Final Project Part 1

I was very excited when we were assigned to work on the project to instruct proper hand-washing, because I was very excited about my idea of making trees that would turn green. However, I was very quickly told that such an idea may not be applicable to the age group that we will be working with and that we should come up with a more direct visual to cue the children. Since our focus is the ensure what we make fits our "clients'" needs, we then sadly abandoned our tree design and decided to come up with a new visual demonstration, which, as a result, became the focus of our first brainstorm.

We came up with a few ideas. Based on all the materials we have used in class, we already figured that a servo motor would be the easiest to use for our purpose, since we can have very precise control over it. Another prerequisite for the visuals is that we clearly should not use any text, since the children most likely not be able to read.
After some reorganization and summarization, our visual designs all fall into these main ideas.

Brainstorm - Visuals

The first type resembles a clock.

Our idea is to have a circle sectioned, with each section containing pictures of the proper steps of washing hands (like a carnival wheel!). There would be an indicator to indicate which step the child should be doing. We considered using a frame to highlight, an arrow to point, and/or an LED that indicates the current step. We can either rotate the disk of pictures or the indicator. This would be the easiest visual to install with servo, since it requires a circular motion which the servo already has.

The second type is a linear model.

This idea would require a strip of pictures showing the steps of proper hand-washing. Similarly, the indicator could be a frame, an arrow, or an LED. We can either motorize the indicator or the strip itself. This visual would require a gear train that transforms circular motion to a linear motion.

Our third one is a little different from the previous designs. It involves indicators showing what objects near the sink should be used.

The idea is that we would have arrows with lights (or other form of indication) light up when certain objects, for example, the soap or the tap, should be used at the proper step.

With some brief deliberation, it was not hard to eliminate the third type of visual. It is not very direct and can be confusing even for adults. Plus we cannot demonstrate what the child should do exactly and not every step can be demonstrated in such manner (e.g. rubbing would be very hard to demonstrate). At this point we were relatively happy with the types of visuals we have, even though they are not the most creative or sophisticated things one can ever imagine of. We of course would have loved to come up with more visuals, but due to the need of our client, and based on some information regarding child development we received from Professor Banzaert, it was clear that all we needed was a simple and direct visual with pictures. That is what works the best for children at a young age.

Brainstorm - Indicator

Now that we have an idea of the core of our project, we decided to spend more time on the details. As said before, the three major ways of visual stimuli are frame, arrow, and light. Here are some comments we made about each stimulus:

1. Frame: 

the frame is a very strong indication that definitely draws attention to the current step. However, it also blocks part of the pictures next to the current step. We are unsure about how important it is for the children to see the other steps, but it would certainly be helpful if the children can do so.

2. Arrow: 

the arrow is a very typical indicator which would be helpful for the children to understand. However, it is also smaller. The color and thickness of the arrow is very important so that it would not just blend in with the back ground.

3. Light: 

the light could be a visible light bulb, or it could be back light. The light bulb is very direct and visible, but we are worried that it may distract the children. The back light, while not distracting, on the other hand, may not be as easily understood and may not be as obvious in a well-lit room during the day as the bath room is at CSC. The back light may also make it harder to find materials for the front part of the visual, since we will be printing out pictures.
While these are our thoughts, we would need help from the professional staff to decide on what would be the most helpful for the children.

Brainstorm - Sensor

Another important part of our project is the sensor. This is the feedback and control part. Here we have a few things to pay attention to.

• We want to make sure that we can sense the child in some way when they come and wash their hands without mistaking people who walk by.
• We need to pay attention to the installation so that it is water proof. This includes the device as well as the wires.

1. Type of sensor:

What we have worked so far that are applicable to our project include the ultrasonic sensor and the touch sensor.

• Ultrasonic: This sensor is the most intuitive one to use. Our only concern came from the fact that our sensor had some connection issues when we used it with Sciborg. In a far distance, the ultrasonic sensor is also very sensitive and the range it detects is not perfectly clear.
• Touch: The touch sensor can be consciously activated by having a child push on it before the child starts washing hands. However, this is not a step in the regular hand-washing process and would require the children to remember extra information. Certainly not the most ideal. Alternatively, we can install the touch sensor at the front of the counter, so if the child leans against the table, the sensor will be activated. The problem could be that if the child moves during the process, the machine may be confused.

2. Position of sensor:

Keep in mind that being water-proof is important.

