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Is the 555 still a viable IC?
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Zero999:

--- Quote from: baldurn on February 20, 2024, 02:00:13 pm ---
--- Quote from: Zero999 on February 20, 2024, 11:17:18 am ---
--- Quote from: baldurn on February 19, 2024, 10:08:32 pm ---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.

--- End quote ---
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.

--- End quote ---

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.

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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.



--- Quote from: MT on February 20, 2024, 04:20:08 pm ---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
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I don't know whether it was tongue in cheek or a slip of the tongue and he meant to say microchip.
SiliconWizard:

--- Quote from: PlainName on February 22, 2024, 10:15:56 am ---
--- Quote --- All popular multicolored LED strips these days are WS2812 based, which you could not possibly program without using a MCU.
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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 :)

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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:

--- Quote from: TimFox on February 22, 2024, 03:25:03 pm ---I believe the 2N2646 unijunction transistor is still available, but more expensive than a 555.

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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:

--- Quote from: coppice on February 22, 2024, 10:01:50 pm ---
--- Quote from: TimFox on February 22, 2024, 03:25:03 pm ---I believe the 2N2646 unijunction transistor is still available, but more expensive than a 555.

--- End quote ---
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.

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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:

--- Quote from: schmitt trigger on February 23, 2024, 01:31:34 am ---
--- Quote from: coppice on February 22, 2024, 10:01:50 pm ---
--- Quote from: TimFox on February 22, 2024, 03:25:03 pm ---I believe the 2N2646 unijunction transistor is still available, but more expensive than a 555.

--- End quote ---
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.

--- End quote ---

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.

--- End quote ---
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.
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