could i control on /off solenoid valve using pwm to control flow ?or it will just open or close?
here is a valve example http://www.ebay.com/itm/1-2-Brass-E...005&rk=3&rkt=6&mehot=pp&sd=121333061531&rt=nc

 

No, these usually have a proportional valve that is controlled by a ±10vdc amplifier or controller.
Max.

 

what do you mean by "these"?

 

the one you link will draw power to open the valve (you can not control via voltage how open it is; its ether open (via 12v energized) or closed (no power)).

 

Valves similar to the one linked to in post #1 usually use the supply side pressure to assist in closing the valve. When the solenoid is energized, a small bleed port is opened in the diaphragm which allows the pressure holding the valve closed to bleed off and the valve to open. This type valve is not designed to modulate flow, just full or none.

 

what do you mean by "these"?

Ones that will perform the task you describe via PWM etc.
They are called proportional valves as the pilot spool is moved 'proportionally' according to the applied signal. They are used with an appropriate amplifier in closed circuit control of hydraulic equipment and are very expensive compared to the simple single movement spool valve.
Max.

 

could i control on /off solenoid valve using pwm to control flow ?or it will just open or close?
here is a valve example http://www.ebay.com/itm/1-2-Brass-Electric-Solenoid-Valve-12-VDC-Water-Air-Fuels-Gas-VITON-SEAL-B21V/300714222574?_trksid=p2047675.c100005.m1851&_trkparms=aid=222007&algo=SIC.MBE&ao=1&asc=30002&meid=8d8843e16da4462a8036c8e0b53c9781&pid=100005&rk=3&rkt=6&mehot=pp&sd=121333061531&rt=nc

Your problem may be not on the electrical side. I notice that this valve is a pilot-operated valve, not a direct acting solenoid.

 

Your problem may be not on the electrical side. I notice that this valve is a pilot-operated valve, not a direct acting solenoid.

The OP has not got back for 4 months now?
Max.