TDU Microwave/Telsa prize
Tesladownunder, Thu Aug 31 2006, 04:38PMOk, 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
Re: TDU Microwave/Telsa prize
Nik, Thu Aug 31 2006, 05:06PM
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.
Nik, Thu Aug 31 2006, 05:06PM
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.
Re: TDU Microwave/Telsa prize
ReddyK, Thu Aug 31 2006, 05:25PM
I like this! Can I assume that the use of a variac is ok?
Steve
ReddyK, Thu Aug 31 2006, 05:25PM
I like this! Can I assume that the use of a variac is ok?
Steve
Re: TDU Microwave/Telsa prize
Tesladownunder, Thu Aug 31 2006, 05:49PM
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.
Tesladownunder, Thu Aug 31 2006, 05:49PM
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.
Re: TDU Microwave/Telsa prize
Nik, Thu Aug 31 2006, 07:07PM
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.
Nik, Thu Aug 31 2006, 07:07PM
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.
Re: TDU Microwave/Telsa prize
Electroholic, Thu Aug 31 2006, 07:15PM
sounds fun, i will begin my hunt
Electroholic, Thu Aug 31 2006, 07:15PM
sounds fun, i will begin my hunt
Re: TDU Microwave/Telsa prize
Roger, Thu Aug 31 2006, 09:04PM
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
Roger, Thu Aug 31 2006, 09:04PM
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
Re: TDU Microwave/Telsa prize
Marko, Thu Aug 31 2006, 09:12PM
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..
Marko, Thu Aug 31 2006, 09:12PM
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..
Re: TDU Microwave/Telsa prize
Nik, Thu Aug 31 2006, 09:16PM
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.
Nik, Thu Aug 31 2006, 09:16PM
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.
Re: TDU Microwave/Telsa prize
JimG, Thu Aug 31 2006, 09:44PM
In the few microwaves that I've pulled apart the fans have had magnet wire that was easy to remove.
JimG, Thu Aug 31 2006, 09:44PM
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.
Re: TDU Microwave/Telsa prize
Marko, Thu Aug 31 2006, 09:50PM
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..
Marko, Thu Aug 31 2006, 09:50PM
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..
Re: TDU Microwave/Telsa prize
Nik, Thu Aug 31 2006, 09:54PM
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.
Nik, Thu Aug 31 2006, 09:54PM
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.
Re: TDU Microwave/Telsa prize
Roger, Thu Aug 31 2006, 10:18PM
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
Roger, Thu Aug 31 2006, 10:18PM
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
Re: TDU Microwave/Telsa prize
Marko, Thu Aug 31 2006, 10:26PM
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..
Marko, Thu Aug 31 2006, 10:26PM
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..
Re: TDU Microwave/Telsa prize
..., Thu Aug 31 2006, 10:53PM
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...
..., Thu Aug 31 2006, 10:53PM
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 2Top 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...
Re: TDU Microwave/Telsa prize
Simon Barsinister, Thu Aug 31 2006, 11:35PM
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
Simon Barsinister, Thu Aug 31 2006, 11:35PM
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
Re: TDU Microwave/Telsa prize
Avalanche, Thu Aug 31 2006, 11:46PM
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
Avalanche, Thu Aug 31 2006, 11:46PM
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
Re: TDU Microwave/Telsa prize
Tesladownunder, Fri Sept 01 2006, 12:42AM
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
Tesladownunder, Fri Sept 01 2006, 12:42AM
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.Here is an idea for creative cheating. Use something like 240v at 120 cycles per sec. as a power source ...
... 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.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 2If 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...
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.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
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
Re: TDU Microwave/Telsa prize
Nik, Fri Sept 01 2006, 02:02AM
my secondary wire snapped. I wonder if there is anything in the microwave that can be used to cover a splice...
Nik, Fri Sept 01 2006, 02:02AM
my secondary wire snapped. I wonder if there is anything in the microwave that can be used to cover a splice...Re: TDU Microwave/Telsa prize
Wilson, Fri Sept 01 2006, 05:19AM
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.
Wilson, Fri Sept 01 2006, 05:19AM
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.
Re: TDU Microwave/Telsa prize
Nik, Fri Sept 01 2006, 06:26AM
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).
Nik, Fri Sept 01 2006, 06:26AM
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).
