Linear Voltage Regulators (LM7805) | AO #17
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- Опубликовано: 8 фев 2025
- Why is the LM7805 is a very popular voltage regulator?
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#linear #regulator #lm7805
The statement you made regarding accidently creating short circuits is so true, Its something engineers never grow out of.
Gotta be honest... your videos are the best mate..... I love how you combine technical aspects with visual learning....
+codedemonelectronics Appreciate you being honest. ;) (Seriously, thanks.)
SERIOUSLY. I just graduated college last year, and circuit design was one of the subjects I was weak at! I wish I found this series earlier!!
Thank you thank you thank you for simply putting everything into a short concise video. I needed this info, and you explained it all perfectly. Great work!
I have watched loads of electronic videos, on youtube, and you have taught me the most, in such a short time. For that, I thank you. You have more than earned my subscription.
Every year we get a new AddOhms video, much joy!
I wish I could make them full time, but I can't. So I'm shooting for one a month or at least more than one a quarter.
Just been swinging through the AddOhms vids on topics I thought I knew. Every single one had at least one nugget of info I didn't know.
Very nice!! Thanks. I dont understand the dislike on this video. I think haters are everywhere. Dont stop making this videos.
+script0r inside Thank you.
this was a perfect video with zero unusefull time . yes there must be sick haters everywhere .
@@tolgadabbagh1877 "Sick haters"
That's quite an extreme view of someone who just pressed a button that was made for pressing.
Great videos. I had no idea I needed decoupler caps. That explains some of the circuit problems I have had in the past. Thanks again!
His explanation is easiest and best to a long time software engineer like me.
Thank you very much for the lesson James. Anxiously waiting for the switching regulator video.Greetings from Brazil.
i have met your videos recently. Thank you for videos you have shared all. Although we learn how the components work seperately, we can't use them efficiently our project when it comes to design something new. For example, we use these capasitors (you explained late in the video) as in its data sheet but can't understand ENTIRELY why we use it in our designs. I appreciate your efforts .
I must say Thank You. After looking for days a simple video regarding a simple electronic components explanation i finally found your channel. My native language is spanish, unfortunately all spanish videos i saw are vague or they aren't focused on the subject, simply i wasted a lot of time. Suscribed.
simply you are doing one of the best youtube tutorials I ever saw!
Thank you, Sir, for this (and others in your AddOhms) videos.
Done simply, objectively ... didactically.
For an old, forgotten youth like me, it's very useful.
Thanks!!!
By the way, if I put a 0.47uF capacitor in the input (instead of .33uF, as manafucter says) there is no problem, right? :) Thanks
anything less than 10 uF is fine.
Great video, easy for anyone to understand you. One of the best channels on YT.
A very good summary of the basics on linear voltage regulators !
thanks for this brilliant video as it allowed me to create a voltage regulator circuit. it was perfect first time!
I forgot I was subscribed to this channel and now taking intro to electronics. Better rewatch videos again.
+Victor P. Yeah, I'd love to post videos faster. But as a one-man education and production shop, this is about as fast as I can go.
Thanks for video! I watch from Poland and look forward to see next great tutorial soon.
Hello Poland! Thanks for watching.
Hi sir, just want to thank you for these videos. I'am busy with my masters in chemistry and require some electronic parts for my project so these videos are damn handy for plugin in gaps in my knowledge. Keep making them please!
Very nice and entertaining video ! Well explained and well done !
Nice. Didn't know about the Thermal Resistance figure. Thanks!
Hello, I have just found your channel and would like to thank you for your awesome work!:)
Thank you so much for your videos. Now I can read datasheets by myself!
Nice! Makes much more sense now. Thanks!
Thanks, cleared up a few if's and but's for me.
They may be inefficient, but are absolutely needed in radio gear as switching power supplies produce noise. I love linear power supplies, they are simple to build and very quiet. In order to use one for higher current a heat sink and fan helps. Switching supplies have their uses as well, but for me the linear is the most needed, In radio.
Great explanation! Your videos are truly helpful!
Amazing explanation and awesome graphics thank u sir ...
Thank you, mister, very much!
Excellent quality! Thank you very much for that!!!!
