Please study the calculation examples in the video description to better understand how to read the results of any calculations you make for capacitance :)
I love your tutorials but I don't understand your capacitance formula. Result say 15.090mF but you call it 15 thousand mF. Does higher capacitance mean more voltage drop?
Raks Electric; OK, first you have to find the peak voltage after rectification. You calculate that simply by multiplying the AC output voltage of the secondary of your power transformer by the square root of 2. That gives you the peak DC voltage output of the bridge rectifier, before adding any smoothing/filter capacitors to it. (A very close example to this video would be a secondary transformer voltage of 50V X 1.4142 = approximately 70.71VDC out of your rectifier bridge.) Then, *you* as a designer of your circuit, have to determine the "minimum acceptable voltage" that your circuit can safely or effectively operate from, which, depending on circuit design and type, can vary *significantly* , however, for *most* electronic items, if you stay within a 5-10% drop from the Peak DC output voltage of your rectifier then you should be fine. Your specific design *may* require tighter tolerances than that, but if so, that increases your required capacitance ( *and cost* ) quite significantly! So, just for an example that's again relatively close to this video for ease of comparison, let's say that in order for your circuit to work effectively and to perform at an optimum level it needs an absolute "minimum acceptable voltage" of 65 volts DC. If you do the math, that voltage would be within about -8% of the peak DC volts out of your rectifier, so that should be just fine in most cases. The *difference* between the peak voltage out of the rectifier and the "minimum acceptable operating voltage" for your circuit would then be the "acceptable voltage drop" that is used in the final equation for determining the required capacitance value. In this example it would be: 70.71 - 65 = 5.71V "acceptable voltage drop" Now comes the (slightly) confusing part; This video didn't explain the discrepancies in the *units* , and *that* is why the answer is not exactly what is shown, but rather off by a factor of 1000 in each case... The (correct) formula for calculating the required capacitance is, (should be); Circuit Current (IN AMPS) x Half Cycle Time (IN SECONDS) / Acceptable Voltage Drop (IN VOLTS) = Required Capacitance (IN FARADS) If you use the above formula with the above shown units then your answer will always be correct... Using the above example's first Voltage calculations, and assuming (again *for example only* ) that your circuit current is 10 Amps and you are in a location that uses 60Hz frequency of AC power, like in the USA, then the correct way to use the formula is as follows; (First calculate the last needed parameter to use in the final formula, which is the *Half Cycle* Time of a 60Hz line frequency, but calculate it in SECONDS, instead of mS, as is the error in the above video... This then equals 0.008333 Seconds.) (1/120th of a Second) Now finally put all of your (correct unit) numbers into the correct unit formula which I showed above and you get; 10 (AMPS) x 0.008333 (SECONDS) / 5.71 (VOLTS) = 0.0146 (FARADS) of required capacitance. (Approximately anyway, due to rounding of answer) Now, since 1 FARAD = 1,000,000 MicroFarads (or uF), then just multiply the above answer by 1,000,000 and you get the *correct* answer of 14,600 uF. In this example's case, I would just use a 15,000 uF capacitor for a filter capacitor, which is the next largest commonly available value above the "minimum required" 14,600 uF. The above example may seem complicated at first, but once you do it a few times with different values and for different electronic projects, you'll get the hang of it quickly. And if you always use the consistent (whole) unit formula above, and then just quickly convert your answer from Farads to MicroFarads (1/1,000,000th of a Farad), then you will *always* calculate the correct answer when doing this! FYI, the formula in this video gives answers in MILLIFARADS (or mF) (1/1000th of a Farad), NOT MICROFARADS, (or uF) (1/1,000,000th of a Farad)!... Simply because they are using MILLISECONDS (mS) (1/1000th of a Second), rather than full Seconds... Somewhere along the line, the units got switched or dropped, (i.e. "lost in translation"), in the formula shown in the video, from the original, correct formula which I gave above... Possibly because oftentimes mF (millifarads) is commonly mistaken for uF (microfarads), simply because of the letter "m"! Anyway, now you know the "rest of the story", LOL!... I hope this detailed explanation helps *someone* out there to better understand this at least, because knowing what is the correct size of capacitor to use to filter your AC-DC power supply is a VERY important part of proper electronic equipment design!
