both liked it. (I didn't like it that much, but since we are making a box-shaped battery holder, I wasn't motivated enough to think of other designs that would give us the same duration as nail do.) Therefore, we kept using this in our lantern design. Oscar said that there is this kind of exercise that you are not allowed to use any of the old techniques you used before. I thought that must be very mind-opening.

2. Pay attention to the weaknesses of the design. Essie and I spent most of our time building the battery case. Therefore, our battery connection turned out to be the best of the three group. But as I said earlier, that could also be a constraint on our flexibility of the design. Also note that you never know at what stage you are going to fail...

Then we started to think about our final project. Kelsey found a cool video about a book with little designs that light up. It was really cute. Essie and I are still considering our screaming dice project, although we are not sure how feasible it is so we are still looking for more ideas.

[Thu Apr 19] Done With Lanterns + Final Project Ideas

Essie finished up our lantern project! We had a little change in design. Instead of letting the arch thing sticking up, we got rid of that and just drew the light-bulb shape on the top layer because we thought having the arch would make it difficult to carry around. We didn't make the LED stick out for the same reason. Also we switched to the brighter and bigger white LEDs because the little yellow and green ones were not bright enough to support reading in dark... We also used a 330 Ohms resistor to adjust the brightness of the white LED. We have the wires from the batteries and the legs of the resistor coming from the bottom of the middle layer, and have the legs of the LED and the switch (for model 2) coming from the top of the middle layer so we can connect them in the middle.

Here is the final design layout from Inkscape:

We have two different models:

(1) Manual switch:

You have to manually make the two wires in contact in order to light it up... Not that great but it works!

(2) Actual switch:

You can turn the light on and off by using the switch. That's good enough.

We thought that we would be the last group finishing it, but we spent enough time outside class to catch up and actually finished it before the other two groups did. Therefore, we moved on to think about our final project. Essie and I searched for ideas online and wasn't very successful. We saw pieces of small designs that we wanted to do but we weren't sure how to put all of them together. We bounced ideas around with Oscar and Oscar stressed that our final project must be user interactive. For example, our lantern project is not very user interactive because all we do is to turn it on and off. If we can somehow make it change the brightness by pressing the switch harder, that would be more interactive. Eventually, two project ideas drew our interest:

1) A dice that depending on which side it lands on, has LEDs light up on the top face of the dice
2) A piano that makes screaming sound because the buzzers and circuits that we used can produce very high pitch and screaming sound...

I thought they were both great because one uses light and the other uses sound. Eventually we decide to integrate the two: make project 1 and add a feature that when you lift the dice up, it's going to scream... just for fun...

We were excited to finalize our idea. Then we start to look for materials. We searched in the tool box and found lots of interesting things, for example, the male and female headers... We thought they were very interesting and would try to use them in our design.

We also got:
1) Pushbuttons
2) 4-pin Red LEDs
3) 4-pin Blue LEDs
4) 2-pin White LEDs
5) Switches
6) 330 Ohms resistors that go with red and white LEDs (blue LEDs do not need resistors)

We then started to put things on breadboard and made sure we know how to connect the devices.

This is a parallel circuit. The white LED on the left is controlled by the switch and the red and blue LEDs on the right are controlled by the touch buttons. It took us a while to test out how to properly connect all the devices since many of them have four legs and we haven't dealt with those before. But we got them all figured out with one of the battery models that we did for our last project.

I am so excited for our final project!

[Mon Apr 9] Lantern Project Second Day

Note: when I was editing my blogs, I pressed "undo" on this page, which leads me to the my entry on April 12. Then I am not sure what I did, but the content in this blog was replaced by my April 12 blog... That was really frustrating... Anyways, I rewrote this entry based on my memory of what I wrote since I just edited it... Therefore, it is not as detailed and comprehensive. Hope you can understand.

Essie and I decided to work on the battery case today. Since Essie is much better at using Inkscape and mapping out the design, and it is hard for two people to draw together, we decided to split our work and I worked on circuits instead.