Great info very clear and informative
thank you so much for this marvelous explanation
Great video, keep them coming!!!
thank u Sir..................I clearly understand..............u are really good at teaching...best of luck Sir
Thanks! Excellent explanation!
Greetings from The Great Northwest! (Spokane), your explanations are terrific! I understood everything, especially since I'm refreshing myself in electronics. Question: At the point of 455 degrees Celsius do you go to the data sheet to determine if you need a heat sink?
I think anything over 450°C is safe to say, you need a heat sink. ;)
Thanks, should I have more questions I know who to ask. LOL.
Thanks for the video realy liked it.
A comparison video about zener diodes regulators efficiency VS switch mode regulators efficiency for low power applications would be great.
If you could also suggest how small a switch mode circuit could be down to the SMT size I'd be happy.
well done, my man. love your videos.
i cannot believe its been that long, you must have got into electronics a couple years before me. :) I assume we were close in age!!! you had a full head of hair back then! :D
+Justin Young Hey Justin! I'm counting from when I was 11 or 12. Not only did I have hair back when I knew you, it was always a total mess!
Muchísimas gracias por este gran aporte
Surprising quality videos ! thank's
Because our other videos aren't high quality?! Just kidding. Thanks for the feedback.
Hey ! Great Job! Can you please make a video on coupling capacitors; tell us everything you know about them? Thank you.
In my (Rather limited) experience I wouldn't place decoupling capacitors near the regulator depending on application. For example, if you have a transformer and rectifier you normally have smoothing capacitors which do the same thing as the regulator's ones. Also, it's best to place decoupling in between ICs so that they don't effect each other. Saying that, I'd just be sure to add some decoupling / smoothing capacitors everywhere so that no problems occur.
i have seen some videos about mosfet and npn transistor they are simply superb they are very clear.
i need to know how a pnp transistor works from addohms
great explanation! Thanks.
Correct if I am wrong, but the lowest voltage the regulator will work out would not be the drop-out voltage. The data sheet shows 2v. I do not thing the 7805 will work at two volts.
It is 2V above the output voltage.
Super useful and definitely explains why my fan circuit didn't need the capacitors (didn't end up working well anyway) but my amp circuit will.
Does the type of capacitor matter, as long as I keep polarity in mind?
Ceramic capacitors are lower ESR and come in smaller values. They are better for high-frequency decoupling/filtering. Electrolytics come in larger values, but also have higher ESR. They are good for low-frequency or (bulk) decoupling.
Great video , do more please i l like your style in explain things
You, Sir, are doing a great job explaning. Thank you! BTW, I like your hairstyle. Sort of very familiar to me :)
it was helpful, thank you
Thank you so much! this is great!
Thanks. IT was very helpful!
Thank you.
Great video but didnt answer any of the questions i had.
What is the flow of electricity when there is more than 5V? Does it go to heat or does it switch like a transistor to cycle 5v back through ground?
What is the minimum voltage needed to induce flow through the regulator?
Is there a built in diode to prevent voltage from reversing direction?
"Electricity" does not flow. "Electricity" is a construct. Current flows when a Voltage is applied. In the case of a linear regulator the current into it is equal to the current out of it (minus some tiny loss.) The regulator, effectively, changes the voltage dropped across itself to maintain the required output voltage. So heat disspiated is equal to the voltage drop across the regulator times the current through it.
A regulator that switches "on and off" is a switching regulator.
Great video, what do you mean by "small buffer for the load"? Thanks
Thank you very helpful
Hi AddOhms, thank you for the great instructional video I am working with ATtiny and ATMega IC which requires a 5Vdc source. I do have a question I hope you may answer for point me in the right direction. I would like to know if I can safely use 100uf Capacitors for the Input Cap and 10uf for the Output Cap.?
yes
Thanks
I have actually killed a few 7805's by neglecting protection diodes between input voltage and output voltage. I used to use whatever big electrolytic capacitor I could get across the linear regulated output for maximum stability, but as it turns out if the input supply is disconnected and the input is shorted, then the charge from the capacitor goes backwards through the regulator and kills them.
