capacitors charge and discharge visualized
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- čas přidán 8. 09. 2024
- We use a real circuit to charge and discharge a capacitor and we display on an oscilloscope how the voltage and the current change across the capacitor during the two cycles of charge and discharge.
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Thank you very much for making this video. It's a lot easier to see what happens to current and voltage as a capacitor is charged and discharged when you see it on an oscilloscope.
I may be 4 years late but this video is perfect and EXACTLY what I was looking for to visualize the terminologies. So when people say capacitors resist changes, it's not that the capacitor is staying stuck at some voltage, it just simply takes some time to change; giving the illusion of being resistant to instant change lol.
Explaining in terms of the potential difference, with a bigger difference = more current flow makes a lot more sense and is more intuitive for me. Capacitor draws more current when it starts charging because big PD. Likewise, it discharges high current because of the big PD, just in another direction. As the PD decreases, so too will the rate of charging/discharging.
358th subscriber 😂 due to coronavirus I cannot observe this event practically, but thanks to you, even seeing it made me very happy. Huge thanks sir
Thank you for watching!
Thank you! The video helped me a lot
I'm glad it was useful to you
After viewing amateur after amateur videos and youtube channels this is refreshing. Noting the following: Though I'd like to know and see the actual specific current running through a capacitor from T1 through T5 on a scope (i.e. the 5 time constants), this I believe will get me started.
Though I've several reasons in monitoring a capacitor for a future project, monitoring and recording by means of a scope rather than to using those 'useful but cumbersome equations' I often get lost in, putting my scope & generator to work will be far more accurate. Also, though I'm sure I would eventually thought of using the lower resistor as you have (as in a 1 ohm for example) I never thought to include that same lower resistor. Thanks. And excellent job on this presentation.
excellent video.
This is my tomorrow's lab =) thanks
Have fun!
Excellent video
Thank you!
Nice ez demo--i like your grande breadboard!
Thank you!
Thank you! Excellent demonstration.
I'm glad you liked it. I'm trying to understand what people likes to see on my videos. Your comment helps a lot. Would you prefer to see more videos describing how electronic components work? Or would you prefer to see more on DIY? Thank you!
@@eleneasy Currently I am trying to learn more about capacitors and inductors, but I would be interested in watching any videos on electronics you would care to provide. However, I also like DIY projects as well. I've subscribed to your channel and will continue to keep up with your videos. (I have a similar scope -- 5202 -- and plan to duplicate the demonstration you provided after I've managed to make a low noise signal generator with an Arduino board.)
Thank you love this.
Glad you enjoyed it!
Thanks - VERY helpful.
Glad it was helpful!
Absolutely excellent......👍🏻 I see that your channel 2 voltage division setting varies between 50V and 500mV in you tutorial video. Could you help me with an explanation please. Is it dependent on your signal generator settings? Thanks for your great videos, I’ve learnt a lot 👌🏻
Thank you! Really appreciate the comment.
Yes, it depended on the amplitude of the signal coming from the generator. Depending on what i wanted to show, I had to adjust the settings to emphasize what i needed. The alternative was to keep changing the values of the capacitor and the resistor.
hello, sir could you please interpret the instantly growth of current from 0 to a constant value , thank you in advance
you need to consider two important things. When a capacitor is charged, the more charges it stores, the higher is its voltage. When a voltageis applied to a resistor, a current flows through it. This current increases when the voltage increases and vice versa.
If you have a capacitor in series with a resitor, and we apply a voltage to the system, since the capacitor is initially discharged, its voltage will be 0V. Therefore, the difference of potential, or voltage, at the resistor, will be equal to the voltage applied to the system. Because of this voltage, a certain amount of current will start flowing. The current, on the other end, will bring new charges to the capacitor, which will start accumulating them and will start increase its voltage. Once the voltage at the capacitor increases, the one at the resistor will decrease proportionally, which will cause the current to diminish as well. So the current is initially high, and then it will become less. Now, if we repeat this same reasoning again, you'll see that the capacitor will increase the voltage due to the new, lower current. This increase in voltage will cause a decrease in voltage at the resistor and a currnet even lower. So, at the end, the current will flow slower and slower until it won't be possible to measure it anymore. Initially it will decrease faster, but then it will decrease slower and slower.. And that is the reason why we see that kind of curve for the charging of the capacitor. The discharge happen in a similar way, but this time we invert the voltage applied to the series of the resistor and the capacitor and, therefore, the curve on the oscilloscope will look like is upside down with respect to the previous cycle.
Hope this helps.
My intro to circuits labs were useless in comparison to this... Felt like nothing more than a way to generate graded material and not a means of learning concepts. This would have explained things that took me weeks to understand... Why are electronics taught so poorly so often?
Videos like yours are the only thing keeping future engineering students who actually give a damn going.
Thank you so much this is perfect I've been trying to do this getting the charging and discharging graph of a capacitor.
Isn't there a way of being able to tell if you could pass her is good or Not by using this graph and some calculation would you mind please doing that?
Yes, there are ways to tell if a capacitor is good or not. The answer won't fit easily in this answer, so I'll make a video out of it. I'll put it on my to do list and make it soon. Thank you for the question!
