Episode 738 How many windings will fit on my toroid. How to calculate the maximum number of turns for a give toroid and wire size. Be a Patron: / imsaiguy
4:15 before you gave the solution I have just calculated it just before to find out if my thinking was correct :D and later you said exactly what I was thinking hehe :)
Also, I usually just look on the table on the Amidon web site to figure out how many windings a toroid can have vs wire guage. You generally never want to fill up a toroid 100% though. You want to leave a gap between the ends of about 1/8 the toroid circumference. This keeps the capacitance between the beginning winding and the last winding low. At high frequencies this can matter and it will lower your self-resonance frequency of the toroid.
Also worked for me in meters in trigonometry lesson, about 50 years ago. At that time we had to pass under the string. P.S. Maybe it was when learning differentials in mathematics, don't remember for sure.
I remember that question posed a slightly different way: if we have a rope running all the way around the earth along the equator, how much longer would the rope have to be if the rope was raised by 1 m all around the earth? 2Pi metres longer. It sounds to many to be intuitively wrong.
the maximm number of given wire dameter produces the highest parasitic capacitance => creating a lowest frequency of self resonance It is very difficult to find a wire diameter that gives the highest frequency self resonance with the same number of turns ; same inductance .
Thank you for this video. On a side note can you show a video how to design a matching balun 50 ohms primary and 120 ohms balanced. Can you recommend a book or design equations on how to design the primary number of turns or inductance in primary to be 50 ohms, and the secondary 120 ohms center tapped ground?
Great video! So here's an idea for one more installment. My biggest problem is figuring out how much wire you need. Perhaps some way to calculate the amount / turn, factoring in the possibility that not every turn will be dead flush to the core's body.
Mean length per turn from core data or measure it. Inside diameter of core time Pi for ID circumference and wire diameter to figure out how many turns are absolute maximum possible x mean length per turn for approx. length. The turns that don't lie flat will be a little longer. You can make whatever corrections you want for the less-than-full rule of thumb cited above. You need a little more than your minimum because not having enough is worse than too much on your shuttle. If you are winding more than one layer (like a power transformer vs. RF inductor) you can estimate additional thickness of any layer insulation. The 2nd layer mean length per turn is longer due to the first layer of wire plus any insulation if used. Remember to count the thicknesses twice as applicable. When winding on a rotary toroid winder with a split ring shuttle, you can't remove the interlinked shuttle from the core until you remove the excess wire...so you REALLY don't want TOO much extra either. There's always going to be some scrap wire to recycle...
Winding a small single-layer toroid with a pull-style shuttle made by cutting notches in the ends of a chopstick, you don't experience the overwound split ring shuttle aggravation.
My output voltage is quite low on hand wound toroid transformer. I did match the frequency to source AC, used proper core, and both wound same direction. What is efficiency "percentage difference" of primary not wound exactly over secondary, just wound separate on core? It just looks visually better with 2 different colors insulation.,at separate placements on core.
4:15 before you gave the solution I have just calculated it just before to find out if my thinking was correct :D and later you said exactly what I was thinking hehe :)
This is a great video. The difference between someone who really knows their stuff and the average person who bumbles their way to an answer.
Nice! I like it when there is a surprise answer like these that is independent of parameters.
Also, I usually just look on the table on the Amidon web site to figure out how many windings a toroid can have vs wire guage. You generally never want to fill up a toroid 100% though. You want to leave a gap between the ends of about 1/8 the toroid circumference. This keeps the capacitance between the beginning winding and the last winding low. At high frequencies this can matter and it will lower your self-resonance frequency of the toroid.
Love these math demos. The wonders of pi...
This is great stuff, as in, you're in W2AEW territory. Really appreciated, thank you!
Also worked for me in meters in trigonometry lesson, about 50 years ago.
At that time we had to pass under the string.
P.S.
Maybe it was when learning differentials in mathematics, don't remember for sure.
Clever, and interesting. Good machine math.
I remember that question posed a slightly different way: if we have a rope running all the way around the earth along the equator, how much longer would the rope have to be if the rope was raised by 1 m all around the earth? 2Pi metres longer. It sounds to many to be intuitively wrong.
I’d like to know how many windings on a toroid with a given material mu (based on ‘B’ gauss and ‘H’ oersteds) to get the inductance in henries.
Oh, sorry...just saw IMSAI Guy drew that out graphically.
the maximm number of given wire dameter produces the highest parasitic capacitance => creating a lowest frequency of self resonance
It is very difficult to find a wire diameter that gives the highest frequency self resonance with the same number of turns ; same inductance .
Thank you for this video. On a side note can you show a video how to design a matching balun 50 ohms primary and 120 ohms balanced. Can you recommend a book or design equations on how to design the primary number of turns or inductance in primary to be 50 ohms, and the secondary 120 ohms center tapped ground?
I would start with the ARRL Handbook
Great video! So here's an idea for one more installment. My biggest problem is figuring out how much wire you need. Perhaps some way to calculate the amount / turn, factoring in the possibility that not every turn will be dead flush to the core's body.
I'd like to know that too...
Mean length per turn from core data or measure it. Inside diameter of core time Pi for ID circumference and wire diameter to figure out how many turns are absolute maximum possible x mean length per turn for approx. length.
The turns that don't lie flat will be a little longer. You can make whatever corrections you want for the less-than-full rule of thumb cited above.
You need a little more than your minimum because not having enough is worse than too much on your shuttle.
If you are winding more than one layer (like a power transformer vs. RF inductor) you can estimate additional thickness of any layer insulation. The 2nd layer mean length per turn is longer due to the first layer of wire plus any insulation if used.
Remember to count the thicknesses twice as applicable.
When winding on a rotary toroid winder with a split ring shuttle, you can't remove the interlinked shuttle from the core until you remove the excess wire...so you REALLY don't want TOO much extra either.
There's always going to be some scrap wire to recycle...
Winding a small single-layer toroid with a pull-style shuttle made by cutting notches in the ends of a chopstick, you don't experience the overwound split ring shuttle aggravation.
No animals were harmed during the production of this video
Can you explain how to use the phasing dots when winding a toroid transformer? Thanks Carl
My output voltage is quite low on hand wound toroid transformer. I did
match the frequency to source AC, used proper core, and both wound same direction. What is efficiency "percentage
difference" of primary not wound exactly over secondary, just wound
separate on core? It just looks visually better with 2 different colors
insulation.,at separate placements on core.
Isn't algebra wonderful?
It makes no sense to wind a toroid with the maximum density # of turns.
Wrong on both answers. The correct answers are more accurately 3.14 and 6.28.