How to build an Electrostatic Spray system with pics.

[richie_rich]

Hi, I'm trying to build an electrostatic spray system. They are commonly used for spraying cars and pesticides onto fields of crop efficiently and easily. The spray is given a negative or positive charge that makes the spray attracted the opositely charged target (car or plant etc), ensuring less spray misses the target thus increasing efficiency.

I'm trying to make a very cheap and simple one for experimenting with. Its a cheap electric motor with a plastic cup on top. The liquid (in my case water) is fed into the cup whilst its spinning and the centrifugal force sends the liquid up the sides and out the cup creating a perfect mist.

However I can't seem to get the electrical charge into the mist. I'm directly charging the water with 25,000 volts and everything seems to be isolated. What is going on? Is there something that I am missing? Any help would be really appreciated! I've included a very simple picture to explain the basis of my design. Thanks

 

[DragonPetter]

How are you charging the water with 25,000 volts? Pure water is not ionized, it is electrically neutral, although it has a dipole.

 

[richie_rich]

I have used a flyback transformer from an old computer monitor. I've used the cable from that and connected it to the end of the tubing where the water comes out and into the rotating cup. What is it that your thinking? Can you think of any possibilities where I am going wrong?

 

[Naty1]

Is the tubing a conductor or an insulator?

 

[richie_rich]

Also the water I am using is not totally pure, it will contain nutrients that will feed the plants

 

[richie_rich]

The tubing is an insulator, along with the tank that I am using. One area I am slightly concerned with is the electric motor shaft that pokes through into the cup making contact with the water. However I've checked to see if the electric can leak out through the electric motor's main wires towards the plug but it all seems isolated to me. Whether or not the high voltage will effect the life of the motor or not is a different story I am not too sure of either!

 

[DragonPetter]

I have used a flyback transformer from an old computer monitor. I've used the cable from that and connected it to the end of the tubing where the water comes out and into the rotating cup. What is it that your thinking? Can you think of any possibilities where I am going wrong?

Is the output of the flyback transformer rectified to a DC level? If not, I'm not so sure that the voltage output waveform is reliable to ionize water.

I don't know much about this, but my thought is that if you are using tap water, then you want to ionize the water with an electrolysis method, where the ions bound to the water molecules will separate the water.

 

[richie_rich]

Perhaps more voltage is needed maybe?

 

[DragonPetter]

Perhaps more voltage is needed maybe?

No, that's not what I'm getting at. I meant that the waveform is some form of AC signal, and I don't think AC signals are good for trying to ionize water. Electrolysis uses DC voltage. I could be wrong of course :)

 

[richie_rich]

The primary winding of the transformer is center tapped and wound such as the output is composed of negative pulses only.

 

[richie_rich]

no i think your right, AC is'nt anygood to directly charge water! atleast we're thinking along the same wavelength.. no pun intended :)
I can't help but think maybe the current is gounding out somewhere because from what i understand you simply charge the water directly with a high voltage DC source and when the water leaves the cup it keeps the net charge it gained... I wonder if there's any easy way to diagnose any problems?

 

[DragonPetter]

no i think your right, AC is'nt anygood to directly charge water! atleast we're thinking along the same wavelength.. no pun intended :)
I can't help but think maybe the current is gounding out somewhere because from what i understand you simply charge the water directly with a high voltage DC source and when the water leaves the cup it keeps the net charge it gained... I wonder if there's any easy way to diagnose any problems?

But how is water charged? Electrons are added to the water molecules, or are there other ions like disolved salt: Na+ and Cl- that are bound to the water molecules that gives it it's negative/positive charge? I also think you would need either to research electrostatic inductive charging or electrolysis.

 

[richie_rich]

Yeah I am not too sure, i think your right that more research is needed. I have had a go with inductive charging but it needs to be set up really precise. I thought maybe this way it would be nice and simple but it turns out that its not the case. I will look into electrolysis now as I am not too familiar with it, thanks for helping out and pointing me in the right direction tho!

 

[DragonPetter]

Yeah I am not too sure, i think your right that more research is needed. I have had a go with inductive charging but it needs to be set up really precise. I thought maybe this way it would be nice and simple but it turns out that its not the case. I will look into electrolysis now as I am not too familiar with it, thanks for helping out and pointing me in the right direction tho!

Not sure if I pointed you in the right direction. I wish there was an expert here who would comment.