Author Topic: How do I test for resonance (Read 15035 times)

Tesluh · « **Reply #15 on:** October 11, 2016, 03:01:40 AM »

lanca, do you hand type the gibberish you use to spam people's threads or do you have a special auto-gibberish generator?

Tesluh · « **Reply #16 on:** October 11, 2016, 03:54:57 PM »

I currently have a primary coil that is 78" long 10ga stranded wire with 4 wraps around a 2" tube.
My secondary is two coils about 3" diameter 16ga solid 158" each (twice as long as the primary and when connected at the center should be 4 times as long).

Math I did put the primary to resonate at 37.5mhz. the nst supposedly puts out something like 9kv at 37.5 kHz. When I fire up the primary and use what I call a "voltage sniffer" I can put the secondary 5 feet rom the primary and the sniffer lights up brightly. This tells me that something is happening in the primary to excite the secondary. I may have to adjust spark gap and primary capicitor to get better resonance in the primary.

Going to try to get a scope today and see what I get for readings on the primary. I have a capacitor across the primary and one half of the secondary.

This part of it is all tesla coil building, anyone who has built tesla coils and can look over my coils lengths and offer advice for tuning I would be appreciative.

Tesluh · « **Reply #17 on:** October 15, 2016, 10:01:29 PM »

https://www.youtube.com/watch?v=TI5XWz8aZvo this is possibly the most convincing demo of a working assembled Don smith device I have seen. questioning if my nst is working properly and giving me problems after seeing this video.

antimony · « **Reply #18 on:** November 29, 2016, 02:59:50 PM »

I also like to master the knowledge of finding the resonant frequency of a coil, or LC circuit.
I recently bought a cheap function generator from China, but i have a problem with it because it only has one probe, and there seems to have to be two probes when I have searched for tutorials on Google and on YouTube.

Tesluh · « **Reply #19 on:** November 29, 2016, 03:08:30 PM »

the "probe" on my function generator has a two pronged lead. you need the signal generator and an oscilloscope which also has a probe. I finally was able to get my equipment to determine the resonant frequency of a coil. I am not sure how exact the frequency i am coming up with is but I get the rising and falling waveform on the scope. tried three different signal generators (not sure if I was using them correctly) and ended up with this one that has a built in frequency counter. https://www.amazon.com/gp/product/B0199SVAIY/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1

Tesluh · « **Reply #20 on:** November 29, 2016, 03:16:42 PM »

the second probe you are referring to might be the frequency counter. I don't understand the use of a frequency counter unless the output on the signal generator isn't easy to determine. when it's a digital readout I'm pretty sure the frequency from the counter and the frequency out but by the generator are the same.

antimony · « **Reply #21 on:** December 02, 2016, 11:35:56 AM »

Quote from: Tesluh on November 29, 2016, 03:08:30 PM

the "probe" on my function generator has a two pronged lead. you need the signal generator and an oscilloscope which also has a probe. I finally was able to get my equipment to determine the resonant frequency of a coil. I am not sure how exact the frequency i am coming up with is but I get the rising and falling waveform on the scope. tried three different signal generators (not sure if I was using them correctly) and ended up with this one that has a built in frequency counter. https://www.amazon.com/gp/product/B0199SVAIY/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1

I had two probes on my oscilloscope but now i am using only one channel, and the other probe on the FG-100.

Im not sure if i have one in this cheap fg, but my oscilloscope is able to measure the frequency.

I will probably get another one if i am not able to figure oiut how to use this one soon.

Tesluh · « **Reply #22 on:** December 02, 2016, 02:30:32 PM »

does your function generator have a lead with two ends? mine has a jack that you plug into that says output and the cord has two alligator clips.

Tesluh · « **Reply #23 on:** December 02, 2016, 02:34:27 PM »

if your scope can measure the frequency and it changes when you change the function generator frequency you are most of the way there.

antimony · « **Reply #24 on:** December 05, 2016, 02:38:31 PM »

Quote from: Tesluh on December 02, 2016, 02:30:32 PM

does your function generator have a lead with two ends? mine has a jack that you plug into that says output and the cord has two alligator clips.

I use my oscilloscope probe. It has one ground clip and one hook.

Tesluh · « **Reply #25 on:** December 05, 2016, 02:59:32 PM »

some people say a resistor is needed to test to find resonance frequency with a scope, im not sure how accurate my tests are but its better than nothing. you can try it how you have it, hook both alligator clips to one leg of a parallel tank circuit and the two probes to the other leg.

do you have an lcr meter to estimate the inductance of a coil? that would give you a good point to start. you want to get your scope on a timebase that will show a single trace, for instance 100khz is 10microseconds. if you have the timebase much higher or lower you might not see the trace properly on the screen.

antimony · « **Reply #26 on:** December 05, 2016, 06:40:52 PM »

Quote from: Tesluh on December 05, 2016, 02:59:32 PM

some people say a resistor is needed to test to find resonance frequency with a scope, im not sure how accurate my tests are but its better than nothing. you can try it how you have it, hook both alligator clips to one leg of a parallel tank circuit and the two probes to the other leg.

do you have an lcr meter to estimate the inductance of a coil? that would give you a good point to start. you want to get your scope on a timebase that will show a single trace, for instance 100khz is 10microseconds. if you have the timebase much higher or lower you might not see the trace properly on the screen.

I'm posting from my phone, so i can't link you to the generator that i have, but it is called FG-100.
I guess I should buy a function generator probe so i use both channels of the oscilloscope, they aren't that expensive.

I have a LCR meter, but I am a newbie when it comes to the oscilloscope, but it is good advice.

I have used Gotolucs yt series about coil resonance, and I haven't been able to get going with anything becouse i don't have the right experience with electronics, but I would figure that i would be able to make use of what I got even if my equipment doesn't match Gotolucs.

Tesluh · « **Reply #27 on:** December 05, 2016, 06:52:32 PM »

try this next time you are experimenting.

probe on your fg100
probe on your scope (one channel, doesn't matter)
capacitor
coil

use your lcr meter to measure inductance of coil usually in uh (microhenries)
input inductance of coil and capacitance of capacitor into this calculator (this will give an estimate of the resonant frequency)
http://www.ham-radio.com/lc.html

put one each of capacitor ends and coil ends together (parallel) and then put your two probe ends on one side of the capacitor, and the two "neg" alligator clips on the other side. set your fg100 to the frequency you got in the calculator and see what shows up on the scope.

Tesluh · « **Reply #28 on:** December 06, 2016, 03:12:29 AM »

this video shows how to connect everything in parallel. The green jumper is just an extension for his probe.

https://www.youtube.com/watch?v=G_RCyDdt2rM

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Author Topic: How do I test for resonance (Read 15035 times)

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