Re: TDU Microwave/Telsa prize
Electroholic, Fri Sept 01 2006, 07:25AM
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?
Electroholic, Fri Sept 01 2006, 07:25AM
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?
Re: TDU Microwave/Telsa prize
Nik, Fri Sept 01 2006, 07:43AM
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.
Nik, Fri Sept 01 2006, 07:43AM
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.
Re: TDU Microwave/Telsa prize
Tesladownunder, Fri Sept 01 2006, 11:23AM
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
Tesladownunder, Fri Sept 01 2006, 11:23AM
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. my secondary wire snapped. I wonder if there is anything in the microwave that can be used to cover a splice...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...I think the secondary would be the most challenging....seeing as you have to make ur own former...
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.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?
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
Re: TDU Microwave/Telsa prize
Marko, Fri Sept 01 2006, 11:27AM
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..
Marko, Fri Sept 01 2006, 11:27AM
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..
Re: TDU Microwave/Telsa prize
Tesladownunder, Fri Sept 01 2006, 11:42AM
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
Tesladownunder, Fri Sept 01 2006, 11:42AM
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
Re: TDU Microwave/Telsa prize
Self Defenestrate, Fri Sept 01 2006, 01:02PM
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.
Self Defenestrate, Fri Sept 01 2006, 01:02PM
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.
Re: TDU Microwave/Telsa prize
Marko, Fri Sept 01 2006, 01:03PM
Bells are another great source of wire too..
Marko, Fri Sept 01 2006, 01:03PM
Bells are another great source of wire too..
Re: TDU Microwave/Telsa prize
Reaching, Fri Sept 01 2006, 02:02PM
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
Reaching, Fri Sept 01 2006, 02:02PM
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
Re: TDU Microwave/Telsa prize
GimpyJoe, Fri Sept 01 2006, 08:14PM
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.
GimpyJoe, Fri Sept 01 2006, 08:14PM
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.
Re: TDU Microwave/Telsa prize
vasil, Fri Sept 01 2006, 08:32PM
TDU, are you thinking to a flat secondary, glued on the glass plate with the primary beneath?
Oh, and for the cap you have to get out from the metalic case (you will be dirty from the oil). Just use enough paper-foil combo to have a few nF cap for the primary tank.
...and you can still increase the input voltage if you rectify it. Just use the magnetron, without the permanent magnets, as a HV diode. It will keep well with the HF spikes (far better than the silicon diode). And you can ballast the MOT just decreasing the fillament current (lower the fillament turns number)
vasil, Fri Sept 01 2006, 08:32PM
TDU, are you thinking to a flat secondary, glued on the glass plate with the primary beneath?
Oh, and for the cap you have to get out from the metalic case (you will be dirty from the oil). Just use enough paper-foil combo to have a few nF cap for the primary tank.
...and you can still increase the input voltage if you rectify it. Just use the magnetron, without the permanent magnets, as a HV diode. It will keep well with the HF spikes (far better than the silicon diode). And you can ballast the MOT just decreasing the fillament current (lower the fillament turns number)
Re: TDU Microwave/Telsa prize
Tesladownunder, Sat Sept 02 2006, 02:53AM
Paper-foil? Paper from where? Perhaps from the circuit diagram that some older MO's had pasted to the chassis lid.
The magnetron/diode idea is interesting and makes me wonder if you can't arrange a two stage CW multiplier rather than just a single. That would be really clever.
After the next reply I will show a pic of my progress.
Peter
Tesladownunder, Sat Sept 02 2006, 02:53AM
vasil wrote ...
TDU, are you thinking .....
..Just use enough paper-foil combo to have a few nF cap for the primary tank.
...and you can still increase the input voltage if you rectify it. Just use the magnetron, without the permanent magnets, as a HV diode. It will keep well with the HF spikes (far better than the silicon diode). And you can ballast the MOT just decreasing the fillament current (lower the fillament turns number)
If I told you what I was thinking, I'd have to kill you of course.TDU, are you thinking .....
..Just use enough paper-foil combo to have a few nF cap for the primary tank.
...and you can still increase the input voltage if you rectify it. Just use the magnetron, without the permanent magnets, as a HV diode. It will keep well with the HF spikes (far better than the silicon diode). And you can ballast the MOT just decreasing the fillament current (lower the fillament turns number)
Paper-foil? Paper from where? Perhaps from the circuit diagram that some older MO's had pasted to the chassis lid.