Accumulator1; I totally understand your confusion, however, you made the same exact (very common) mistake that this video makes, in confusing the units of mF (MILLIFARADS) and uF (MICROFARADS)... The answer actually IS 15mF, however, it is ALSO 15,000uF, because they are a ratio of 1:1000 ... The full, detailed explanation is below; (BTW, A Higher capacitance used for the filtering of a bridge rectifier actually results in LESS of a voltage drop, not more, and therefore a higher capacitance also results in a more stable final DC output!) Now comes the (slightly) confusing part; This video didn't explain the discrepancies in the *units* , and *that* is why the answer is not exactly what is shown, but rather off by a factor of 1000 in each case... The (correct) formula for calculating the required capacitance is, (should be); Circuit Current (IN AMPS) x Half Cycle Time (IN SECONDS) / Acceptable Voltage Drop (IN VOLTS) = Required Capacitance (IN FARADS) If you always use the above formula with the above shown FULL units then your answer will *always* be correct... Using this video's "Acceptable Voltage Drop" calculations for an example, and assuming (again *for example only* ) that your circuit current is also 10 Amps and you are in a location that uses 60Hz frequency of AC power, like in the USA, then the correct way to use the (correct unit) formula is as follows; (First calculate the last needed parameter to use in the final formula, which is the *Half Cycle* Time of a 60Hz line frequency, but calculate it in SECONDS, instead of mS, as is the error in the above video... This then equals approximately 0.0083 Seconds.) (1/120th of a Second) Now finally put all of your (correct unit) numbers into the correct unit formula which I showed above and you get; 10 (AMPS) x 0.0083 (SECONDS) / 5.5 (VOLTS) = 0.015091 (FARADS) of required capacitance. (Approximately anyway, due to rounding of numbers) Now, since 1 FARAD = 1,000,000 MICROFarads (or uF), then just multiply the above answer by 1,000,000 and you get the *correct* answer of 15,091 uF. In this example's case, I would just use a 15,000 uF capacitor for a filter capacitor, since it is so very close to the calculated value, and that value is the closest commonly available value. Plus, since most electrolytic type capacitors generally tend to measure slightly higher than stated anyway, especially when new, then you should be just fine! The above example may seem complicated at first, but once you do it a few times with different values and for different electronic projects, you'll get the hang of it quickly. And if you always use the consistent (whole) unit formula above, and then just quickly convert your answer from Farads to MicroFarads (1/1,000,000th of a Farad), then you will *always* calculate the correct answer when doing this! FYI, the formula in this video gives answers in MILLIFARADS (or mF) (1/1000th of a Farad), NOT MICROFARADS, (or uF) (1/1,000,000th of a Farad)!... Simply because they are using MILLISECONDS (mS) (1/1000th of a Second), rather than full Seconds... Somewhere along the line, the units got switched or dropped, (i.e. "lost in translation"), in the formula shown in the video, from the original, correct formula which I gave above... Possibly because oftentimes mF (millifarads) is/are quite commonly mistaken for uF (microfarads), simply because of the letter "m" being common between the two unit names! In addition, the "u" in uF isn't actually a "u" anyway, but instead it is only the closest resemblance on a common keyboard to the real unit measure, which is actually the Greek letter "mu", shown in lowercase, but to make matters even worse, that same Greek letter in Uppercase is also "M", and sometimes people state MILLIFarads as MF instead of the more proper mF!... This all results in *very much* confusion between the MICRO- and MILLI- prefixes of the FARAD capacitance unit!! (I see that mistake being made almost all the time, so it helps to understand the difference!) Anyway, now you know the "rest of the story", LOL!... I hope this detailed explanation helps you to better understand this, because knowing what is the correct size of capacitor to use to filter your AC-DC power supply is a VERY important part of proper electronic equipment design!
You are very good at explaining what can seem a complex subject. 50 years ago I was into electronics (valve amplifiers) it's been quite a struggle to bring myself up to date. I did try and tighten a connection with 240V on it whilst well earthed. Seems at 70 odd years old my heart is pretty sound. Good videos young fella me lad, greetings from the old country.
thank you. I've been trying to sort this aspect of AC-DC rectification for a number of days. YOURS was the first well explained, thorough description I've found. Thanks, again.. GeoD
Id like to agree with this persons statement, thank you for explaning this and walking us threw how to do it! Btw popping caps can be fun I got a good chuckle outta that
The forward voltage drop shown at 4:24 in your video (Vf = 1.1.V) is the forward drop per diode in the bridge. The positive and negative paths through the bridge each have 2 diodes in series. You need to make allowance for double the voltage drop i.e. 2.2 volts and consequently double the power dissipation. Selection of the "right" capacitor also requires consideration of the load current. If the ripple current rating of the capacitor is inadequate it will have a short life.
Thanks for posting this. It takes me back to basic electronics I used during my military service. Well thought out and explained. You have a new follower!
Excellent explanation and demonstration, I managed to follow every part of it, very clear and at a speed that someone like myself can follow. I will definitely watch more of your videos.
It is such a shame you decided to stop your videos. Giving that microwave transformer 'what for' brought a smile to my face. For gawds sake keep this bloke away from a power station. However I am about to do exactly the same to a microwave transformer. I need 40V so my wire choice in amps and insulation will be a bit tight. Perhaps you could add a comment as to whether you will do any new videos. I hope you do. Happy New Year from Pomland.
I learned a lot here. Great video! Thank you for including an example calculation for 60Hz too that was very helpful. Now to go find a huge capacitor and pray I don't wire it up backwards. :)
GREAT video! I learned a lot from it. You're video is the first I've come across that not only talks about choosing the right capacitor, but HOW to choose the correct capacitor. You do a great job in your explanation of things! Keep up the good work.
These are really interesting and well explained videos. Your arithmetic at the end fired my awkwardness a bit, multiply the result by 1000 to get the microfarad result. (Because we don't say the mili word with capacitors!)
Great video thanks, the only slight issue is that the formula states that it equals ųF but it actually equals mF. Though in your example you had already converted it (15000 vs 15)
@Nohr Tillman Aaaahhhh. You are correct!! I always forget about the milliFarrad due to it not being used as the other three (u, P, N) in reference to electrolytics or in reference to capacitors. And since i am unaware of a single instance where milli has been used in terms of capacitor. My bad, homie. Thanks for correcting me
This was great. I am ok with transforming and rectification etc but was never too sure about a good capacitance selection. Now I have it. Subscribed for good clear presentation of material. PS. Kiwis rock!
Very interesting ! The method of calculating the required capacitor is very clear and easy .. thank you so much I really enjoyed your video it was a wonderful morning :)
I am so pleased that I have found your channel. I am going to make a battery charger as I have been told that the new type solid-state chargers are not much good. I want a charger that will charge a tractor battery, so I am looking at 4-5 Amps output current. I can get a transformer from Jaycar, now I know what size rectifier and capacitor I need to get.
In my case adding a smoothing capacitor leads to an increase in power consumption from the grid (x3 times more). Why is this happening and what should be done to eliminate this effect?
From what I'm understanding, there's a drop in AC voltage on the way through but you still get a higher DC voltage at the end. The question I think you're wondering is do you multiply the initial AC voltage by 1.414 or do you multiply it after the forward drop? According to the video (at 3:37), it's 1.414 times the INPUT acv to get the dcv output. The loss of 1.1v on input of 50acv would be about 2%, so it's not that much of a loss even if we were to multiply the input voltage after the 1.1 voltage drop. I guess this is why it's important to size your rectifier correctly. If you pick one with a relatively large drop, it'll be inefficient and needlessly overheat your rectifier. Based on his choice, a drop of 2-3% is what you'd expect. If it's larger, you probably need a smaller rectifier. I think...
