Quote Originally Posted by magicniner View Post
Thanks A!
I for one have printed this to hard copy and filed it in my Mach3 workshop folder.
Do continue,
Regards,
Nick
Thank you. I will continue as soon as I can.

I am actually pretty surprised how little interest there is in both Mach3 brains and the use of RS484 Modbus to control and monitor VFD. It is an industry standard and very common there for a reason. It is an extremely reliable way of controlling machines in generally noisy environment, suitable for many purpose, not only controlling VFDs, but it allows easy adding other type of inputs/outputs which have RS485 interface and Modbus protocol. Even in home environment, for hobby use, I think is very suitable and much better than the one wire one input/output type of solution which is widely spread. OK, as discussed elsewhere, like in every other serial communication, there is a delay introduced, but to be honest, the few milliseconds lost because of the serial communication can be ignored in this type of slow machinery. Advantages definitely overweight the disadvantage of that delay. It is pretty cool to be able to make the VFD do all the things with only two thin wires instead of several relays, using up many inputs and outputs and connecting several thicker wires, which still will NEVER allow the same kind of control and monitor as the Modbus allows. The expansion possibilities are large, adding other extra units with additional digital or analog inputs and outputs is pretty simple as well, just hanging these on the same pair of communication line, since each are addressed, so there is no conflict, each unit knows which one is asked and which one supposed to send an answer.

Reading back values like real RPM, frequency, temperature, output voltage, current, torque or whatever else you are interested to read back is impossible unless you use a communication line. OK, one digital output on my VFD is a pulse output, so I think that could be used for some of that, as well as one analog output cold be configured for another of those values, but it would be so much more complicated to read those two and would need two more wires...

Anyway, I will DEFINITELY use Modbus over RS485 as far as that is possible and see no reason not to. Until recently, I thought that the use of Modbus was out of the question for me, unless I write a plugin to Mach3, so I am pretty happy that this assumption was wrong and nothing more than some configuration and creation of brain file is needed. OK, for the additional functions, what I call "Bonus functions", there is a need for modification of Mach3 windows and some simple macro changes, but that is no big deal, anyone can do it with the free software provided by Artsoft.