hi i really like your quality work in putting that thing together, i am almost done building mine, since yours is doing a good job in producing good voltage i was just wondering, i read somewhere that said it is better to put the brushes on the side where the belt is rolling away or off from the roller, does this matter or do you know which side works better to put the brushes at and can i put brushes on both sides of one roller to make it more effective, or to eliminate guessing??
I'm trying to make a van de graaff generator like this but when I tested it I only got 1/2 cm sparks do you know why? The video about the van de graaff is on my channel.
@AHW214 Try to control the room moisture, often moisture is the main problem, and try to dry the entire machine (external and internal part) with an hairdryer, works very well for me!. After, control that near the dome aren't some kind of spikes, like aluminium foil spikes or uncovered wire spikes.
could you do me a favor? Get a spray bottle of water.. and spray a stream of Mist right down between the 2 spheres while its sparking, maybe the water will explode..
salad bowls, and for the rolles I used two PVC rolles, but one of them are covered with aluminium foil, in order to obtain PVC negative effect at the bottom and aluminium positive effect at the top.
The value is calculated using the air dielectric strenght value, which is 2kV\mm, so 20kV\cm.
If it's right that 1 inches = 2,5 cm, and I measured my VdG generated spark, that I found as 5 cm long, it's the same to say that spark is 2 inches long ('cause 2 inches = 5 cm), so we have 20kV/cm * 5 cm = 100kV with a 2 inches long spark.
Well I'd like to see an actual measurement with a high-value resistor or something. In fact, I have a few long multi-megohm resistors which would be perfect for that application.
You're estimating and not measuring. True, I can only comparatively measure, but I've had a 30kVDC power supply that popped off sparks as long as that. DC does behave differently than ac, I'll give you that, so it not rightly fair for me to compare it to something like a neon transformer, but still...
Yes, you're totally right. I'm only estimating, the electric field isn't uniform and it has lots of discharges due to corona effect. I'm estimating the voltage value only on mathematic, as you can see on my first comment.
I'm sorry but it's impossible to measure the right value because i hadn't a so large resistor...but I appreciate your comments :D
Thanks you all guys! I hope you want to continue discussing about that!!
I'm sorry for my english, but I'm an 19-years-old italian guy ;)
Please look up "sphere gap tables". You will have to interpolate a little because of the non-uniform field, but the estimate of 20 kV per centimeter is actually conservative. This machine is easily reaching 100 KiloVolts, as the presenter states.
I won't accept a measure of the electric field over specific gemoetries to be an accurate representation of the voltage. I'm sure if you had a needle on top of that van-de-graff it would just bleed corona, you might get an electric field value somewhere in the range of 'megavolts' in its local electric field.
I'm willing to send him a large resistor if only so he can measure with a volt meter and equations the accuracy of his statements.
High voltages like these are measured with calibrated gaps between spheres. If the spheres are generally larger than the gap being measured, the figure of 30 kV per centimeter is pretty close. Needles and spheres smaller than the gap will give longer gaps for the same voltage. Your 30 kV supply clearly was not sparking between large spheres.
Please Google "sphere gap tables" and you will see for yourself.
The problem with resistors at those voltages is just that--everything conducts!! It takes a very special resistor to have a precisely known value at 100+kV. This is why it's done with gaps--they are actually more accurate, if done right.
hey, do you sell these generators, grtzzz
branders2589 10 months ago
@branders2589 Hi! I'm sorry but I'm a private and I built it only for hobby!
theunreal89 9 months ago
I used plate shears
theunreal89 1 year ago
can i ask you how you cut your hole in the dome?
tikifish28 1 year ago
This has been flagged as spam show
hi i really like your quality work in putting that thing together, i am almost done building mine, since yours is doing a good job in producing good voltage i was just wondering, i read somewhere that said it is better to put the brushes on the side where the belt is rolling away or off from the roller, does this matter or do you know which side works better to put the brushes at and can i put brushes on both sides of one roller to make it more effective, or to eliminate guessing??
hadabeesago 1 year ago
I'm trying to make a van de graaff generator like this but when I tested it I only got 1/2 cm sparks do you know why? The video about the van de graaff is on my channel.
