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EEVblog: The 555 Timer is 55 years old [video]

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Re: EEVblog: The 555 Timer is 55 years old [video]

#91

Post by laughing_man »

lightedman wrote: post #86
laughing_man wrote: post #78

Earlier quoted context omitted.

Until you go to lay out your circuit board. There's a reason microcontrollers are used for tasks like debouncing switches.

"There's a reason microcontrollers are used for tasks like debouncing switches." Because people are too cheap (or fail that hard at basic analog electronic control) to get a proper single-pole single-throw switch with a pair of MOSFETs in a monostable mode, or use an S-R flip-flop latch to debounce, or even a very simple R-C filter circuit. "Throw a microcontroller on it and call it a day" is the surest sign of someo…

All of that stuff is more expensive and uses more board space.

Re: EEVblog: The 555 Timer is 55 years old [video]

#92

Post by Brian_K_White »

lightedman wrote: post #86
laughing_man wrote: post #78

Earlier quoted context omitted.

Until you go to lay out your circuit board. There's a reason microcontrollers are used for tasks like debouncing switches.

"There's a reason microcontrollers are used for tasks like debouncing switches." Because people are too cheap (or fail that hard at basic analog electronic control) to get a proper single-pole single-throw switch with a pair of MOSFETs in a monostable mode, or use an S-R flip-flop latch to debounce, or even a very simple R-C filter circuit. "Throw a microcontroller on it and call it a day" is the surest sign of someo…

I think it's like living under a waterfall.

If you live under a waterfall you'll use 1000 gallons of fresh water pumped at blasting high speed to wash a cup.

We live under a waterfall of cpus and gates in general, and organisms don't care if their environment is perverse. A thoughtless organism will happily consume 1000 units of a free resource just to get 1 unit of some other non-free resource.

And a lot of humans are the worst. Thinking beings who elect not to care about anything like that. Like spammers that operate simply because sending email is free for the sender. They get almost nothing from it, and it costs everyone else a lot, but it costs them even less than the tiny bit they gain, and the external costs don't matter to them the tiniest bit.

But the environment is perverse, created by economies of scale and Asian slave labor and the push for advancement for it's own sake which makes existing useful things artificially low value by being "obsolete".

A software version of that might be making apps with Electron. It doesn't matter how much cpu and ram and disk and general mass of tech stack it takes to make some trivial app. The developers precious time outweighs all other considerations. If they can make the app in a few minutes with no effort instead of a few hours, it doesn't matter how much of everyone else's resources they consume since their time is valuable and 1M other people's cpus are free.

Re: EEVblog: The 555 Timer is 55 years old [video]

#93

Post by ralferoo »

lightedman wrote: post #83
ralferoo wrote: post #79

Earlier quoted context omitted.

Why is no software so important? If you design your board well enough, you can route the programming ports somewhere you can program it in-situ, possible with other components that also need programming. But in terms of cost, a simple microcontroller is usually cheaper than a 555 nowadays, often doesn't require external components, and so even if all you wanted was a single function like an edge-triggered pulse, or g…

"Why is no software so important?" Because nothing is faster and more responsive than direct hardware logic. "a simple microcontroller is usually cheaper than a 555 nowadays, often doesn't require external components," Often? Every UC I've ever used has required a whole slew of caps and resistors just to get the thing to take in operative firmware through a programming port. Even the simple light flashers for vehicle…

> "a simple microcontroller is usually cheaper than a 555 nowadays, often doesn't require external components,"

> Often? Every UC I've ever used has required a whole slew of caps and resistors just to get the thing to take in operative firmware through a programming port.

ATtiny for example. Many others only requiring an external capacitor, and complaining about a decoupling cap on a chip replacing a 555 that also needs an RC network to function seems rather petty.

> And accomplish things at a glacial speed that a basic hardware-only solution would've solved.

Most of these uCs operate at least 1 MHz or higher. The ATtiny85 can run at 8MHz from the internal oscillator and has an interrupt latency of 4-6 cycles. To achieve anything that's replacing something you'd do with a 555, you'd have to try incredibly hard to get latency as bad as you're describing. Perhaps they're actually doing something significantly more complicated than just replacing a 555?

Re: EEVblog: The 555 Timer is 55 years old [video]

#95

Post by brucehoult »

raverbashing wrote: post #69
brucehoult wrote: post #54

Earlier quoted context omitted.

Trivial with a 10c microcontroller ...

"Trivial" But then you realize you forgot to account for a 32 bit counter wrapping up. Or potential failures in the power supply or other capacitors

That 10c microcontroller has 15 32 bit registers, allowing you to make up to a 480 bit counter. That ought to be enough until long after the heat death of the universe.

It also has 2k (16384 bits) of SRAM, allowing even larger counters.

It runs off 2.8V - 5.5V DC, so supplying power is pretty trivial. Doesn't need a crystal, though of course adding one will improve the timing accuracy.

Re: EEVblog: The 555 Timer is 55 years old [video]

#96

Post by brucehoult »

mishellaneous wrote: post #76
raverbashing wrote: post #69

Earlier quoted context omitted.

"Trivial" But then you realize you forgot to account for a 32 bit counter wrapping up. Or potential failures in the power supply or other capacitors

somewhere else they were discussing how to use a 555 to time 55 years, and how for such a long period you'd need impractical resistance and capacitance values. easy workaround would be to set a more reasonable period, say, 1 sec, and use a counter to know when you hit 55 years. coincidentally, 55 years is 2 ** 30.7 seconds, so it'd just fit in a 32 bit register. though i take you were thinking about counting clock cy…

The size of a register is not the largest value you can conveniently count on a computer. You can use multiple registers.

Old computers often had a "carry flag" specifically to make this easier e.g.on Arm:

    add r0,r0,#1
    adc r1,r1,#0
But even on RISC-V, often criticised for not having a carry flag, it's not hard:

    addi  a0,a0,1
    sltiu t1,a0,1 # set to 1 if a0 wrapped back to 0
    add   a1,a1,t1

Re: EEVblog: The 555 Timer is 55 years old [video]

#97

Post by lightedman »

laughing_man wrote: post #91
lightedman wrote: post #86

Earlier quoted context omitted.

"There's a reason microcontrollers are used for tasks like debouncing switches." Because people are too cheap (or fail that hard at basic analog electronic control) to get a proper single-pole single-throw switch with a pair of MOSFETs in a monostable mode, or use an S-R flip-flop latch to debounce, or even a very simple R-C filter circuit. "Throw a microcontroller on it and call it a day" is the surest sign of someo…

All of that stuff is more expensive and uses more board space.

Which is why my bluetooth keyboard/mouse controller pad has that (specifically resistor/cap circuit under each key) riiiiiiiiiiiiiiight?
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