More details: https://www.reddit.com/r/amateurradio/comments/1eo9ki7/xiegy...
For something feeling like a fairly specific IC, I remember seeing many projects that use it throughout the years in wacky ways - and seeing it makes me happy to know that the sentiment for this little piece is shared.
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.
There's a lesson in there somewhere.
https://hackaday.com/2011/08/05/building-a-computer-out-of-5...
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.
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.
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
Fun fact: his original concept needed 9 pins and therefore was going be forced to have a 14 pin package. A late epiphany got it down to the 8 pin version we know today.
PDF version here https://worldradiohistory.com/UK/Bernards-And-Babani/Babani/...
https://www.applefritter.com/appleii-box/APPLE2/NibbelingAtT...
The joystick itself just had 1 potentiometer per axis, wired directly to the port. The port had no A/D, no timer, and no interrupt. Instead there was a GPIO and a capacitor. You discharged the capacitor with a GPIO write, and then polled the GPIO to measure when the capacitor was charged again. The number of iterations through your polling loop would be proportional to the position of the axis.
This is a pain to emulate if you aren't doing cycle-accurate emulation. IIRC Dosbox has a bunch of kludges and still doesn't get the joystick right for every game.
[edit]
To clarify the game port used a 558 (quad stripped-down version of a 555) as a schmitt trigger, so it generated pulses of a width proportional to the potentiometer position. I looked up the Apple II interface and it looks very similar, but with the caveat that accelerated versions (e.g. the IIgs) would always clock to 1MHz when reading the joystick port, compared to the PC that could run at a huge range of clocks (and CPI) over the lifetime of the port.
See: https://mirrors.apple2.org.za/Apple%20II%20Documentation%20P...
One nice thing about the 555 is that at least it aged well and still is very usable in those beginner tutorials. Unlike for example the uA741 which no one should use.
I'm curious about this claim. It's certainly easier to just wire up a modern microcontroller, but is there a better option that involves no software and is likely to still work the same today as it did 50 years ago?
For that matter, a 16 pin CH32V003 can emulate a vast array of 7400 series devices as long as you don't need ns timing — no problem for µs. It's also cheaper.
'Grab laptop, fire up IDE & plug in programmer cable' vs. 'configure the circuit using a soldering iron'. Both have their place.
But in terms of cost, a simple microcontroller is usually cheaper than a 555 nowadays, often doesn't require external components, and so even if all you wanted was a single function like an edge-triggered pulse, or generate a single frequency, it probably still makes sense to use a microcontroller from a board design perspective. As soon as you want anything slightly more complicated, odds are you can replace a ton of other circuitry on the board with that single chip and a small program.
Because nothing is faster and more responsive than direct hardware logic.
"a simple microcontroller is usually cheaper than a 555 nowadays, often doesn't require external components,"
Often? Every UC I've ever used has required a whole slew of caps and resistors just to get the thing to take in operative firmware through a programming port. Even the simple light flashers for vehicles that I've made using a UC and accelerometer need at least two caps and two resistors to make a proper circuit that allows for flashing info to the controller.
"so even if all you wanted was a single function like an edge-triggered pulse, or generate a single frequency, it probably still makes sense to use a microcontroller from a board design perspective."
Frequency generation? Inductor, capacitor, input voltage. Zero UC required and guaranteed to be cheaper.
"As soon as you want anything slightly more complicated, odds are you can replace a ton of other circuitry on the board with that single chip and a small program."
And accomplish things at a glacial speed that a basic hardware-only solution would've solved. As an example - BOSS pedals have basically zero latency because it is all analog. All these newer Line 6 and POD and other digital FX pedal makers have horrible latency, some I've measured past 50ms (almost as bad as trying to live-monitor a Windows Audio device.) It has been this way for the over 30 years I've been playing guitar.
Most times, raw hardware with zero software is THE way to go. Anything else is just a performance loss.
https://shop.evilmadscientist.com/productsmenu/tinykitlist/6...
Very cool. (Looks like it uses 26 transistors. I assume the die is similar.)
Though surprising the family at dinner with a small explosion was a much more innocent purpose.
https://www.i3detroit.org/reset-on-lan-an-ethernet-aware-rem...
It can be configured as a versatile oscillator like the 555, but it can also implement an FM modulator / demodulator, a FSK modem, a tone discriminator, a clock multiplier, a phase detector, a voltage to frequency and frequency to voltage converter a speed control loop and much more.
Not bad for a $1 chip. My circuits professor always carried a bunch in his lab coat pocket and handed them out like candy almost everyone anyone needed a circuit to do something to do with oscillation.
Maybe it could work if you used 5 timers?
https://www.digikey.com/en/products/detail/tecate-group/PBLH...
For your chosen capacitor, manufacturer doesn't even bother providing the tolerances. :) Good luck with that.
It also has 2k (16384 bits) of SRAM, allowing even larger counters.
It runs off 2.8V - 5.5V DC, so supplying power is pretty trivial. Doesn't need a crystal, though of course adding one will improve the timing accuracy.
though i take you were thinking about counting clock cycles or something in which case surely your register would overflow
(I just made half y'all crash out with old internet nostalgia. The rest of you are like "huh?")