+Power Max Another issue with large capacitors on the output is when the regulator first turns on, the initial inrush current of that large capacitance can cause the regulator to go into thermal shutdown. So you end up with a linear regulator which a huge oscillation, while trying to charge up the output capacitor--the same cap that was put there to help it!
AddOhms Yikes! I do notice that when I attempt to design a opamp based LDO from scratch in LTspice, if I use ideal capacitors (ESR
AddOhms Something that I hope to do is to design my own accurate, arduino controlled lab power supply. One that will be at least 0-15V with 2 isolated channels, at at least 0-5A, which will allow full voltage and current range adjustment. That is proving to be a challenge with things like power dissipation, loop stability, transformer / preregulator stages, dropout voltage of the pass transistor element, etc. It is all getting quite complex!
I have a dual-rail design in LTspice that seems to work well, I can give you a link to my old instructables question about it.
+Power Max For the longest time I wanted to design my own: power supply and oscilloscope. Eventually I bought them instead. Both are going to be "someday" projects for me.
Nice video as usual XD.
On 1:40 and 5:16 the capacitors seem to be filtering not coupling as mentioned in video.!! Am I correct?
+majdinj I think you mean "decoupling", not "coupling." They are definitely not coupling capacitors.
The language I used was very intentional. "Decoupling", "filtering", and "bypass" are often used mis-used or interchanged.
In a linear regulator both capacitors are there for decoupling. Since there is no switching noise generated inside of the regulator, their primary function is to decouple, not to filter. The input capacitor decouples the regulator from the supply. The output capacitor decouples the regulator from the load.
Switching regulators, the capacitor's functions a very different. In that case the input is generally decoupling capacitor while the output is there for filtering.
+AddOhms Oh thanks man.
I have a few questions.
1. Can you use electrolytic caps for decoupling.
2. And if so. Can we use higher values? Thanks
For low-frequency or bulk decoupling they work fine. But you'll want to put a low-value ceramic in parallel with it for higher frequency noise. While called a decoupling or bypass capacitor, the ceramic is really a filter cap in that case.
The caveat here is if you use polymer aluminum (or polymer tantalum) capacitors instead of traditional wet aluminum electrolytics. Polymers have significantly lower ESR.
Awesome Video Old Man!
i think i noticed that the data sheet said you needed the capacitances in uF(micro) and you said nF(nano)
can you please check i may be wrong
+Chetan Amrao I converted to nF. 0.33uF is 330nF.
okay i didn't notice that! LOL
Nice video as always! ;)
Q: I haven't got a lot of small caps and that's my reason for using caps with a higher capacity... (like 470uF instead of 20uF)
Is this a big deal?
Greetings from Germany!
+MrLookslikeMani Hi Germany! Yeah 100-470uF get used pretty often. I just want to make the point they aren't always necessary.
If you go with much larger values than 470uF, you may actually cause the regulator to oscillate when it first powers-on. Capacitors are a short circuit when they first start to charge. So too much capacitance can cause too much current, activating the thermal shutdown.
Looking back, I should have added that in this video. I may make a separate one to explain better.
+AddOhms Thanks a lot. :)
My $0.02 - I've been using 10 mF caps for these for years. Never had a problem. I had always assumed that this was the norm.
Are electrolytic caps okay if you're using a DC power supply like what you'd get with a wifi router?
That's what most designs do. The bulk electrolytic cap is *decoupling* the circuit from the power supply. Hence the name, "decoupling capacitor."
Thank you
Hello, that was the most useful video on this topic thank you some much, now i understand everything about this device thanks to you,
but actually something confused so much, at 4:56 you stated that the output volt will change if we change the input voltage or the LOAD , and it did not make any sense to me, as I understood the output voltage is totally independent on the load and that is the most important property of this device, so please explain this to me ,
and one more thing which is not related to this topic actually, what is the difference between a variable resistor and a potentiometer ?
The point of the regulator is to provide a stable voltage regardless if the input voltage changes or if the load's current draw changes. If the load's current draw changes, ohm's law would suggest its voltage drop changes, so the regulator must adjust its output to maintain a stable output.
