Final Project, Phase 3

A recap of previous phases:

In phase 1, we:

            Decided on the layout of the visual

            Visited the CSC to learn about the handwashing process and the best method of approaching                      our targeted group of people

            Creation of a gear train that would translate servo’s 180° rotational movement into linear                            movement spanning 14” of visual (1:5 lego gear train ratio)

            Attaching the input gear to servo (change from piano wire to glue)

            Brainstorming the position of the ultrasonic sensor(s)

In phase 2, we:

            Created an Arduino program that would rotate our servo motor with different time delays to                       correspond with the different steps in the handwashing procedure: filled with placeholder                     values and designed for 8 steps.

            Designing a working circuit to make sure all components function and integrate correctly

            Changing the position of the ultrasonic sensor to rest below the visual

            Creation of the box – front piece (which was also printed again for the back piece) and the                         bottom piece

            Creation of a new, heatstaked indicator

Now, in phase 3, we completed our final project.

To fully complete our project we had to:

1.     Change the box dimensions due to some complications

2.     Visit the CSC for concrete values and to watch the actual handwashing process performed by a number of people in our targeted audience

3.     Finalize the information in our visual

4.     Fine tune our program with correct values

5.     Add an indicating LED light to the circuit and program

6.     Assemble the components of our project and adjust due to some minor issues

7.     Affix the visual and provide the means of attaching our project to the wall

8.     Present our project!

At the beginning of the week, we printed out our original solidworks pieces for the front of the box (x2) and the base of the box. We realized we had to make some changes in order for the box to be eligible for heatstaking and also to enable the visual to rest properly against the front edge of the base.

Our first correction was to lengthen the pegs on the front piece slightly. Although we had measured correctly given the thickness of our piece of Delrin, we decided we needed slightly more material to work with in order to properly heat stake the pieces together. Extending the pegs gave us more material protruding from the holes in the base to work with.

Our second correction was based upon how we thought about the visual’s orientation. We wanted the visual to rest behind the indicator, but in front of the gear train and be out of the way of the chain as well. Giving this some thought, we thought that if we positioned the top of the visual accordingly, the bottom would have to be vertically in line with the top. This meant that the visual had to be affixed to the base at a point beyond the gear train (and therefore, beyond the front wall of the delrin). We needed to move the pegs in by 2cm to create the proper distance (needed for the gear train) between the front edge of the base (in line with the visual) and the front wall of the box.

                            

Our next objective was to revisit the CSC and witness the handwashing process as well as measure accurate values integral to our Arduino program.

We watched and timed more than 10 people engaged in the handwashing process. We noticed that some skipped steps, and there was variance in the time spent on each step of the process. We decided that because there are regulation times for rubbing and rinsing hands, we would focus on getting an accurate sense of how long our delays should be for turning on/off the water or grabbing soap. Over the course of 10+ trials, we agreed on time intervals that we thought best for the process. These values allowed for more time, which could help slow the process or allow people who may be behind to catch up.

Next, we measured the distance between the ultrasonic sensor and the edge of the sink, with the intention of going back to the lab and using the sensor at the same distance from an object to see the relevant readings. However, we were able to download Arduino software in time to take the readings on-site.

If a child is flush with the sink’s edge, the reading is approximately 25. Given a little more space of about 10 cm (a reasonable buffer zone), the reading is approximately 30. We decided that a reading of less than 30 would be consistent with every attempt to wash one’s hands.

While we were at the CSC, we also asked a director about her preferences for our project’s visual. We had constructed two choices, one with 7 and one with 8 steps.

Our first idea for the visual (seen in the foam core prototype in phase 1) had the steps:

            Roll up sleeves/wet hands/turn off water/get soap/rub hands/rinse hands/turn off water/dry hands.

Our second option removed the first turn off water command.

Although there was an interest in not wasting water, the director advised us to pursue the second option to simplify the process for the audience.

