N0VUSUN and Mitsubishi-D700-SC

[JAZZCNC]

Dave the thing that's concerning me is that Analog Gnd is shared with the Common Gnd to the outputs and not isolated. I'm sure it will work as I described but it's not a good setup in my eyes for the reasons Doddy stated with noise etc feeding back into the Analog and vise versa.!

Personaly I would feel more safe by using the outputs to control a relay and then feed the For/Rev thru it's contacts then if any stray voltages/currents get fired out they don't fry the VFD logic. You still may get noise issues and the Odd strange behavior but at least the VFD is safe.

Also regards your earlier comment about twisted wires and not being too concerned about noise, then if your actually wiring the machine rather than just testing on the bench I strongly suggest you re-think that because if you get any noise issues it will send you crazy and I mean proper hair pulling sessions so it's worth doing correctly straight off the bat.

[JAZZCNC]

I'll shut-up now, Jazz is giving clear instruction and it helps no-one for me to talk over the top of another.

No don't Doddy you have actual experience with this controller and more experience than me with electronics so your the perfect man to help him. Crack on and I'll just dip in if I see something that gets missed.

Edit: Perfect example I also missed the pulling up not down in the VFD manual which proves "you-the-man" . .

[Daveo]

Nvem S-Axis out1 Orange and White twisted pr goes to STF on the VFD..... through relay
Nvem S-Axis out2 Green and White twisted pr goes to STR on the VFD.......through relay
S-axis /Gnd1 goes to terminal 5 on Vfd which is Analog Gdn
S-axis/VSO goes to terminal 2 on VFD which is 0-10V.

So do i keep the above connections but with the addition of a relay,
i have these relays that came with a box of parts i ordered.

[Doddy]

From the manual...



The outputs are opto-coupled, max 50mA. But that "max" is the maximum capability of the opto's transistor, not a guarantee of switching current (this might, probably will, be less).

I've googled the coil resistance of the MY4N-J and not getting anything sensible, similar OMRON power relays, 24V are around 650R so we can guess a switching current for reliable operation around 50mA. Whether you get that out of the NVEM will need you to experiment but I wouldn't bet the house on it working. If not, you'll need a current amplifier (a simple NPN transistor would do).

And you'd need to protect against the back-EMF from the relay, regardless.

If that makes sense then I won't bother with a diagram, but if a diag would help then let me know.

Mike

[Daveo]

sorry mate, a diagram would be great,
is it the Mitsubishi VFD that is causing the problem as i sooner change it
thanks Dave

[JAZZCNC]

I use these Omron MY4N-J and they typically pull about 36ma. Dave if you have a meter that can read current then test on the bench to be safe.

[Doddy]

Quick and dirty schematic:-



First option if the NVEM will source enough current to switch the relay. There's a reason why it might not, and I'll put this on the bottom of this reply, but try that first. The diode is connected across the coil, it's purpose is to protect the NVEM from back emf. I'll let you google the reason for this rather than lying. It's important.




The second option introduces a transistor (any general purpose PNP would do with a VCEO rating of 30V, Ic of 50mA, and a hfe (gain) of at least 100. That describes pretty much any general purpose transistor. I'd guess at a 2N3706 but any similar would do. If the output from the NVEM is switched - it goes low - that will drag the base voltage on the transistor significantly below the emitter voltage (24V) and the transistor will conduct C-E, and the relay will actuate. The current through the NVEM will be in the order of 1mA.


The reason why I'm uncertain if the NVEM will source the current for the relay directly is centred around Lies, Damned-Lies, and Data-Sheets.

The EL3H7 opto-isolators internal to the NVEM are rated at 50mA Ic (collector current). That is, beyond 50mA you risk damaging the transistor. But, the actual Ic is a product of the CTR (Current Transfer Ratio) of the device and the forward current through the LED internal to the device. Typically designed around 10mA, could be 20mA, but the CTR is specified as between 40% and 320%. So, guessing a 20mA current flow through the opto-isolator LED, the actual transistor current will be between 40% (4mA) and 320% (64mA), depending on the manufacturing process. So... 4mA won't switch the relay, whereas 64mA would (though the relay coil resistance would limit this to 36mA).

That's why you'd be best doing a bench-test on the relays first.

[Daveo]

thanks Doddy
so am i just using the out1 on my NVEM an no other connections
Dave

[Doddy]

Sorry, I meant that as means of example of interfacing a digital output from the NVEM to the VFD. That's the control for... STF. Repeat for Out2 and the STR input the VFD (if you think you'll use reverse - you can omit this otherwise). Then the analogue 0-10V output (and ground) is as Jazz said.

[Daveo]

hi
sorry i have to hold my hands up as i am just not getting it,
heres my controller

heres my VFD


I need it in a bit more basic terms so if a diagram with what goes where on the nvem. vfd and relay would be very much appreciated
thanks Dave