Posted 10/16/2020 06:04 (#8548201 - in reply to #8547306) Subject: RE: Gandy System
Don't call it a 'gator, it's a Ranger
Its been a while for me since I worked with those but the motor Gandy used was controlled by a Raven Motor Control. The Motor control used PWM to vary the speed of the motor. A modified Raven controller (600) was used. The 600 was a modified 440 that was modified in the sense that it could work with granular products and granular sections.
Controlling sections with a Gandy requires different thinking than on a sprayer. For example, with a two section sprayer set at a certain rate, if one section is shut off, the flow meter still reports the total flow rate which should be changed if necessary to provide half the flow to maintain the correct rate for that half. With a two section Gandy if one section were shut off, the metering wheel shaft needs to continue to turn the same speed as before. Thus the logic for control is different.
The INC/DEC circuit that is often used to control a butterfly type control valve in a sprayer was used as an input to the Motor Control box. This box took 12V directly from the tractor battery and created the PWM source that actually ran the motor. This was prior to the time when Raven offered a PWM output directly from their controllers. This was essentially the same approach that Raven used to control their injection pumps at first. Later the PWM circuitry was built into the controllers and could handle "light" loads such as hydraulic valves.
When a "large" load such as a motor was involved it was often necessary to use a motor driver that took its cues from the PWM output from the controller but produced its own heavy duty PWM output that actually ran the motor. A motor control actually creates a PWM signal that is based on cues from the INC/DEC circuit and sometimes a tach feedback circuit. A motor driver in contrast produces a PWM signal that mimics the PWM signal coming from the controller.
When your say the one Gandy offers is for fixed rate only, this refers to the idea that the controller was not able to use Variable Rate maps, not that the controller and related components couldn't run the spreader at different rates. limitations.
For example, if you entered in a certain application rate, the system would change the speed of the metering wheels in response to a change in ground speed. If you entered a slightly higher rate, the system would run the metering wheels slightly faster. Like a sprayer this is possible within
The Raven/Gandy 600 did not have the ability to read an Rx from a memory card/stick.