Near Intersection of I-35 & I-90 Southern Mn. | Lance - thanks for the detailed reply. I knew some of this but reading your explanation is helpful. From experience I have observed that sometimes one could "get by" with only a single terminator in a system especially on a test stand. Other times not so.
I believe that the Ag Leader harness has one of the terminators built in close to the display since it would be at one end of the potential chain of devices and usually meant that another physical terminator was to be used on the "other end" of the chain. In most layouts this was simple - put a terminator at a location as far away as possible form the display.
I personally have some layouts where the CAN chain is not linear in the sense that a branch feeds a module but continues on to more modules and branches. This layout has the CAN chain branch with one branch leading to the side of the tractor but another branch leads back to the planter. In this situation I put the terminator on the branch that is the greatest distance from the display and this has worked fine.
I notice that on a combine install, Ag Leader avoids that by running a CAN cable to the flow sensor module and then back to another module rather than branching it off. Apparently it can work either way.
Someone speculated that the terminator plug in an Ag Leader system is just a resistor inside a dust cap. That is true. Ag Leader has dust caps and terminators. They use a color code to separate them externally. If you look at one that is a terminator, two of the pins are present. If you pull out the plastic plug on the other end you will notice that a common resistor is connected between the two pins. As Lance has stated this is a 120 Ohm resistor. If you look inside a dust plug, there are no pins and it acts just as a plug and has no electrical effect on the system. Raven CAN systems seem to operate in a similar fashion, they seem to use 180 Ohm resistors in parallel.
Someone mentioned having lots of problems with the terminators. I have never had a problem with one other than possible corrosion issues in nasty environments such as fertilizer.
Edited by tedbear 3/22/2017 08:27
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CANBus terminators... what are they anyway?
