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Pneumatic PWM Solenoid Valve 3
- Thread starter CBlundell
- Start date
Dear CBlundell,
If you need a pulse width modulating solenoid valve, Danfoss Industrial Controls Division in Baltimore (410-931-8250) has that type of valve. But then you mention pneumatic? That's a different animal. Confusing. Asco is probably the largest solenoid valve supplier in the USA, you could try finding a distributor and ask them (ascovalve.com).
KevinF
If you need a pulse width modulating solenoid valve, Danfoss Industrial Controls Division in Baltimore (410-931-8250) has that type of valve. But then you mention pneumatic? That's a different animal. Confusing. Asco is probably the largest solenoid valve supplier in the USA, you could try finding a distributor and ask them (ascovalve.com).
KevinF
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- #3
Do you mean an ON-OFF highj speed pneumatic valve where the valve is closing and opening the inlet/outlet orifice at high frequency using a PWM Duty Cycle command to control the pressure? Or where the electric power supply is PWM driven such as common with Brushless motors power supply?
- Thread starter
- #4
CBlundell
The advantage with such application using ON-OFF 3-way or two valves of 2-way to contol the pressure in a controlled volume is that the average pressure in the controlled volume is a function (S shaped like curve function) of the Duty Cycle only with no need for pressure sensor.
The frequency of the PWM will detemine the ripple size however, the higher the frequency the shorter the valve orifice seats life.
I have developed and designed such high frequencey valves for the last 25 years and have the analytical tools and knowledge to calculate and simulate the pneumatic time response of the control volume (constant and variable) and the electrical and mechanical time response of the valves.
However, pay attention to the fact that the forces on the valve plunger are function of the average pressure meanly, a function of the Duty Cycle. Therefore, the valve mechanical time delay (dead time from the command to open or close until it close or open the orifice) is not constant and will change with the Duty Cycle. This can make a difference at high frequency.
The advantage with such application using ON-OFF 3-way or two valves of 2-way to contol the pressure in a controlled volume is that the average pressure in the controlled volume is a function (S shaped like curve function) of the Duty Cycle only with no need for pressure sensor.
The frequency of the PWM will detemine the ripple size however, the higher the frequency the shorter the valve orifice seats life.
I have developed and designed such high frequencey valves for the last 25 years and have the analytical tools and knowledge to calculate and simulate the pneumatic time response of the control volume (constant and variable) and the electrical and mechanical time response of the valves.
However, pay attention to the fact that the forces on the valve plunger are function of the average pressure meanly, a function of the Duty Cycle. Therefore, the valve mechanical time delay (dead time from the command to open or close until it close or open the orifice) is not constant and will change with the Duty Cycle. This can make a difference at high frequency.
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- #6
I would think a standard valve would work fine with PWM (of lower carrier frequency) using at least a diode across the coil. This should not hamper any valve or reduce its life (since no real high switching frequency). My experience has been with air and hydraulic. Unfortunately (fortunately for me) I was not around when the company tested this thing (I left the company). So maybe I could be wrong but seems you would not need any special valve to use PWM signals to drive it.
I would come up with a way to get some feedback on this valve opening so you can calibrate out any error every day or there abouts (due temp variation, humidity, etc).
I would come up with a way to get some feedback on this valve opening so you can calibrate out any error every day or there abouts (due temp variation, humidity, etc).
- Thread starter
- #7
Thanks buzzp. I was told by the Burkert people that both the valve and the solenoid have to be special. I am not sure I trust the answer though. My observation is that the technical expertise of the average industrial supplier is going down not up and all to often they don't know what they are selling. I do remember when this technoligy came to hydraulics it seemed most people were just using normal solenoid valves and turing them into proportional valves with pwm.
You might try Eaton. I believe they were bought out. Not sure by who.
I was thinking of something else when I posted, my apologies if some of my comments are off base.
I dont think the valve would have to be any thing special. The solenoid design is probably more important. My experience is with hydraulic valves and pneumatic cylinders. I do believe the vendor (Eaton) had designs to be used for only DC (PWM) control. I think some generic valves can be controlled via PWM and on the other hand, I think some can not. I believe it all depends on the design. I hope this gives you some ideas.
I was thinking of something else when I posted, my apologies if some of my comments are off base.
I dont think the valve would have to be any thing special. The solenoid design is probably more important. My experience is with hydraulic valves and pneumatic cylinders. I do believe the vendor (Eaton) had designs to be used for only DC (PWM) control. I think some generic valves can be controlled via PWM and on the other hand, I think some can not. I believe it all depends on the design. I hope this gives you some ideas.
Kavin, You would of been better off with a new post but try all the vendors listed above. Eaton has been bought out, I believe. Maybe by Tyco? Not sure but still think their web page is up. They should have one to use. Ask for proportional valve if you need something other than fully open or fully closed. If all you need is full open or full close then use a standard DC valve and drive it with your PWM but put something across the valve coil (diode, RC network, etc) to suppress the transients. Careful, because whatever method you choose for suppression will affect the open/close times of the valve. This is usually not a problem with most applications (affects times by no more than 0.5 second - usually much, much lower like milliseconds).
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