@@MichaelApproved I did some research since and I understand better. So yes the bridge converter will convert ac to dc. But let’s say a 230v ac is in fact a curb of 320v but the vrms is 230v. So after beeing dc it can be 50v but still the same it’s vrms and peak will be higher corresponding by X1.414. So it’s the capacitor which will make the vrms equal to the peak by blending thoses peaks. So yeah the increase is either the voltage after the capacitor or how you mesure between peak and vrms value. Hope it helps.
Can a full bridge rectifier be used as a choke in place of an inductor between a control board and a DC treadmill motor? The inductor that came with the treadmill had a bullet hole in it and was beyond repair. Also, don't know how to use a transformer as an inductor because I don't know what values would be needed. You probably have a video on inductors that I should watch. Cheers
Hello, I have an ATV with no battery, just pull start which outputs AC power and I want to run a 12 V DC fan for the radiator (no other powered accessories such as lights etc.). The stator has a lighting coil that outputs 150 watts. I cannot find the wattage of the fan but I did measure the resistance and got 3.8 ohms, so I believe the wattage is about 38 through calculation. The engine manual says the lighting coil produces 32V at 2000 rpm, 50V at 3000 rpm and 67V at 4000 rpm. The motor is rated at a peak rpm of 7200 (not sure if all of this info is needed). This is a retrofit so I have not added the voltage regulator yet but I assume it will bring the voltage to 12V? With that information, can you provide guidance of which rectifier and capacitor to use? I am somewhat electrically helpless, so any assistance would be appreciated. Thanks!
Hi a very explanatory video, its appreciated greatly. The question it brings to mind is, how did you decide on the minimum acceptable voltage and for a long service life how does this acceptable voltage effect the life of the capacitor. From the data sheet I only see the recommended ripple current and not ripple voltage.
Hello, I've got a specific problem that I just can't solve. I am trying to rectify an ac pover generated by my mopeds generator (rated for 12v 50w). I used a diode bridge (200v 15a with 1.1v drop) and got out only about 3v max. I even bought already made rectifier and got the same results. All the loads together sum up to 12v 39w (excluding a 10w brake light) Do you have any idea where all this voltage is going?
As someone who knows nothing about electronic components, what is the capacitor used for with the bridge rectifier. Is this called a "full wave" bridge rectifier when you add the capacitor or is that with a resistor added? I am trying to repair a set of LED christmas light string, which is 110V at .02 amps. There are 36 LEDs. The rectifier was burned out during a bad rainstorm and the plug got underwater. The LEDs are still good (I tested them). I can't get another rectifier (tried many places that sell christmas lights) and the place I bought them from recommended my to build one.. I was thinking a 150V 2amps rated but don't know if I need to add a capacitor and/or resistor. What components do you recommend I use? Thank you
at the end when talkin about the cap blowin up, u said "it adds a little drama to ur life, but makes for a poor power supply" ..i dont Need anymore drama in my life lol i have pLENty!
Excellent video & tutorial. I am in the process of replacing the Bridge Rectifier in a Daiwa PS-30XMII. When I removed the faulty BR it had a 14mm brown ceramic disc capacitor across the AC terminals. I can find nothing about this on the schematic. Is the capacitor of any real value in this situation or would you recommend fitting the new one without it please?
A full bridge rectifier is basically four hardwired diodes .... great piece of electronic hardware ... they commonly have a hole in the middle to allow mounting on a heatsink if you are going to push its limits ....
Why is your calculation on the calculator off by a factor of a thousand? Just a little confused because you used the basic unit for amps and multiplied it by the milli unit for seconds rather than the basic unit for seconds. But the formula still checks out with matching units, the final unit is microfarrads and using matching units, I get 0.015090farrads which is 15.09 millifarrads which is also just 15k microfarads. Apart from that, this video was very useful. I wanna make a diy circuit to power a car radio from an outlet for a sort of home made boom box type deal. The power supply is the hardest part, and I feel the diy transformer is gonna be the hard part of the hard part. Considering the radio is gonna power speakers at at least 15w rms to 4 outputs, including the other internal that need to be ran , I’m guessing between 5-7 amps to run the radio and thinking of designing a circuit that can handle 9 amps. Course, figuring out how to make a diy transformer to convert 120vac to 10vac at 9 amps is a whole other thing in itself. This would leave me with a 14.1v peak and assuming a 1.4v drop between the positive phase and negative phase diodes, I’m left with a 12.7v peak and should at the very least aim to stay above 12.3v since that’s about the minimum good voltage of car batteries with no alternator. But this isn’t accounting for the radios amplifiers efficiency. Anyways, using the formula, to run and rectify a circuit running at 12.7v peak at 9 amps while maintaining at least 12.3 volts……. 186,750uF…. So definitely gonna have to redesign this and probably run the radio closer to its max operating voltage to allow a larger voltage ripple because that’s a crap ton of capacitance. All this makes me realize just how much thought has to be considered in circuit designing. Really makes me respect the people who design motherboards and gpu’s, bet that stuff is a complete nightmare compared to this stuff.
Hi, I am replacing the rectifier on my car battery charger and it has a 22UF cap on it and the new one that I ordered tuned up and is only half the diameter and the two legs come out the same end as each other where as the old one comes out both ends, will this still be ok or should I look for another one, also does the capacitor connect positive to positive and negative to negative on the DC pins. Thanks.
