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by exoesquitur 2802 days ago
The 555 was great.

These days I usually just drop in a 6 pin microcontroller though. Less external parts, cheaper, less environmental instability, much more operational flexibility, and often I can have it perform several circuit functions. If I go to 8 pins, woah, look out!

I do so much digitally now that I've "forgotten" 75 percent of my analog stuff... Once in a while I come upon a cool analog trick though. Sad part is, that usually the "super simple, bulletproof" analog solution with just 5 parts usually ends up being more expensive in qc, bom, and board space that throwing a million transistors at it.

It's a strange world we live in.

2 comments

Is this for a production device or like a hobby type thing? Reason I ask is that I'm often resistant to adding auxiliary microcontrollers to things just due to the extra hassle of maintaining, building, and distributing the firmware for them. Like, even if it's a device with JTAG, that's still a program-once-in-the-factory affair, unless you go the trouble of also setting up an SPI bootloader or something on it.

I guess the counter argument is that a 555 circuit can't be reprogrammed either, but it also doesn't have to be programmed even the first time.

With analog solutions, the complexity gets pushed into designing the test rigs, validating your component supply, thermal compensation, etc. Dealing with firmware instead may or may not be a net win, but the bottom line is you can change the firmware but you can't change the board.
The 555 is already overkill if you want a simple oscillator with fixed parameters. You can build one with two transistors.
Transistors are essentially free nowadays. Packaging and assembly are the cost drivers.
I was wondering this, even the leads seem enormous and wasteful compared to the actual device.
Compare:

https://www.mouser.com/ProductDetail/Diodes-Incorporated/ZXT...

https://www.mouser.com/ProductDetail/Microchip-Technology/PI...

Notice that the discrete transistors actually cost more than the microcontroller.

Wow, it's like the two extreme endpoints of "Powers of Ten".

https://www.youtube.com/watch?v=0fKBhvDjuy0

Those two transistors had better be hella good to justify the price difference.

Those transistors can drive 60V and 1A; hardly any controller can do such things. You might expect some special controller pins to drive e.g. 100 mA at 5V; more often, something like 20 mA at 3.3V.
Very telling