As for difference "variable resistor and a potentiometer". In practice, nothing. By definition a variable resistor would only have two terminals. A potentiometer a 3 terminal devices that forms a voltage divider on its own
now i understand better , I was wrong about one point, Thanks so much
what do you think about connecting 2 or more lm78xx series in parallel ? something like 2x7805 - for continuous 5v 2A output .. thank you vry much
You. cannot. Series makes no sense and parallel they would try to regulate each other.
So does the thermal shutdown action reduce to zero the likelihood of letting the magic smoke out?
It helps but does not eliminate it. It’s just a positive thermal coefficient.
@@AddOhms How protective is that action - thermal runaway usually happens so quickly - how would I calculate a safe margin?
It's not something I would ever have a design that relies on [for a linear regulator.]
If it is "thermally running away" there is a serious problem in the design.
Have you done any videos on Earthing ? and its various configurations.
+TheProCactus Nope
Would it be something relevant to you?
No. I'm not an electrician and I don't know electrical codes well enough to talk about them.
Well thanks for your thought, I look forward to watching more of your videos.
I like them 780x. I take a single sided copper board. Then drill a hole for a bolt then draw a circuit. Then dremmel out the Cooper to form lands. Add a pair of caps one on input. the other on out put. Then remount the 780x on board with a drop of silicone paste. #1 goes to input. # 3 goes to the output. (With a 0.1 UF cap ))for noise) #2goes to ground rail.( If i want a little boost) say a whole volt I add a pair of diodes to the #2 pin about 6.2 volts goes out from this rig over a 5 volt chip. Very cheep
How to know if the value of mosfet is leaky and good value.. In the digital.multimeter tnx
can i use a bigger capacitance capacitor on output than is written in datasheet?
Yes, but you shouldn't. A decouple capacitor DECOUPLES a device from the power supply. So you should place the larger capacitor close to your load, not the regulator.
nice video. in some schematic, I've seen electrolyte capacitor along with ceramic capacitor and or alone, at any or both of the input and output side.
PL explain it.
Large electrolytic respond to slow changes while smaller ceramics respond to faster changes.
If you forget the capacitor in your design, you can still solder at least ceramic smd chips between the tht leads of the to220 package.
Question...Can I series 2 Power regulators across a single power source to split the power?
As long they each step down the voltage by least 2 volts, yes. The dissipated power would be spread across them.
hi, thank you for the video, I have 10 volt AC that I want to convert to DC using a bridge rectifier; should I use a regulator too in my circuit ?
Without a smoothing capacitor and a regulator, you won’t have DC.
Is there another way of knowing the right decoupling capacitator without looking at the data sheet?
what regulator would you use if the input volt if HIGH like 50, 60, or 75 volts?
You would probably need a switching regulator.
Why are the coupling capacitors used...?
Does the ground of ic, input and output have to be same if I am using the ic in my circuit..? Pls. explain in details
They are decoupling capacitors, which are different from "coupling." I explain why starting at 4:52.
Yes, all grounds must be the same. Ground is a reference point.
what is the difference between a voltage regulator and a zener diode?
Voltage regulators actively (and accurately) regulate voltage. Zeners are passive, so they drift under various conditions. Watch: Voltage Dividers as Regulators ?! | AO #22
ruclips.net/video/-kEh0TYjYYE/видео.html
Yeah new vid!
Sir can we limit the output current of a voltage regulátor upto a particular value for ex 1.5A.
If yes How can it be achieved.
With an external circuit yes. Do a search for "LM317 Current Limiter."
Thankyou sir Got the idea :-)
Very nice. I want to make a solar mobile charger using this 7805. but I am facing some discharging issue. How can I solve it?
You probably want a switching regulator. Or at the very least, an LDO with an enable pin. Either way, not a circuit I can help with.
Hi there, could I connect many linear voltage regulators together so I can get a much higher amperage on the output? How would I adjust the calacitor requirement?
I want to run lots of 5.5W 12v led lights off a solar-charged battery array and there are cheap 12v x 1.5 amp regulators available. Would this be the easiest and cheapest way to do this?
+Matt Hunter You can't just wire regulators in parallel with each other. They will attempt to regulate each other.