We designed the 7 remaining steps in the visual by using pictures from the actual bathroom the handwashing is conducted, which made the images the most concrete. Each image became 2” wide, for the visual to span 14,” fitting in nicely between the axles of the gear-pulley system.

 The electronic design

Our next steps in the lab were to complete the visual and tweak the code.

We printed out and laminated the steps we would use, and taped them together into a single strip. We formed bold black lines between the steps to effectively differentiate them. We also colored the indicator black to track its progress more easily. We also made a rectangular cut at the plastic bottom of the visual, in the middle where the ultrasonic sensor was positioned. This removed interference with the sensor by the visual.

 Printed visual & its placement

While in the process of tweaking the code, we thought about whether the people would know if the process had started or not. Before, when our code took a reading below 30, it would check back in 5 seconds to see if the reading was still below 30. This would confirm that a person was indeed before the sink, and also would give that person time to roll up their sleeves before moving to the next step. But wouldn’t people want to know if the sensor registered them the first time, and not have to catch up if they thought that it didn’t?

We thought that an LED would help resolve this problem. We added to our code some commands that would tell the LED to light up at certain times, which would inform the participant that the program was running.

When the sensor reads a value of less than 30, the LED will turn on for .5 seconds. If, after 4.5 more seconds, the person is still there, the LED will turn on and remain on for the rest of the process (which starts after the initial 5 seconds if both readings < 30). It will shut off when the program resets. If the second reading is greater than 30, the process will not proceed.

The initial blink will tell people that the sensor “recognized” that a person is in front of it, and that if the person remains there for 5 seconds, the process would start. The audience can be taught that when the light blinks the first time, then is the time to roll up their sleeves before the next step begins.

Addition of a red LED bulb, adhered with electrical tape

Lit LED bulb while program is running

LED circuit: orange and yellow connect the components to the voltage and ground terminals. Green and yellow go to the LED, where green is positive. There is a 10kOhm resistor.

To get the final program:

We added the LED program into our existing code.

We changed the delay values based on the timings we gathered from the CSC trials

We had to change the program to accommodate 7 steps instead of 8. This meant that we needed to partially rotate the servo motor 6 times, with a turn of ~25 degrees per rotation.

 Final code

~

Assembly:

We next had to assemble all the components of our project together.

Having cut out our box components, we heatstaked the pegs to the box base.

We installed the gear train into the axle holes in the box walls. We decided to file down the posterior ends of the axles to allow the back of the box to be more flush with the wall.

We hot glued the servo motor in place after dropping it down the shaft. We needed to file the shaft down to ensure that the servo fit correctly; it ended up needing slightly more width than we had measured.

We left the battery pack unattached but nested in the box for easy battery removal. It is also a distance away from the Arduino board to allow the Arduino cable to easily connect with the board without dislodging the battery pack.

We screwed the Arduino board into two legos (one of which was filed down to avoid interfering with important components on the bottom of the board) attached to Velcro, with corresponding velcro pieces on the bottom of the box. This prevents permanent damage to the Arduino board.

We placed the breadboard to the right of the Arduino board so that the leads to the ultrasonic sensor were long enough to reach the middle of the box underneath. This is a picture that shows the relative orientation of the internal position of the components (looking in from the right side):

The ultrasonic sensor fastens to a lego which attaches to the underside of the box with Velcro. The front face of the sensor is flush with the front face of the box base.

We covered the ends of the box with plastic wrap. While we were at the CSC, a few members from our targeted audience were interested in seeing the inside of our project. The see-through quality of plastic wrap enables this exploration without touching while providing a layer of water protection.

The final step in assembling our project was to secure the visual on to the box with Velcro. This allows for the strip to be removed and replaced by other visuals. The flexibility of this feature lends itself to the uses our project could have. Slight changes in the Arduino program, in combination with a new visual, could succeed in guiding people through new tasks and procedures.












Completed project:

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