Can someone explain? At 3:38 we are told that _"To calculate the volts after rectification multiply AC input voltage by 1.414... "_ . Why then does the calculation at 8:27 only use 70.5V for the capacitor calculation? Both the 100V (approx.) *and* the 70.5V are referred to as DC voltage "after rectification". Is this because the 100V is only a peak (as referenced in the RMS calculation), and the capacitor should be calculated based on the nominal 70.5V? Thanks for any explanation.
Thank you for that great explnation. I have ? if i have only normal diode & i have to make BR from it with Capacitor. if I want 18V & 15A or higher, from 220 transformer. How much should be the diode & capacitor? Thank u for answering if you can.
Good video. So the result of cap with not enough uf will not fully smooth out the current as well as a cap with the proper uf required by your calculation? Does a toroid core wrapped with copper wire, and connected to the cap, help smooth out the current even more than without it?
Thanks. So I can replace a broken bridge rectifier with a other one, that has a higher voltage and amp rating, without cousing problems to the circuits?
Would a 100volt 3,700 or 5,000 or 10,000 Farrad capacitor be dangerous ? I need 100volt because a bicycle bottle or hub dynamo can output up to around 100 volts ac on very fast down hill descents. I plan to use it to make a full wave bridge rectifier as a smoother for my vintage bicycle dynamo lights to stop the very annoying strobing that occurs with the AC & to hopefully enable the light to glow for a few minutes when stopped at traffic lights when the current from the dynamo is no longer flowing - the capacitor discharging into the load ( a 3 watt total of front & rear led bulbs). How long could I expect the lights to glow for before going out completely with these value capacitors please?
what is the ominal voltgage hard to beieve the voltage peaks at 100V - maybe a cheapuit or badly designed such caps are quite expensive, so I would limit the votgae - maybe use a power zener
How long could I expect the lights to glow for before going out completely with these value capacitors please? depends on the cap value, current and drop-out voltage you can google th cap dischrage formula but it is a bit nasty
Well presented thanks..I have one question regarding my DIY project/experiment..I'm trying to rectify the HV/HF output from the Secondary of my mini Slayer Exciter tesla coil and not sure about the type and the current rating of the rectifier I require..any input appreciated thanks
While you could purchase an ultra-fast recovery diode, the problem is the voltage. A quick browse online shows a mere 40kv or higher diode is in $$$$ range. Even though the humble slayer exciter is a baby tesla coil in the grand scheme of things. It's very capable of outputting over 40kv. I've never heard of anyone rectifying such a high voltage/frequency before.
So I guess my questioning would be can you use multiple compasitors to reach the compasitance you require? Like idk if that would even work in series or parallel or dose it have to be one compassitor i guess depending on the application?
How do i calculate the capacitor value if the ac source is from a bicycle dynamo? Any way to make an estimate? Also, does the ready-made bridge rectifier comes with capacitor??
hello i started making a toroidal power supply ive seen the videos people plugging in the toroid to find neg and pos current before hooking up the capasitor i tried with mine it immediatly blew my breaker any suggewstions would be appreciated
Hello I have a magnetic drill base that does not work, it uses a bridged rectifier . AC TO DC how do I find out what size the magnet needs? and or how to test if rectifier is bad not knowing the size of it and drop....I believe the label of magnetic base says 300v and or 30v its hard to read and the rectifier has no markings besides AC markings, any help would be appreciated
Thanks for the video, I need a 60 micro farad cap by the calculation and I have a 360v 60mf cap from a photo machine flash circuit. But I am not sure about using it, Is it safe to use it? It is above the voltage I need (16v) but still don't feel safe :)
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Please study the calculation examples in the video description to better understand how to read the results of any calculations you make for capacitance :)
Schematix Hi there I was wondering if how you find out the minimal voltage drop and the peak voltage after rectification.
thanks
I love your tutorials but I don't understand your capacitance formula. Result say 15.090mF but you call it 15 thousand mF. Does higher capacitance mean more voltage drop?
Raks Electric; OK, first you have to find the peak voltage after rectification. You calculate that simply by multiplying the AC output voltage of the secondary of your power transformer by the square root of 2. That gives you the peak DC voltage output of the bridge rectifier, before adding any smoothing/filter capacitors to it. (A very close example to this video would be a secondary transformer voltage of 50V X 1.4142 = approximately 70.71VDC out of your rectifier bridge.)
Then, *you* as a designer of your circuit, have to determine the "minimum acceptable voltage" that your circuit can safely or effectively operate from, which, depending on circuit design and type, can vary *significantly* , however, for *most* electronic items, if you stay within a 5-10% drop from the Peak DC output voltage of your rectifier then you should be fine. Your specific design *may* require tighter tolerances than that, but if so, that increases your required capacitance ( *and cost* ) quite significantly!
So, just for an example that's again relatively close to this video for ease of comparison, let's say that in order for your circuit to work effectively and to perform at an optimum level it needs an absolute "minimum acceptable voltage" of 65 volts DC. If you do the math, that voltage would be within about -8% of the peak DC volts out of your rectifier, so that should be just fine in most cases.
The *difference* between the peak voltage out of the rectifier and the "minimum acceptable operating voltage" for your circuit would then be the "acceptable voltage drop" that is used in the final equation for determining the required capacitance value. In this example it would be:
70.71 - 65 = 5.71V "acceptable voltage drop"
Now comes the (slightly) confusing part; This video didn't explain the discrepancies in the *units* , and *that* is why the answer is not exactly what is shown, but rather off by a factor of 1000 in each case... The (correct) formula for calculating the required capacitance is, (should be);
Circuit Current (IN AMPS) x Half Cycle Time (IN SECONDS) / Acceptable Voltage Drop (IN VOLTS) = Required Capacitance (IN FARADS)
If you use the above formula with the above shown units then your answer will always be correct... Using the above example's first Voltage calculations, and assuming (again *for example only* ) that your circuit current is 10 Amps and you are in a location that uses 60Hz frequency of AC power, like in the USA, then the correct way to use the formula is as follows;
(First calculate the last needed parameter to use in the final formula, which is the *Half Cycle* Time of a 60Hz line frequency, but calculate it in SECONDS, instead of mS, as is the error in the above video... This then equals 0.008333 Seconds.) (1/120th of a Second)
Now finally put all of your (correct unit) numbers into the correct unit formula which I showed above and you get;
10 (AMPS) x 0.008333 (SECONDS) / 5.71 (VOLTS) = 0.0146 (FARADS) of required capacitance. (Approximately anyway, due to rounding of answer)
Now, since 1 FARAD = 1,000,000 MicroFarads (or uF), then just multiply the above answer by 1,000,000 and you get the *correct* answer of 14,600 uF.
