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Van de Graaff generator

Discussion in 'Projects, Builds, Woodworking, Metalworks' started by EricTheCat, Jan 29, 2017.



  1. EricTheCat

    EricTheCat Silver Member Silver Miner

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    Greetings,
    I thought there might be a few members here who would find this interesting.

    A Van de Graaff generator is an electrostatic generator that uses a belt that runs on two rollers of different materials to transfer and accumulate electric charge onto a dome (over-simplification for brevity). If you have ever seen a physics demonstration where someone puts their hand on a metal dome and their hair stands up most likely it was done using a Van de Graaff generator.

    First I made a very little one that uses a single regular rubber band for the belt, a piece of a pen for the bottom roller and a Christmas light for the top roller. It worked better than expected giving me 1" sparks and to my surprise even the little one is capable of raising my hair.

    Then I made a slightly larger prototype that uses 3 rubber bands cut and glued to make a slightly longer belt (around 7 inches spacing between rollers). This one uses nylon spacers for rollers and I coated the top roller with electric tape to give it a negative charge. This one runs incredibly smooth and quietly and also exceeded my expectations giving me 3-4 inch sparks.
    Edited to add: The base of this is a PVC drain adapter and inside it there is a AA battery holder that holds 4 AA batteries that run the motor that is housed inside of the "T" adpater.
    VanDeGraaffGenerator-MediumPrototype-2017-Img_3514SSS.jpg

    VanDeGraaffGenerator-MediumPrototype-2017-Img_3418SSS.jpg

    Then I made this build, which I am calling my medium Van de Graaff generator. It too uses a pair of nylon spacers for the rollers. This time I coated the bottom roller with electric tape (vinyl) which gives me a positive charge on the top dome and a spacing of around 14 inches between rollers. For a belt I am using a section of a therapy band that I cut to shape (27" by .5") and glued to form a belt. I get >6" sparks off of it but they are very faint but branch out like lightning.

    VanDeGraaff-Medium-2017-01-29-Img_3630SSS.jpg

    Here I have a part of a light bulb that is coated in aluminum duct tape on top of it to act as a break-out point and encourage it to spark out into the air
    VanDeGraaffGenerator-2017-01-27-Img_3629SSS.jpg

    Anyway, probably more here than you wanted to know. I hope you enjoy. This is one way to get through winter. ;)
     
  2. BackwardsEngineeer

    BackwardsEngineeer If I weren't a snowflake, I'd have no luck at all Silver Miner

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    Hey Eric, are you any relation to Fritz?
     
  3. Goldhedge

    Goldhedge Modal Operator/Moderator Site Mgr Site Supporter

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    Thanks for the tech! Love this stuff!
     
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  4. EricTheCat

    EricTheCat Silver Member Silver Miner

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    No. At least I don't think so.
     
  5. EricTheCat

    EricTheCat Silver Member Silver Miner

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    Thanks! I am glad you like it.

    I forgot to mention, I have a larger one in the works. :)
     
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  6. Eyebone

    Eyebone Midas Member Midas Member

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    Do you have an estimate of the voltage and amps produced?

    Thanks and I like your presentation.

    There must be finer points of low voltage electrics that I don't understand so bear with me.
     
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  7. Someone_else

    Someone_else Gold Member Gold Chaser

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    From the bottom chart, here, it looks like 200k to 300k volts.
    http://www.kronjaeger.com/hv/hv/msr/spk/
    Current must be negligible, but you could get a very rough idea by measuring the input power (motor watts), subtracting some fudge factor for friction loss and dividing by the voltage. For a simplistic example, if one watt is going into the motor and one third of the power is wasted, we might expect 2 microamps.
     
