This week, I learned characters of servo motors in pcomp class. My partner is Xuhui Xu, we worked in pairs and made this simple application using a servo motor and a photoconductive resistance. The application is called “OPEN SESAME”, which is used to help our roommates open the apartment door when we forget to bring door card with us.

I made brainstorm with my roommates to get some ideas about a simple application using servo motor. There is a big problem bothers all of my roommates: We have five people but only one door card, which brings a lot of inconvenience.  If we have not bring the card and there is no one at home, we should wait outside our apartment door for a long time, waiting for someone lives in the building to show up to open the door.  Xuhui came up with an idea that we can use servo motor to create a robot who can open the door for us. We decided to work in pairs on this application.

Firstly, we observed the communication device in our living room, and we found when the room number was called,  the bell started to ring and the screen on the device lit up, and in the meantime video chat  would be available. We can use the photoconductive resistance to detect the light on the communication screen and let the servo motor to make response. We detected the range of light intensity.

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Secondly, we detected how to trigger the buttons on the communication device to open  the door. We use different material to touch the button to see what materials could made it respond and what could not. We figured out fingers, water bags, and even gingers could trigger the button, but plastic or conductive wire could not. We guessed it was a capacitive screen. To confirm, we separated the communication device to see the embedded panel, found out the button is a capacitive screen with a pressure sensor. Then we made the conductive wire connected to the ground but it still could not trigger the button. Searching reasons on web and we found out we need to expand the contact area. We made many contact tentacle for the servo motor, and finally made one that has the best precision and success rate to trigger the button.

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