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4hv.org :: Forums :: Tesla Coils
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TDU Microwave/Telsa prize

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Tesladownunder
Thu Aug 31 2006, 04:38PM Print View
Joined: Thu Feb 02 2006, 09:45AM
Location: Bunbury, Australia
Posts: 1424
Ok, I reckon that there is not enough ingenuity and resourcefulness going on in budget coiling these days.
I propose a prize of $US 50 to be paid by PayPal by me to the person who makes a Tesla coil with the longest sparks from a standard microwave oven.

Conditions:
This is meant to be fun
One standard domestic MO (microwave oven) less than 1000W to be obtained free.
MO must be the transformer type not the inverter type.
Only the parts of one oven to be used. No other parts to be used apart from solder, hot glue or epoxy in reasonable amounts (not large amounts to make secondary formers).
This also means no PVC, tape, paper or other extraneous substance.
How you adapt the internal parts is up to you.
Progress, results and sparks must all be photographed to confirm use of only parts of one MO are used. Spark length measured from the photo with a ruler adjacent.
Enter as many times as you wish
If you think you might be bending the rules in some way post your question or PM me if it is confidential.
I will be the sole judge (possibly - may be a group vote is best)
Competition closes December 1 2006.

And you thought that was hard. The hardest thing is that you will be competing with me who doesn't want to lose his money!

I expect the useful parts to be the 2000V transformer, 1uF mylar capacitor, 10kV diode, fan, wires and round glass plate. Also turntable motor, low voltage transformer etc.
Clearly none of these parts are ideal at all and would normally not be associated with coiling.
I reckon they can make a successful coil with a 1 or more inch spark at zero cost but you need to think outside the box here. I have a lot of ideas and have done some preliminary work.

Comments?

Peter
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Nik
Thu Aug 31 2006, 05:06PM
Registered Member #53
Joined: Thu Feb 09 2006, 04:31AM
Location: Ontario, Canada
Posts: 627
This sounds like a great challange, I will begin my hunt for a <1000w microwave. I have a 1100 in the basement but there is a blunk garbage pick up soon so I will find one shortly.
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ReddyK
Thu Aug 31 2006, 05:25PM
Registered Member #92
Joined: Thu Feb 09 2006, 03:11PM
Location: Indian Trail, NC
Posts: 39
I like this! Can I assume that the use of a variac is ok?
Steve
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Tesladownunder
Thu Aug 31 2006, 05:49PM
Joined: Thu Feb 02 2006, 09:45AM
Location: Bunbury, Australia
Posts: 1424
Variac from the mains seems OK. I can think of some creative cheating by using 15kV as the power source but a variac should be no problem. I don't think you will need to turn it down much though

Peter

EDIT Sorry, I have had a rethink on this. I think it is an expensive add-on that does not enhance the project. So no variac, sorry.
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Nik
Thu Aug 31 2006, 07:07PM
Registered Member #53
Joined: Thu Feb 09 2006, 04:31AM
Location: Ontario, Canada
Posts: 627
Will you makes alowances on things like marrets (screw on wire connectors) for joints? I would rather not have all my joints laying around and exposed while the thing is plugged in.
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Electroholic
Thu Aug 31 2006, 07:15PM
Registered Member #191
Joined: Fri Feb 17 2006, 02:01AM
Location: Esbjerg Denmark
Posts: 716
sounds fun, i will begin my hunt
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Roger
Thu Aug 31 2006, 09:04PM
Registered Member #221
Joined: Mon Feb 20 2006, 05:36PM
Location: Chillicothe Ohio
Posts: 12
This sounds like fun. I normally power my larger coil with two microwave oven transformers but I cant really tell what my maximum spark length would be because my garage isn't big enough. If I set it up to run with just one MOT maybe I can tell. Ops, I just took a closer look at the rules of the contest. Now I see that every thing has to come from just one microwave oven. That might be a little harder.

