12v control valve

[outback]

I know this is getting out there, but nothing ventured nothing gained.

I'm after a 12v valve for controlling the flow of a liquid. I need to be able to control the flow rate going through the valve. I've looked at irrigation places, pump places, pool places etc. All I can find is a solenoid type valve which is no good as its only on or off.

Any ideas, options, thoughts all gratefully received.

[echnidna]

Coupla ideas
1. You could use several solenoid type one, each fitted with a different size jet or restrictor.
2. Use a step motor with the shaft connected to a tap.

[himzol]

Outback,

This is even more out there ... Check the RS electronics catalogue (or online), I think they may have something like what your after. Look in the pnuematic/fluid control area.

Himzo.

[rick_rine]

its a long shot but maybe a hydroponics company as they have controlled amounts of fertilizers in a liquid form added to the tanks automatically .

[echnidna]

What about a model aircraft RC unit hooked up to a valve

[DavidG]

outback
Can you control the pump rate rather than using a valve.

[outback]

OK,
Different solenoids with different valves sounds messy.

Stepper motor I had thought of, and was looking the answer.

RS Australia may well have what I want, they must have a brazillian different bits and pieces, I can't find it tonight, so I'll ring tomorrow/next week.

Can't control the pump speed, it has to remain constant.

I looked at RC stuff, couldn't really hit upon anything which got me excited.

Tried Hydroponics, couldn't see anything there either.

The problem is I need to vary the valve on the run so to speak. I can find stuff to vary pressure but not flow.

[Ashore]

Outback what volume of fluid are you talking about
What size pipe , flow and output of the pump
How accurate does it have to be


Russell

[gazaly]

From a hydraulic perspective WRT a variable DC linear solenoid, there are basiclly 2 types. One is force controlled and one stroke controlled. Both are driven by a controling DC amplifier.

A force controlled solenoid is used to output an change in output force for a set output stroke. For example, for a given input signal, the output force of the solenoid will be X neutons over a stroke of approx. 1.5mm. If the input signal is doubled, the output force will double, but the stroke length will remain constant.

A stroke controlled solenoid is basiclly the opposite. For a given input, the variable is the length of stroke. From what you have said, I think this is the type you are after.

Now, in the fluid power world, these are bloody expensive ($thousands), mainly due to the closed loop signal amplifier needed to drive the solenoid, but also becuase of the extreme accuacy. Bosch are one of the big manufacturers. They bought the German company Rexroth a few years ago, who where the big producer.

Hope this helps

[gazaly]

Just read your last post. Are you where the valve is when you want to vary its output? If so, you just need a simple flow control valve. This may need to be pressure compensated though.

[Ashore]

Gazaly
but can the pump handle the restriction on its output pressure , thus should it be a feed foward control system .
I was thinking as you however on a stroke type valve, but with control from a second hand car electric window winder with reduction via a belt pully as a cost effective alternative


Russell

[Cliff Rogers]

Hmmm... you need a proportionally controlled valve, most of them are current loop & need a controller to go with them.


Try the control shop at Honeywell. AC Controls for big AC installations. Mining control suppliers, Best, Leeds & Northrup.

[Munga]

We use bypass valves on boom sprays to vary the flow rate but only if the fluid can be recirculated back to the tank but in your case this may not be possible.

Cheers Arch.

[DavidG]

Outback
How about a full description of the proposed system please.
It is a bit hard trying to advise what is possible when we do not know the what or why of the question. :confused: :confused:

[echnidna]

Yeah - watcha makin"