Is the 555 still a viable IC?

[ejeffrey]

Funny that you say software development is the reason to avoid a MCU and use 555. These days most people think the other way around. We go with a MCU even when a 555 would have done the job. It is easier to figure out a simple program than it is to do "real" EE with discrete components.

I don't think programming an MCU is any more or less "real" than configuring a 555.  I don't think trying to make a value judgement there is helpful.  But there is a big difference in what makes sense for a hobby project, prototype, or one-off than for something that is going to need to be manufactured and supported in production.

An MCU is great because it's super flexible, you can drop it in your schematic and start manufacturing without even being sure what you need it to do. It also can easily be hooked up to a computer for automation.  But in a manufacturing setting, even for low volume it adds steps to the process and additional configuration to manage.  Unless you as the designer wants to manually program hundreds or thousands of units before they go to end users you need to document the flash process and make sure your manufacturer is doing it correctly, and possibly deal with a situation where the process was messed up and you have a bunch of defective units in inventory that need reflashing.  You can order pre programmed chips for a reasonable setup cost and that's a decent option but still comes with process overhead.

Again, in high volume you can sort this out and it's worth it to save a few cents on the BOM.  Or more likely you integrate the functionality into a part that already exists on the design and ask the software team to add some timers to their existing code base.  But for low volume products I have found that the fewer programmable devices  the better.

[Zero999]

Another example of a digial replacement is the 74HC5555, but it's no longer made.
https://www.mouser.com/datasheet/2/302/74HC5555-1597181.pdf

The original NE555 is not the most beginner friendly of ICs. It draws nasty spikes, when the output changes state, which can cause interference and spurious triggering.

Newer CMOS variants such as the TLC555 and ICM7555 don't have the same issue of current spikes, but they have much weaker output pins, especially when sourcing.

[ejeffrey]

Also to be clear , I'm not suggesting nobody should use a MCU when a 555 will do the job.  Just that there are factors beyond per unit cost, and that the programmability of a MCU is not always in the + column.  As always it is situational but I don't think the 555 is obsolete even when a small microcontroller can do many (but not all) of the same jobs for lower cost.

[Bud]

I am wondering why noone yet said "Just use an FPGA!", as it typically happens. 

[Ian.M]

Hmm.  FPGA board with three ADCs, and some level shifters and output drivers implementing a soft core CPU running a SPICE simulation of  a 555 in realtime . . .     

The only flies in the ointment are the quiescent current, power dissipation and board area used!      Lets not even mention the price. 

[Zero999]

I find myself being drawn more towards other jellybean ICs, for simple timing/oscillator functions, when it's not critical: the LM393, LM311, 74HC123 and CD4060 spring to mind.

[tooki]

Yet, they still sell..... Who would be the potential customers?

As previously mentioned, this is only curiosity.

My guess is learners and classes are buying many of them. One hobbyist after another, one learner after another, year after year. Each person learns using one or two, burns a few by mistake, and moves on. Look at all the tutorials for 555 timers that are out there.

I wonder what the quantity of new or good 555 timers are just sitting in parts drawers never to be used again. Nothing wrong with them. If we could only get these to new learners they'd never have to make any more ever again. 

There is no way the “newbies” market can consume a billion 555s a year. Heck, I doubt it could consume 1% of that. Nor are people squirreling them away at that pace, there’s no logic in that, now that basically everyone has access to distributors that can get us common parts in a day or two. They have to be going into products. I know we occasionally see them pop up in teardown videos.

[tszaboo]

Viable? Did I miss it, when did it become NRND?

It has quite a bit up it's sleeves, works from 12V, it can drive a relay without any external transistor, and you don't need a firmware engineer (big plus).

I am wondering why noone yet said "Just use an FPGA!", as it typically happens. 

No, use an Arduino.

[coppice]

That "1 billion" number may be outdated. It seems to go back to a 2004 interview with the designer, Hans Camenzind. He mentions that number, and that the 555 was mostly produced by Samsung in Korea back then -- surprising to me, and maybe a hint that the information actually predates 2004?

http://semiconductormuseum.com/Transistors/LectureHall/Camenzind/Camenzind_Index.htm
Click the link to "page 2" for the relevant section of the interview.

No idea whether production numbers have gone down due to obsolescence since then, or even up due to various lower cost manufacturers?