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  8. Ensoniq

    Ensoniq Midas Member Midas Member Site Supporter ++

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    Man I thought this was going to be a prog rock thread

     
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  9. EricTheCat

    EricTheCat Silver Member Silver Miner

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    Thanks! Someone_else's answer sounds about right. I was thinking the voltage is around 200KV with some loss as the sphere on top is only really rated to 140 KV. The amount of current is very little. I know some people try to measure the current by tracking how quickly a spark will occur to another sphere. I haven't done that yet because "exceedingly low" current is accurate enough for my uses. ;)
     
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  10. Eyebone

    Eyebone Midas Member Midas Member

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    At work this morning I noticed that Seattle has a 'Spark Museum'.

    There was an article in a very local paper about it.


    Same type of thing only bigger.

    I'll post a link and story Wednesday.
     
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  11. Ragnarok

    Ragnarok I'd rather be Midas Member

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    I have yet to build a Van deGraaf machine, but I did some playing with different materials, a short piece of 4" aluminum pipe, a "belt" made of a 4" wide strip of mylar held together with packaging tape, and a piece of 2-1/2" PVC rod. Placed the PVC in the loop of the belt and hung the belt over the aluminum pipe. While holding the assembly off the ground I turned the aluminum pipe section in my hands and could feel the static build up. Very interesting stuff.

    There are many resources on the web that explain which materials are best st generating static charges. Here is one for those interested.

    http://www.esdjournal.com/techpapr/ryne/ryntribo.doc

    R.
     
    Last edited: Jan 30, 2017
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  12. Bigjon

    Bigjon Silver Member Silver Miner Site Supporter ++

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    h ttps://www.youtube.com/watch?v=dabJMBGMVqI



    http://www.keelynet.com/
    http://www.keelynet.com/news/013017a.html

    Great news. A company has just started selling a free energy device that produces over 7300 Watts of power using no fuel. It's designed to work 24 hours a day and is warrantied for 5 years. The company allows you to try out the machine for 30 days before paying for it.

    It looks a lot like a clone of the Swiss Methernitha device by Paul BAUMANN which is called the Testatika Generator and uses electrostatic energy collected from the air. Testatika details and Testatika photos.

    Methernitha Testatika free energy machine part 1

    Testatika clone

    Testatika power theory

    Free Energy: Methernitha, The Testatika Machine, Inventor, Paul Baumann
     
    Last edited: Jan 30, 2017
  13. EricTheCat

    EricTheCat Silver Member Silver Miner

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    Neat. I used the triboelectric series to plan roller materials. Yeah it certainly does not take anything too complicated to generate some good static electricity. My first experiments were as a teenager using a piece of PVC pipe and a shirt. I would rub the shirt on the PVC with a wire to charge up laden jars that I made using glass mellow yellow bottles filled with salt water with aluminum foil taped around the outside (not the old style bottle, they had glass into the 90s for whatever reason). I grounded the aluminum foil to the screw on my heat vent. If you touched both sides it had quite a bite!

    I ordered the top dome for my larger build today. This could get interesting. This dome is 14 inches in diameter and should be capable of managing 500 KV. I will be using bed castors for the rollers and 3" PVC for the enclosure. Probably going to be a lot like my medium build just scaled up.
     
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  14. Ragnarok

    Ragnarok I'd rather be Midas Member

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    I wonder if it would be possible to build a double-ended VdG generator to maximize the potential difference. Teflon/glass rollers, cotton belt, etc.

    R.
     
  15. EricTheCat

    EricTheCat Silver Member Silver Miner

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    I would think that should be possible. I have thought about this myself. It would be a neat experiment. There would be some interesting design questions when it comes to how to run the belt. You don't want anything conductive near the dome if you want it to build up a good voltage. I am sure there might be some good way to get around that.

    One fun alternative is to build two generators of opposite charges and run them side by side as far as they will still spark. I can get 9" sparks between my medium prototype and my medium build. Each one I built I kept reversing polarity so I can run them against each other.
     
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  16. Someone_else

    Someone_else Gold Member Gold Chaser

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    (Obligatory Ghostbusters reference)
    Just don't cross the beams. It would be bad.
     
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  17. Ragnarok

    Ragnarok I'd rather be Midas Member

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    I'm waiting for someone to put a shortwave UV laser or other ionizing source inside the suitably perforated top terminal of a VdG or TC for some directed energy mischief.⚡️

    R.
     