The magnetron/diode idea is interesting and makes me wonder if you can't arrange a two stage CW multiplier rather than just a single. That would be really clever.
After the next reply I will show a pic of my progress.
Peter
Re: TDU Microwave/Telsa prize
vasil, Sat Sept 02 2006, 05:43AM
Ok, my mistake, wrong word. I mean mylar - foil, what you find inside the MO cap.
Unfortunately I only can play with ideas. No MWOs to distroy around....just a few separate parts.
vasil, Sat Sept 02 2006, 05:43AM
Ok, my mistake, wrong word. I mean mylar - foil, what you find inside the MO cap.
Unfortunately I only can play with ideas. No MWOs to distroy around....just a few separate parts.
Re: TDU Microwave/Telsa prize
Tesladownunder, Sat Sept 02 2006, 05:59AM
Vasil has exposed my secret about the caps. Damn
Here is a high voltage test of my former. I should have done this before I started the winding. Seems that it doesnt conduct at least.
Can you see where I got the former from? Yes it is out of the MO.
Peter
Tesladownunder, Sat Sept 02 2006, 05:59AM
Vasil has exposed my secret about the caps. Damn
Here is a high voltage test of my former. I should have done this before I started the winding. Seems that it doesnt conduct at least.
Can you see where I got the former from? Yes it is out of the MO.
Peter
Re: TDU Microwave/Telsa prize
vasil, Sat Sept 02 2006, 06:14AM
Is it the piece of plastic that covers (and protect) the microwave window (between magnetron and oven)? I saw something like that in a few ovens.
vasil, Sat Sept 02 2006, 06:14AM
Is it the piece of plastic that covers (and protect) the microwave window (between magnetron and oven)? I saw something like that in a few ovens.
Re: TDU Microwave/Telsa prize
Tesladownunder, Sat Sept 02 2006, 06:25AM
That is a reconstituted mica window. Almost all MO's seem to use them. Nice and heat resistant and I used a stack of 4 or more for the base of a static gap on a Tesla coil I made recently for the Physics Dept. PVC was getting too hot with the 110 mA NST. They are easy to miss but can be pried out by approaching from the cooking cavity side being careful not to crack them.
A useful part for this project, no doubt but not what I used.
Peter
Tesladownunder, Sat Sept 02 2006, 06:25AM
That is a reconstituted mica window. Almost all MO's seem to use them. Nice and heat resistant and I used a stack of 4 or more for the base of a static gap on a Tesla coil I made recently for the Physics Dept. PVC was getting too hot with the 110 mA NST. They are easy to miss but can be pried out by approaching from the cooking cavity side being careful not to crack them.
A useful part for this project, no doubt but not what I used.
Peter
Re: TDU Microwave/Telsa prize
Nik, Sun Sept 03 2006, 02:26AM
I found a MWO put out on the side of the road because there was a peice of metalized cardboard where that mica sheet usualy is. THe thing had caught on fire and the owner threw it out it would seem.
Nik, Sun Sept 03 2006, 02:26AM
I found a MWO put out on the side of the road because there was a peice of metalized cardboard where that mica sheet usualy is. THe thing had caught on fire and the owner threw it out it would seem.
Re: TDU Microwave/Telsa prize
Tesladownunder, Sun Sept 03 2006, 08:27AM
Here are a couple of progress photos.
The display board usually has a small mains transformer on it which can be unwound and has 43 M of wire on the smaller winding. The larger winding with smaller wire should be much longer but it wouldnt break through the lacquer and snapped.
The secondary is being wound fronm the fan motor wire.
Peter
Tesladownunder, Sun Sept 03 2006, 08:27AM
Here are a couple of progress photos.
The display board usually has a small mains transformer on it which can be unwound and has 43 M of wire on the smaller winding. The larger winding with smaller wire should be much longer but it wouldnt break through the lacquer and snapped.
The secondary is being wound fronm the fan motor wire.
Peter
Re: TDU Microwave/Telsa prize
Michael W., Sun Sept 03 2006, 01:41PM
I'm not participating but heres a coil I wound from a microwave fan motor. It measures 4"X1", not sure of the gauge. I didn't even break the wire once, winding by hand.
