Hi,
total noob, so forgive me please my ignorance. I am still waiting for my new VFD to arrive and was reading the manual http://www.mototecnica.eu/ebay/Inverter/Manual%20eng%20VFNC3.PDF these days.

The VFD has 4 input options and apart of this Modbus:
0: Voltage signal input (0 - 10 V)
1: Current signal input (4 - 20 mA)
2: Logic input
3: Voltage signal input (0 - 5 V)

i am interested in option 2 -Logic Input and the possibility to interface my BOB directly without buying additional stuff like PWM and having to learn Modbus

the logical input is described at section 6.5.2 at the manual http://www.mototecnica.eu/ebay/Inverter/Manual%20eng%20VFNC3.PDF
but for ease i made some snapshots of the pages :







so from what i understand the VFD accepts frequency pulses and can be programmed to distinguish frequencies and lengths of the pulses and this pulses can transmit the basic commands, but i am up till here
and from my ignorance i have the following questions:
1. Is this the Step and Dir ? and if so can Mach 3 be interfaced directly using its Step and Dir capability?
2. Can the VFD be adjusted so that PWM from mach3 drives it, i mean only frequencies without reading directional and additional signals , this by adjusting the frequency response at the VFD

This all comes because this inverter is pretty capable and cheap for all the functions it offers/150eur here in EU/, so if this can be done and shared, maybe it can become the ultimate Mach3 inverter 

3: Voltage signal input (0 - 5 V)

...so from what i understand the VFD accepts frequency pulses...
1. Is this the Step and Dir ? and if so can Mach 3 be interfaced directly using its Step and Dir capability?
2. Can the VFD be adjusted so that PWM from mach3 drives it, i mean only frequencies without reading directional and additional signals , this by adjusting the frequency response at the VFD

From the pictures you have posted, I don't think option 2 will work with Mach. At the top of the second page you posted, you need the following lines from Mach to enable this: DIRECTION; UP; DOWN; SET (ie four lines). Mach can't do this. The VFD is not step-and-dir in the way Mach understands it.

What is interesting is option 3, 0-5v voltage signal. If you put a voltmeter across the PWM signal, at 20% speed, the meter should read 1v; at 50% speed, it should read 2.5v etc. Basically, you are using the PWM signal as an analogue output. Depending on the sensitivity of the VFD, you might need a low pass filter on it (just a resistor and capacitor). Have a Google for PWM to analogue or look over on the Arduino forum for further details.

Take a look at Chris Humphris document here http://www.cjh.com.au//PWM%20Spindle%20Control%20using%20Mach3.pdf it contains a lot of useful information.

Tweakie.

thanks for the advices,
the thing is i have a very nice Romaxx BOB/ in fact Sound logic/  which came with my machine, which before some days stopped to function cause of a blown IC, with the strong points of a build power supply and 4 relays
I thought of buying one and what I liked were a hungarian one 100eu, with double power supply, and instead of 0-10v it simulated potentiometer which is the best solution i believe,  but with centronix socket and also CNC4PC 100$ with socketed IC  for easy change if blown which i liked very much, but without relays and power supply. After a " deep search" en ebay i found for just 30eu a board with charge pump and relays and output for spindle control, i am not quite sure from the lousy manual in chinese, anyway, the chinese is just temporary until they repair my BoB so i will build that from the PDF, looks simple and interesting.