In this example's case, I would just use a 15,000 uF capacitor for a filter capacitor, which is the next largest commonly available value above the "minimum required" 14,600 uF.
The above example may seem complicated at first, but once you do it a few times with different values and for different electronic projects, you'll get the hang of it quickly. And if you always use the consistent (whole) unit formula above, and then just quickly convert your answer from Farads to MicroFarads (1/1,000,000th of a Farad), then you will *always* calculate the correct answer when doing this!
FYI, the formula in this video gives answers in MILLIFARADS (or mF) (1/1000th of a Farad), NOT MICROFARADS, (or uF) (1/1,000,000th of a Farad)!... Simply because they are using MILLISECONDS (mS) (1/1000th of a Second), rather than full Seconds... Somewhere along the line, the units got switched or dropped, (i.e. "lost in translation"), in the formula shown in the video, from the original, correct formula which I gave above... Possibly because oftentimes mF (millifarads) is commonly mistaken for uF (microfarads), simply because of the letter "m"!
Anyway, now you know the "rest of the story", LOL!... I hope this detailed explanation helps *someone* out there to better understand this at least, because knowing what is the correct size of capacitor to use to filter your AC-DC power supply is a VERY important part of proper electronic equipment design!
Accumulator1; I totally understand your confusion, however, you made the same exact (very common) mistake that this video makes, in confusing the units of mF (MILLIFARADS) and uF (MICROFARADS)... The answer actually IS 15mF, however, it is ALSO 15,000uF, because they are a ratio of 1:1000 ... The full, detailed explanation is below;
(BTW, A Higher capacitance used for the filtering of a bridge rectifier actually results in LESS of a voltage drop, not more, and therefore a higher capacitance also results in a more stable final DC output!)
Now comes the (slightly) confusing part; This video didn't explain the discrepancies in the *units* , and *that* is why the answer is not exactly what is shown, but rather off by a factor of 1000 in each case... The (correct) formula for calculating the required capacitance is, (should be);
Circuit Current (IN AMPS) x Half Cycle Time (IN SECONDS) / Acceptable Voltage Drop (IN VOLTS) = Required Capacitance (IN FARADS)
If you always use the above formula with the above shown FULL units then your answer will *always* be correct... Using this video's "Acceptable Voltage Drop" calculations for an example, and assuming (again *for example only* ) that your circuit current is also 10 Amps and you are in a location that uses 60Hz frequency of AC power, like in the USA, then the correct way to use the (correct unit) formula is as follows;
(First calculate the last needed parameter to use in the final formula, which is the *Half Cycle* Time of a 60Hz line frequency, but calculate it in SECONDS, instead of mS, as is the error in the above video... This then equals approximately 0.0083 Seconds.) (1/120th of a Second)
Now finally put all of your (correct unit) numbers into the correct unit formula which I showed above and you get;
10 (AMPS) x 0.0083 (SECONDS) / 5.5 (VOLTS) = 0.015091 (FARADS) of required capacitance. (Approximately anyway, due to rounding of numbers)
Now, since 1 FARAD = 1,000,000 MICROFarads (or uF), then just multiply the above answer by 1,000,000 and you get the *correct* answer of 15,091 uF.
In this example's case, I would just use a 15,000 uF capacitor for a filter capacitor, since it is so very close to the calculated value, and that value is the closest commonly available value. Plus, since most electrolytic type capacitors generally tend to measure slightly higher than stated anyway, especially when new, then you should be just fine!
The above example may seem complicated at first, but once you do it a few times with different values and for different electronic projects, you'll get the hang of it quickly. And if you always use the consistent (whole) unit formula above, and then just quickly convert your answer from Farads to MicroFarads (1/1,000,000th of a Farad), then you will *always* calculate the correct answer when doing this!
FYI, the formula in this video gives answers in MILLIFARADS (or mF) (1/1000th of a Farad), NOT MICROFARADS, (or uF) (1/1,000,000th of a Farad)!... Simply because they are using MILLISECONDS (mS) (1/1000th of a Second), rather than full Seconds... Somewhere along the line, the units got switched or dropped, (i.e. "lost in translation"), in the formula shown in the video, from the original, correct formula which I gave above... Possibly because oftentimes mF (millifarads) is/are quite commonly mistaken for uF (microfarads), simply because of the letter "m" being common between the two unit names! In addition, the "u" in uF isn't actually a "u" anyway, but instead it is only the closest resemblance on a common keyboard to the real unit measure, which is actually the Greek letter "mu", shown in lowercase, but to make matters even worse, that same Greek letter in Uppercase is also "M", and sometimes people state MILLIFarads as MF instead of the more proper mF!... This all results in *very much* confusion between the MICRO- and MILLI- prefixes of the FARAD capacitance unit!! (I see that mistake being made almost all the time, so it helps to understand the difference!)
Anyway, now you know the "rest of the story", LOL!... I hope this detailed explanation helps you to better understand this, because knowing what is the correct size of capacitor to use to filter your AC-DC power supply is a VERY important part of proper electronic equipment design!
