automatic flow control

Hello,

Is anybody out there doing a programmed variation of the flow out of the nozzle? For example, making the arc slowly grow longer for a while, stopping, and then getting shorter. If so, how are you controlling the flow rate? I had expected to just have a pump with a ball valve after it so that I could manually throttle the flow to the nozzle. When I started thinking about using a microcontroller to vary the arc, I at first thought about connecting a stepper motor to the ball valve. I suspect, however, that the initial torque to get the ball valve moving is going to be too high for most stepper motors. Anyone know if I am wrong and a stepper will work? I have heard that a globe valve might be a better choice. Anyone using one of those? I haven't seen any of those as 1.25 inch PVC - but haven't looked terribly hard at this point. Or should I maybe be looking for a pump with some special capabilities? Or maybe I should be somehow trying to do PWM to the pump (though I guess I don't see how I could if it runs on standard AC mains)? Any thoughts are appreciated. I would hate to go and spend a lot of cash on a pump only to find out that I got one lacking some needed capabilities.

Thanks,

-David

Hi Davo

I did that, but i used a selfmade 230V dimmer, controlled by a microcontroller. Its not a big deal, but my final version has a fixed output. i dont need it anymore. But your solution of the ball valve sounds also good.
But i think its easier to build a Dimmer. I made something simmilar than this http://www.hoelscher-hi.de/hendrik/light/dmxdimmer.htm#Lastteil

Have fun, Regards Mario