    Last edited: Feb 1, 2017
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  18. EricTheCat

    EricTheCat Silver Member Silver Miner

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    I like the idea very much. It probably will not be me, however. I value my eyesight to the extent that I do not trust myself with super powerful lasers.

    Now laser pointers I have played with, which reminds me of a project I built around 10 years ago (I might add a thread about it here). I was cleaning up my work bench and found a 2n3022 transistor sitting out. I did not know if it belongs in my good transistors drawer or my broken parts drawer. So I looked around my bench to see if I had something to test it with. I noticed a laser pointer and an MP3 player. I wired the MP3 player up to the transistor and then wired the laser pointer so that the audio from the MP3 player would control the laser. Next thing you know I had a pulsing laser that pulsed with the music. I realized I could probably receive that sound on the other end so I hooked up a photodiode to the mic input on my laptop and sure enough I could hear the music over the laser and it sounded good. I thought that was pretty cool so I mounted the laser circuit into an altoids tin and added a switch, an audio jack and even a tripod mount. All because I wanted to clean up my work bench one day. lol
     
  19. Someone_else

    Someone_else Gold Member Gold Chaser

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    Wow, fancy! I would have just put a pot on the base and a power resistor and current meter on the collector.
     
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  20. EricTheCat

    EricTheCat Silver Member Silver Miner

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    The 14" dome for my larger build came yesterday. It's beautiful!

    I am still deciding what motor to use. I have a nice 120v motor with power supply. The power supply is not rated for continuous duty though. I had half a mind to just strap a heat sink on the bridge rectifier and call it good. That might work fine but before I go on building I am going to look for something more suitable. Something with good speed control would be better. I may even end up getting a dremel tool or drill with speed control to use (may not be continuous duty either but I feel like they would hold up). I have considered fan motors as well. Some people use sewing machine motors because they tend to have nice speed controls but I feel like that could be getting too bulky.

    Hand me that RAM stick, could you?
    Hair-Img_2078.jpg
     
    Last edited: Feb 5, 2017
  21. EricTheCat

    EricTheCat Silver Member Silver Miner

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    For those that weren't frightened off by the above pic :winks2:

    I decided against a drill or a dremel for the motor after seeing how much my drill sparks on the commutator (and they probably all do). Trading speed control for reliability. I ordered an AC motor that wasn't too expensive and is continuous duty. Not sure if it will work being 1450 RPM but I'm going to give it a shot even if I end up having to add some gear or belt type reduction. I don't mind taking my time on this larger build so it will hopefully last. (someone out there is thinking "I could have made dozens of these by now!").
     
  22. EricTheCat

    EricTheCat Silver Member Silver Miner

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    I finished the motor control circuit for the large build today. It will be mounted to the platform. It allows me to take advantage of the motor being reversible. The switch on the left controls power. The switch on the right controls the direction the motor turns. The control circuit contains a capacitor that is required for the motor in addition to the switches and power adapter. I used a standard PC power socket for the power adapter so that I can use a common PC power cable to run power to it. The green wire is the ground wire that will eventually be trimmed.

    VanDeGraaff-Big-2017-02-16-MotorControl-Img_3665SSS.jpg

    VanDeGraaff-Big-2017-02-16-MotorControl-Img_3666SSS.jpg
     
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  23. Ragnarok

    Ragnarok I'd rather be Midas Member

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    Series wound motors like those in tools do spark a lot. I think the motor you chose will be fine.
    Question: If you reverse the direction of the motor how fast will the machine discharge itself?

    R.
     
  24. EricTheCat

    EricTheCat Silver Member Silver Miner

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    It would charge in either direction and in the same polarity in either direction.

    If you're wondering why I bothered with the reverse control then, to be honest mainly because the motor supports it. There is also a slight chance it will run better in one direction vs. the other in a physical sense.

