Hi everyone,
My question is one that isn't about inductors, but CHOKES, specifically inductors used for blocking the passage of high-frequency signals into/from different circuits. Those of you who know exactly what I'm talking about will probably say "Say no more", à la Monty Python. So, my question about chokes is this: If I wanted to make my own choke for power supply purposes, specifically preventing... I'll come back to this... As I'm writing this I realize just now that I am unsure of WHAT exactly is being blocked in what direction. Anyway, let's suppose it's the 60Hz from the AC line, which is coming from the transformer. I'm not sure how to decide how much inductance I need to have, but I know it has something to do with the impedance of the power supply circuit itself, but that depends on the load that it's supplying, right? I believe there's an actual mathematical derivative function (I could be talking up my father Jack here)that states that the current drawn by the circuit relates to what inductance can be chosen, or something to do with current... I'm not making much sense here, but IF I tell you all that my load will draw 2 amps, what kind of choke do I need to make to cut out the AC? To what degree you may ask : well, I'm not sure, I guess that in itself depends on how big I can allow this inductor to be... About 3/8" diameter by one inch long, or so?
Now, earlier I said, " specifically preventing... I'll come back to this... As I'm writing this I realize just now that I am unsure of WHAT exactly is being blocked in what direction."
In my application,. which is a power supply for a tape deck that I'm building, we all know that the bias circuit oscillates at very high (not VHF, I'm just using the term casually) frequencies, in the order of 80 to 150kHz, typically. So, I may be wanting to prevent the leakage of this frequency, however small it may be, back into the power supply and muck things iup in there, I'm not sure. Is that possible, would that risk happening? I am concerned about creating. resonant circuit by putting the choke in an L-type circuit next to the final filter cap... but I realize that I'm going to put the same types of chokes on both amplifier cards, and that would also complete this resonant circuit...
Am I overthinking this? your thoughts are appreciated. I wish I had a schematic, but I do not currently have one. Typical transformer, linear, transistor-Zener diode regulated topology.
Thank you all for taking the time to read my mini novel!
My question is one that isn't about inductors, but CHOKES, specifically inductors used for blocking the passage of high-frequency signals into/from different circuits. Those of you who know exactly what I'm talking about will probably say "Say no more", à la Monty Python. So, my question about chokes is this: If I wanted to make my own choke for power supply purposes, specifically preventing... I'll come back to this... As I'm writing this I realize just now that I am unsure of WHAT exactly is being blocked in what direction. Anyway, let's suppose it's the 60Hz from the AC line, which is coming from the transformer. I'm not sure how to decide how much inductance I need to have, but I know it has something to do with the impedance of the power supply circuit itself, but that depends on the load that it's supplying, right? I believe there's an actual mathematical derivative function (I could be talking up my father Jack here)that states that the current drawn by the circuit relates to what inductance can be chosen, or something to do with current... I'm not making much sense here, but IF I tell you all that my load will draw 2 amps, what kind of choke do I need to make to cut out the AC? To what degree you may ask : well, I'm not sure, I guess that in itself depends on how big I can allow this inductor to be... About 3/8" diameter by one inch long, or so?
Now, earlier I said, " specifically preventing... I'll come back to this... As I'm writing this I realize just now that I am unsure of WHAT exactly is being blocked in what direction."
In my application,. which is a power supply for a tape deck that I'm building, we all know that the bias circuit oscillates at very high (not VHF, I'm just using the term casually) frequencies, in the order of 80 to 150kHz, typically. So, I may be wanting to prevent the leakage of this frequency, however small it may be, back into the power supply and muck things iup in there, I'm not sure. Is that possible, would that risk happening? I am concerned about creating. resonant circuit by putting the choke in an L-type circuit next to the final filter cap... but I realize that I'm going to put the same types of chokes on both amplifier cards, and that would also complete this resonant circuit...
Am I overthinking this? your thoughts are appreciated. I wish I had a schematic, but I do not currently have one. Typical transformer, linear, transistor-Zener diode regulated topology.
Thank you all for taking the time to read my mini novel!
There are books on transformer and inductor design. A quick google search turned up this archive: https://dl.icdst.org/pdfs/files/ad7821099d2d926cbb61105d36cf751d.pdf
Besides the usual idealized physics equations for induced voltage and or inductive reactance, etc., you need to know about core materials, self-resonance, hysteresis, etc.
Much of the rest of what you are asking about is given by Kirchhoff's laws.
So maybe you should start by telling us how much you know about electronics and math type stuff? Also, what is the exact application you have in mind, including a complete schematic? Then it may be possible to get better focused on what you would need.
Besides the usual idealized physics equations for induced voltage and or inductive reactance, etc., you need to know about core materials, self-resonance, hysteresis, etc.
Much of the rest of what you are asking about is given by Kirchhoff's laws.
So maybe you should start by telling us how much you know about electronics and math type stuff? Also, what is the exact application you have in mind, including a complete schematic? Then it may be possible to get better focused on what you would need.
Perhaps also look at example tape deck schematics to appreciate how the erase signal is generated and transferred to the erase head. Older decks with valves appear to just use a simple RC filter from the main B+ to power the oscillator. Erase signal could pass back through the B+ feed into audio circuits, but similarly could couple over to audio signal wiring along the whole path from oscillator through to erase head.
