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Registered Member #42712
Joined: Fri Jan 10 2014, 01:21AM
Location:
Posts: 21
For a club I started at my high school, everyone agreed on making a tesla coil as a project.
I am starting to struggle realizing how everything has to be tuned, resonant, and I can't just throw a random number of turns on a random size PVC pipe. We are limited in price, so I will say our progress so far of what we have and ask a few questions.
•A piece of 4 inch Diameter 5 foot PVC pipe (actually have 2 of those) and a toilet plounge to hold it up 90 degrees
•A bucket capacitor made out of salt water, beer bottles, oil, I will post the capacitance today when I bring my capacitance meter
• 4 MOTS, we might have to get another for the ballast, correct? We will be hooking two outlets together for the Power Supply
•A stable spark gap (planning on rotary probably in the future, I have a 3400 RPM BIGG motor that may work)
Our Price is very limited, for we have few sponsors, (just my friend and I's parents and our own money)
So what are some next steps, and is the PVC not the right size? (From another question on the forum the pipe seems to be not the right size, my dads gonna get mad that he wasted his money on that and probably wont buy another :'(
I am sort of confused when working with JavaTC so if anyone could help me with that, it would be great!
Safety wise, I Know 4 mots is enough to KILL YOU so we are taking every safety precaution including being at least 10 feet away when any transformer is plugged in.
What should I use for Primary wire?
Thanks for ANY help, Im just a dumb high school student, and need a bit of help from people who know what they are doing
Registered Member #8817
Joined: Mon Dec 17 2012, 05:16AM
Location: Australia
Posts: 110
the for 5" length 4" diameter makes the coil very skinny, that means it has a height to diameter ratio of: 15:1.
The proper ratio sits between 5:1 and 3:1 for bigger coils, so you might wanna cut the secondary down in size.
In java TC,
first choose measurements cm/inch and centigrade/Fahrenheit
Then choose your tank capacitor size.
then using the units provided, choose the radius of the secondary coil, so for 4 inch diameter put value of 2 in for Radius 1 and 2 in for Radius 2.
Next is the secondary coil height, if at ground level put 0 in Height 1 then if its 5 foot, put in 60 in Height 2.
Choose the amount of turns you suspect roughly and what wire gauge size.
repeat with primary data for the primary radius, height, turns and wire gauge size.
next do the toroid, enter the height of the toroid into the minor diameter field. then enter the diameter of the toroid in the major diameter field. then enter the how high the toroid sits on the secondary, so if the secondary coil is 60" tall, put the toroid center height at a tad over 60.
That should get you by, click RUN JAVATC and it should pump out a drawing and all the values, you can fine tune the parameters again and again after.
Registered Member #42712
Joined: Fri Jan 10 2014, 01:21AM
Location:
Posts: 21
Fiddy wrote ...
the for 5" length 4" diameter makes the coil very skinny, that means it has a height to diameter ratio of: 15:1.
The proper ratio sits between 5:1 and 3:1 for bigger coils, so you might wanna cut the secondary down in size.
In java TC,
first choose measurements cm/inch and centigrade/Fahrenheit
Then choose your tank capacitor size.
then using the units provided, choose the radius of the secondary coil, so for 4 inch diameter put value of 2 in for Radius 1 and 2 in for Radius 2.
Next is the secondary coil height, if at ground level put 0 in Height 1 then if its 5 foot, put in 60 in Height 2.
Choose the amount of turns you suspect roughly and what wire gauge size.
repeat with primary data for the primary radius, height, turns and wire gauge size.
next do the toroid, enter the height of the toroid into the minor diameter field. then enter the diameter of the toroid in the major diameter field. then enter the how high the toroid sits on the secondary, so if the secondary coil is 60" tall, put the toroid center height at a tad over 60.
That should get you by, click RUN JAVATC and it should pump out a drawing and all the values, you can fine tune the parameters again and again after.
Thank you, I think I will look for some pipe that is at least 6 inches in diameter
Registered Member #31557
Joined: Tue Aug 06 2013, 02:38AM
Location:
Posts: 58
4" PVC is fine. Assuming you get some 22awg magnet wire, make your secondary about 24" long. With a 6" aluminum dryer duct toroid, that puts you around 275khz.
4 MOT's is overkill for a coil this size. 2 will work if you must. If you can get hold of a NST for free at a sign shop, don't use the MOT's. Static spark gaps don't work well with MOT's unless you do a voltage doubler setup which will make things more complicated and expensive. If you can do a rotary gap, then MOT's are awesome. Seriously, if you can get a 12kv 30ma NST, that would be great for a 4" coil!
Use 1/4" or 3/8" copper tubing for your primary coil. It already comes shaped as a spiral, and just needs to be adjusted for your form. You may need a lot of turns. Assuming you decide on a 12kv NST, a 10nf cap, and all the other stuff I mentioned, then it'll be tuned around 10 turns.
Beer bottle / salt water caps will work, but expect them to occasionally pop. Have a bunch of spare beer bottles ready. DO NOT USE brown glass! Get clear Corona bottles.
