Near Intersection of I-35 & I-90 Southern Mn. | As I recall the Ag Leader system could use Servo or PWM control for the apron. The spinner control had to be PWM. A frequency of 100 seems to be quite common.
With PWM control, a plunger in the PWM hydraulic valve can be controlled to be fully closed, partially open or fully open. This in turn affects the hydraulic flow and ultimately the apron speed and the spinner speed.
PWM works on the concept of turning a 12VDC circuit ON/OFF rapidly. The rate that this happens is called the frequency.
With a frequency of 100 (means 100Hz or 100 times/sec), each 1/100 of a second can be split into an ON portion and an OFF portion. The ratio of the ON portion to the total time is called the Duty Cycle. Internally this is represented with a binary number but is displayed a a Percent for the user to observe.
The Duty Cycle could range from 0% to 100%. For normal operations, the Duty Cycle would be somewhere in between and the hydraulic valves would be partially open.
One way to stop the apron or the spinners would be to change the Duty Cycle to 0%, the plungers would close and the apron or spinners would stop.
This might not be desirable since when you want action again, the system might take a while to ramp open the plunger to the point where the apron or spinners start turning again.
To improve this situation, a setting called the Zero Flow Offset can/should be used. This can be thought of as a low limit for the output. This means that when you shut off the apron or spinners, the Duty Cycle just goes to the Zero Flow Offset point and action stops although the plungers would still be partially open. When you want action again, the plunger is already partially open and action can begin much quicker.
With a sprayer and PWM control, the idea of keeping the pump running when the booms are off can get involved. This might be for agitation while turning around on a Headland etc. This is another limit value that can be used. This is referred to as the value that should be used when all booms are OFF. If used, this would be higher than the Zero Flow Offset. I did not have ths set properly for our Hagie sprayer with PWM pump control the first time out. The result was that the system was slow in responding after coming out of a Headland when the ground increased rapidly. This would not apply to this apron situation
Another factor or setting is "how quickly should the system respond" to a change in ground speed or a rate change. Gain is a term that comes to mind. If the Gain is too low, the system will eventually respond but be very sluggish in getting back on the target rate. If the Gain is too high, the system will likely overshoot the target rate and get into an oscillation situation.
The Zero Flow Offset can be determined by trial & error. It is possible to observe the current Duty Cycle on one of the diagnostic screens. The Duty Cycle can be changed manually with the UP/DOWN arrow keys. One could observe at what Duty Cycle the apron just starts to move. This value would be a good starting point for the Zero Flow Offset. It could be refined from that point as seems necessary.
The Gain value can be determined by trial & error also. Guess I would go with a certain Gain and try it. Then make minor changes to observe the effect as an effort to improve the response.
Other factors such as the product, desired rate, hydraulic capacity etc. can all enter into the situation.
Edited by tedbear 1/10/2025 07:35
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Loftness 1210 PWM settings Ag Leader Help
