Electromagnetic valves for old sprayer

Hello, I would like to upgrade my old field sprayer, I plan to put electromagnetic valves behind the manual valves and then control them using the relays. Does it work? Has anybody already tried that? And can i use a 8 Relay Board?



when only closing the line to the boom, the pressure compensation (Gleichdruck= die kleinen Drehregler) will not work any more.
so new valve unit? Not sure, but I think Arag needs +/- to open and -/+ to close. So DPDT (2 polige Wechsler) needed.

If two valves are in line in the boom line, how can it change the operation of the pressure correction compared to using a manual valve (only one valve in line)?
I have an old Hardi srayer for which I will try solenoid valves.
Initially, I am going to test with a 12 V valve, similar to those used in washing machines. The passage of the flow is a bit suspicious, though there will be only five nozzles after the valve.
I’m just going to test

I am using this Arag parts. If you have any questions I can maybe help.

The pressure compensation valves in the picture have 2 output lines: one to the boom, the other to a adjustable gap (6 pink turn elements in the picture), simulating the nozzles. If you open/close the boom line the fluid goes either to the boom, or through the gap back into the tank. So flow resistance doesn’t change. You may test by closing the gap by turning the small levers, but I’m not sure if they are fully closable.
These construction uses as main pressure adjustment also a gap (and a overpressure valve), so the pressure rises/falls linear with the motor/pump rotation speed and with the ground speed. So allways the same rate.

OK. My old sprayer have only one regulation point before line valves, so pressure must be adjusted allways if some of line is closed.
I’m planning automation to that adjustment.
Maybe some kind geared motor controlled with Pressure transmitter will rotate the adjustin knop.

I didn’t think about that! Thanks for the information! I thought because I would put these behind the pressure regulating valves, it would work, I could also simply try it out by simply closing the hose and watching whether the pressure remains constant!

I’ve done this in the past on my old sprayer.
I’ve changed all the distribution unit :

  • Section 3 ways valves (return has adjustable flow to set it same as section)
  • General valve to release pressure
  • Pressure regulation with meter in the cab of the tractor
    It has “changed our life” (at the time beeing) and has worked very well for years.

Be careful about 2 points :

  • some valves requires to invert polarity, it requires 2 relays SPDT (or one DPDT) / valve
  • for controlling the general, you must do a logical OR on sections
    Diods is a solution but I have choose software
    with additional channel in Arduino (ESP8266 in my case)

just to give you an impression of an possible implementation likei did and @Francois discribed.

IMG_20200517_092405 IMG_20200517_092413

Initialy I used the relayboard, as on your first picture, for all motor-valves (2x each valve for invert the polarity - direction of movement). After some time i changed to L298N to slow down movement of the proportionalvalve (pressure adjustment) with pwm signal. (Now very fine and coarse adjustments are possible mith my software)


There is a complete rate control for AOG, programmed by SK21. So maybe buy a flowmeter and a motor pressure valve…

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Just had an idea. How about a 3-way valve, 3 outlet to return, so the pressure should stay the same?

my Rau D2 has a separate Main valve and pressure valve (lower left). From there the “spray” fluid goes up to the 5 valves (left side) and the “rest” fluid goes to the tank. So you can put the flowmeter there in between.
I have Altec valves (fromerly Rau) Modular-Fit Ventile - Altek


may work. No idea about the resistance of the used brass. On my Holder vineyard sprayer I had brass and allways small pieces of it in the nozzeles.

You would have to combine this valve with some sort of adjustable restriction, or you won’t have pressure left at all. Other issue, this type of valve has 3-5 sec. opening/closing time, that does not seem acceptable. I think I would prefer the rate control option. Pressure compensation could than be a proactive action on the pressure regulator upon closing/opening a section.

But if i understand it correctly the existing rate control code should be revised to act as a “plugin” to AOG