I pulled out the materials we picked out from last class. I first learned how to connect a switch in a circuit:

As shown above, the switch can be up (at the position in the picture) or down. If the switch is up, then A and B are connected in the circuit; if the switch is down, then B and C are connected in the circuit. For the purpose of our design, if we just have wires extending from one of the outside points (A or C) and from the middle point (B), we would be able to connect and disconnect the circuit by putting the switch up and down. 

I started with putting the yellow LED with the 270 Ohms resistor all in the same row, connected to a switch in a different row because I couldn't fit them all in the same row. I tested with the two batteries we picked out, but it didn't light up. After examining everything, I asked Oscar for help. Apparently I am not supposed to put the two LEDs' legs in the same row because then I'd be shorting the LED and there wouldn't be a voltage difference across the LED. I am pretty sure we learned that when we dealt with circuits earlier in the semester but I completely forgot. It is not going to be that important in our design though because we will build the circuit directly on acrylic.

Anyways, I fixed the layout of the circuit but it still didn't work. Oscar gave me a battery tester to test whether the batteries were charged. One of them was a little weak so I changed it. Then it worked fine.

I put in the green LED and here is the final circuit:

The white and blue wire coming out from the board was connected to the positive and negative end of the batteries.

Then I took some time to measure the thickness of the wires and legs of switches, LEDs and resistors with a calibre. They all turned out to be slightly different, but I don't know how much a difference it is going to make since they are all so small.

I showed the circuit to Essie then joined her in her battery case design. That involved drawing, cutting, assembling, getting angry, cooling down, rethinking and redrawing again. Although having a company definitely felt better than doing this alone...

By the end of the class, we had a not so fit battery case. I did not get a picture of it but it looked pretty similar to a more advanced version later in the week.

[Thu Apr 12] Lantern Thid Day + Engineering Weekend

I had an interview today so I went to class late. Apparently Essie over napped, so it turned out that I didn't get that behind.

Essie successfully built a battery case that fit well. But because we trashed lots of our models when we cleaned up, I couldn't find the model at the beginning of the class any more. It looked pretty much the same as the next picture except for it did not have wired connections.

With that, we start thinking about ways to connect the batteries together. We cut a piece of metal and put it inside the battery holder. We didn't like it that much because it is very sharp and not aesthetic. But no matter what, we realized that in order to connect the two batteries together, we need to leave some space for wires/metals (whatever we decided to use), so Essie went back to lengthen the case. In the mean time, Oscar said that since our battery holder was well-designed, we could just build our lamp on top of the battery holder instead of putting it inside another box like we were thinking about before. Essie and I decided that was a good idea because that would make our lantern much smaller. We got rid of the box idea and decided to build our circuit on top of the battery holder.

Since Essie and I were both late, we didn't get much done during class. Therefore we met up on Friday and started our 11 hours' engineering party (a couple hours more for Essie...)

We started our model on Thursday and decided to only use wires to connect the batteries. 

(We had so many models that I forgot the sequence of our progress. This might be a later model with lengthened body because of reasons that I would talk about later, but the whole structure was correct.)

As shown, we used a piece of wire going through the left side of the battery case and connect the negative end of one battery with the positive end of another battery. (It is not very clear in this picture, but if you look carefully, you can see a small piece of wire outside the left side of the battery case.) On the right side of the case, we had two extending wires connecting the positive end of a battery and the negative end of another battery. We thought it looked prettier than having metals stuck in the case and we tested this with the circuit that I built on Monday. After several adjustments of connections, IT WORKED!

Here is the back of the case:

That was great, except for we realized that the borders (left and right piece of the case in the first picture) was still a little tilted. Therefore, Essie went to lengthen the case.

Meanwhile, Essie documented our design process of the battery holder:



These were all the little pieces that Essie tried. We definitely worked hard, although it was not until later did we realize how a little mistake would lead to adjustments of all other pieces...





At some point, we decided to move on to the electrical part. I was excited because I got very lost looking at the complex Inkscape that Essie was doing and could contribute a lot more on circuits.
On the left side is our circuit diagram.

We drew the holes on Inkscape using the measurements that I took last week. We documented our data as shown on the left.
We made all numbers smaller than measured because we knew that the laser cutter was going to cut bigger holes.

Except for the holes were too small that wires couldn't go through... The dimension of the three holes for the switches was also off. I poked for 20 minutes and gave up and decided to fix the holes...