    I am hopeful about this motor. It seems really well built, it runs very well and it doesn't use very much power. Not a bad deal for $10. There is a chance it will not have enough torque even with the 1/5 reduction gearing I will use but my gut tells me it will do just fine now that I have seen the motor run.

    Thanks for the comments, I appreciate it.
     
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  25. EricTheCat

    EricTheCat Silver Member Silver Miner

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    I have made some good progress on the large build. The base is ready, the motor and motor control circuit mounted, the rollers, bearings, gears and belt are all installed. The bottom brush is done. It sure is nice to see that the belt runs centered on the rollers with no issues at least in my initial tests. Only thing left is the top brush assembly which I am waiting on a part for. I don't want to count my eggs before they hatch but it looks very hopeful that this design is going to work well. Hopefully I'll have some pics including some nice sparks soon. It is hard to wait for the part I need, I might end up just hacking something together for the short term.
     
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  26. Goldhedge

    Goldhedge Modal Operator/Moderator Site Mgr Site Supporter

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  27. EricTheCat

    EricTheCat Silver Member Silver Miner

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    lol. Know where I can score some catnip? :don't know: Not growing here for a couple months.

     
  28. EricTheCat

    EricTheCat Silver Member Silver Miner

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    Here is the base with bottom brush
    VanDeGraaffGenerator-Large-2017-02-26-Img_3675SSS.jpg

    About what it will look like. 35" between bottom roller and top roller. Top dome is 14" in diameter.
    VanDeGraaffGenerator-Large-2017-02-26-Img_3674SSS.jpg
     
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  29. Ragnarok

    Ragnarok I'd rather be Midas Member

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    That is an impressive looking machine.
    Looking forward to seeing it run.
     
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  30. EricTheCat

    EricTheCat Silver Member Silver Miner

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    I found a part that would do just as well at another store and have achieved first sparks! :troll:

    Initial result. Nothing. o_O

    Made some adjustments on the brushes and tried again. Nothing. o_O

    Realized that I did not clean the dome after I got it. Wiped off the dome. Like magic, it is working great now. Likely there was some metal debris causing leakage. It produces strong 8" sparks to the back of my hand. They sting a little. :)

    I will try to get some pics tonight after dark.
     
  31. EricTheCat

    EricTheCat Silver Member Silver Miner

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    Here are some of my first spark pics from the large build. The last pic is a composite to show scale (dome is 14" in diameter). Most of the sparks are going to my fingertips in these pics. I am getting sparks up to about 14". Thanks for looking.
    :beer:

    VanDeGraaff-Large-2017-02-27-Img_3740C1SS.jpg
    VanDeGraaff-Large-2017-02-27-Img_3778C1SS.jpg VanDeGraaff-Large-2017-02-27-Img_3732C1SS.jpg VanDeGraaff-Large-2017-02-27-Img_3713C1SS.jpg
    VanDeGraaff-Large-2017-02-27-Img_3787-3751-CompositeSS.jpg
     
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  32. Ragnarok

    Ragnarok I'd rather be Midas Member

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    Bravo!
     
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  33. EricTheCat

    EricTheCat Silver Member Silver Miner

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    Thanks! Here are a few more pics.

    The gearing.
    VanDeGraaff-Large-2017-02-28-MotorGears-Img_3796SSS.jpg

    This is the top brush assembly. Just like the lower brush it is built on to a PVC drain piece. The top of the inside of the dome sits right on the bracket.
    VanDeGraaff-Large-2017-02-28-Top-Img_3791SSS.jpg VanDeGraaff-Large-2017-02-28-Top-Img_3792SSS.jpg

    A few more sparks just for fun.
    VanDeGraaff-2017-02-28-FromVideo1SSS.jpg VanDeGraaff-2017-02-28-FromVideo2SSS.jpg VanDeGraaff-Large-2017-02-28-Sparks-Img_3811SSS.jpg VanDeGraaff-Large-2017-02-28-Sparks-Img_3841SSS.jpg

    Thanks for looking,
    Eric
     
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