Thanks for the reply
The proportional valve require unidirectional PWM pulses
By varying the PWM duty cycle I have to control the valve position
I am using Proportioning Solenoid Valve from
https://www.electro-tech-online.com/custompdfs/2008/08/SVP_iom-3.pdf
Regards
nari
hi nari,
I have looked at the pdf.
What you need to do is control the pulse width as well as the frequency.
Taking a very rough example:
Assume the 100% operating speed from closed to open was say, 1 sec
If you applied 24V, the 400mA would flow and the solenoid would fully open in 1 sec.
If you now applied 24V for 0.5sec the valve would reach its 50% open point before the current was shut off,
the valve would then start to close.
If now you repeatedly applied a short pulse of 24V the valve would held at the 50% open point.
By increasing or decreasing this 'holding' pulse width the valve could be held at any position.
The graph on the pdf is just a guide, you will have to experiment with the PWM timing to get it just right.
What I would do is to set up a variable freq 555 driving a variable delay monostable.
The output of the mono would drive a power FET, which would power the valve.
While varying the freq of the 555 and the delay of the mono, use a scope to get an indication of the range of the PWM.
Once you have these values you could then program a PIC.
Use the PIC's adc inputs and connect two pots, one for freq and the other for the PWM period. [use the on PIC PWM of course].
Does this help.?