This was my second design.
You can't really see the difference but I changed the holes to be 0.035 inch (switches) and 0.032 (resistors) and 0.030 (LEDs) and adjusted the distance between the three holes of the switches and cut again.



I poked for another 20 minutes and finally got all the holes out... (Although later I developed a great hole-poking skill, so later assembling became much easier at the cost of breaking my nails...) Anyways, that was exciting... to finally have a sheet to build circuit on. Therefore I took materials off the breadboard and start building the circuit on acrylic.

The circuit design was easy enough, but the actual building part was a lot harder than building a circuit on breadboards... The biggest challenge was connecting wires, especially since our design was so small. I guess I just needed more practice. I started with the circuit with the yellow LED and tested with the battery model. It worked. Then I went on to connect the green LED circuit.

After an hour, I got this:

(From above, it was connected with the battery case, but we took it out before I got to take a picture...)

(From the bottom)

I don't understand why that took an hour... all I remember was my fingers really hurt... At that point, I was doubting the easiness of manufacturing our lantern... But I had fun building this circuit and finally understood how Essie could keep working with Inkscape for hours. I think I could spend hours building circuits too :) We turned off the lights and tested how bright it was - definitely not bright enough to read... but at that point, Essie and I decided to deal with this and thought it's good as long as they light up...

While I was doing this, Essie worked on the battery case again. She coiled the wires and made a spring inside the case.

She also did more work on the extending wires. Even though the model with purple skin wires we had before was prettier, the connection was not as good as this one. But again, manufacturing could be tricky as you have to manually coil it.

We brought our two pieces together and started to think about how to integrate them into one piece. We decided to lengthy the side the of the battery and make an additional layer on top of the battery case. We could have the top layer for the circuit... sort of like the picture on the left... except for not titled (of course and prettier).

This is a picture taken from the top:

Half an hour later, our design came out. It would essentially be a little box. On the top layer, we have the LEDs and switches (we decided just to leave a split for the switches instead of three holes to make our life easier). The resistors face down towards the battery with legs coming out to be connected with the LEDs.

Finally we added our arch design. It will eventually look like this! So cute... I was going to build the circuit with the new model while Essie kept working on the case. However, I couldn't find extra switches and the two switches we got were already soldered
with a bunch of wires... I will work on the circuit once we get more switches.

I took a picture of the first sheet of acrylic we used... These are all the models we did... We were running out of our second sheet as well...

[Mon Apr 5] New Project

At the beginning of the class, Oscar showed us "the most useless machine" that is based on boxes that we just learned to make. Apparently you can do all sort of cool things with boxes...

Anyways, today we officially started our new project - a lantern! We are going to work in groups this time and my partner is Essie. We are going to use AA/AAA batteries (two or three), LEDs and resistors, and we will make battery holder and switches to make the circuit workable. We could also add more complicated designs such as potentiometers, but Oscar said those were too complex to do with the time and knowledge we have.

First we learned the basics of LEDs. They have two legs.
The longer end is positive while the shorter end is negative. In order for the LEDs to function as light sources, there are two things that we need to pay attention to: LEDs' colors and the current going through them. Human eyes' ability to perceive lights of different colors differ, and the ranking  of the our eyes' detection of light color is (from high to low): red, green, yellow, blue, and white. Essie thinks that red LED is not very pretty, so we selected yellow and green.


Then we have to think about the current in the circuit. LED has a negligible resistance itself. Therefore, we need some resistance in the circuit to adjust the appropriate current going through the circuit. The most basic design is:

We can calculate the resistance needed in the circuit to have a certain amount of current going through the LED.

We can always think of different designs to make the circuits do different things:

(1) We can have one LED on at each time or two on at the same time by controlling which part of the circuit is connected using the switches.
(2) We can have one LED on at each time by controlling which part of the circuit is connected.
(3) We can change the brightness of the LED by controlling the resistor being connected in the circuit.
(4) We can change the brightness of the LED by controlling the resistance in the circuit.

Essie and I decided that we want to use design (1) because it's simple and we are more familiar with the set up. We could have designed something original, but we thought that would probably come out to be too complex to build.