Michael W., Sun Sept 03 2006, 01:41PM
I'm not participating but heres a coil I wound from a microwave fan motor. It measures 4"X1", not sure of the gauge. I didn't even break the wire once, winding by hand.
Re: TDU Microwave/Telsa prize
ragnar, Sun Sept 03 2006, 09:58PM
You could probably cut slots into those fanblades to assemble them into an BP-memorial "anticoil" of some description... although if it ends up with a conical shape, the wire will just slide off... Low-loss, though =)
ragnar, Sun Sept 03 2006, 09:58PM
You could probably cut slots into those fanblades to assemble them into an BP-memorial "anticoil" of some description... although if it ends up with a conical shape, the wire will just slide off... Low-loss, though =)
Re: TDU Microwave/Telsa prize
Part Scavenger, Mon Sept 04 2006, 03:11AM
Geez Mike, that thing looks like a pipe bomb.
Part Scavenger, Mon Sept 04 2006, 03:11AM
Geez Mike, that thing looks like a pipe bomb.
Re: TDU Microwave/Telsa prize
Tesladownunder, Wed Oct 25 2006, 08:57AM
I wound a primary and made a secondary from fan wire then tested them on a small NST.
Photo 1 shows the filament winding from the MOT.
Photo 2 shows the stripped winding wound on to the 3 pronged base support for the glass cooking plate in the MO.
Photo 3 shows sparks of up to 1 inch from it from a 4kV NST and a 2 gap static gap.
Photo 4 shows a racing spark and an interturn short
The windings moved and there was overlap causing the short.
Edit: I have now got sparks using a capacitor from the microwave oven. Those are the hard parts, now to arrange current limiting for the MOT somehow. Perhaps add a microwave "ping" and I have my (initial) entry.
Tesladownunder, Wed Oct 25 2006, 08:57AM
I wound a primary and made a secondary from fan wire then tested them on a small NST.
Photo 1 shows the filament winding from the MOT.
Photo 2 shows the stripped winding wound on to the 3 pronged base support for the glass cooking plate in the MO.
Photo 3 shows sparks of up to 1 inch from it from a 4kV NST and a 2 gap static gap.
Photo 4 shows a racing spark and an interturn short
The windings moved and there was overlap causing the short.
Edit: I have now got sparks using a capacitor from the microwave oven. Those are the hard parts, now to arrange current limiting for the MOT somehow. Perhaps add a microwave "ping" and I have my (initial) entry.
Re: TDU Microwave/Telsa prize
Tesladownunder, Sat Dec 09 2006, 03:38AM
Well no one won it. I didn't get the time before Dec 1. However I have done it - just 9 days late. Shown here with 1/2 inch sparks only but best in development has been 1 inch and plenty of scope for improvement with better design.
Here's how:
Power supply is the MOT. This needs current limiting and this is achieved with a 150nF capacitor and the voltage is boosted by a one stage multiplier using the MOT diode to give 6kV peak. Note that power is taken off across the diode not across the cap to get the voltage multiplier effect. Hey what's this about a 150nF cap? Where is that in a microwave oven? Well that is the key to this project. The 1uF 10kV DC mylar and oil cap (that is in all non-inverter MO's) needs to be taken apart and unwound. Lengths of the multilayered dielectric and foil are taken out and cut to length. It took about 10 feet of the windings to make 150nF. This is perhaps only 30% of the total. New electrodes were added.
Tank cap. This is a 1nF cap. The technique is similar but I retained the original electrodes from the cap to use in this section as they were better suited to a high current. Construction of this cap was different in view of the much higher voltage/current and frequency stresses. It used about 30% of the length of the cap windings. The plates were only about 1 foot long by 2 inches, however I used two sections of foil/dielectric between them. The foil was not connected and was kept to equalise voltage stresses. All in all something like 12 layers of mylar and 2 foil layers separate the main electrodes.
Being mylar they do warm up a bit.
Spark gap This is two aluminium electrodes (from the frame of the MO fan) bolted to part of the MO timer circuit board with all the components and printed circuit ground off. It really needs another section to give better quenching.
Primary is the MO transformer 6V winding which is heavy copper. This is stuck on to the 3 legged wheeled frame that the glass food tray sits on and rotates.
Secondary former is the cardboard internal cardboard insulation from the HV cap. It was washed but became a bit soft but still usable.
