Extruder controller V2.2 optional termination resistor

Hi,

I was going through the Extruder controller v2.2 build instructions and i noticed an optional 180ohm resistor that is supposed to be inserted if you are only using one extruder per motherboard. It is a termination resistor for the RS485 communication port.

Is this necessary?

in theory, it's necessary on the last board in the chain, however the boards are star-wired by default which destroys any noise-immunity provided by a transmission line.

If you have only one extruder, install the resistor.

If you have more than one, it probably won't make much difference unless you chain them instead of connecting them all to the mainboard, in which case only install the resistor on the last one in the chain.

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Wooden Mendel
Teacup Firmware

It is not necessary at the baud rates and cable lengths used by RepRap. Fitting it will make absolutely no practical difference.

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[www.hydraraptor.blogspot.com]

Thanks for the speedy replies