I expected an alarm clock using a capacitor for timing. Either charge it to a delay-dependent level, or charge it to a fixed level and discharge through a delay-dependent path, or trigger when it drops below a delay-dependent level.
Show HN: Capacitor Alarm Clock
31–40 of 49 posts
Re: Show HN: Capacitor Alarm Clock
#32The actual "make it go bang" bit here isn't the most potent. (I think I have capacitors here which wouldn't care in the least about this, despite their datasheet ratings.)
If you need to take it to the next level, consider something based on a xenon photoflash driver. These aren't as common as they used to be, but they're still not hard to make. I had to make one of these a while back and ended up using one of those $5 LTC chips but that was appropriate for the situation; there are certainly other ways to do it. This will basically charge a 400V capacitor up for you, which you can then dump into the 5V part. High-quality 5V capacitors will handle small spikes of this. But using a big 400V capacitor will make a big spike, which is not kind to the other capacitor. (I must confess I didn't try blowing up a lot of things on the one I made, but it was medical test gear, not technically a capacitor-blower-uper, and I was on deadline anyway. I also had other, significantly more destructive, equipment available to me should that be the goal.)
Re: Show HN: Capacitor Alarm Clock
#33Is this not technically an IED?
This is absolutely how IEDs are made. You buy an old Nokia phone and wire the speaker/ringer to the detonator. Call phone -> boom.
In fact, TFReadme directly references Electroboom/Mehdi Sadaghdar who did this with an old-school analog alarm clock (the kind with an actual bell) and in the video he muses that it's literally a time bomb, har har get it.
Re: Show HN: Capacitor Alarm Clock
#34That sounds completely safe and healthy! Hmmmm, I love the smell of vaporized electrolyte, particularly when waking up!
But it's got electrolytes!
Re: Show HN: Capacitor Alarm Clock
#35Tangent: I remember when hackaday posts about building cool and or useless circuits were posted constantly to HN. Now I can't remember the last time I saw one. (I know this link isn't hackaday, but it's exactly like what they feature).
Re: Show HN: Capacitor Alarm Clock
#36Wondering if we can adapt this for our pulsed power system :)
Re: Show HN: Capacitor Alarm Clock
#37So 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?
You could, but from my measurements the capacitor tends to pull ~1A before it bursts, so you'd be running up against the 3A limit of USB. At voltages below 12V, they don't seem to go off reliably.
Re: Show HN: Capacitor Alarm Clock
#38So 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?
You could, but from my measurements the capacitor tends to pull ~1A before it bursts, so you'd be running up against the 3A limit of USB. At voltages below 12V, they don't seem to go off reliably.
Have you tried a backwards polarity tantalum capacitor?
I've seen those go off just on their normal voltage when installed backwards. Sometimes immediately and other times with significant delay.
Eye Projectile and Eye Flash protection along with hearing protection are required.
Re: Show HN: Capacitor Alarm Clock
#39"Sorry I overslept, the capacitor didn't go off" gonna be funny excuse
Re: Show HN: Capacitor Alarm Clock
#40For anyone jumping into this thread hoping to see capacitor use for timing, there is this blog post about something like that:
https://notes-huy-rocks.translate.goog/posts/diy-pomodoro-ti...
(google translate link because the original post was in Vietnamese)