Roger
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Marko
Thu Aug 31 2006, 09:12PM
Registered Member #89
Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145
I think most interesting part is going to be finding wire and something to wind the secondary around. Wire may come from a relay or something (if there is any) but the form is tricky thing

Making spark gap that is going to work with 2 kV is also going to be challenging, we may see some new ideas over there..

I unfortunately can't get a MO for myself but challenge is very interesting anyway..
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Nik
Thu Aug 31 2006, 09:16PM
Registered Member #53
Joined: Thu Feb 09 2006, 04:31AM
Location: Ontario, Canada
Posts: 627
fan motor may help for some sort of rotary


Thats what I thought too but it is also a VERY good source for secondary wire. I wish I still had that 80's microwave. It had a 4kv reed switch in it.
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JimG
Thu Aug 31 2006, 09:44PM
Registered Member #52
Joined: Thu Feb 09 2006, 04:22AM
Location: Austin TX
Posts: 57
I think most interesting part is going to be finding wire and something to wind the secondary around. Wire may come from a relay or something (if there is any) but the form is tricky thing


In the few microwaves that I've pulled apart the fans have had magnet wire that was easy to remove.
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Marko
Thu Aug 31 2006, 09:50PM
Registered Member #89
Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145
Yes, depending on luck motor may have a winding with easily removable wire

You can use fan motor for gap and use wire from plate rotation motor, and etc..
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Nik
Thu Aug 31 2006, 09:54PM
Registered Member #53
Joined: Thu Feb 09 2006, 04:31AM
Location: Ontario, Canada
Posts: 627
All good ideas but now thing about what you have to work with, there arent alot of materials you can use to make the rotary gap, or even a static one for that matter. This is going to be harder then i thought.
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Roger
Thu Aug 31 2006, 10:18PM
Registered Member #221
Joined: Mon Feb 20 2006, 05:36PM
Location: Chillicothe Ohio
Posts: 12
Here is an idea for creative cheating. Use something like 240v at 120 cycles per sec. as a power source instead of 120v at 60 cycles per sec. This is assuming that your microwave oven was designed for 120v 60 cps. Correct me if I'm wrong but I'm thinking that if you increase both the input voltage and the line frequency to a MOT you can get higher voltage and more power out of it.

Roger
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Marko
Thu Aug 31 2006, 10:26PM
Registered Member #89
Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145
TDU didn't define the power source in rules, but it's somehow logical that anything more than mains is considered as a part of coil (otherwise someone couls just bring a MOT stack or something and dumb up everything)

Variac is a more of a tool than a coil part (I would say), like you are allowed to use your soldering iron or multimeter..
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...
Thu Aug 31 2006, 10:53PM
Registered Member #56
Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2435
I don't have time to even start to work on something like this, so I will offer my ideas:

Secondary:
Wire-out of the table rotation motor
Former- take the manual (might need to print it off the net unless you found a brand new one ) and roll up a page or 2
Top load-big ball of wadded up wire from the motor you took the secondary wire from

Primary:
Wire: Wire- from power cord or other wiring (I am gonna say you only need 1 turn in order to try to use that 1ufd tank cap
Former: the plastic in the front door

Tank cap- the voltage doubler cap (unless there are enough caps on the pcb's to make one)

Spark gap- 2 bolts from the oven sanded to have a conical shape with the fan blowing across it

Power source- the mot (might also want to add in the diode in series with it in case it can't charge the cap fast enough, but wintesla said 1.2uf would be perfect)

If the manual is too far of the stretch for TDU I would recommend you either try to make one out of the plastic on the front door (ala blackplasma style) or if you have one with the digital timer rip the plastic sticker off it and roll it up...
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Simon Barsinister
Thu Aug 31 2006, 11:35PM
Registered Member #116
Joined: Fri Feb 10 2006, 03:19AM
Location: Erie Pa, USA
Posts: 29
In my dissection of many u-waves, I found a Amana radar-range that had a seperate filament transformer. That would have yielded plenty of wire for a secondary. So keep your eyes open for a 1980's vintage Amana.
Rich
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Avalanche
Thu Aug 31 2006, 11:46PM
Registered Member #103
Joined: Thu Feb 09 2006, 08:16PM
Location: Derby, UK
Posts: 829
I suppose you could wind a flat secondary, totally by hand, on the plate. It would probably take a couple of days

I might have to enter this now
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Tesladownunder
Fri Sep 01 2006, 12:42AM
Joined: Thu Feb 02 2006, 09:45AM
Location: Bunbury, Australia
Posts: 1424
Roger wrote ...