JoeJ8282 thankyou very much now I understand
You are very good at explaining what can seem a complex subject. 50 years ago I was into electronics (valve amplifiers) it's been quite a struggle to bring myself up to date. I did try and tighten a connection with 240V on it whilst well earthed. Seems at 70 odd years old my heart is pretty sound. Good videos young fella me lad, greetings from the old country.
thank you. I've been trying to sort this aspect of AC-DC rectification for a number of days. YOURS was the first well explained, thorough description I've found.
Thanks, again..
GeoD
Id like to agree with this persons statement, thank you for explaning this and walking us threw how to do it! Btw popping caps can be fun I got a good chuckle outta that
I have always wondered how the capacitor value was calculated, a clear and concise explanation.
Thank you for the explanation. You just answered all my questions I had about the topic, 7 years before those questions even came up in me.
Thank you. Best explanation I have yet come across on YT!
The forward voltage drop shown at 4:24 in your video (Vf = 1.1.V) is the forward drop per diode in the bridge. The positive and negative paths through the bridge each have 2 diodes in series. You need to make allowance for double the voltage drop i.e. 2.2 volts and consequently double the power dissipation. Selection of the "right" capacitor also requires consideration of the load current. If the ripple current rating of the capacitor is inadequate it will have a short life.
Thanks for posting this. It takes me back to basic electronics I used during my military service. Well thought out and explained. You have a new follower!
Thanks kindly for your support ;)
Excellent explanation and demonstration, I managed to follow every part of it, very clear and at a speed that someone like myself can follow. I will definitely watch more of your videos.
It is such a shame you decided to stop your videos. Giving that microwave transformer 'what for' brought a smile to my face. For gawds sake keep this bloke away from a power station. However I am about to do exactly the same to a microwave transformer. I need 40V so my wire choice in amps and insulation will be a bit tight. Perhaps you could add a comment as to whether you will do any new videos. I hope you do. Happy New Year from Pomland.
very interesting and well descriped I am from Malta, and I really enjoy your lessons Thanks for your time
I learned a lot here. Great video! Thank you for including an example calculation for 60Hz too that was very helpful. Now to go find a huge capacitor and pray I don't wire it up backwards. :)
Cool I needed a refresher course on rectification and this did the Job. especially about how to determine capacitance!
Great job I understand more now than I ever have
I really appreciate that you are sharing your experience worth us
GREAT video! I learned a lot from it. You're video is the first I've come across that not only talks about choosing the right capacitor, but HOW to choose the correct capacitor. You do a great job in your explanation of things! Keep up the good work.
Thank you that was exactly the info I needed. Very informative, I am subscribed. Keep up the good work
Excellent explanation and demonstration
The best explanation out there on this topic! Thank you!
These are really interesting and well explained videos. Your arithmetic at the end fired my awkwardness a bit, multiply the result by 1000 to get the microfarad result. (Because we don't say the mili word with capacitors!)
yes the cycle time input in the formula is in ms and the capacitance im mF. I specially enjoyed the definitions of a poor power supply.
Your information was a BIG help to me. Thanks
I really like your content, very informative and to the point, really cool to see a fellow kiwi sharing his knowledge! :)
Thanks mate :)
Old info, bin there, done that 25 years ago.
These vids are the king keep them coming teacher many thanks.
Short, simple and well explained
You have a wonderful way of explaining
Great video thanks, the only slight issue is that the formula states that it equals ųF but it actually equals mF. Though in your example you had already converted it (15000 vs 15)
Nice one, I just made a comment on this too haha
uF (microfarrad) IS mF (microfarrad).
They represent the same thing.
They are the same thing.
@@googleedwardbernays6455
uF is microFarad (x10-6)
mF is milliFarad (x10-3)
@Nohr Tillman
Aaaahhhh. You are correct!! I always forget about the milliFarrad due to it not being used as the other three (u, P, N) in reference to electrolytics or in reference to capacitors. And since i am unaware of a single instance where milli has been used in terms of capacitor. My bad, homie. Thanks for correcting me
This was great. I am ok with transforming and rectification etc but was never too sure about a good capacitance selection. Now I have it. Subscribed for good clear presentation of material.
PS. Kiwis rock!
Thanks for your videos Schematix, they are Excellent.
Very interesting ! The method of calculating the required capacitor is very clear and easy .. thank you so much I really enjoyed your video it was a wonderful morning :)
Great video. I also appreciate your humor.
You answered so many of my questions but show us what ur wiring up for ur example so I can see a finished setup thanks keep making videos!!!
perfect,, this is exactly I have been looking for .. you do really nice job. thanks !
This is the stuff why i subbed to this channel, good for people like me who have to start from the beginning. :-)
This was so clear! Thank you! Thumbs up and suscribed!
Thank you sir. I was planning to build myself an amplifier PSU this video helped me a lot :)
This was so helpful. I went down to subscribe, but saw i already was. Rad
Very easy to understand,thank you 👍
Great videos and very well explained, cheers mate
Thank you this really helped me understand the calculations.
Great job all around. Quality and content.
Thank you so much i learn allot with this video.
I am so pleased that I have found your channel.
I am going to make a battery charger as I have been told that the new type solid-state chargers are not much good.
I want a charger that will charge a tractor battery, so I am looking at 4-5 Amps output current.
I can get a transformer from Jaycar, now I know what size rectifier and capacitor I need to get.
Thank You for this video, well done.
Your videos are great! You've got yourself a subscriber
Thanks ;)
You've made my day ;)
Hi Schematix, hope you're doing well! I've enjoyed the couple of videos you've posted on transformers and other power supply components.
In my case adding a smoothing capacitor leads to an increase in power consumption from the grid (x3 times more). Why is this happening and what should be done to eliminate this effect?
Thanks for the explanation. I don't understand frequency, farads etc.
Still very engrossing tutorial.👍🏻
Awesome explanation!!
By any chance have you done a full video of DC power supply using transformer and capacitors? Great video by the way. Nicely done!
liked and enjoyed .. thank you for sharing.