Secondary windings use wire from the fan motor and less than half was used. The hot glue didn't stick the cardboard former together properly and the windings slipped and overlapped. I have had some interturn shorting (and may still have) so I can't really push the power much without a rewind. No idea how many turns.
Toroid I did try winding lots of turns of wire on the fan blades but it didn't improve the performance. so I just left the metal mesh spacer that sits on the output of the magnetron for a nice colour.
Pics show the plan and sparks close up. Not fabulous performance but the proof of principle is there are plenty of opportunities to do better.
Peter
Tesladownunder, Sat Dec 09 2006, 03:38AM
Well no one won it. I didn't get the time before Dec 1. However I have done it - just 9 days late. Shown here with 1/2 inch sparks only but best in development has been 1 inch and plenty of scope for improvement with better design.
Here's how:
Power supply is the MOT. This needs current limiting and this is achieved with a 150nF capacitor and the voltage is boosted by a one stage multiplier using the MOT diode to give 6kV peak. Note that power is taken off across the diode not across the cap to get the voltage multiplier effect. Hey what's this about a 150nF cap? Where is that in a microwave oven? Well that is the key to this project. The 1uF 10kV DC mylar and oil cap (that is in all non-inverter MO's) needs to be taken apart and unwound. Lengths of the multilayered dielectric and foil are taken out and cut to length. It took about 10 feet of the windings to make 150nF. This is perhaps only 30% of the total. New electrodes were added.
Tank cap. This is a 1nF cap. The technique is similar but I retained the original electrodes from the cap to use in this section as they were better suited to a high current. Construction of this cap was different in view of the much higher voltage/current and frequency stresses. It used about 30% of the length of the cap windings. The plates were only about 1 foot long by 2 inches, however I used two sections of foil/dielectric between them. The foil was not connected and was kept to equalise voltage stresses. All in all something like 12 layers of mylar and 2 foil layers separate the main electrodes.
Being mylar they do warm up a bit.
Spark gap This is two aluminium electrodes (from the frame of the MO fan) bolted to part of the MO timer circuit board with all the components and printed circuit ground off. It really needs another section to give better quenching.
Primary is the MO transformer 6V winding which is heavy copper. This is stuck on to the 3 legged wheeled frame that the glass food tray sits on and rotates.
Secondary former is the cardboard internal cardboard insulation from the HV cap. It was washed but became a bit soft but still usable.
Secondary windings use wire from the fan motor and less than half was used. The hot glue didn't stick the cardboard former together properly and the windings slipped and overlapped. I have had some interturn shorting (and may still have) so I can't really push the power much without a rewind. No idea how many turns.
Toroid I did try winding lots of turns of wire on the fan blades but it didn't improve the performance. so I just left the metal mesh spacer that sits on the output of the magnetron for a nice colour.
Pics show the plan and sparks close up. Not fabulous performance but the proof of principle is there are plenty of opportunities to do better.
Peter
Re: TDU Microwave/Telsa prize
Tesladownunder, Sun Dec 24 2006, 03:43AM
.. and finally mounted in a microwave oven. Push START to run and STOP to stop or "cook" for as long as you like. (the electronics still work in the MO)
The final result is not that great really as I have blown the 150nF cap twice now and have to unwind it and chop a piece out. The caps certainly get warm. The spark is less than expected for the power increase and I think I have a shorted turn. It should be capable of perhaps 2 inches but a rewind would be a tedious affair - unless someone wants to put up more prize money
It looks odd having the diode across the spark gap but thats how you get the voltage multiplier to get 6kV peak (2kV RMS, 3kV peak and doubled to 6kV).
Peter
Tesladownunder, Sun Dec 24 2006, 03:43AM
.. and finally mounted in a microwave oven. Push START to run and STOP to stop or "cook" for as long as you like. (the electronics still work in the MO)
The final result is not that great really as I have blown the 150nF cap twice now and have to unwind it and chop a piece out. The caps certainly get warm. The spark is less than expected for the power increase and I think I have a shorted turn. It should be capable of perhaps 2 inches but a rewind would be a tedious affair - unless someone wants to put up more prize money
It looks odd having the diode across the spark gap but thats how you get the voltage multiplier to get 6kV peak (2kV RMS, 3kV peak and doubled to 6kV).
Peter
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