EEVblog: The 555 Timer is 55 years old [video]

Posted by brudgers 18 hours ago

EEVblog: The 555 Timer is 55 years old [video](www.youtube.com)

289 points | 74 comments

wkjagt 8 minutes ago|

A couple of years ago I used a 555 in an attempt to fix a problem I had with my Xiegu G90 ham radio. When sending CW (morse code), the radio would sometimes not see a "dit" (the short tone in morse code). I could reproduce it by tapping the paddle too quickly. My theory is that the G90 doesn't use interrupts to detect paddle presses, but rather polls those lines, and sometimes misses when a pulse happens completely in between polls. I made a little circuit using a 555, where the dit side triggers the 555 and closes the dit line just long enough to always be picked up by the G90, but short enough to never cause two dits (at least not at the speed I was going at). I didn't bother doing the same for the dah side, because apparently my index finger is slower than my thumb and the problem never came up there. It worked flawlessly, but only when not transmitting. As soon as RF got involved, it behaved weirdly. I tried adding ferrite beads, but it didn't solve it. In the end I never used it, and just learned to not slap the dits so fast, but it was a fun experience and see the 555 work.

More details: https://www.reddit.com/r/amateurradio/comments/1eo9ki7/xiegy...

3form 17 hours ago||

5:55 video released on May 5th, as per description :)

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.

Scoundreller 8 hours ago||

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.

regularfry 16 hours ago|||

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.

cbdevidal 15 hours ago||

Can even build a computer out of them

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

FarmerPotato 17 hours ago|||

Two videos tomorrow at 5:56!

zephen 16 hours ago||

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

mrsvanwinkle 5 hours ago|||

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

genewitch 8 hours ago||

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

longwave 17 hours ago||

Big Clive is currently livestreaming to celebrate the 555's birthday: https://www.youtube.com/watch?v=jzNjFJdaw_I

PhaseLockk 10 hours ago||

You can learn about the origin of the 555 timer from its creator in his free book here: http://www.designinganalogchips.com/

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.

SoleilAbsolu 17 hours ago||

I still have the Forrest Mims III Radio Shack "555 Engineer's Mini-Notebook" somewhere in my basement. And rumor has it that Sammy Hagar can't drive 555 because his car just isn't fast enough!

stevekemp 16 hours ago||

I have a paper copy of "IC 555 projects" kicking around on my bookshelf still!

PDF version here https://worldradiohistory.com/UK/Bernards-And-Babani/Babani/...

MisterTea 16 hours ago|||

The Mims books are fantastic. As a kid I collected every mini notebook and the green Radio Shack "Getting Started in Electronics." They were my intro to electronics along with the Radio Shack kits.

jshprentz 10 hours ago||

Also consider the IC Timer Cookbook by Walter G. Jung.

JKCalhoun 12 hours ago||

Evil Mad Scientist makes a giant, discrete version as a soldering kit:

https://shop.evilmadscientist.com/productsmenu/tinykitlist/6...

Very cool. (Looks like it uses 26 transistors. I assume the die is similar.)

jedimastert 9 hours ago|

I believe they based the design off of the reference schematic from a datasheet of one of the popular 555 timers, but I don't remember which one.

tubetime 7 hours ago||

it's based off the original Signetics design :)

darrinm 15 hours ago||

As a kid I didn’t understand what the 555 timer chip on the Apple II disk controller was doing but I learned the hard way that when you misalign the pins on the drive connector cable and the 555 chip releases its blue smoke you can’t use the drive anymore :(

JKCalhoun 12 hours ago||

I have read as well that the 555 was used in the game paddles for the Apple II. 555 + potentiometer (the part you turned) varied the length (duty cycle?) of a square wave which the Apple II used to determine the paddle position.

tmoertel 9 hours ago|||

The Apple II family did indeed use 555 timers, in either 558 or 556 chips, to drive the timing circuit used to read paddle and joystick positions. The following article explains both the circuit and the reading code:

https://www.applefritter.com/appleii-box/APPLE2/NibbelingAtT...

aidenn0 11 hours ago|||

The port that was standardized on for PC joysticks was the dumbest possible one:

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.

PunchyHamster 10 hours ago||

I remember using similar trick to use LEDs to sense light. Basically, charge the (reverse biased) LED capacitance, then measure how long it takes to discharge. The lil circuit I had was LED bar, so I used it to sense finger position using that (other leds providing light, LED doing the sensing judging that light and comparing to rest

drob518 8 hours ago|||

Yea, definitely don’t let out the magic smoke. That stops all the fun right away.

fortran77 15 hours ago|||

There was a 556 on the Apple ][ disk controller (a dual 555).

See: https://mirrors.apple2.org.za/Apple%20II%20Documentation%20P...

huflungdung 10 hours ago||

[dead]

davidwritesbugs 17 hours ago||

Oh god I feel old. I remember being an excited schoolboy thinking how magic this was when it debuted.

Brian_K_White 16 hours ago||

For me that is blue leds.

davidwritesbugs 16 hours ago|||

Yes! I remember thinking "damn you band gap physics, if we only had blue leds we could do colour displays with LEDs, but that can never happen."

mhh__ 12 hours ago|||

"rareleds" on Instagram is fantastic. Vintage LEDs set to apex twin and so on

davidwritesbugs 17 hours ago||

I also remember being amazed, and did a forehead slap, when an old army bomb disposal man explained how, what I thought was an innocent device, was used by the IRA in bombs.

nickcw 17 hours ago||

Ha. When I was a teenager I used to build 555s into timers for the same purpose using a no PCB rats nest construction.

Though surprising the family at dinner with a small explosion was a much more innocent purpose.

tuvix 17 hours ago||

Built an atari punk console using these with my late father. Still have it hanging on my wall in a shadow box.

swed420 17 hours ago|

I recently dug one out to use as a hardware shutdown timer to power off an rpi's PSU once it has presumably halted without having to resort to a dedicated MCU for the task.

deepspace 4 hours ago|

Another allrounder and close cousin in time and but with much more functionality is the 4046 CMOS Phase Locked Loop.

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.

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