Registered Member #10052
Joined: Thu Feb 07 2013, 11:31PM
Location: Overland Park, Kansas
Posts: 78
The price of a proper MMC (such as using the cornell dubillier 942C20P15K-F) seems prohibitive, but the investment will pay off in time you would have spent running through beer bottles and power wasted heating a bucket of salt water. MOT's push a lot of current, which means you will get the most out of them with a very high spark gap breakrate (> 3000 BPS or so). With that amount of average current, you'd be vaporizing a non-tungsten static spark gap. You'll also be putting much more stress on the capacitors. More reason to go with the 942c20p15k-f.
Remember:
RSG 942c20p15k-f Use 2x the capacitors you think you'll need based on the datasheet peak current and DC voltage ratings for the capacitor.
These are just time savers, I can't tell you how much effort and money I wasted on lossy, failure-prone DIY capacitors.
Registered Member #42712
Joined: Fri Jan 10 2014, 01:21AM
Location:
Posts: 21
HighVoltageFeathers wrote ...
The price of a proper MMC (such as using the cornell dubillier 942C20P15K-F) seems prohibitive, but the investment will pay off in time you would have spent running through beer bottles and power wasted heating a bucket of salt water. MOT's push a lot of current, which means you will get the most out of them with a very high spark gap breakrate (> 3000 BPS or so). With that amount of average current, you'd be vaporizing a non-tungsten static spark gap. You'll also be putting much more stress on the capacitors. More reason to go with the 942c20p15k-f.
Remember:
RSG 942c20p15k-f Use 2x the capacitors you think you'll need based on the datasheet peak current and DC voltage ratings for the capacitor.
These are just time savers, I can't tell you how much effort and money I wasted on lossy, failure-prone DIY capacitors.
Have fun!
Well we have a large supply of bottles from a local bar! they just give em away like trash
Registered Member #1403
Joined: Tue Mar 18 2008, 06:05PM
Location: Denmark, Odense C
Posts: 1968
skyler wrote ...
HighVoltageFeathers wrote ...
The price of a proper MMC (such as using the cornell dubillier 942C20P15K-F) seems prohibitive, but the investment will pay off in time you would have spent running through beer bottles and power wasted heating a bucket of salt water. MOT's push a lot of current, which means you will get the most out of them with a very high spark gap breakrate (> 3000 BPS or so). With that amount of average current, you'd be vaporizing a non-tungsten static spark gap. You'll also be putting much more stress on the capacitors. More reason to go with the 942c20p15k-f.
Remember:
RSG 942c20p15k-f Use 2x the capacitors you think you'll need based on the datasheet peak current and DC voltage ratings for the capacitor.
These are just time savers, I can't tell you how much effort and money I wasted on lossy, failure-prone DIY capacitors.
Have fun!
Well we have a large supply of bottles from a local bar! they just give em away like trash
Just because they are free, doesn't mean they will do you any good, it will just be a waste of your time. Spend the time working, mowing lawns etc instead and pay for some proper capacitors. Have you read through this thread?
Noone says you have to use CDE 942C capacitors, almost all MKP/FKP (metallized / foil film polypropylene) capacitors can be used, just be sure to have a good rating for withstanding the voltages, rms and peak currents. There is a drop down list with capacitors on my MMC calculator, here you can atleast get a feeling of how many capacitors are needed for getting your goal capacitance/voltage rating and compare costs to build such mmc.:
Registered Member #31557
Joined: Tue Aug 06 2013, 02:38AM
Location:
Posts: 58
Although these guys are correct that building a real 942c based MMC is obviously going to be superior, I also understand a zero budget build. My first coil was 3", salt water caps, NST, and it threw 20" streamers. I built it with garbage I got for free, and it worked. There is also something to be learned from building your own caps, and building a TC from scrap.
To just keep telling newbs "Its a waste of time" is bullshit. Tesla didn't have 942c's or other polypropylene caps around.
Build the salt water caps. Learn from it, then upgrade to an MMC later when you have the money.
I actually managed to dig up a video of my first coil. Here ya go, salt water caps and all! LOL at the tiny topload.
Registered Member #42712
Joined: Fri Jan 10 2014, 01:21AM
Location:
Posts: 21
Hopefully we are getting down there on getting the tesla coil working.
We have finally assembled the secondary out of a 12 inch by 48 inch sona tube, with enough 24 gauge wire with fishing line to wind to the top (we estimated 900-1200 turns based on how much wire we had, 3500 feet, using almost all of it)
We have a bunch of MOTS, at least Five good ones, and 5 more that we don't know are good or bad and hope to get that power supply working (maybe voltage doublers or something if they keep arcing internally- we have almost 10 microwave diodes and capacitors)
3500 RPM spark gap is almost complete with the tungsten rods ordered
And we still have not got MMC capacitors, but will hopefully get the funds for that after we get it to work with the beer bottle caps.
For the primary, we currently have 5 turns of copper tubing, 20 feet, and probably will need more copper tubing to get more turns, but that stuff is pretty expensive so we will try it with this first.
For the toroid, we just got some heater duct at the local home depot, hope that works
Any problems popping up to anybody? We are out out of major money, so hopefully we don't have to redo the whole thing!
And I will try to get some pictures when I get to school tomarow
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Tesla Coil Help