Hello, Thanks for the video. My question is can this setup be replicated with a DC Load Power Supply instead of the generator. I would appreciate your swift response. Thanks
The generator helps because it can repeat over and over again the process. But, if you are only looking at execting the charge process once, then you can power the circuit through a DC power supply or a battery in series with a switch. Leave the switch open and conenct everything like it was the generator. Then, close the switch and the capacitor will charge. If you set the oscilloscope to see only one shot, you will see the charge cycle. To see the dicharge cycle, open again the switch but, this time, connect the other end of the switch to ground instead of the DC power supply/battery. When you close the switch the capacitor will discharge and, again, you can see that single discharge on the oscilloscope if you use it to show a single shot.
Your function generator doesn't seem to be available anywhere anymore & that is to be expected after 5 years.
Can you recommend one of similar lower end specs that I could use to emulate your vizualization. I can only see higher end expensive units for professional use & most are only signal generators anyhow.
Well, yes that function generator you see in the video was made by myself way before I started making videos, that's why you couldn't find.
If you are interested in buying one at low cost, I see there are several options on Amazon, ranging from about $10 to $100. It all depends on what you want to use it for.
This one, for example, is based on the same IC i used for mine, but is very basic:
www.amazon.com/ICQUANZX-Precision-Generator-Adjustable-Frequency/dp/B07V674HZY/ref=sr_1_5?crid=WEIEEXDT4N4K&keywords=function+generator&qid=1706289323&sprefix=function+generator%2Caps%2C122&sr=8-5
This other one has a smaller range, but it seems good enough for Audio applications, and It ha a nice display and controls:
www.amazon.com/1HZ-500KHZ-Functional-Generator-Seesii-Frequency/dp/B08NSR5GYR/ref=sr_1_3?crid=WEIEEXDT4N4K&keywords=function%2Bgenerator&qid=1706289323&sprefix=function%2Bgenerator%2Caps%2C122&sr=8-3&th=1
Finally, I could suggest an entry level instrument that is also capable of creating any shape you like, a true function generator, rather than a signal generator, but it is around 100 bucks:
www.amazon.com/Koolertron-Generator-Precision-Dual-channel-Arbitrary/dp/B07211YWMK/ref=sr_1_4?crid=WEIEEXDT4N4K&keywords=function+generator&qid=1706289323&sprefix=function+generator%2Caps%2C122&sr=8-4&ufe=app_do%3Aamzn1.fos.18ed3cb5-28d5-4975-8bc7-93deae8f9840
This last one is actually very similar to the one I currently use in my lab.
Question: Hi, I have a question regarding single phase AC motors that use a start capacitor. If I disconnect the start capacitor from my motor, it will only hum, but will not start. When I reconnect the capacitor, the motor starts immediately. Which current from the capacitor helps the motor start? Is it the surge current when the capacitor is charging or the surge current when the capacitor is discharging that helps the motor start? Thanks for your help.
Actually is neither. The motor runs with alternate current, right? The capacitor, when working in AC, has a different behavior from a high level perspective. In AC, the capacitor behaves like a resistor. And it's resistance is actually called reactance. It is different than resistance itself because it changes the phase of the current with respect to the voltage. The motor has also a reactance. But this one works in the opposite way as the one of the capacitor. Putting the two together, the phase difference of the voltage and current are neutralized and so an active power can be generated, as opposed as a reactive power, and the motor can use this active power to convert the corresponding electric energy in mechanical energy. And therefore the motor can start running.
Thanks for the quick reply. I think I understand it now. The start capacitor is added to correct the lagging current caused by the inductive load of the motor. This increases the power factor by putting the current and voltage waveforms closer into phase with each other. In short, you add the capacitor to correct the power factor. Thanks again!
@@bernardocisneros4402 Exactly to the point!
Hello, I have reproduced the same as showen but as I cannot see the charge and discharge curve I see as you the current ....( I have the Hantek 4252C, and I've used the internal generator set =2 V and 1,4khz)..... With the probes I've done exactly the same as you show . What I wrong?... many thanks in advance
You have to use a frequency corresponding to at least 10 times less that the timing constant provided by the capacitor and the resistor you are using. Otherwise, the generator will switch the polarity of the signal before the transient can still be visible. Try to reduce the frequency of the generator and you should be able to see the transients.
what voltage and frequency did you set your function generator at?
It can actually be seen from the oscilloscope itself, although I didn't mention it in the video. Sorry about that.
The input square signal has an amplitude of 15V and a frequency of about 1.4kHz.
Note that the amplitude of the output signal is not displayed correctly, because I was using an attenuated probe (x10) but the oscilloscope was not set to measure the attenuated signal. So, although you see 50V/div on the second channel of the oscillosco, it is in reality 5V/div. So, as it is supposed to be, the max amplitude of both input and output signals is the same: 15V.
Also, note that although I used a frequency of 1.4kHz, you will probably need to change it if you are using values of capacitor and resistor different than what I did. The frequency needs to be adjusted based on the timing constant of the circuit: T = RC. In general you have to calculate the timing constant and then use a frequency of the same order of magnitude as 1/T = 1/RC.
I have degree in electronic. Never do this in my college
Sorry to hear that.This should be basic stuff to learn. Hope you enjoied my video.