The trick is that it's sold as a timer but it's really a kit of parts from which you happen to be able to build a timer.

There's a lesson in there somewhere.

Can even build a computer out of them

https://hackaday.com/2011/08/05/building-a-computer-out-of-5...

When I was designing hardware we used the 555 almost exclusively to build one-shots.

I learned (long ago) it’s trivial to fool my satellite receiver’s modem’s dial tone verification for remote pay per view ordering (it doesn’t phone home right away but gets angry if it’s not connected to a phone line).

Turns one a single frequency that’s remotely close to one of the two tones of a dial tone will convince it. Wasn’t sine wave either but not a problem! 555 powered by a 9V battery.

I remember reading somewhere that it's the highest-selling IC of all time, which is a little surprising! I'd have guessed the winner would be an op-amp of some kind.

555s are such delightful little guys. I used a pair of them, plus an ebay telephone line driver, to make an old telephone ring: https://hardfault.life/p/telco-2

One timer runs at the ~20Hz ring frequency, and the other runs at ~0.2Hz on a 20% duty cycle. The slow one's output feeds the enable line of the fast one, so you get 1-second burts of ringing, then a few seconds of silence, then ringing... just like a normal phone.

I moved about 5 months ago and haven't had time to get back to this project. The goal is to build a little phone company in a box, so I can have all my old PCs talk to each other with their modems.

Just a guess:

building an amplifier from transistors is sometimes simpler/cheaper than using an op amp. And some designs don’t need the benefit of op amps.

On the other hand, building a timing circuit from discrete components is less obvious. And the 555 does so much of what often needs doing.

Also, the design was not patented so they were commodity chips right away.

Two videos tomorrow at 5:56!

That's fine, but you know you have to concatenate them and sell them as one unit, right?

my favorite use of a 555 is in a solar charge controller. It is a voltage controlled switch!

i have the page archived, but it's called A New Solar _ Wind Charge Controller Based on the 555 Chip (2_7_2026 12

I can upload the webrip if anyone wants it

otoh i.m surprised the accelerometer was already available since 1927. since microcontrollers only the hardcore eecs kids build pid controllers from opamps for fun (only do hn on phone hard to link to that maker article of a fully analog segway where the writer missed the "analog" part and was like WOW a self balancing 2 wheeler by a grad student and not another baby's first Arduino bday kit