555 Timers - Monostable Multivibrator Configuration
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- เผยแพร่เมื่อ 13 พ.ค. 2024
- After reviewing 555 timers in general, in this tutorial we go over one of the 3 common 555 timer configurations, the monostable multivibrator configuration. Josh reviews how the monstable configuration acts and goes into painstaking detail about why it acts the way it does, moving step by step through what happens internally to the 555 timer. He finishes up with a real life example using a 555 timer on a breadboard that's hooked up to an oscilloscope, showing how the timer actually works in normal conditions.
This video tutorial is based on the written tutorial that Jayesh created, so go check out the written portion that Jayesh did here: www.circuitbread.com/tutorial...
0:00 Introduction
1:44 External Monostable Configuration
3:13 Internal process
6:14 Recap of the internal process
7:46 High level review of the process
8:35 Physical circuit and performance
11:28 Overview and summary
12:02 The toast will never pop up
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I love this channel and what you are teaching.
For the people out there wondering what this configuration is good for:
1: Debouncing keys. If you press a little tactile switch, there isn't just a sudden ON state, in fact all mechanical switches bounce, generating a lot of noise before settling on the contact.
If you have very fast electronics reading that switch, that circuit might interpret that as 10 or 20 rapid button presses. Especially in applications with limit switches or implenting toggle functions, this is a crucial circuit if you cannot do this in a uC in software.
2: Peak detector follower. A peak detector is an OpAmp circuit that takes super short pulses and converts them into longer pulses. You might think, yeah, that is what this is doing anyways so why would i need it?. The answer is sensitivity. The higher the capacity of your integrator capacitor on the opamp, the lower you sensitivity. So you want this to generate another pulse long enough to trigger i.e. an interrupt on a uC or for a counter to react (this is more for scientific purposes like SIPM detectors)
3. Timebased exclusion of concurrent incomming signals. This is a bit more esotherical, but if you are ever in a situation where you want another signal to be ignored for a while when another one just hit, you can use this.
Awesome! Thanks for these applications, that's fantastic.
Haven't used the old 555 for many years but interesting to watch. Well explained as usual.
Yeah it's the kind of stuff that is always there, but usually, how the world is hurling towards more and more digital stuff, if people need something done, they just slap on a 3 cents uC
What a nice coincidence, i just finished a 1kHz 50%dC Sqarewave gen with the last 555 i could find (turns out that my imagined massive stock of NE556 in fact where all NE5532 Dual OpAmps ^^)
I just needed a little something to inject into possibly faulty 74xx chips to see if they still play ball. (did not want to abuse the calibration gen on the scope and my function generator is single channel only)
Which reminded me of something: If you plan on building something with a target frequency precission of ~0.1% do yourselves a favor and add in some trimmers.
1kHz is in the audio range, so even if your souncard cannot represent the a sqarewave coming in at that freq you can still meassure from zero crossing to zero crossing to adjust the timings.
There are many usefull programs out there that turn your sound interface into a low bandwith scope. Perfect for starting out without commiting a few hundret bucks. Ofc any halfway decent scope will do a much better job, esp. in troubleshooting.
Thank you so much - I always shied away from the 555, but now I've got one working based on your tutorial and it's fantastic!!
Awesome!
Very well explained. Thanks
This was a very good explanation. Very good animations. Thank you!!!
It would be nice to also talk about the edge cases: What happens if you press and hold the button continiously. Also: Please measure the cap, there is typically +/-20% tolerance. With the actual value you can verify the intervall better. Furthermore you could use cursors or the measurement function of the scope to measure the intervall more precisely.
super and cool
It means, if you trigger the timer several times within the unstable state nothing will happen. But if one of the trigger pulses holds during the end of the unstable state another unstable state will be added. Am I right?
Dear CircuitBread, can I get your opinion on the video about the 555 timer that I published on my TH-cam channel?
excuse me can i ask something?
Is it right that to use this as timer we need to push and release the button constantly as animated in the video?
im sorry if this is a dumb question..
That's understandable but you're looking at the wrong configuration! If you'd like to use a 555 timer as an actual timer without having to push the button all the time, you'll want the *astable* configuration, which we talk about here: th-cam.com/video/APghHcA-MOI/w-d-xo.html
Does anyone know how can i do the trigger switch automatically
You can control that trigger with an external device such as an MCU. Or you could manually rig something to physically touch the button. It really depends on the context of your needs.