• Near the water tap: this is where many automatic taps have their sensors. This maybe problematic in our case, however, because our ultrasonic sensor is not very water proof, and we may include steps like rolling up sleeves that is not detectable by the sensor.
• On the wall near the visual: this seems to be an ideal place. It is close to the rest of the device, making wiring easier. It's not close to water. The only concern may be how effective the ultrasonic sensor would be detecting the person. We will need some testing at the bathroom where it will be installed.
• In front of the counter: we can use ultrasonic sensor or touch sensor at this location. The sensor would be close to the person we want to detect and would thus be more precise. However, it is far from the rest of the device and may make wiring hard (also need to consider water near wires). We also need to know whether the children lean against the counter top and how both sensors will be affected.
• Right below the counter: to avoid children touching the ultrasonic sensor in front of the counter but also to have proximity between the child and the sensor, we considered putting the sensor below the counter. However, this may become problematic if anything is stored below the counter. We are also unsure of the range of the sensor. We will need testing in the bathroom if we were to choose this location.

Tips from the Experts

Now that we have a fairly clear idea of what we want to do and what we need to know, we visited Becky to ask some questions. and here are some important points from Becky.

• The best visual for young children should be linear. This narrows down our visuals to type I.
• It is very helpful to see all the steps. This eliminates frame as an indicator.
• We do not want visual stimulus to be distracting. This makes an arrow the best indicator.
• Children already start to associate colors with genders. We should avoid using gender-specific color (which is, of course, only a social construct, but is affecting the children at such an early stage) and stick with primary colors and/or black and white. In fact, a big, thick black arrow would work the best.
• The steps of washing hands are: roll up sleeves, turn on water, rinse hands, turn off water, get soap, rub for 20 seconds, turn on water, rinse for 20 seconds, turn off water, dry hands.
• We should use real photos to illustrate the steps. Thus, we took a series of photos with Meredith demonstrating the proper way of hand-washing. (Shout out to the super star.)
• The visual on the wall should be no longer than 15 inches.
• Children lean against the counter to wash hands.

Initial Assembly
Our visit to Becky made us decide on a very simple model of a linear visual with a moving black arrow that indicates each step. Our first step was then to figure out the gear train that would move the arrow indicator. We would build the rest of the supporting structure around the major gear train.

Our servo only turns 180 degrees. This means that a gear train is necessary to amplify magnitude of the linear motion created by the circular motion of the motor. Based on the length limitation of our device, we decided that the strip would be 14'' long. Based on this length, we used three pieces of lego beams with length of 16 lego units. We also used chains as a way to carry the indicator.

There are a few things to discuss here.
First is the gear ratio. We did some research on the servo motor and it turned out that the motor is not as powerful as the PicoCricket we used on the lego racer. As a result, even though we do not require much speed, which is good for creating enough torque, we still want as few gears as possible to reduce friction. Fortunately, since we have very precise control over the servo, we do not have to find the exact ratio that moves the indicator for 14'' after an 180 degree turn of the input gear. This means that as long as the indicator can go further than the linear distance of the chain when the input gear turns 180 degrees, we are good to go. We would only need some testing to figure out the number in the code. With a couple tries, we eventually settled down with a ratio of 1:5, using a 40-tooth gear as the input gear and an 8-tooth gear as the output gear. The 8-tooth gear is shares the axle with another 40-tooth gear which supports the chain and the indicator.

Then we look at the chain. It is fairly straight-forward to build the chain at the beginning, but the decision we actually had to make was at the last piece of the chain. When the chain is perfectly straight, it is, in fact, relatively tight on the gears. This creates more friction on the axle turning, and may potentially cause problem when connected to the servo motor. If we add one more piece of the chain, we will get a slightly saggy chain, but it is much freer to move. This is fine since we used a 40-tooth gear to support the chains so that the top and bottom would not interfere with each other. We thus put the indicator on the top chain and have it hang above the strip of pictures.

Last but not least, the indicator. We made a simple indicator of foam core. It should rest nicely on the chain and over the visual illustrations. We consider connecting the two pieces either through press fit or heat staking.

Now the next step is connect the gear train to the motor.

In the picture we can see that there are small holes on the servo for us to fasten things to it. Our first idea is to piano wire the input gear, so that it is aligned with the motor in the center and will transfer the motion into the gear train. We only had time to secure the gear by the end of class and didn't have time to test it. Here is a picture.