CSC Final Project Week 3

This week, we ordered our materials, identified those available in the lab for us, and started making prototypes. 

The materials we ordered were:

i) A "music maker" shield, an SD card, and a 0.5 W speaker

ii) A sheet of Velostat 

Ordered Materials

i) A music maker shield

Since we wanted music to entertain the children while encouraging them to wash their hands properly, we searched for shields compatible with Arduino Uno that can play recorded music. We found "Adafruit 'Music Maker' MP3 Shield for Arduino w/3W Stereo Amp - v1.0" (shown in the images below) that can take an SD card and play different tracks of music saved in mp3 format. We also ordered the SD that would go with the music maker.

To go with our music maker, we also ordered an 8 Ohm, 0.5 Watts speaker thinking the low power would save us battery life.

Although this speaker looked tiny and exposed (without a case), we believed it was appropriate for a project of our scale and budget. We also planned to either build a container for it or mount it higher up to prevent children from splashing water on it. 

ii) An 11'' by 11'' Pressure-Sensitive Conductive Sheet/Velostat

We had originally planned to use a force sensor (force plate) that reads the weight of the person standing on it and allow us to only activate the actuator if a child (under a certain weight) stands on it. However, we couldn't find any force plates within our budget and of the appropriate size.

First, we settled for a button under a hard lamina that would push the button as a person stands on it. But since this would involve building a platform that is both stable and effective in pushing the button even if the child stands slightly beside the button, we went with Amy's suggestion of a Velostat. 

A velostat is a sheet of material whose electric resistance decreases when pinched. This allows us to put conductive wires on either side of the sheet and have the sheet act as a poor conductor when relaxed and a better conductor (low resistance) when stood on. This, if it works, would be a cheap and convenient input method for our design. 

This is what a sheet of Velostat looks like

Early Prototyping

We started our prototype by reviewing and building on some of the Arduino exercises we had done before. 

We built on the "Blink" example from the Arduino program to control first one and then multiple LEDs. This prepared us to to set up the LEDs that would shine at specific times behind each instructional picture to help students focus on the appropriate step of hand washing at a given time. 

We also revisited our "Sweep" example with servos and adjusted the angles of rotation of the servo motors to resemble a more realistic wrist rotation. We cut out cardboard and foam board models of tiny hands (almost real-life-sized models of a child's hands) and taped them to the servo to simulate moving hands, which when put next to each other look like they're washing. 

First, we had attached a servo to each hand and oriented the hands such that they face perpendicular to the wall. Later, Amy suggested we use a servo on one hand and keep the other stationary. That way, we can orient the hands better for visibility, and minimize power consumption by only using one servo. The relative motion between the hands would still make them look like they are scrubbing/washing.

Overall, this week was spent ordering and trying components of our design for functionality. We were also able to solder parts of our music maker shield in preparation to use it the next week.