Great video great teacher you are
Very informative. Thanks learned a lot on transformers and rectifiers.
Great video, thank you for the calculations
I'm confused, you are saying the voltage increase by 1.414 and later you are saying it drops by 1.1 ... so it increases or it drops ? thanks
From what I'm understanding, there's a drop in AC voltage on the way through but you still get a higher DC voltage at the end.
The question I think you're wondering is do you multiply the initial AC voltage by 1.414 or do you multiply it after the forward drop?
According to the video (at 3:37), it's 1.414 times the INPUT acv to get the dcv output.
The loss of 1.1v on input of 50acv would be about 2%, so it's not that much of a loss even if we were to multiply the input voltage after the 1.1 voltage drop.
I guess this is why it's important to size your rectifier correctly. If you pick one with a relatively large drop, it'll be inefficient and needlessly overheat your rectifier.
Based on his choice, a drop of 2-3% is what you'd expect. If it's larger, you probably need a smaller rectifier.
I think...
@@MichaelApproved I did some research since and I understand better. So yes the bridge converter will convert ac to dc. But let’s say a 230v ac is in fact a curb of 320v but the vrms is 230v. So after beeing dc it can be 50v but still the same it’s vrms and peak will be higher corresponding by X1.414. So it’s the capacitor which will make the vrms equal to the peak by blending thoses peaks. So yeah the increase is either the voltage after the capacitor or how you mesure between peak and vrms value. Hope it helps.
Thank you , really helpful
Excellent video!! Thanks very much
God bless u, thanks for a very nice job
Great video!
Can a full bridge rectifier be used as a choke in place of an inductor between a control board and a DC treadmill motor? The inductor that came with the treadmill had a bullet hole in it and was beyond repair. Also, don't know how to use a transformer as an inductor because I don't know what values would be needed. You probably have a video on inductors that I should watch. Cheers
Hello, I have an ATV with no battery, just pull start which outputs AC power and I want to run a 12 V DC fan for the radiator (no other powered accessories such as lights etc.). The stator has a lighting coil that outputs 150 watts. I cannot find the wattage of the fan but I did measure the resistance and got 3.8 ohms, so I believe the wattage is about 38 through calculation. The engine manual says the lighting coil produces 32V at 2000 rpm, 50V at 3000 rpm and 67V at 4000 rpm. The motor is rated at a peak rpm of 7200 (not sure if all of this info is needed). This is a retrofit so I have not added the voltage regulator yet but I assume it will bring the voltage to 12V? With that information, can you provide guidance of which rectifier and capacitor to use? I am somewhat electrically helpless, so any assistance would be appreciated. Thanks!
Hi, any advice on the brand to choose, there are so many ! Thank you
Hi a very explanatory video, its appreciated greatly.
The question it brings to mind is, how did you decide on the minimum acceptable voltage and for a long service life how does this acceptable voltage effect the life of the capacitor. From the data sheet I only see the recommended ripple current and not ripple voltage.
Hello, I've got a specific problem that I just can't solve. I am trying to rectify an ac pover generated by my mopeds generator (rated for 12v 50w). I used a diode bridge (200v 15a with 1.1v drop) and got out only about 3v max. I even bought already made rectifier and got the same results. All the loads together sum up to 12v 39w (excluding a 10w brake light) Do you have any idea where all this voltage is going?
i want more videos on your channel, related to electrical engineering.
As someone who knows nothing about electronic components, what is the capacitor used for with the bridge rectifier. Is this called a "full wave" bridge rectifier when you add the capacitor or is that with a resistor added? I am trying to repair a set of LED christmas light string, which is 110V at .02 amps. There are 36 LEDs. The rectifier was burned out during a bad rainstorm and the plug got underwater. The LEDs are still good (I tested them). I can't get another rectifier (tried many places that sell christmas lights) and the place I bought them from recommended my to build one.. I was thinking a 150V 2amps rated but don't know if I need to add a capacitor and/or resistor. What components do you recommend I use? Thank you
at the end when talkin about the cap blowin up, u said "it adds a little drama to ur life, but makes for a poor power supply" ..i dont Need anymore drama in my life lol i have pLENty!
Excellent video & tutorial. I am in the process of replacing the Bridge Rectifier in a Daiwa PS-30XMII. When I removed the faulty BR it had a 14mm brown ceramic disc capacitor across the AC terminals. I can find nothing about this on the schematic. Is the capacitor of any real value in this situation or would you recommend
fitting the new one without it please?
are you sure its cap....could be a MOV
such a cap can reduce line noise/spikes
at 5:57 bridge generate 2 x VF or 33 Watts . great vid
thank you very much for making the film
Very useful.....thanks mate!
A full bridge rectifier is basically four hardwired diodes .... great piece of electronic hardware ... they commonly have a hole in the middle to allow mounting on a heatsink if you are going to push its limits ....
Why is your calculation on the calculator off by a factor of a thousand? Just a little confused because you used the basic unit for amps and multiplied it by the milli unit for seconds rather than the basic unit for seconds.
But the formula still checks out with matching units, the final unit is microfarrads and using matching units, I get 0.015090farrads which is 15.09 millifarrads which is also just 15k microfarads.
Apart from that, this video was very useful. I wanna make a diy circuit to power a car radio from an outlet for a sort of home made boom box type deal. The power supply is the hardest part, and I feel the diy transformer is gonna be the hard part of the hard part.
Considering the radio is gonna power speakers at at least 15w rms to 4 outputs, including the other internal that need to be ran , I’m guessing between 5-7 amps to run the radio and thinking of designing a circuit that can handle 9 amps.
Course, figuring out how to make a diy transformer to convert 120vac to 10vac at 9 amps is a whole other thing in itself.
