ZH version is available. Content is displayed in original English for accuracy.
I made an alarm clock that blows up capacitors to wake you up.
There are more details on the Github repo but it's made from an esp32-c3 as the microcontroller, with 3 capacitor slots. There are relays on each capacitor slot to put 15v reverse voltage on the capacitor, with 5.1 ohm resistors on each slot for current limiting in case the capacitor shorts out. I also chucked in an SSD1315 OLED to show the time and a menu to configure it, although there's a web UI as well. The esp32 also means you can fetch the time from NTP.
It also functions as a small heater since I used LDOs to step down 15v to 3.3v for the esp32, I was lazy and didn't use a buck converter circuit :)
Discussion (22 Comments)Read Original on HackerNews
Sadly I could not get free samples from my Vishay Rep, that I was in good standing with. MEPIC85N8R0KTT come in lots of 10,000 to buy.
Be sure to check out the application note "A Guide to Using EPIC / MEPIC Igniters in Pyrotechnic Applications".
https://www.vishay.com/en/product/53058/
National Semiconductor, bought by TI, used to make a similar part, check out the application note:
https://www.ti.com/lit/an/snoa217/snoa217.pdf
This is what I wrote about the MEPIC parts a long time ago:
"MEPIC resistors, also known as bridge resistors, are resistive elements that convert electrical energy into heat energy in a precise electro-thermal profile for the purpose of initiating a series of pyrotechnic events in a controlled energetic reaction. [They go BOOM on command, which is different than Rapid Spontaneous Self-Disassembly.]
The new Vishay Sfernice resistor is optimized for electronic igniter applications in automotive safety systems for the deployment of airbags and other safety devices; digital blasting in mining applications; and in fireworks applications for better synchronization of fireworks, music, and special effects.
With firing energy down to 1.5 mJ and a typical ohmic range of 2 Ohms (+/- 10 %), the device provides designers with very predictable, reproducible, and reliable behavior.
Offered in the standard 0805 case size for the wraparound and flip chip versions, with other sizes available upon request, the resistor features easy set-up of firing levels, and is compatible with various pyrotechnic compositions.
Offering ESD withstanding to 25 kV without extra protection, the MEPIC resistor's performance meets no fire/all fire conditions and the requirements of USCAR, AKLV16, and major car manufacturer standards.
The device is RoHS-compliant and conforms to Vishay "Green" standards. [Is it not great that Fuzes are 'Green'?]"
But it is also art. It represents the waste in our devices that play out over 1-4 years (or say a few weeks for a vape) but in one night.
But yeah. Don't do it. Indoors? wtf!!!!
https://github.com/ArcaEge/capacitor-alarm-clock#Demo
Did anyone else smell capacitors when they watched the video? The brain does funny things.
Do you need the 15V input to torch the capacitors and run the relays? Could I use a 5V USB ESP32 dev board instead, and just put a boost circuit or MOSFET on the relay load side for the explosion circuit when it needs to go off, or are there other components that need the higher voltage?
A current is passed through the capacitor and a thin film of oxide is built up in one of the terminals, according to the polarity. This is why electrolytic caps have polarity, if you use them with their polarity inverted, you flake off that oxide layer and thus short them out.
A free running current in that electrolyte boils it off, and you get an exploding cap
a Life limiting machine