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Networks Of Multivibrators

HowardMiller

Mar 20, 2022
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Thank you. It's been over 40 years since I studied 555s and maybe 20 years since I last built a project from one.
What I'm looking for are projects and applications that used a large number of these types of devices.
 

Nanren888

Nov 8, 2015
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555 timers.
At $0.50 they are a popular choice, even if their current consumption while switching gets some negative comments.
Googling 555 timers gets lists of projects devoted to these guys.
 

Harald Kapp

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Imho not a very sensible approach. Of course you could set up a bunch of LEDs, each with its own 555 based multivibrator for a firefly effect as linked to in post #5.
The sensible question would be - just my two cents - I have a project where I want to "whatever you want to do": How would I tackle this project?

I take it you dabbled in electronics many years ago and now want to come back to your old hobby? While the 555 is a venerable component and still widely available: have you considered starting with a fresh view e.g. by using microcontrollers? The Arduino line of microcontrollers is an excellent starting point - even comes with a blinking LED as your first project ;)
 

HowardMiller

Mar 20, 2022
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My original idea was to emulate the processes of a neuron. That part's pretty straightforward, but assembling a number of 555s to emulate the behavior of a cluster of neurons was beyond my ability to design. I was just wondering if anyone ever did anything using a number of interconnected 555s.
I know my initial question wasn't very clear, but I wanted to see if I would get useful replies from directions I hadn't thought of.
 

HowardMiller

Mar 20, 2022
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Imho not a very sensible approach. Of course you could set up a bunch of LEDs, each with its own 555 based multivibrator for a firefly effect as linked to in post #5.
The sensible question would be - just my two cents - I have a project where I want to "whatever you want to do": How would I tackle this project?

I take it you dabbled in electronics many years ago and now want to come back to your old hobby? While the 555 is a venerable component and still widely available: have you considered starting with a fresh view e.g. by using microcontrollers? The Arduino line of microcontrollers is an excellent starting point - even comes with a blinking LED as your first project ;)
A 555 type approach is essentially analog. You can vary your output along a ramp of input voltages, while in digital circuitry you're confined to a series of ones and zeros. Neural topologies can be modeled, but they aren't actually created.
 

HowardMiller

Mar 20, 2022
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555 timers.
At $0.50 they are a popular choice, even if their current consumption while switching gets some negative comments.
Googling 555 timers gets lists of projects devoted to these guys.
I know there are much more modern versions of this useful timer, but I think my last project was with something that had 4 timers in an IC, and, unfortunately, that's what was familiar to me.
 

AnalogKid

Jun 10, 2015
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I know there are much more modern versions of this useful timer,
Not really. There is a CMOS version with the same pinout, and a couple of 5-pin SMT versions that can be either astable or monostable, but not both. There probably are other variants for high-volume use; the 555 was not patented, so things happen. But the old bipolar and CMOS versions still reign.

For lotsa oscillators at a lower cost, you can get 6 squarewave oscillators in a single hex inverter if it is a Schmitt trigger type. 74LS14, 74AC14, CD40106, etc. Frequency stability with temperature is not as good as the original 555, but serviceable in many applications.

ak
 

HowardMiller

Mar 20, 2022
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Thank you. This is pretty much what I was looking for. Now, I'm going to pursue this and see what kind of projects came out of it.
 

AnalogKid

Jun 10, 2015
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Harold - excellent find. But . . . Not to be picky or anything, but this is from the link in post #16:

"the fact that monostable multivibrators are implementable in large quantities as counters in digital programmable hardware"

No.

Not a fact; in fact, a significant error. In the real world, monostables are not used to form counters. They can be a divider, as a type of gated frequency discriminator, an experimental curiosity. But the billions of counter/divider stages and static memory cells produced each day (!!!) are ***not*** monostables. Not sure how this affects his project, but it does not speak well of his training or perception.

If he is talking about a bistable multivibrator, a 2-transistor form of a flipflop that can be used to create a binary counter or 1-bit memory, then he still is incorrect. First, that is not how counter circuits in chips are done - too many Rs and Cs. More important, at their cores a monostable is an R-C timer and a bistable is not. In fact, there are design elements in a bistable circuit specifically to reduce R-C timing effects.

Also, I'm very disappointed that there is not a schematic in the paper. There are two basic types of monostable, non-retriggerable (what I call a "true' monostable) and retriggerable. Fun fact: a 555 is neither of these. It ignores a retrigger input under some conditions (true-ish), and partially implements it in others, acting more like a retriggerable monostable variation called a pulse stretcher. I'm not saying his circuit won't work - it probably does exactly what he needs very well. But I'm curious about the details; the schematic would tell me more about his theories than three pages of text.

ak
 
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Harald Kapp

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@AnalogKid . I have to admit that I haven't read the paper thoroughly. This link was one of the first hits in a quick Google search. @HowardMiller may perform his own search as seemingly there is no knowledge of this kind available from members of this forum.
One could interpret the statement you cited as meaning programmable timer/counters such as you can find in microcontrollers. In that case you can use such a timer/counter as a programmable one-shot which is triggered by an input signal, then counts up to a programmable threshold (or down from a programmed value to zero) and stops when the end has been reached, all the while having an active output (e.g. logic high), going inactive (e.g. logic low) otherwise. This is not exactly a multivibrator but the effect is the same: an active output for a defined time after a trigger signal.
I guess the full paper will reveal more detail.
 
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