It’s 10 PM on a Wednesday night, and you’re starving. Dinner was 5 hours ago and you’re a big growing teenager, so you head down to the kitchen to whip up some food. Taking some leftovers from the fridge, you throw them onto a plate and hurl the dish into the microwave. Pressing 2:00 and then enter with 4 loud beeps, you wait for your food to cook, with hunger draining all of your energy. Since you don’t want to wait in front of a microwave for an eternity, you leave and do something else, coming back later to the sound of ear-piercing beeps. However, as you hear these beeps and make your way back, your parents scream at you to keep it down. This is the reason we created the Micro.wav.
The idea was that we wanted people to be able to use their microwave without having to wake your entire family up in the process. Unless you’re waiting at the microwave the entire time, ready to open the door when it hits 1 second, the loud beeps will come and your tired family will begin throwing your belongings into a suitcase.
During our sticky note phase, we were torn between a couple of ideas. The big ones being having the microwave send a notification for when it’s done via Bluetooth to your phone and an external signal like a fan that blows when the microwave is done instead of beeping, but our favorite was to create a night mode. Through the use of an external switch, we would send a signal to the microwave that would block the signal of the food being done if the button has been pressed, completely muting the microwave. However, after discussing with a few of our classmates, we found that the beeps at night are still somewhat crucial, so we thought of a way to perhaps change the nature of the noise. At first we thought of a volume switch, but we weren’t able to fit that in in the time given to us, so we settled for just changing the internal sound to be more quiet/soothing so it wouldn’t wake up your folks but could tell you if your leftovers or hot pocket was done as you studied or got a bodacious Vic royale in Fortnite. So, with somewhat of a plan, we imagined that we’d pry open a microwave find the source of our sound, remove it via a soldering iron and attach something that could perhaps change our sound.
After planning all of this out and coming back to school, we found ourselves with 5 total microwaves, which we took apart to really see how microwaves worked. We spent a little too much time taking our microwaves apart, accidentally undoing too many wires and such, but we settled with one of the more modern microwaves that we ended up using in our final model. After testing out multiple microwaves, we found where the sound came from (a little piezo speaker that looks like a chip) and talked to Mr. Moody about how we could change the sound and put our plan in place. He suggested that we use an Arduino with an AudioShield that has an SD card where you can change what sounds are emitted when it’s active. We would then have to remove the sound chip entirely (via solder) and send the interaction at that spot to the Arduino. Doing all of this, we were left with two empty spots where the sound chip was attached. With immense help from Mr. Moody, we found out how the sound is utilized by the microwave through the use of a voltmeter. By sending a certain voltage to the two spots where the chip was attached, the voltage causes the sound chip to generate the beeps one would hear if they used the microwave.
So, with this knowledge, we wanted to test how a more simple prototype Arduino would work when wires from it were attached to and then to a computer. We didn’t want to cause any possible harm to the main Arduino, so we used a prototype so we wouldn’t be set back as far. So, we connected two wires to the board and connected them to the empty spots the sound chip had occupied. However, this is where our process began to travel down Coding Hell. The first issue was that the microwave worked, and then the S.D card had reading errors. Then my computer had troubles running the code due to the FatReader not working on my computer. It only worked if the code was run on Mr. Moody’s computer, so we borrowed his laptop for multiple classes at a time so we could test it. Lastly, we also originally had a button that would prevent the sound from occurring, but no matter what we did the computer couldn’t pick up the input. After our coding was all sorted (immense thanks to Mr. Moody), we tested the code and ran the signal through a spare Arduino with barebones code that was just intended to detect the electrical signal the microwave was trying to send to its internal speaker. However, as we did so, the Arduino worked for the 10 second long run of the microwave until it overheated and died. The microwave fried the Arduino — we think due to too much voltage being sent to the analog input channel. We had connected the ground of the microwave to the ground of the Arduino and one of the speaker connections to an analog in pin. But when we used a voltmeter to test the voltage between the microwave ground and a speaker input, it was pretty high — fluctuating over 15V. When we tested the voltage just across the speaker + and - terminals, it was about 5V, which is a much happier voltage for an Arduino. So we got a new Arduino and tested again by connecting one speaker terminal to Arduino ground and one to an analog in pin. This time the Arduino showed a clear signal when the alarm went off and didn’t fry like a chicken tender in the hot Alabama sun.
With the signal detected, we had to find something that could still alert you with a sound but not wake up your parents that would also work during the day, since when a microwave is used during the day when everyone is up, the beeps aren’t that big of an issue. So, with some help, we picked the soothing sound of a ‘Re’ (like Do-Re-Mi) note on a xylophone, and through the use of a speaker, got the sound to be produced everytime we pressed a button or the microwave was finished (or, more simply, everytime voltage was sent to the speaker). It was glorious, and using the volume control on the AudioShield we could get exactly what we wanted.
From here, we plan to package everything we used into a simple-to-use kit that a hand7 DIY-er could install themselves (and others could have installed). The kit will include a pre-wired Arduino, a built-in speaker of much higher quality than the microwave chirper, and an SD card with pre-installed sounds and instructions on how to download or create your own sounds. All the user would have to do is unscrew a few screws to get to the microwave control panel and clip a couple of alligator-like clips onto the metal legs of the microwave speaker — no soldering required for most microwaves! This simultaneously quiets the internal speaker and allows the Arduino to detect that a sound needs to be played. In future versions, we might even use a WiFi-enabled microcontroller (Arduino or Particle Photon or other) so that you can have alerts sent to your phone or smart-watch for truly silent alerting.