Is the 555 still a viable IC?

Thread Starter

schmitt trigger

Joined Jul 12, 2010
917
DISCLAIMER: I am not building anything with a 555, this question is only sheer curiosity.
Having cleared that out of the way…
It can be safely said that the 555 is one of the most ubiquitous and influential ICs in history. I am also sure that most if not all of the old-time forum members have used it at least once.
But the IC is almost 52 years old, and although it has been updated to CMOS versions, its age and limitations show up.
The question would be: do you think that the 555 is still a viable IC in 2024?
Let me give my personal opinion; the problem with the 555 are the required external passive components. To obtain a modicum of stability and accuracy, the cost of those components may exceed the cost of the IC itself.
 

WBahn

Joined Mar 31, 2012
30,233
By this reasoning, all opamps should be considered nonviable, since they rely on external components, often passive, to obtain a the desired results and the cost of those components can easily exceed the cost of the IC itself.

For the 555 to no longer be viable, there has to be something else, either one thing or some collection of things, that fills all of the needs/uses that it currently fills, and does so just as well, if not better, in each of them.

What is that something?

Various programmable devices may fill SOME of the needs, but the very fact that they requires programming and all the things that go with it, mean that they cannot fill all of the needs at least as well, since someone that needs a simple oscillator or one-shot can get a 555-based solution up and running, starting from never having heard of a 555 to having it working, in a fraction of the time that they could do the same thing with any other device I'm aware of.
 

Papabravo

Joined Feb 24, 2006
21,256
I think the part is appealing to a different segment of the industry. It is used in one off and hobby projects for sure, but I can't recall ever seeing one in a commercial product that was fabricated and sold in even modest volumes like as few as 100+ units or so. My experience covers the period from 1969 to 2014 and is admittedly limited so I would not put much stock in it.
 
Last edited:

nsaspook

Joined Aug 27, 2009
13,413
It's still used in lots of industrial equipment even with advanced controllers. A typical application would be as a independent hardware (isolated from software issues with controllers) watchdog timer on equipment.
 

Papabravo

Joined Feb 24, 2006
21,256
It's still used in lots of industrial equipment even with advanced controllers. A typical application would be as a independent hardware (isolated from software issues with controllers) watchdog timer on equipment.
Watchdog hardware on micros has become increasing sophisticated over the years. Never saw a problem with one integrated on the processor. Your mileage may vary.
 

MrChips

Joined Oct 2, 2009
30,924
I would say, yes it is still viable, depending on the application.
Firstly, one needs to know its limitations and sometimes quirky behaviour and characteristics.

1) It is not good for stable time/frequency generation. It cannot go above 1-3MHz. Use a quartz crystal instead.

2) NE555, LM555 can source and sink 200mA. However, it is notorious for generating a lot of noise on the supply rail. If you want low power, low noise operation, use the CMOS version, LMC555, TLC555, ICM7555.
For awhile, NE555 was very popular in after-market automotive flasher modules.

3) They are great for introducing electronics to new hobbyists, making flashing LEDs and sirens.

4) If you want a quick and dirty square-wave clock pulse generator, 555-timer is the solution.

5) Granted, for fancy pulse generating sequences, one can do a lot more with an 8-pin MCU.

6) For awhile, the ARRL Handbook featured a morse code practice oscillator with a classic NPN+PNP BJT oscillator circuit. I was a bit taken aback when they replaced it with a 555-timer.
 

nsaspook

Joined Aug 27, 2009
13,413
Watchdog hardware on micros has become increasing sophisticated over the years. Never saw a problem with one integrated on the processor. Your mileage may vary.
Absolutely but lots of equipment have belts and suspenders when people's lives are at stake and 30yo design specs (that won't change) say what 'things' must have.
 

BobTPH

Joined Jun 5, 2013
9,116
I cannot think of anything I might do that could use a ‘555, where I would not use a PIC instead. Even without a crystal, it makes a better timer, and the ability to update it with a software change always favors a programmable device IMHO.
 

nsaspook

Joined Aug 27, 2009
13,413
It's still a viable IC for a class of applications. Not my first or enth choice for the job but not eliminated because it's proven and reliable under conditions would would fry most modern controllers.
 

Thread Starter

schmitt trigger

Joined Jul 12, 2010
917
I think the part is appealing to a different segment of the industry. It is used in one off and hobby projects for sure, but I can't recall ever seeing one in a commercial product that was fabricated and sold in even modest volumes like as few as 100+ units or so.
I saw one on a telecom power supply (-48V input) for the bias supply.
There was also an integrated magnetics (transformer + inductor) demonstration kit which used as its controller a 555
 

WBahn

Joined Mar 31, 2012
30,233
Like I said, there is still 555 demand in current designs using all SMD devices. People make and stock what sells. Decades old PIC16 devices are another good example.

https://www.microchip.com/en-us/product/pic16f72
It would be interesting to have an estimate of what fraction of the 555 market is hobbyist and educational purposes.

More interesting would be to have a feel for whether this portion of the market is sufficient to keep any component in production by itself. My gut feel is that the answer is no. There's a lot of schools out there, but how many 555s would a given school purchase annually? I wouldn't be surprised if annual sales to hobbyists dwarfs annual sales to educational institutions, but again, that's just a gut feel.
 

MisterBill2

Joined Jan 23, 2018
18,928
Th whole concept that just because a design is old that it must be useless is rather shortsighted and poor thinking. consider that the 4000 series CMOS line has been around even a bit longer than the 555 timer, and is still sold by most electronics distributors, IN QUANTITIES!!
And unlike so many of those programmable devices, the 555 can be put to work as soon as it arrives with no code development at all. The example of op-amps is a good one, they had been around long before the 555 was even considered, So while improvements can be made in almost every area, some tools never become obsolete.
 
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