Mueler/Muller Spraydos AgOpenGPS section control

I made an electromechanical approach to open source section control of Mueler/Müller Spraydos spraying computers through software as AgOpenGPS. This project provides the mechanical design for a non-intrusive addon mod to automatically control the sections on a spraydos computer through a gps system. All needed parts and other information are discribed on github

I provide some limited print service for Western europe. Contact me through github or on this thread

The system consists out of a bracket, that clamps around the spraying computer and doubles as electronics box, and a servo box on a hinge. The main section switch and all other buttons remain freely accessible.

The servo box contains servos to control the section switches through specially designed lever arms. The servo box is mounted on a hinge and can be swung away to regain manual control. The servo box can be kept closed through magnets or an M4 bolt

The electronics box on the back has mounting points to accommodate a 8ch servo controller, A DC buck converter and a 8 channel relay card (optional). The optional relay card can be replaced with a second servo controller when you need 9 sections (mounting holes are there in the new models). Two 16mm holes for input power and section signals and a threaded hole for a sleeve to the Servo box are foreseen.

Why control the buttons mechanically and not switch section through relays?

  • Motorised valves need 2 relays per section (18 in total…).
  • You cannot put relays in parallel to the buttons, you will create a short.
  • To keep the switches as manual backup they cannot be replaced by relays.
  • Breaking the lines going to the the valves and changing the state there with relays could work. But the rate controller will not work anymore since it does not know the real state of the sections. (You could compensate this by changeing the speed signal however)
  • To keep the mod as a bolt-on add on to keep the controller original for resale when the time comes.

Looks great!

Probably a good reason, but could you replace the section control switches on the Spraydos terminal, with 3 position switches?

Using the third position with a relay.

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You say you need 18 relays? Can you not use 9 DPDT?

The rate controller must be getting a signal from the power on of the relay for each section, no reason you cannot replicate this.

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Completely true, but boils down to the same thing, you need two contactors per section. The reason I phrased it like this is becquse many people including me like to use completly ready boards and most of the cheap ones sold dont use 2C relays.

Completely true, but boils down to the same thing, you need two contactors per section. The reason I phrased it like this is because many people including me like to use completly ready boards and most of the cheap ones sold dont use 2C relays.

There are no relays in the original controller only bistable 2C switches. They tap of the on off signal from the power lines going from the switches to the motorised valves. You could probably simulate these signals. However, it would conflict with my last point to keep the controller as close to original as possible to original for resale/backup. Also since these signals are not present on the outside connectors you would need to add wires in an already overfull box.


I understand what kind of functionality you try to add but do not really understand what kind of contacts you would plan for the third state of the switch to make this work electrically? Could you maybe make a sketch?

Very nice box!

The main switch would still have to be integrated into the box. I don’t know which sketch you are using, but AOGmatic also controls the main switch.

Thank, for our application i used the following logic concerning the main switch.
The main switch is not controlled by AOG. It is free to manually controll the on/off state of the sprayer as a safety/override to make shure it cannot turn on when AOG turns on a section unexpectidly. Futher AOG does not need the main switch:
-Main on → AOG can controll the sections (all section off and main on = sprayer off, this causes no problems for this sprayer)
-Main off → Does not matter what AOG does with the sections, nothing turns on

I understand the security considerations. :+1:
For me it was important that the main switch was also switched on and off with the first/last section. So I no longer have any problems with regulating the spray pressure.

My switches are not covered by the servo box. This means I can switch manually at any time in an emergency.