Decoupling Capacitor Example
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- čas přidán 1. 07. 2024
- Decoupling Capacitor Example
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in this video we set up to separate 555 timers in astable mode. Without the bypass capacitors they nearly lock into rhythm with no physical connection, except power and ground.
But by placing a capacitor across VCC & GND as close to the IC as possible, we break this "lock" and the two times can be set for differing frequencies.
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Could you do a related video with a more in depth explanation of why they sync up despite different settings and what the decoupling cap does to change it?
That's excellent. I have a degree in microelectronics engineering and yet I can't recall ever being taught about decoupling capacitors in university, only afterwards with actual practical exercises.
Whatever we learn...... It's only from the practical work.
Brilliant. Never realized that the noise from one IC would affect another IC. Now I understand why 7400 series logic chips in old computers all had a decoupling capacitor across their positive and negative terminals.
Good job Paul. 🌟
☮️✌️
Awesome, I'd heard/seen that decoupling capacitors are a best practice, but really never saw a demonstration of why. Thanks for the awesome video.
Thanks Paul, I think you have given me renewed hope!! I became disheartened with a project as pushed it to the back of the bench two years ago. 3 different frequency multivibrator chips (for tones) being triggered by three different timings chips, no decoupling caps anywhere! I was observing spurious unexplainable trigger signals firing all outputs simultaneously. I'm very excited now to bring this back to the front of the bench. - Cheers!!
good to see you're still there and thanks for all your efforts!
Great video....In the past I've often had more than 1 555 on a board and noticed the same thing, going in phase that is....really frustrating since I was clearly trying to get 2 different pulse values. I just chalked it up to a strange anomaly and went about finding another way. I never thought of putting caps across the vcc and grd. Keep up the good work. And yes, maybe a theory as to why they sync would be nice....I have no clue.
Good morning Paul. Keep up the great channel content.
Thanks for the lesson. Made it very easy to understand.
Good demo!
very nice and effective example
Cool demonstration, and always nice when I already have all the components and gear to reproduce an exercise. :-) As others have said I'd also appreciate a video expanding on the topic if possible. Certainly got the gist from this though, thanks Paul.
This effect is a factor in design of pcbs as well. A large amount of work is done to eliminate " crosstalk" and "ghosting " in major assemblies. The actual resistance of the traces along with the capacitance can form rc circuits that can cause major problems
Excellent! Thank you.
Another great vid
Nice Job Paul, I learned me something new today. Guess you can teach an old dog new tricks!
Thanks
Nice video, thanks for sharing it :)
if you connect them to diffrent power sources this wont happen. i think there is a small current flow between the two circuits because of the potential diffrence. so slowly that potential diffrence gets smaller and they are in sync
Nice video
Amazing!
Your camera settings:
First thanks for all your interesting videos.
Now just one idea: If you would put your camera on the opposite side of your breadboards we could see very much better what you are doing. At the moment there is often your hand in the middle of the screen hiding e.g. the parts that you are inserting in the board. What do you think about it? Will you give it a try?😊 Thanks a lot. Regards, Bo, Switzerland🇨🇭
Great demo, signal is literally decoupled when those caps are added.
Yep
Thanks for great Video. where is the link to the grabber file for download?
That was great Paul! I didn't realise that the transients could actually cause two circuits to sync like that! You never stop learning eh?
INTERESTING
Hey Paul.
A couple years back I built up some pcbs for a synthesizer project that uses 3 dozen 555 timers. My first pcbs did not have provision for decoupling caps so I could never keep them in tune. For me to keep them in tune I discovered that placing a 100n cap between pin 5 and gnd got them to stay in line but when I placwd the same cap between vcc and gnd on each chip the problem persisted. In my design all of the pin 5's are commoned together for master tuning so maby thats why I had different results?
hey paul, did you put a cap on pin5?
i think the syncing is because the noise on Vcc messes up the voltage divider inside the 555. a cap on pin5 should do the trick for small circuits as well. greeting
I am currently working on a synthesizer that uses 3 dozen 555 timers. Each set of 12 tuned to the top octave.
Each set of 12 timers has their pin 5 commoned together to give each set a master tuning control. When I populated my first set of pcbs I did not have decoupling caps between pin 5 and gnd and I could never get them in tune. My second attempt has a 100n cap between pin 5 and ground on each chip and now they all stay tuned. Iirc putting a cap between vcc and gnd for each chip didn't help but between pin 5 and gnd it worked.
So I think your theory is correct :)
Would you do this to all IC’s? How do you know if you need them or not on a particular IC? Thanks for the info!! 😁👍
Digital logic chips require decoupling.
Sweet board man! Those stem kids in your area will touch a pcb even before they graduate. You can't say that for most of the stem kids out there.
I think this says as much about the 555 timer susceptibility to supply noise as it does about supply decoupling. I stopped using 555timers when 8 pin pic's became cheap, as the 555's can be a pain in the butt for resetting on a supply spike even with decoupling caps. The car environment was never clean enough for them, motor or horn current dumping would normally cause a reset or some strange affect.
Good explanation on "what", but no explanation of "why"
Been looking over your old videos for making function generators. I noticed the main event in those circuits is the integrator. That got me thinking... PID controllers need to do integration, but they also need to do differentiation as well. What's a differentiation circuit like?
Same as an integrator actually, but with the resistor and capacitor swapped. Current through the capacitor is directly proportional to the derivative of input voltage, then because of virtual ground effect the output voltage across the resistor is directly proportional to that current, so you end up with the output voltage being directly proportional to the derivative of input voltage
That's way easier than I thought it'd be.
Thanks!
So I presume this happened because of voltage drop between timer circuits?
No, transient spikes.
That doesn't make sense by adding decoupling caps across +Vcc to ground would isolate the syncing 555 timer issue. I'm not sure why adding decoupling caps across +Vcc to ground will separate the syncing issues of both 555 timers. Can you explain more of the theory behind this?
I think it's due to noise on the power lines affecting the behavior of the 555's.
@@Enigma758 The Decoupling Caps are allowing separate syncing for some reasons
@@waynegram8907 Without decoupling of the supply, you may get periodic noise from the supply which affects both chips. Without decoupling of the chips, you may get periodic noise from one chip affecting the other chip.
That’s interesting bud.
If this was true, it would work with separate isolated power supplies or batteries. There is some pickup via the common psu your using. It is totally unscientific.
If this was true? Lol
Look at a computer circuit board. See all those little caps by every IC? What do you imagine they are there for, company?
@@learnelectronics there is only one way to find out, & run each circuit on a separate supply.
OK, but _Why_ ?
Caps block DC. Transients cause glitches. A cap across the power of an IC blocks DC transients.
@@learnelectronics Thanks!
The choice of color on that board was not good. If this is to be an educational adjunct tool, it should be as clear as possible.
All of my boards are black. All have the "happy bear" logo. Must maintain brand identity.
Neither the students nor the instructor have had any problems.
So electronics without decoupling capacitors is similar to a room of women syncing their cycles 🤔