Near Intersection of I-35 & I-90 Southern Mn. | I have no experience yet with the Direct Command direct control of the Raven Sidekick Injection pump that is being offered on a somewhat limited basis this year.
I have used a workaround with a second Direct Command Liquid Control Module feeding a Raven Injection motor control on my personal sprayer for a couple of years. Another DC LCM controls the carrier. This was a fairly complex workaround and required several custom cables. This plan was not approved nor encouraged by Ag Leader.
Your fears about small boom widths are somewhat warranted in certain conditions. The fact that several booms could be involved (the Ag Leader Switchbox would allow 10) is not a problem. A slight problem may occur on the "low end" of the flow range when only a small boom section is ON.
The Injection pump can be controlled or run by several consoles in the Raven family and now Ag Leader's DC Direct Injection Module. The consoles use the Target Rate, Ground Speed and the Total Width of Booms that are ON at to calculate the proper flow rate per minute. They then try to run the pump at the correct speed to attain this pumping rate. If the flow demands exceed the capacity of the pump there would be a problem. Likewise if the flow demand on the pump is very low, the pump can stall.
Raven has had a low flow limit on their consoles for some time. The purpose of this value is to set a "floor" on the flow rate. Its original purpose was to prevent tips from "checking off" on a sprayer.
For example, when a sprayer really slows down for a waterway, the flow requirments drop considerably meaning the control circuit should shut down quite a bit. When this happened it is possible that the pressure becomes so low that the tip checks shut the tips off stopping the spray completely.
The Raven low limit is a value that can be entered so that the flow rate will never drop below this value. Other controllers handle this situation with a minimum pressure setting.
During the time the low limit is in effect, the sprayer will be over applying but this is generally more desirable than having the tip check off. Raven made this value proportional to the boom width that is currently ON. For example if you set the low flow limit at 12 Gallons/Minute, the low flow limit is 12 GPM when the entire sprayer width is ON. If only half the width is ON then the effective low flow limit is really 6 GPM.
At first thought one might think that the low flow limit would be the answer for the Injection pump stall that could possibly happen. Because the low flow limit is proportional to the booms that are ON, this is not really helpful in small width situations for Injection.
I have been told that Ag Leader followed this same concept. Personally I would have preferred an "absolute low limit" that is not proportional to the boom width for Injection situations. Then the operator could set a value that would keep the pump from stalling. This would cause overapplication of the product during this time which may or may not be a concern.
With all this being said I am confident that the Ag Leader DC concept with the Injection pump will work out fine. I don't want to dwell on these low flow situations too much since in my real field experience this wasn't really a problem for me.
You also ask about going from a total width of 6 or 12' to the full width of 90'. The Injection pump will react very quickly to this situation since the pump is controlled by a PWM circuit. There will be some delay as to when the "new rate mixture" gets to the ground but this hasn't been a problem. This problem would be no better or worse with the DC setup vs a true Raven setup.
I think one has to weigh the cost, complexity and disadvantages of having a large number of small boom sections. For example on my 60' sprayer I could have 10-6' sections. This would require 10 boom shutoffs and a lot of feed line. The wiring and plumbing would be considerable. This would also increase my chances of a low flow problem since it would be conceivable that only one 6' section might be ON for a point row situation.
I feel it is better to have this sprayer split into 4-15' sections. True I will have more doubling than would be the case with more boom sections but I feel this is a good compromise.
I believe this same type of reasoning is true with Planter shutoff sections for Seed Command. Here the added complexity of a large number of sections isn't much, but the possiblily of inappropriate row shut off increases dramatically. Having a reasonable number of somewhat wider sections seems like a better plan here also.
Edited by tedbear 3/5/2008 07:02
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Raven Sidekick and auto swath
