The 555 timer is one of the most versatile integrated circuits available. It can generate PWM signals, tones, and single-shot pulses. You can even put one in a bi-stable mode similar to a flip flop. All of these modes are available by only changing a few components outside of the IC itself. It’s also dirt cheap, so it finds its way into all kinds of applications its original inventors never imagined. There’s a bit of a trope around here as well that you ought not to use a microcontroller when one of these will do, and while it’s a bit of a played-out comment, it’s often more true than it seems. This video shows a few uncommon ways of using these circuits instead of putting a microcontroller to work.
After a brief overview of the internals of the hallowed 555, [Doctor Volt] walks us through some of its uses, starting with applications for digital inputs, including a debounce circuit and a toggle switch. From there, he moves on to demonstrating a circuit that can protect batteries from deep discharge, and a small change to that circuit can turn the 555 into a resetting fuse that can protect against short circuit events. Finally, the PWM capabilities of this small integrated circuit are put to work as an audio amplifier, although perhaps not one that would pass muster for the most devout audiophiles among us.
Even though it’s possible to offload a lot of the capabilities of a 555 onto a microcontroller, there’s certainly an opportunity to offload some things to the 555, even if your project still needs a microcontroller. However, offloading tasks like debounce or input latching to hardware rather than spending microcontroller cycles or pins can make a project more robust, both from reliability and software points of view. For some other useful circuits, some of which have been forgotten in the modern microcontroller age, it’s worth taking a look at some of these antique circuit books as well. While we are sure the 555 designers hoped it would be a big hit, no one imagined this giant one.
My all time favorite in this topic: https://www.youtube.com/watch?v=uXeSsevsNNE – 555-based analog robotics
I used Walter Jung’s book on timer chips a lot. One use of a 555 that was a bit unusual was a touch-switch circuit.
Experimenters should look for 7555, or LMC555, the CMOS version/s. (There’s a one-resistor astable that you can do with it, but not so the bipolar NE555.)
-hmmmm I’m missing a timer for my project
-Fear not! I have what you need right here!
-A 555?
-Nope, an Arduino programmed to work as a 555
-Oh! It’s a brand Arduino or a chinese knockoff?
-Nope, It’s custom one I made with discrete logic and a 555 timer!!!
-Wouldn’t be easier to-
-NO!
Pretty sure there’s a cpu made out of 555 in a project somewhere here…
There are web sites about building a CPU from NAND gates.
So, if you can turn a 555 into a NAND gate, the rest is already documented.
Can it run Doom?
If you use enough of them you can run just about anything.
With Cortex-M0s at 9 cents: why?
Because you need a compiler (most likely along with an IDE) and some way to get your code into the Cortex flash. It isn’t just the cost of the processor. You can get an open source (free) compiler and IDE, but no matter what you do, you will still need a piece of hardware to get your code into the processor. There’s also a learning curve to using the tools (software and hardware.)
A 555 doesn’t cost much more and it doesn’t require an investment in extra tools. If it does what you need, use it.
Forgot the link. Cortex M0 development tools:
https://en.wikipedia.org/wiki/List_of_ARM_Cortex-M_development_tools
It also won’t bug, brownout, has no flash, is more resilient to high energy particles etc…
But I already know how to program a microcontroller and have those tools or built my own years ago. It’s a lot faster to write a few lines of C than to work out the math and run a simulation to make a 555 do what I need.
If it does what you need, use it.
“If all you have is a hammer, don’t get more tools, just treat everything like a nail!” ;-p
To what Joseph said, a cortex is much pickier in power requirements, both voltage and noise.
You can’t run a Cortex directly off any voltage between 4-16V, the IO pins can’t sink/source 200mA, the 555 doesn’t crash because you coded something wrong, it’s simple, incredibly well known and reliable and costs pennies
Found the video to be educational and helpful. Especially the circuit board he designed, which I could probably use to keep watch over some NiCd batteries I use to power an electric winch when cutting down trees. Thank you.
I used a NE555 to make a VCO for a PLL in the RDS decoder I’m constructing. I found 2 ways of controlling the frequency. The first one which I tried requires changing the CONT voltage. However, I’m not sure about it’s reliability, because it changes also the duty cycle. What’s worse, when changing the voltage in one way, frequency first rises and then falls, so it could make the circuit stuck in the wrong frequency.
The other method requires changing a resistance between OUT and THR, but what electrically controlled element can do that? I chose a solution that’s not elegant, but simple and it works: I connected there a photoresistor with a LED which shines on it.
for variable impedance, look to FETs. The size of the conducting channel (between source and drain) is controlled by voltage on the Gate.
555? Should have used a transistor!
Forrest Mims helped me fall in love with that chip when I was young. He had plenty of fun circuits for it. Also, Talking electronics has a nice eBook of creative 555 uses you won’t often see elsewhere.
Forest Mims little books were so good back learning basic op amp configs too. An excellent resource.
Ah, Talking Electronics. Had a few of their books and built a few of their bugs back in the 1990s. Thanks for the reminder, I’m downloading the 555 book now. Their site is nice and lean too.
I used a 555 in school around 1980, but since then have always used Schmitt-trigger gates to do the same things, or an 8-pin microcontroller which added more functions at the same time.
Please someone make FPGA with 555 as the main component. Tinytapeout maybe?