This would leave me with a 14.1v peak and assuming a 1.4v drop between the positive phase and negative phase diodes, I’m left with a 12.7v peak and should at the very least aim to stay above 12.3v since that’s about the minimum good voltage of car batteries with no alternator. But this isn’t accounting for the radios amplifiers efficiency.
Anyways, using the formula, to run and rectify a circuit running at 12.7v peak at 9 amps while maintaining at least 12.3 volts……. 186,750uF…. So definitely gonna have to redesign this and probably run the radio closer to its max operating voltage to allow a larger voltage ripple because that’s a crap ton of capacitance.
All this makes me realize just how much thought has to be considered in circuit designing. Really makes me respect the people who design motherboards and gpu’s, bet that stuff is a complete nightmare compared to this stuff.
Hi, I am replacing the rectifier on my car battery charger and it has a 22UF cap on it and the new one that I ordered tuned up and is only half the diameter and the two legs come out the same end as each other where as the old one comes out both ends, will this still be ok or should I look for another one, also does the capacitor connect positive to positive and negative to negative on the DC pins. Thanks.
Great video. To the point and well organized. Well done. Count me in as a subscriber.
Can you build a simple power supply for testing a inverter compressor. Where it is not known if the compressor or inverter or both are bad.
Can someone explain? At 3:38 we are told that _"To calculate the volts after rectification multiply AC input voltage by 1.414... "_ . Why then does the calculation at 8:27 only use 70.5V for the capacitor calculation? Both the 100V (approx.) *and* the 70.5V are referred to as DC voltage "after rectification". Is this because the 100V is only a peak (as referenced in the RMS calculation), and the capacitor should be calculated based on the nominal 70.5V? Thanks for any explanation.
Perfect, thanks.
Thank you for that great explnation. I have ? if i have only normal diode & i have to make BR from it with Capacitor. if I want 18V & 15A or higher, from 220 transformer. How much should be the diode & capacitor? Thank u for answering if you can.
Thanks man...🙏🙏
Good video. So the result of cap with not enough uf will not fully smooth out the current as well as a cap with the proper uf required by your calculation? Does a toroid core wrapped with copper wire, and connected to the cap, help smooth out the current even more than without it?
Interesting, very well explained
:)
Awesome video!!!
If I'm hooking a 200 Volts 4 Amp rectifier to a wall plug. Does the rectifier only draws 4 amps from the socket or is there a flow of 16 amps then?
Very useful, thanks. Subbed.
In the datasheet, there somewhere written "half wave", so does it mean I'm gonna only get half the signal using this diode?
no
Thanks. So I can replace a broken bridge rectifier with a other one, that has a higher voltage and amp rating, without cousing problems to the circuits?
yes
I wanted to know when to use a Zener Diode and where to put in the set-up. Please let me know.
Zener diode is used when you need a specific vpltage , you now get a zener diode of dat rating connect as required
Thank you sir...!!!!
How do you calculate the 'half-cycle time'?
Creative video, thanks :)
intuitive, so if I want 50amps and 16 volts what type and how many capacitors would I need?
Nice vid series thanks.
Would a 100volt 3,700 or 5,000 or 10,000 Farrad capacitor be dangerous ? I need 100volt because a bicycle bottle or hub dynamo can output up to around 100 volts ac on very fast down hill descents. I plan to use it to make a full wave bridge rectifier as a smoother for my vintage bicycle dynamo lights to stop the very annoying strobing that occurs with the AC & to hopefully enable the light to glow for a few minutes when stopped at traffic lights when the current from the dynamo is no longer flowing - the capacitor discharging into the load ( a 3 watt total of front & rear led bulbs). How long could I expect the lights to glow for before going out completely with these value capacitors please?
what is the ominal voltgage
hard to beieve the voltage peaks at 100V - maybe a cheapuit or badly designed
such caps are quite expensive, so I would limit the votgae - maybe use a power zener
How long could I expect the lights to glow for before going out completely with these value capacitors please?
depends on the cap value, current and drop-out voltage
you can google th cap dischrage formula but it is a bit nasty
Well presented thanks..I have one question regarding my DIY project/experiment..I'm trying to rectify the HV/HF output from the Secondary of my mini Slayer Exciter tesla coil and not sure about the type and the current rating of the rectifier I require..any input appreciated thanks
While you could purchase an ultra-fast recovery diode, the problem is the voltage. A quick browse online shows a mere 40kv or higher diode is in $$$$ range. Even though the humble slayer exciter is a baby tesla coil in the grand scheme of things. It's very capable of outputting over 40kv. I've never heard of anyone rectifying such a high voltage/frequency before.
thanks
Hey raydan18, does your project works? I am also trying to rectify a HV HF voltage with f=49khz. May I know what are the specs of ur rectifier?
So I guess my questioning would be can you use multiple compasitors to reach the compasitance you require? Like idk if that would even work in series or parallel or dose it have to be one compassitor i guess depending on the application?
How do i calculate the capacitor value if the ac source is from a bicycle dynamo? Any way to make an estimate? Also, does the ready-made bridge rectifier comes with capacitor??
hello i started making a toroidal power supply ive seen the videos people plugging in the toroid to find neg and pos current before hooking up the capasitor i tried with mine it immediatly blew my breaker any suggewstions would be appreciated
Hello I have a magnetic drill base that does not work, it uses a bridged rectifier . AC TO DC how do I find out what size the magnet needs? and or how to test if rectifier is bad not knowing the size of it and drop....I believe the label of magnetic base says 300v and or 30v its hard to read and the rectifier has no markings besides AC markings, any help would be appreciated
Thanks for the video, I need a 60 micro farad cap by the calculation and I have a 360v 60mf cap from a photo machine flash circuit. But I am not sure about using it, Is it safe to use it? It is above the voltage I need (16v) but still don't feel safe :)
higher WVDC is fine
Why choose electrolytic capacitors vs. say ceramic or plate or a coil capacitor?