Here is an idea for creative cheating. Use something like 240v at 120 cycles per sec. as a power source ...

Really this should run on mains only as a variac gives a 10% advantage and real cost in a zero cost project. So I have changed my mind about the variac. You don't need a variac to run a MO anyway.

... wrote ...

Former- take the manual (might need to print it off the net unless you found a brand new one ) and roll up a page or 2
If the manual is too far of the stretch for TDU I would recommend you either try to make one out of the plastic on the front door (ala blackplasma style) or if you have one with the digital timer rip the plastic sticker off it and roll it up...

Manual is not on, nor is the packing box etc. Just a plain empty MO that you found on a street corner.

Simon Barsinister wrote ...

In my dissection of many u-waves, I found a Amana radar-range that had a seperate filament transformer. That would have yielded plenty of wire for a secondary. So keep your eyes open for a 1980's vintage Amana.
Rich

I'm not sure that this gives a level playing field or is in the spirit of this competition. The usual domestic MO's seem remarkably similar and fair.

There are several sources of wire in an MO, and I think enough to make it work. I have already started winding my secondary and it is not on anything mentioned yet but is part of the MO that you rarely see.

No-one has really considered the tank cap properly. You are going to have to get your hands dirty - hint.

Peter

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Nik
Fri Sep 01 2006, 02:02AM
Registered Member #53
Joined: Thu Feb 09 2006, 04:31AM
Location: Ontario, Canada
Posts: 627
my secondary wire snapped. I wonder if there is anything in the microwave that can be used to cover a splice...
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Wilson
Fri Sep 01 2006, 05:19AM
Registered Member #78
Joined: Thu Feb 09 2006, 11:27AM
Location: Sydney, Australia
Posts: 133
Perhaps make a plate capacitor from the door and the metal sides? ohoh, i'm not sure if this is correct, but i think i recall reading somewhere that the magetron kinda acts like a capacitor?

The fan has lots of good wire...but i guess you'll want to use that for quenching. I think the secondary would be the most challenging....seeing as you have to make ur own former...

btw nik, you could try melting some wire insulation on the broken patch ;) or just strip a thin wire, and use the insulation as a sheath.

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Nik
Fri Sep 01 2006, 06:26AM
Registered Member #53
Joined: Thu Feb 09 2006, 04:31AM
Location: Ontario, Canada
Posts: 627
I grabbed the turntable motor for the secondary wire. It is so fine I would hazard a guess and say it is in the 36-40awg range. My calliper doesnt even register it (it is mechanical and accurate to ~1/100th on an inch). There is miles of the stuff so I might unwind and try again.

Ive noticed that alot of the parts I would normaly throw out look like they could become usefull in this project. Things like injencion molded plastic parts will be great for holding hv connections away form eachother.

Keeping in the spirit of microwave parts only I think I may attempt this with 0 outside parts. If I do end up resorting to anythign it will be hot glue to prevent connections from toughing eachother (if you look hard enough plastic stickers can even replace the glue).
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Electroholic
Fri Sep 01 2006, 07:25AM
Registered Member #191
Joined: Fri Feb 17 2006, 02:01AM
Location: Esbjerg Denmark
Posts: 716
does it have to run for a long time?

how about a strip of plastic with screws on it as a spark strip.
like a multi gap, that way you wont' need a fan to quinch

and also the plastic sheets from the door can be rowed up for the secondary
might need a hot air gun for that tho.

main problem would be teh cap... hummmm
doubler -> inductor -> plastic parallel plate cap?



