Is the 555 still a viable IC?

[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.

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.

That would be two ICs, since the MCU requires a 5V regulator.

Unless it's just a hobby project, I would be hesitant at using an MCU for such an application because there's only one supplier and the firmware cost. The LM339, is just one IC, which runs directly off 24V, is cheaper than any MCU and can be bought from multiple suppliers. The only downside is more passive components are required, but they're very cheap.

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.

The downside of the TLC variant is the output is much weaker, than the NE555. It can only source 10mA, which isn't enough to drive a relay and will considerably slow down the turn on time of a MOSFET. It can sink 100mA, but sometimes sourcing is required because the relay or driver transistor needs to be on, when the output is high.
https://www.ti.com/lit/ds/symlink/tlc555.pdf

[AndyBeez]

I recently encountered a 556 (dual 555) on a plug-in mouse scarer. One stage provided a low frequency pulse that gated the second stage; which ran 40KHz into a transducer. The DIL packaged chip was dated c.2010, so there were a few analogue diehards out there. But they possibly have long retired, leaving mouse scaring to the Arduino kids.

[baldurn]

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.

That would be two ICs, since the MCU requires a 5V regulator.

Unless it's just a hobby project, I would be hesitant at using an MCU for such an application because there's only one supplier and the firmware cost. The LM339, is just one IC, which runs directly off 24V, is cheaper than any MCU and can be bought from multiple suppliers. The only downside is more passive components are required, but they're very cheap.

For this extremely simple purpose, you could probably get away with just a resistor and a diode for a voltage regulator accepting anything between 6 to 24 volts. The total BOM could be 1 resistor, 1 diode, 1 MCU, 3 MOSFET, 3 pots. But I am not convinced this is a real product - frankly it looks like a beginner project for DIY :-)

Anyway, using an op amp for saw tooth is not an example of the usefulness of the 555 chip.

[MT]

5:23 Big Clive about the 555 quote: "its ancient, one of the earliest "micro controllers", goes back long long way. 
https://youtu.be/0WHFwqzyu0U?t=322

Interview with Hans Camenzind inwentor of 555.
http://www.semiconductormuseum.com/Transistors/LectureHall/Camenzind/Camenzind_Page2.htm


https://www.planetanalog.com/at-50-years-the-555-timer-ic-defies-conventional-wisdom/

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



David

[PlainName]

I recently encountered a 556 (dual 555) on a plug-in mouse scarer. One stage provided a low frequency pulse that gated the second stage; which ran 40KHz into a transducer.

Sounds like a perfect use for one (albeit dual). Just does what it's meant to and you don't have to worry about battery voltage or anything.

[EPAIII]

Perhaps a bit late in this thread so you may need to read the first 20 posts which this follows.

I just want to say that I am fully aware of the value of programmable devices. I just looked in my personal stock which goes back for many years and I did find 10 555s and 3 556s. They were in a plastic drawer with the paper napkin packing on top of them from my last move back in 2011. So I haven't touched them since then.

OTOH, on the workbench to my immediate right and out in plain sight, there are several different types of single chip processors that I have been playing with. Arduino, Raspberry Pi, etc.

In this wonderful world of electronics that we live in, THERE IS ROOM FOR BOTH TYPES OF CIRCUITS!

[PlainName]

Clearly, there is room for only one on your bench with the loser being relegated to the drawer 

[Smokey]

Clearly, there is room for only one on your bench with the loser being relegated to the drawer 

Hey you chips punks!  Get off my lawn!

[tszaboo]

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.

The other components are literally 0.1 Cents each in quantity, and you need like 10 of them?
Programming a board is expensive on the other hand. I looked at production programmers for microchip, the SOFTLOG ICP2 is about 500 EUR, so below ~10K boards the 555 wins hands down. Above 10K boards the time spent on programming is significant. A worker at 20 EUR/hour which is almost minimal wage, cannot program more than say 120 boards an hour, which is 16 cents. Microchip's programming fee for pre-programmed part is 5 cents for this part for 5K pieces.
And I can buy NE555 compatible parts for 2 cents in China.

