Show HN: Capacitor Alarm Clock

#1

Post by arcaege » Sun, Jun 14, 2026, 11:19 AM UTC

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 :)

Show HN: Capacitor Alarm Clock
github.com

Re: Show HN: Capacitor Alarm Clock

#2

Post by kavyanshkh » Tue, Jun 16, 2026, 11:19 AM UTC

gng thats crazy!

Re: Show HN: Capacitor Alarm Clock

#3

Post by beeforpork » Wed, Jun 17, 2026, 11:05 AM UTC

That sounds completely safe and healthy! Hmmmm, I love the smell of vaporized electrolyte, particularly when waking up!

Re: Show HN: Capacitor Alarm Clock

#4

Post by uberex » Wed, Jun 17, 2026, 11:16 AM UTC

Based. Unhinged. Don't try this at home.

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!!!!

Re: Show HN: Capacitor Alarm Clock

#5

Post by andai » Wed, Jun 17, 2026, 11:28 AM UTC

There's a video demonstration about halfway down the GitHub

https://github.com/ArcaEge/capacitor-alarm-clock#Demo

Re: Show HN: Capacitor Alarm Clock

#6

Post by block_dagger » Wed, Jun 17, 2026, 11:40 AM UTC

How about a flux capacitor clock?

Re: Show HN: Capacitor Alarm Clock

#7

Post by bilsbie » Wed, Jun 17, 2026, 11:42 AM UTC

What’s happening at the electron level that makes them do this? Anyone know?

Re: Show HN: Capacitor Alarm Clock

#8

Post by fc417fc802 » Wed, Jun 17, 2026, 11:43 AM UTC

beeforpork wrote: post #3

That sounds completely safe and healthy! Hmmmm, I love the smell of vaporized electrolyte, particularly when waking up!

I feel like a wire detonator would be safer plus the consumables would be cheaper however even then I doubt vaporized copper or aluminum is good for you. Honestly just roll some firecrackers and use the ESP to light them off.

Re: Show HN: Capacitor Alarm Clock

#9

Post by adnaahmed » Wed, Jun 17, 2026, 11:43 AM UTC

the alarm clock for the ai age, it needs an LLM

Re: Show HN: Capacitor Alarm Clock

#10

Post by peterabbitcook » Wed, Jun 17, 2026, 11:57 AM UTC

So it’s not UL listed?

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?