When Good Controllers Go Bad
It’s 10:00 PM, the wind finally died down to a mild breeze and the rain has stopped. You get the sprayer out of the barn, fill the tank with water add the required chemicals, then go to work spraying the orchard. Three hours in, the valves on the right side of the sprayer won’t open. You check the electrical connections and fuses you’re familiar with, and everything looks good. What happened? The next day, you have a technician troubleshoot the control system. Now for the bad news. The entire right channel that controls the on/off signal to the valves is no longer working. A new spray controller is needed. Now for the worst news: that controller is no longer manufactured, and there is no drop-in replacement available. When an obsolete sprayer controller fails, the problem can quickly become much larger than replacing one electronic component.
This scenario is not hypothetical, and it has happened more than once. It also seems to happen when the sprayer is needed most. If the grower has a spare or multiple sprayers available, that helps. Not everyone has that option. So, what happens next? A new sprayer? New controls? A missed application can increase disease pressure and ultimately affect fruit quality and yield.
The mechanical and hydraulic portions of an older sprayer may still have many years of useful life remaining. When a controller or operator display fails and the original hardware is obsolete, replacing the entire machine may not be necessary. In many cases, the electronic control system can be modernized while retaining the pumps, valves, plumbing, sensors, structure, and other serviceable components.
When the Replacement Part No Longer Exists
A failed controller cannot always be replaced quickly by installing a different controller. The original system may contain proprietary communications, undocumented logic, unusual sensor interfaces, or custom wiring. The amount of engineering required depends on how complex the original control system is and how much of the existing system can be reused.
Before committing to modernization, it is worth determining whether the original controller or display can be repaired, whether new old stock or used components are available, or whether the manufacturer offered a replacement or upgrade path. In some cases, one of those options may be the fastest way to get the machine operating again. When those options are no longer practical, modernization becomes the next path to evaluate.
Understanding the Existing System
The replacement process begins by understanding how the sprayer is required to function. What inputs does the operator need? What information needs to be displayed? What sensors and valves are connected to the system, and what types of input and output signals do they use? Then there is the part no one can simply look at: the control logic and algorithms. How does the system regulate flow or pressure? How are sections turned on and off? What interlocks, delays, alarms, and operating conditions were built into the original controls? In many older systems, that information may not be documented anywhere.
What Can Stay and What Must Be Replaced
Next comes the decision about what can remain and what needs to be replaced. When an obsolete sprayer controller has to be replaced, many of the sensors, valves, flow meters, pressure sensors, and other components may still be serviceable. This is no longer simply a parts-replacement problem – it is a system-integration problem.
The sprayer’s operating environment must also be considered. Electronics may be exposed to chemical spray, moisture, pressure washing, dust, vibration, tree branches, temperature extremes, and rough driving conditions. Any replacement system must be designed and installed for that environment, not simply made to function on a workbench.
Selecting a Replacement Sprayer Controller and Display
Once the keep-and-replace list is created, the next step is selecting a controller that fits the application. The decision begins with the required number and types of inputs and outputs, along with CAN, serial, Ethernet, or other communication interfaces the machine requires.
I/O count alone is not enough. The controller also needs to be appropriate for the machine environment. Connector type and sealing, operating temperature, vibration and shock resistance, electrical protection, serviceability, and long-term product availability all matter. The goal is not simply to make the machine work again, but to select hardware that can remain dependable for many years. In some applications, that equipment may remain in service for 15 or 20 years.
The display deserves just as much consideration as the controller. Sunlight readability, touchscreen operation, physical buttons or knobs, display size, environmental protection, and the way the operator interacts with the machine all need to be considered. Those decisions also influence how the user interface is designed and how quickly an operator can understand and use the system. Multilingual support may also be important, particularly in agricultural applications.
Designing and Testing the Modernized System
Now it’s time to design the wiring harness and develop the controller software and display application. Once the new system is installed on the sprayer, testing and commissioning begin. All required functions of the original system need to be verified, along with any new features included in the modernization. This is a critical part of the upgrade process—the system must do more than simply operate; it must behave as the machine requires.
Perhaps the best time to address an obsolete control system is before it fails. If a controller or display has already been discontinued, documenting the system during the off-season can make a future failure much easier to deal with. Wiring, I/O, machine functions, software behavior, and replacement options can be evaluated without the pressure of a spray window closing.
C9 Controls works with equipment owners and machine builders to evaluate obsolete mobile-control systems and determine practical controls modernization options.