He might be referring to the original 555. There are huge volumes in the various derivatives made by a variety of companies in the small linear and logic IC business.

[ftg]

Echoing what others have said, good availability, predictable and well known behaviour.
No production programming needed is definitely a plus for me.
And this "no production progamming, no FW development" was the reason why some 555's recently got designed into a product by me. Managment not wanting any firmware in the loop also helped. 

[xrunner]

Yet, they still sell..... Who would be the potential customers?

As previously mentioned, this is only curiosity.

My guess is learners and classes are buying many of them. One hobbyist after another, one learner after another, year after year. Each person learns using one or two, burns a few by mistake, and moves on. Look at all the tutorials for 555 timers that are out there.

I wonder what the quantity of new or good 555 timers are just sitting in parts drawers never to be used again. Nothing wrong with them. If we could only get these to new learners they'd never have to make any more ever again. 

There is no way the “newbies” market can consume a billion 555s a year. Heck, I doubt it could consume 1% of that. Nor are people squirreling them away at that pace, there’s no logic in that, now that basically everyone has access to distributors that can get us common parts in a day or two. They have to be going into products. I know we occasionally see them pop up in teardown videos.

Well I did say hobbyists et al. buy many of them, not that they bought all of them. I'm very careful how I say things on this forum after so many years here, I know what kind of trouble you can get into if you don't carefully word things. 

However, I did some research just now and i can't find any objective evidence of the total sales number for "555 timer". As others have stated, the One Billion number seems to have stemmed from some interview with this person Hans Camenzind. We simply do not know it's correct now. We also do not know how many new learners and existing hobbyists are out there (do we?).

I just checked the price for 555 timer DIP package on Digikey. It's $1.31 ea., or $1.17 ea, for quantity 10.

So this is like filling in numbers for the Drake equation. Many of the numbers come out of my a$$. If you have 1 billion being sold ( it's probably less but ...) the hobbyists / learners / educational institutions are buying some. But that doesn't mean each individual entity each buys ONE 555 timer. It means the parts go to far less entities because they buy more than one ea.

How about the individual learner / hobbyist? How many are there? 10 million worldwide? Maybe they buy five ea. on average because the price is very low. Now we're talking 10 million entities buying 50 million 555 timers per year.

The teaching institutions buy even more. Maybe the institutions that use them buy 5000 555 timers ea. (on average) and the number of institutions are 10,000. (we're talking worldwide now). So they all buy 5000 * 10,000 = 50 million 555 timers.

Now we are up to 100 million 555 timers per year just for the hobbyists / learners / teaching institutions. That's 1/10 of the mysterious One Billlion number. The rest is industry buying. If we want to agree the 1 billion number is really less now, I can easily support my claim that hobbyists / learners / teaching institutions buy many of them. But I have no way of knowing how many they buy, but like the Drake equation I can get the answer I want if you give me a little time to play with the numbers. 

Note: And each person can get the answer they want too because we do not have enough objective evidence.

[PlainName]

I just checked the price for 555 timer DIP package on Digikey. It's $1.31 ea., or $1.17 ea, for quantity 10.

Seems a bit high to me. Add a cap or two and resistors and a tiny 8-bit micro is looking quite attractive in comparison for some uses.

[Zero999]

I just checked the price for 555 timer DIP package on Digikey. It's $1.31 ea., or $1.17 ea, for quantity 10.

Seems a bit high to me. Add a cap or two and resistors and a tiny 8-bit micro is looking quite attractive in comparison for some uses.

It's always more expensive in small volumes and through hole.

The 555, can run at up to 15V, some versions go as high 18V, others will work down to 1V, it doesn't have firmware development and maintenance costs and can output 200mA, which is enough to drive a decent relay directly or switch a MOSFET, at a reasonable speed.

[themadhippy]

I just checked the price for 555 timer DIP package on Digikey. It's $1.31 ea., or $1.17 ea, for quantity 10.

Time to get a new supplier,cpc  over here have them at  32p ea  or 25p ea for 10,including  the tax.

[coppice]

I just checked the price for 555 timer DIP package on Digikey. It's $1.31 ea., or $1.17 ea, for quantity 10.

Seems a bit high to me. Add a cap or two and resistors and a tiny 8-bit micro is looking quite attractive in comparison for some uses.

In any significant quantity they are a few cents. Looking up 1 off prices for components is just silly.

