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« on: October 27, 2008, 12:55:26 PM »
If you are connecting up seperate electrical systems - which you are, then you only need one reference point - 0volts.
Let us go through the Inputs to your inverter first.
The inverter will require 3 inputs. Forward signal, Reverse signal and a speed voltage signal. Looking at it , your Denford may require a spindle on signal as well.
Mach 3 puts out two signals for M3 and M4 - spindle forward and spindle reverse. There is no spindle on signal. This will have to be generated from the M3 and M4 signals that Mach 3 provides.
As you are probably aware, Mach 3 can be configured to put out these signals on any wire, but if the cnc4pc has a predetermined wiring plan then follow theirs. Connect your PC to the BOB board, and configure Ports and Pins/Spindle Setup.
Untick "disable spindle relays" and assign M3 and M4 to an output - say 1 and 2.
Then go to Ports and Pins and assign Outputs 1 and 2 to a pin number on your output. If this is done for you on the Bob then make sure they are allocated to the right pins.
On you Bob board, you can now check the M3 and M4 output by typing in the command on the MDI line and checking the pins outputs on your Bob board. See if they change from +5 to 0v, or 0v to +5 when they are set.(The problem is that some Bob boards invert the outputs) Check now what your Inverter input requires - does it require an 5v+ signal, or a 0v signal to drive it. IF the wrong signal is being output, then go to Ports and Pins, Output signals, and tick Active Low, and this should change the output. Check it again.
Once you have the right output for the M3 (forward) and M4 (reverse) signals, then to generate a Spindle "on" signal you connect a diode between the M3 and "Spindle on" and another diode between M4 and "spindle on" and this will provide the spindle on signal, whether M3 or M4 is active. The direction of the diode depends on whether a negative or a positive signal is required - but you can't do any harm by connecting it the wrong way, it just won't work.
The Ov connection on your Bob should be connected to the 0v on the Inverter - which I feel will be the spindle common or the spindle on common.
Inverters, unfortunately are fickle beings, and on some, the higher voltages are not necessarily tied to Ov earth potential.
Inverters normally provide a Ov and 12v supply, which goes to a converter - which in my case converts the PWM output from Mach 3 to a 0 to 10v signal - my board is a Digispeed.
The "high" voltage side of a Digispeed is electrocally isolated from the "low" voltage (computer) side, and so you connect the 0 and 12v supply to the "high" side of the Digispeed - and it returns a 0 - 10v signal back to the inverter to control the speed.
I would ring up cnc4pc and ask if this is what they have done - I think it may be- in which case you can connect the 12 volt supply from your inverter - and the associated 0v supply - to the appropriate Bob board input and you will get back from the Bob a 0 - 10v motor control voltage.
This is the best I think we can do on this forum - because every Bob board is different - but I seem to remeber that this was the case when I studied their circuit diagrams. I feel, however, that you must ask the supplier.
By all means come back if you are having any more difficulty.