All posts by Wendy Gao

Personally Victimized by Small Robot Hand

I made a video detailing my process here. The basic algorithm is that when I put my phone down (aka when the force resistive sensor (FRS) registers a reading), a twenty five minute timer starts counting down and the ultrasonic sensor & servo kick in. I tried to make it as precise as possible, so that the servo with the tiny hand starts beating down when my hand is in range of the phone. When the phone is taken off (aka FRS no longer registers a reading) the annoying piezo alarm goes off until phone is put back down, and the timer resets. When timer reaches 00:00, a break timer begins for five minutes and it’s safe to take the phone off without any consequences.

Here’s a picture of the final product with all the components. It involves some super tight breadboarding of five individual components: LCD, ultrasonic, FRS, piezo, and servo motor. I could have definitely used a bigger space but I was pretty amazed at how I organized it, and plus there was the added comedy effect of the hand just destroying the ultrasonic sensor.

Code here! Big thanks to the CountUpDown library for timer help and the tutorial on playing melodies with piezo. I still need to come back to update with a few older blog posts but I really enjoyed making this project for class and my friends LOVED it.

Put Yo Phone Down progress

Here was my original project idea presentation.

First I tested the FRS to be able to detect the weight of my phone. However this did not work as I hoped, because of the uneven surface of the phone and also because the FSR works better with a sharper pressure (e.g. finger pressing down on sensor). I will be ordering a phone stand to see if that works and if not I will be exploring alternatives.

Next I worked on the sound feedback of the project, and managed to program it to play the Chicken Dance song whenever there is no force placed on the sensor. Over the course of the next week I will work on the representation of time in this project. What I’m likely to do is a servo-powered laser timer/clock. Inspiration:

Final Project Ideas

I’m hoping to make some kind of alarm clock/timekeeper and explore different ways of depicting time visually, or even with sound (for example, clapping five times sets a five minute alarm). It would be helpful for daily activities such as cooking, studying, and exercising. Here are some inspirations:


Make Some Noise

I wanted to build some kind of drum with the servo motor and prototyped different models. The simplest way to do so would probably be to fix the servo motor to my desk and attach something to the wings of the motor so it can hit the desk.

Then I thought about how I could create a more pleasant noise, for example a ringing sound (like a triangle). I tried hitting different objects I had, and ended up attaching a hairclip to the motor to hit a metal can. This was controlled by a potentiometer. Unfortunately this sounded awful.

I realized the instrument will probably ring better if one of the metal objects was suspended (like a triangle). I played around with different ideas and thought of converting the can into a Chinese spin drum, which is a drum that is spun around and the action triggers the drum to be hit by suspended ball bearings.

So I created my own drum prototype by attaching hairpins to both ends of the can.

I then attached the noisemaker to the motor, which created the same noise when automated (code here). The only concern is that the sound of the motor overshadows the ringing a little bit.

Sound Sensor

I bought a electret mic breakout to make a sound sensor. The input and output are both in analog form. It doesn’t show up that well on camera but it works, however I would like to experiment more with delays so the LED lights up for a longer time. It is also not very sensitive to small changes in sound.


Tea Time

I wanted to make a switch that would turn on the LED when I set my tea cup down, in other words a sort of two-piece coaster that will only touch and close the circuit when pressure is applied. I started by wrapping two cardboard circles in aluminium foil and attaching them to jumper wires. I then taped a piece of sponge to the middle of the bottom piece so that the two pieces will remain separated unless pressure is applied by a heavy object such as a cup.

Initially, I cut the sponge into a larger piece but it made the coaster very wobbly, and I didn’t want the cup to topple and spill and possibly set my apartment on fire. So I cut the sponge down to minimise wobbliness and to make the circuit more sensitive to pressure.

And here we are. Reviews from friends include “plsssssss hahahahaha”, “cute”, but also “dumb”.