There are techniques to isolate them, but generally that's not efficient. The best approach is to get a single supply that sufficient for the load.
This could mean, splitting the load up. Example, half the LEDs on one and the other half on the other.
Ah, I see.
They will be in pairs, might it be ok to have one regulator at each pair of lights? (11W total with the regulator supplying 12v at 1A)
That way the main wiring is unregulated but each module is safe
Thanks... What are the value of the capacitor for regulator 5v-12v and 24v for power supply and battery charger... I'm starting working it by watching RUclips... Make me confuse. God bless.
When I measure the voltage I get almost the input voltage or slightly (1 V) less than the input (16.5V), instead of 5V. Do I have to connect a load resistance first?
Regulators usually have a minimum load specification. It's the minimum current they need to regulate the output. If there is no load, there is nothing for the regulator to, well, regulate. If you're using a LM7805, it's minimum load is probably 5 milliamps. Add a 1 kohm resistor for testing.
Hello,
what about the output current ?
how do we determine it ?
these days I have been studying converters and regulators, like buck and boost, and I do not understand what the output current depends on
+Mohannad SMARTHERO The load determine the current drawn. The regulator's inductor and capacitor determine the current it can provide.
almost clear enough, I still need to make some tests, thanks alot
to do what you are doing should i study electronic engineer or a telecomunication engineer?
I don't know what you mean by "what you are doing". I have an Electrical Engineering degree.
Excellent explanation. One question please. We have been using hundreds of micro farad smoothing capacitors after the full wave rectifier while you are suggesting only 0.33 microfarad capacitor. Is this an extra capacitor along that hundreds of microfarad capacitor or we need just that 0.33?
Regulator itself only need a few hundred nanofarads. The large decoupling capacitors depends on the load and needs to be near the load, so that it *decouples* from the regulator.
That video is awesome :)) I like it!!! Thank you guys so much but I wonder what RJA stands for. Can someone help me ? :)))
Resistance. Junction (to) Ambient. What's the thermal resistance between the junction (the silicon) and outside air.
Hi dude please specify link for Fairchild 78×× regulator data sheet which u mentioned in video
+Shawnak Sawaikar Google “fairchild lm7805”
ok
Great video. In my project I am using many IC's. All powered via an LM7805. I currently have a large 220uF cap on the VI side and another 220uF electrolytic on VO plus a 0.1uF ceramic on the VO too. I've seen this many times in projects and to be honest, I just copied it. But it sounds like that is a bad idea. Any ideas why designs like that are popular? I guess people just keep copying them. Any harm in such a design?
Overall you're okay. 220uF on the input is fine. You're decoupling the regulator from the rest of the circuit. 220uF directly on the output might be a bit high. On an older linear like the 7805, it'll be fine. But it's better to put a small capacitance (1-10uF) on the output for filtering while putting the big caps near large loads, like a motor or LED strip.
1:07 actually I think the 555 timer is the most important IC
Can I get 5 volts out even if the input voltage is inconstant between 7 and 9 volts ?
Yes! That is the point of a regulator. If is constantly changing between 7 and 9 volts, you might need to add some more capacitance on the input to help smooth it out. Watch the output to see how much it varies, if at all.
"Good", very good 😉
I'm trying to add a battery to a snowmobile that never had one i installed a regulator rectifier it outputs 6.4vdc at idle and more as the rpm increases which is overcharging the battery ... what can I use to regulate the dc voltage to a maximum of 14.5vdc so I don't overcharge the battery ... any help is greatly appreciated
I have zero experience with this kind of system. But if the output voltage changes with RPM, it isn’t a regulator.
@@AddOhms thanks for the reply ... any idea what I can use to regulate the dc? Something like dc to dc that's adjustable? I just don't want it to go over 14.8vdc that's all ... thanks again 👍
Nice 555 kit. I want one so bad, but I'm too cheap!
perfect
Thanks, so how do one test if a voltage regulator is bad?
Measure the input and output voltage with a multimeter, while there is a load on the regulator. Unloaded regulators, like batteries, may not output the right voltage.
Need help. I am planning to use one to charging cellphone from my motorcycle. I am not an electronic guy & hence don't know which capacitors to use.
Thanks ..