[baldurn]

That board also needs to be mounted in some product. The same worker or robot can do the programming. You will have a jig where you drop the board for a few seconds until a LED turns green. The worker will be mounting a board while the jig is programming the next board. This way the worker will never wait on the programmer and the extra working time per item is a few seconds at worst.

And really? Expensive to make a firmware that reads three ADCs and programs three PWM outputs accordingly? Anyone can do that in less than an hour, even a total beginner.

This is a strange product by the way. All popular multicolored LED strips these days are WS2812 based, which you could not possibly program without using a MCU. This simple MCU could do it however and with even less components (no MOSFETs).

Also the price for the programmer is really nothing as you can make your own using nothing but an old Arduino or Raspberry Pi Pico.

The Raspberry Pi Pico debug probe at €13: https://raspberrypi.dk/en/product/raspberry-pi-debug-probe/

If that is too much, you can get the Raspberry Pi Pico at €4 https://raspberrypi.dk/en/product/raspberry-pi-pico/ and download the software yourself. Takes less than 5 minutes to convert that thing to a debug probe.

Then all you need is a cable with three pogo pins and a small jig. I would 3D print it. I could easily design and print such a thing in about an hour.

[SiliconWizard]

I recently encountered a 556 (dual 555) on a plug-in mouse scarer. One stage provided a low frequency pulse that gated the second stage; which ran 40KHz into a transducer. The DIL packaged chip was dated c.2010, so there were a few analogue diehards out there. But they possibly have long retired, leaving mouse scaring to the Arduino kids.

Arduino? Nah! You need at least a RPi 5 for this and the WiringPi library. Probably Python to run on top of this, all in all requiring nearly 1GB of RAM.
But, then you'll be tickling true progress. You can even connect to some cloud provider to log the pin toggling action that happened locally and see that on a nice graph on your mobile phone.

55... what? You said?

[tszaboo]

That board also needs to be mounted in some product. The same worker or robot can do the programming. You will have a jig where you drop the board for a few seconds until a LED turns green. The worker will be mounting a board while the jig is programming the next board. This way the worker will never wait on the programmer and the extra working time per item is a few seconds at worst.

And really? Expensive to make a firmware that reads three ADCs and programs three PWM outputs accordingly? Anyone can do that in less than an hour, even a total beginner.

This is a strange product by the way. All popular multicolored LED strips these days are WS2812 based, which you could not possibly program without using a MCU. This simple MCU could do it however and with even less components (no MOSFETs).

Also the price for the programmer is really nothing as you can make your own using nothing but an old Arduino or Raspberry Pi Pico.

The Raspberry Pi Pico debug probe at €13: https://raspberrypi.dk/en/product/raspberry-pi-debug-probe/

If that is too much, you can get the Raspberry Pi Pico at €4 https://raspberrypi.dk/en/product/raspberry-pi-pico/ and download the software yourself. Takes less than 5 minutes to convert that thing to a debug probe.

Then all you need is a cable with three pogo pins and a small jig. I would 3D print it. I could easily design and print such a thing in about an hour.

I take it you never had to setup a real production line?
I've sit behind production workers with stopwatch to optimize speed. Even if you as an engineer can demonstrate it very quickly what to do, that's not sustainable on the long term. It's not possible to make 15 second tack times 8 hours straight doing the same boring task without mistakes. Also programming is often times a separate step at a separate station, because they will simply skip the test if there isn't something blocking them to do so. And then you might need to rework hours of production.
You also don't use "Arduino or something like that" to program in a real production facility. Each testing JIG is valued at ~5K EUR just because engineers had to design it, order it put it together. Also production programmers are a LOT faster. And you didn't address the bottom line, that I can make the circuit for ~3 cents in components.

[PlainName]

All popular multicolored LED strips these days are WS2812 based, which you could not possibly program without using a MCU.

Hope I've joined the right pedant's thread...