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Nik
Fri Sep 01 2006, 07:43AM
Registered Member #53
Joined: Thu Feb 09 2006, 04:31AM
Location: Ontario, Canada
Posts: 627
Im going to take TDU's hint and get my hands dirty for the cap. This also means I won't be using a doubler, I hope it works.
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Tesladownunder
Fri Sep 01 2006, 11:23AM
Joined: Thu Feb 02 2006, 09:45AM
Location: Bunbury, Australia
Posts: 1424
nik282000 wrote ...

my secondary wire snapped. I wonder if there is anything in the microwave that can be used to cover a splice...

Mine too. Hotglue it.
Wilson wrote ...

..I think the secondary would be the most challenging....seeing as you have to make ur own former...

Its a challenge but there are a few materials available to you. There are TC secondaries without any former after all.
Electroholic wrote ...

does it have to run for a long time?
..might need a hot air gun for that tho.
main problem would be teh cap... hummmm
doubler -> inductor -> plastic parallel plate cap?

It has to last long enough to get the best photo. And you may want to keep it as a display piece.
Hot air gun or a big dollar CNC machine is OK to work on it.
The caps are feasible otherwise I wouldn't have proposed this.

Has anyone thought of a microwave excited TC? (is there such a thing)

Peter
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Marko
Fri Sep 01 2006, 11:27AM
Registered Member #89
Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145
Has anyone thought of a microwave excited TC? (is there such a thing)


Secondary of such a TC would end like piece of short wired , and would have such a low Q factor thatit couldn't be called a TC anymore.

Besto would be just to try setting it at quarter wavelength of microwave frequency and hoping it to spew some small streamers just from antenna nffect.

If one had a magnetron or klystron operating at few tens of Mhz maybe it could exscite a small TC secondary, but size difference would still be funny..

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Tesladownunder
Fri Sep 01 2006, 11:42AM
Joined: Thu Feb 02 2006, 09:45AM
Location: Bunbury, Australia
Posts: 1424
I should add a safety note. MO's are extremely dangerous compared to NST's. You must really be careful with these. At a minimum you should keep the interior light active to indicate the power is on and make a rule of never touching it unless the power cord is draped across the top.

Peter
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Self Defenestrate
Fri Sep 01 2006, 01:02PM
Registered Member #87
Joined: Thu Feb 09 2006, 01:36PM
Location: San Jose
Posts: 191
This is a great challenge, TDU. If I can locate a microwave, I'm definetly in. If I were me(wich I am), I'd be on the lookout for a non-digital microwave that has a real bell inside. Not suggesting what it should be used for on this toroid-less coil, but it could be usefull.
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Marko
Fri Sep 01 2006, 01:03PM
Registered Member #89
Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145
Bells are another great source of wire too..
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Reaching
Fri Sep 01 2006, 02:02PM
Registered Member #76
Joined: Thu Feb 09 2006, 10:04AM
Location: Hemer, Germany
Posts: 458
you can build a nice plate capacitor by using the cases metal and the front glass plate, this thing should have some 500pf or so and a high enough voltage rating. use a pvc former with a sheet of paper around it and wind your secondary with wire from the motor or the bell or the small rotating disc motor, then coat it with something and remove the former, voila a very good secondary without any former,. you can use the remaining parts of the bell for a toroid and the top of the MO can act like a base to build the tc on .use bolts for the spark gap and when you still have a working fan then use it to quench the gap. the primary can be build out of the power chord cable or out of the cables inside the MO.hehe and you can build a dc resonant tc too, use the MO cap and the diode to build a 1phase voltage doubler, then the plate cap and the spark gap, that should perform much better
nice project, but i only have one working MO okay its an old one but i use it to heat up my acid for pcb making etc so i wont cut it in pieces
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GimpyJoe
Fri Sep 01 2006, 08:14PM
Registered Member #316
Joined: Mon Mar 13 2006, 01:30PM
Location: Marietta, GA
Posts: 212
Reaching, I don't know if coating the secondary fits with the zero cost thing. I think the best thing in a MO for a secondary former would be to cut a piece of the plastic that guides the air from the fan and use a heat gun to bend it. Then you would still have the big piece of plastic from the door to make a capacitor.
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