I'd suggest you try and measure the erase signal using a scope, to confirm its frequency and levels in various sections of the deck. Then I'd suggest you try and measure what level couples over to your audio signal - if the erase frequency is under say 90kHz, then using a soundcard and software with 96kHz bandwidth would provide much better discrimination than a scope.
After doing all that, you may be in a far better position to support your premise of that signal 'mucking things up'. You also need to appreciate that so much of the recording industry used tape-decks for the highest quality of recording and reproduction, so any thoughts of your sound quality being mucked up may not exist, depending on your deck and how technically adept you are at measuring such artifacts.
I'd suggest you try and measure the erase signal using a scope, to confirm its frequency and levels in various sections of the deck. Then I'd suggest you try and measure what level couples over to your audio signal - if the erase frequency is under say 90kHz, then using a soundcard and software with 96kHz bandwidth would provide much better discrimination than a scope.
After doing all that, you may be in a far better position to support your premise of that signal 'mucking things up'. You also need to appreciate that so much of the recording industry used tape-decks for the highest quality of recording and reproduction, so any thoughts of your sound quality being mucked up may not exist, depending on your deck and how technically adept you are at measuring such artifacts.
Thank you for your replies, although I feel that maybe I wasn't exactly understood. I was hoping for a "quick-and-easy" answer in the sorts of :use this equation to calculate (whatever parameter) in this situation, or "the rule of thumb is (whatever that may be in this situation). However, I blame that on me because I did not explain in full detail exactly what I am doing. In any case, if I reformulate my question as : Generally, what value of inductance is used to filter out 60Hz before hitting the bridge rectifier (full wave if that makes any difference, I'm kind of thinking it does) for a value of ripple no greater than (ex -60dBc, or less than say, I don't know, 5mV p-p).
The experience I have in electronics is superior to my math skills, I don't do calculus or derivatives for anything, I stray away from it because generally I have been taught with methods that require only linear and simple arithmetic. I am an electronics technologist, versed in analog, digital and Radio Frequency, for the past 25 years or more.
I cannot measure anything in the deck because it is still in the design phase. Nothing fancy here, folks, it's based off of simple designs put together, at least that'S the plan 😉
(ps: I apologize for the lack schematic, my current schedule did not even allow me to eat supper last night. I will try later this week)
The experience I have in electronics is superior to my math skills, I don't do calculus or derivatives for anything, I stray away from it because generally I have been taught with methods that require only linear and simple arithmetic. I am an electronics technologist, versed in analog, digital and Radio Frequency, for the past 25 years or more.
I cannot measure anything in the deck because it is still in the design phase. Nothing fancy here, folks, it's based off of simple designs put together, at least that'S the plan 😉
(ps: I apologize for the lack schematic, my current schedule did not even allow me to eat supper last night. I will try later this week)
When converting AC into DC, the rectifier does that. After the rectifier, some power supplies do use an inductor
before the filter capacitor, but most do not. Here are some examples of some passive power supply circuits.
https://www.hammfg.com/electronics/transformers/rectifier
In an active regulated power supply, the low output impedance normally prevents interaction among circuits it powers.
before the filter capacitor, but most do not. Here are some examples of some passive power supply circuits.
https://www.hammfg.com/electronics/transformers/rectifier
In an active regulated power supply, the low output impedance normally prevents interaction among circuits it powers.
hmm... it would seem that I put the choke placement in the wrong... place. Oh well, lesson learned for Rev 2!
thank you for the link, Rayma. That's a good liitle push in the right direction. Somehwere I have a power supply design book. It's just, where is that somehwere? 😆
thank you for the link, Rayma. That's a good liitle push in the right direction. Somehwere I have a power supply design book. It's just, where is that somehwere? 😆
Apologies if you already have came across this in your design, but there is the so called "bias trap", the LC filter that blocks the bias signal -which also applies to the recording head- to reach the analog signal. Usually, a tiny choke like the attached or even integrated with the capacitor.
Oh neat, they still make these? That'S great! They actually say it can be used for this, that's wonderful. I have not yet come to this point, I was actually considering making my own coils and measuring them with equipment at work, but this can simplify the task a lot. Thank you, MagicBus. I don'T suppose you're a fan of The Who? 😉
Well, I meant my book, but this is definitely similar to what I had. Thank you!
Actually it's from a greek song but the transport could be the same... 🙂
If you have access to advanced equipment, it would be interesting to check if a dedicated regulated power supply could isolate the oscillator.
If you have access to advanced equipment, it would be interesting to check if a dedicated regulated power supply could isolate the oscillator.
Hi, there are one thing you need to do before making an inductor. you need a spectrume to measure what exactly the freq is you want to "block"
Once you know this targeted freq, you could design a filter circuit. With a target insertion loss.
Remeber inductors and capacitors are not "ideally" compnents, for example if you are working at 2A， you will need a inductor who can work under 2A without saturation. Also from the freq dimension, L and C are not always presenting the value they specified. If your calculation is 400uH from your filter network, you will need this inductor presenting 400uH at your freq band. same story for Caps.