AHW214 1 year ago
@AHW214 Try to control the room moisture, often moisture is the main problem, and try to dry the entire machine (external and internal part) with an hairdryer, works very well for me!. After, control that near the dome aren't some kind of spikes, like aluminium foil spikes or uncovered wire spikes.
P.S.: I'm sorry for my english, I'm italian =)
theunreal89 1 year ago
Very nice generator you have there.
jupy921 2 years ago
could you do me a favor? Get a spray bottle of water.. and spray a stream of Mist right down between the 2 spheres while its sparking, maybe the water will explode..
teslanumbertwo 2 years ago
probably wrecked that cd you had down there
chaosmutt 2 years ago
ehehe yes probably :)
theunreal89 2 years ago
cool
acromine579 3 years ago
what did you use for collecter dome, and rolles?
tikifish28 3 years ago
For the collector dome I used two aluminium
salad bowls, and for the rolles I used two PVC rolles, but one of them are covered with aluminium foil, in order to obtain PVC negative effect at the bottom and aluminium positive effect at the top.
theunreal89 3 years ago
sounds like sex
unleashdabastards 3 years ago
useless...
theunreal89 3 years ago
The value is calculated using the air dielectric strenght value, which is 2kV\mm, so 20kV\cm.
If it's right that 1 inches = 2,5 cm, and I measured my VdG generated spark, that I found as 5 cm long, it's the same to say that spark is 2 inches long ('cause 2 inches = 5 cm), so we have 20kV/cm * 5 cm = 100kV with a 2 inches long spark.
theunreal89 3 years ago
Well I'd like to see an actual measurement with a high-value resistor or something. In fact, I have a few long multi-megohm resistors which would be perfect for that application.
You're estimating and not measuring. True, I can only comparatively measure, but I've had a 30kVDC power supply that popped off sparks as long as that. DC does behave differently than ac, I'll give you that, so it not rightly fair for me to compare it to something like a neon transformer, but still...
RotogenRay 3 years ago
Yes, you're totally right. I'm only estimating, the electric field isn't uniform and it has lots of discharges due to corona effect. I'm estimating the voltage value only on mathematic, as you can see on my first comment.
I'm sorry but it's impossible to measure the right value because i hadn't a so large resistor...but I appreciate your comments :D
Thanks you all guys! I hope you want to continue discussing about that!!
I'm sorry for my english, but I'm an 19-years-old italian guy ;)
theunreal89 3 years ago
pretty good english I'd have to say.
your estimation was correct as far as it seems the debate has panned out...
RotogenRay 3 years ago
Since when was 2 inches 100kv?
thats 15, maybe 20kV.
RotogenRay 3 years ago
Please look up "sphere gap tables". You will have to interpolate a little because of the non-uniform field, but the estimate of 20 kV per centimeter is actually conservative. This machine is easily reaching 100 KiloVolts, as the presenter states.
TinselKoala 3 years ago
I won't accept a measure of the electric field over specific gemoetries to be an accurate representation of the voltage. I'm sure if you had a needle on top of that van-de-graff it would just bleed corona, you might get an electric field value somewhere in the range of 'megavolts' in its local electric field.
I'm willing to send him a large resistor if only so he can measure with a volt meter and equations the accuracy of his statements.
RotogenRay 3 years ago
High voltages like these are measured with calibrated gaps between spheres. If the spheres are generally larger than the gap being measured, the figure of 30 kV per centimeter is pretty close. Needles and spheres smaller than the gap will give longer gaps for the same voltage. Your 30 kV supply clearly was not sparking between large spheres.
Please Google "sphere gap tables" and you will see for yourself.
TinselKoala 3 years ago
...Ok, you may be correct about that
Nevertheless, I'd STILL like to see a measurement with a resistor... but I'll accept that the 100kV estimate lends itself more towards the truth.
RotogenRay 3 years ago
The problem with resistors at those voltages is just that--everything conducts!! It takes a very special resistor to have a precisely known value at 100+kV. This is why it's done with gaps--they are actually more accurate, if done right.
TinselKoala 3 years ago