[ejeffrey]

However, I did some research just now and i can't find any objective evidence of the total sales number for "555 timer". As others have stated, the One Billion number seems to have stemmed from some interview with this person Hans Camenzind. We simply do not know it's correct now.

It easily could have dropped but TI alone has about 14 million in stock.  That's not counting stock at distributors, much less all the other manufacturers. 

It's still a huge volume mass production part not significantly dependent on hobbyists and education markets.

I just checked the price for 555 timer DIP package on Digikey. It's $1.31 ea., or $1.17 ea, for quantity 10.

But a reel of SOIC parts is $.07 each.  The single part price is irrelevant.

[baldurn]

The ATtiny 212 is about $.4 in the same 8 pin package as the 555 chip. It might be more compared to 555 if you buy the later in quantities, but you save on other components. It won't accept the same voltage or current ranges as 555, but for the saved components you could pair it with a mosfet.

In circuit programming is really easy. Just make three pads (vcc, gnd and program). Touch it with a pogo pin device for a few seconds and it is programmed. Can easily be automated.

[factory]

Bigclive found a new product using the 555 only 2 years ago.



David

[Zero999]

Bigclive found a new product using the 555 only 2 years ago.

David

It uses the 555 as a Schmitt trigger oscillator to generate a sawtooth, which compared against a potentiometer, using a comparator to generate PWM. I would have used a quad op-amp/comparator IC: one channel for the Schmitt trigger oscillator and the rest as comparators for the PWM. The LM339 will directly run off 24V, so no voltage regulator is required.

[SiliconWizard]

Definitely consider the TLC variant which is under $1 per 1 at Digikey, $0.37 per 1, $0.23 per 100 at LCSC. It's also better on almost all counts than the original.

[baldurn]

Bigclive found a new product using the 555 only 2 years ago.

David

It uses the 555 as a Schmitt trigger oscillator to generate a sawtooth, which compared against a potentiometer, using a comparator to generate PWM. I would have used a quad op-amp/comparator IC: one channel for the Schmitt trigger oscillator and the rest as comparators for the PWM. The LM339 will directly run off 24V, so no voltage regulator is required.

The 8 pin ATTiny212 would have done the job with one chip instead of three chips and a much simpler schematic. You would configure three pins as ADC to sample the potentiometers and three pins as PWM output. The remaining two pins are VCC and GND.

[julian1]

The pattern of having analog comparators, controlling the inputs of a S/R flip-flop for stateful behavior, is really common in things like smps etc. 
I feel like the Camenzing's 555 would be more general purpose/have higher utility, without the 5k/5k/5k biasing divider, which needs to be worked-around when a circuit that is not a simple timer/oscillator is called for. Although it's possible there is also a pin count constraint. 
Perhaps someone made a variant?

[Gyro]

There is the Control pin (pin 5) which gives direct access to the other input of the Threshold comparator, but this also interacts with the Trig comparator other input via the 5k/5k divider formed by the bottom two resistors in the internal chain. There was never any variant without the resistor chain that I'm aware of though.

[schmitt trigger]

A classic book, copyright 1976. Although this particular edition is 1978.

[tooki]

How about the individual learner / hobbyist? How many are there? 10 million worldwide? Maybe they buy five ea. on average because the price is very low. Now we're talking 10 million entities buying 50 million 555 timers per year.

The teaching institutions buy even more. Maybe the institutions that use them buy 5000 555 timers ea. (on average) and the number of institutions are 10,000. (we're talking worldwide now). So they all buy 5000 * 10,000 = 50 million 555 timers.

Now we are up to 100 million 555 timers per year just for the hobbyists / learners / teaching institutions. That's 1/10 of the mysterious One Billlion number. The rest is industry buying. If we want to agree the 1 billion number is really less now, I can easily support my claim that hobbyists / learners / teaching institutions buy many of them. But I have no way of knowing how many they buy, but like the Drake equation I can get the answer I want if you give me a little time to play with the numbers. 

I’d guesstimate those numbers at something like 10% of that. Me, I haven’t bought a 555 in years — and that time included my 3 years of electronics technician training. In that, we did use the 555,  but because we breadboarded them, almost all of them were kept for reuse, so very few being purchased. These days, for better or worse, in education you end up simulating more than testing actual hardware.

And I don’t anticipate buying any more 555s because I think there’s a better solution for almost every application. At least that’s been the case so far.