Near Intersection of I-35 & I-90 Southern Mn. | Great, I somewhat follow your workaround of using two relays to create a polarity reversing output. I was not aware that D.J. used a PWM signal to control their valves. Their valves must be servo valves where the system controlled the position of the butterfly or ball valve based on the Duty Cyle of a PWM input. They needed power and ground to do the actual "work" of moving the ball or butterfly.
Your device "converted" that output to the basic +/- or -/+ to nudge a two wire valve either slightly more open or slightly more closed. The advantage of the D.J. approach could be that the system could remember the PWM output from the past if that would be useful for an initial setting.
My experience is coming from Raven where they use a very basic polarity reversing scheme directly and PWM is not involved with control for their two wire control valves. The newer Ravens do allow for a PWM output for control to work with hydraulic PWM valves or DC motors (they often needed an external driver). |
Dickey john rate controller with 2 wire flow control valve