Then we talked about the battery holder. Oscar offered a couple designs:

But Essie and I decide to build something similar to an actual battery holder like this:

http://www.google.com/products/catalog?hl=en&q=battery+holder&bav=on.2,or.r_gc.r_pw.r_cp.,cf.osb&biw=1366&bih=643&um=1&ie=UTF-8&tbm=shop&cid=5183386961189604477&sa=X&ei=eqiNT9HePMWs0AHH5_28Dw&ved=0CKUBEPICMAM

Although it looks very complex and I don't know whether we would stick with it in the end.

Lastly we talked about switches. Oscar offered us some ideas, but someone found switches in the lab, so we are just going to use those:

(Taken by Essie)

Lecture ended there. We broke into groups to start our design process. Essie and I searched on the Internet and got some idea. It is going to have a box at the bottom. The LEDs will come out of the box, and the circuit will be in the middle layer inside the box. There will be a light-bulb shaped arch going over the LEDs. We will also make a slide opening at the bottom of the box so we can switch batteries from the bottom. It is going to be made out of wood because it's prettier. Then we started to select materials:

(1) Yellow LED with a 270 Ohms resistor (we put the LED in the circuit and change resistors to find the one that gives the LED the most brightness).

(Taken by Essie)

(2) Green LED with a 330 Ohms resistor (chosen with the same method above).

(3) AAA batteries (because they are smaller than AA)

(Taken by Essie)

Here are the materials we are using for the circuit:

(Taken by Essie)

That was all we had time for during class. Essie worked outside the class to draw the design for the box. I helped her cut out part of the design and assembled it. Here is what we got so far:

(Taken by Essie)

We also realized that we wouldn't be able to make our lantern out of wood because there is only one piece of fine wood... We compromised to use clear acrylic.

[Thu Mar 29] Last day of boxes

I started the class by cutting the design from last class:

I cut two of them to make sure they work before I moved on. I assembled them, fingers crossed....

But the sides were screwed... : -(

At least the hinges worked fine. The sides could be easily bent, although I was struggling a little cutting the hinges. I tried speed 0.5 and the hinges were melted but if I used 0.6, the other lines were not cut through. Therefore I set the speed to 0.5 first to cut through all the lines then set the speed to 0.9 to re-cut the melted hinges... It came out to be a little ugly but at that point, I wasn't concerned about that...

I asked Oscar for help about the screwed part. We decided that if I move the holes the distance of the skewed gap, they should close up. I did that but it turned out that only fixed half of the sides. The rest of the sides were still screwed... Therefore, I fixed the other sides as well. Oscar also suggested that I move the holes and the splits on the longer ends to one corner so it looks neater. I didn't bother to move those on the shorter ends because those sides already fit perfectly. The diagram looked like this:

It sounds pretty easy but there were lots of spatial mapping involved that I was struggling with. It took me a while to figure out the measures and persuade myself that this box can indeed be made out of three identical pieces...

Anyways, I came up with the above diagram and cut three in a row. I assembled them with fingers crossed...

And it worked!!! I finally have a box now!

That was exciting. The problem is the opening is "springy" but cannot stay closed. Therefore, Oscar directed me to look at Kelsey's dovetail design:

(Taken from Kelsey's blog)

If I can do a dovetail design to "click" the lid so it can stay close, that'd be a more functional box. Oscar suggested that I could even make three sides "clickable" - looking at the second last picture above, I can make three sides close together using techniques such as dovetail or even magnet (that's just an idea...) I tried dovetail before and found it really hard to control. Since my material is thicker than Kelsey's, I imagine that directly copying her measures wouldn't work. There is also the possibility that my material is too thick that it does not have enough stretch that dovetail technique requires. But if I had more time, that would have been the first thing I work on.

This project took me three weeks to finish and as I said, there are still lots of things that can be done to improve my design. I think it's a great project to start with because it made me experience all the subtleties in the design and manufacturing process that I could not have imagined if I did not go through this process myself. I definitely became more aware of the engineering designs around me (which is almost everything) and thought more about how they could be done and the difficulties in doing them. I also decided that I am not a mechanical type of person because I am not very good at 3D imagination. At least between mechanical and electrical, I prefer the latter.