You could use WS2812 sans MCU with some memory and a shift register, perhaps a 74HC165N. Of course, you would need have a clock, and a 555 could be great for that

[jonovid]

by the bucketload from Shenzhen Yes.

[TimFox]

I believe the 2N2646 unijunction transistor is still available, but more expensive than a 555.

[Zero999]

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.

That would be two ICs, since the MCU requires a 5V regulator.

Unless it's just a hobby project, I would be hesitant at using an MCU for such an application because there's only one supplier and the firmware cost. The LM339, is just one IC, which runs directly off 24V, is cheaper than any MCU and can be bought from multiple suppliers. The only downside is more passive components are required, but they're very cheap.

For this extremely simple purpose, you could probably get away with just a resistor and a diode for a voltage regulator accepting anything between 6 to 24 volts. The total BOM could be 1 resistor, 1 diode, 1 MCU, 3 MOSFET, 3 pots. But I am not convinced this is a real product - frankly it looks like a beginner project for DIY :-)

Anyway, using an op amp for saw tooth is not an example of the usefulness of the 555 chip.

It's an example of the uselessness off a 555 and that there is a more suitable IC for said application.

Here's an LM393 PWM circuit I designed awhile ago. Just use the LM339 and repeat the comparator section another two times. If it's going to be run off 24V then make the pull-ups higher, say 4k7 or 5k6, instead of 1k, and add a pull-down, say 12k or 18k, to the outputs driving the MOSFETs, to limit the gate voltage to below 20V.

5:23 Big Clive about the 555 quote: "its ancient, one of the earliest "micro controllers", goes back long long way. 
https://youtu.be/0WHFwqzyu0U?t=322

I don't know whether it was tongue in cheek or a slip of the tongue and he meant to say microchip.

[SiliconWizard]

All popular multicolored LED strips these days are WS2812 based, which you could not possibly program without using a MCU.

Hope I've joined the right pedant's thread...

You could use WS2812 sans MCU with some memory and a shift register, perhaps a 74HC165N. Of course, you would need have a clock, and a 555 could be great for that

Well, yes. Implementing the required encoding for the 0 and 1 could be directly stored in the memory.
And for the clock, just a single gate inverter with Schmitt trigger input would do.
Possibly a fun exercise, rather than very practical.
But while this would work with only "discrete" logic, with some programmed memory, technically it would still be "programmable logic". You would have effectively designed a very simple and dedicated processor.

Anyway, the initial question was weird from the start. There are thousands of references of BJTs these days, so is the 2N3904 still a viable transistor?
PIck whatever fits your requirements and (if longevity matters) is reasonably (/or guaranted) likely to be available in a few years from now. Maybe that's called engineering, or something. Not sure anymore.

[coppice]

I believe the 2N2646 unijunction transistor is still available, but more expensive than a 555.

That takes me back. I used quite a few of those in my youth. They seemed like such a cool device when they were launched.

[schmitt trigger]

I believe the 2N2646 unijunction transistor is still available, but more expensive than a 555.

That takes me back. I used quite a few of those in my youth. They seemed like such a cool device when they were launched.

Even cooler were the Programmable Unijunction Transistor, PUT.
Which I called the triple-lie semiconductor:
-It wasn’t “programable”, it was adjustable.
-It wasn’t a single junction, but three junctions.
-It wasn’t a transistor but a thyristor.

Nevertheless a very useful device.

[tooki]

I believe the 2N2646 unijunction transistor is still available, but more expensive than a 555.

That takes me back. I used quite a few of those in my youth. They seemed like such a cool device when they were launched.

Even cooler were the Programmable Unijunction Transistor, PUT.
Which I called the triple-lie semiconductor:
-It wasn’t “programable”, it was adjustable.
-It wasn’t a single junction, but three junctions.
-It wasn’t a transistor but a thyristor.

Nevertheless a very useful device.

In analog electronics, “programmable” is sometimes used as a synonym for “adjustable” or “settable”. It means nothing more than that there is some property that is not fixed at the factory, but is instead designed to be user-configured, especially in cases where non-configurable is the default for that type of product.