[ronncat]

Would someone please comment on ways to wire my the VFD to my lathe so that I can switch between manual and CNC control of the spindle. Would like to retain ability to control speed, direction and on/off using either manual pushbuttons on the lathe or Mach3. Thanks.

[Al_The_Man]

Fortunately you should not have to change anything in the VFD, for the speed control, wire a 5~10k linear pot, outer ends across the common and 10v, the centre slider would need to be wired to a small single pole double throw relay, the common contact would go to the analogue input, the other two contacts would switch between Mach signal and the pot slider.
How the FWD REV inputs are fed or taken care of at present will depend on how the manual control can be implemented.
IOW, is Mach controlling a couple of relays for the VFD run?
Al.

[ronncat]

Thanks for the reply Al. At this point, my lathe is strictly manually operated. The VFD uses the 3 wire approach with both start and stop buttons. In addition, I have a 10k pot wired for speed control and a switch for F/R. I have not started the electronics portion of my build, but am preparing for it as my conversion is nearly complete.

When I did my mill conversion, I used 12v relay to a Gecko G540 to turn the spindle on and off via Mach 3. I would like to know if there is some easy way to completely switch all functions between Mach3 control and full manual. Ie is there a switch that will change all the connections from cnc to manual with a single throw. Thanks

[Al_The_Man]

Can you set the VFD up for the alternative method of using just either FWD or REV and no STOP START?
IOW, when either FWD or REV is made the VFD will start, most VFD's can be set up this way.
This could then be done then with one small relay with 3 DPDT contacts, the centre common contact of each D.P. contact would go to the FWD REV and Analogue VFD input, if the N.C. contact goes to the Mach commands and the N.O. contacts goes to your manual FWD REV switches and Pot slider, then all you have to do is set up a supply to the relay coil through a simple S.P.D.T. Man/CNC toggle switch which either picks the relay coil up for Manual or drops it out to enable the Mach mode.
Al.

[ronncat]

Al,
I think that I might have found a solution that could work. What do you think? I have found relay boards that have multiple relays triggered off a DC source. How about getting a four relay board? One relay for each for on/off/F-R and speed? In the previously mentioned 3 wire on/off setup, I can wire the first relay NO in parallel with the manual on switch for ON. The second will be wired NC in series with the OFF. Even though the switches would be latching with Mach 3 input and my buttons are momentary, I hope this would work since they merely influence the internal relay in the VFD (I think) I tried this out by holding my manual on switch in to make it "latching". The motor started and stayed on. Then, while still holding the on switch, I pushed the off and the motor stopped. The third switch can control F/R (again using the 3 wire scheme), and the last, would connect to the speed pot and to the variable output of my G540. Gotta run to work now, I'll add more details later if needed. Thanks!!

[Al_The_Man]

You can use several different relays, the pot outer ends can be left connected all the time, most VFD's have an opto intput that is pulled low by the input device.
Al.

[ronncat]

Oops,
On the way to work I realized that my idea wouldn't work...at least the way I intended. If I had a switched external DC source that triggered the relays, then I wouldn't have control of them via Mach3. They would always be in a triggered state. I would have to cascade relays to get the desired result.

Al, I must investigate your suggestion. I also think that individual relays might be better to use. The on/off relays could be switched by Mach3 and just be used to create an NO or NC connection through the use of the spindle output triggering the two relays. The speed control could be done as you previously suggested. The F/R control could remain manually controlled with the existing switch. Is there any reason to have reverse? I don't seem to use it too often when manually turning things?

[Al_The_Man]

There are times when reverse is handy on a lathe, if you don't use it then don't bother putting it in, you can always add it later.
Al.

[ronncat]

Al,
Sorry, my brain is semi-fried...Work has been extremely brutal with the end of the year rush. I reread your post from yesterday and it's starting to meke sense to me. I will probably put all of these ideas into diagrams so I can really understand how the flow would work, then pick one. Thanks

[ronncat]

Al,
I really gave your advice some thought over the weekend and I think I have come up with a workable solution. At first, I wasn't willing to change out the switch layout for my lathe...just being stubborn. However, with more thought, I have come to the following conclusion. Please correct me if I'm missing anything...


1) Replace the existing 3 wire setup (F/R switch, momentary on switch and momentary off switch) I was able to source a 3PDT Toggle SWITCH (not relay) on fleabay. I will substitute this for the on button and an E-Stop in place of the off switch. The F/R will be replaced by a F/O/R switch

2) Wire the F/O/R switch to two of the poles of the 3PDT switch and the analogue output from my manual pot slider to the third

3) From Mach3, configure spindle settings to use two separate outputs for forward and reverse. Unfortunately, this will eat up all my available outputs on my Gecko G540. If I want to add coolant or something later, I'll have to figure out a way to get a signal off the PP that connects to the Gecko. Or add a spindle control board and free them both up.

4) Wire 12V power supply to the outputs on the G540, and then add relays for Forward and Reverse.

5) Wire the relays into the 3PDT Switch. Also wire the VFD out from the Gecko to the switch. I think I can feed the 10V DC supply to the Gecko from a regulated 12V supply in the controller box as opposed to bringing it in from the actual VFD. The manual switch still gets its 10V from the VFD.

6) Wire the commons from the switch to the VFD

7) Change the VFD function to: Forward/off Reverse/off

8) GO FOR IT!:cheers:

One question that has come to mind.The Gecko outputs are simply microswitches that go to ground. What would happen if I didn't use any relays at all and simply connected the wires from the Gecko in the circuit so when the switch closed, it would close the contact in the VFD, thereby acting similarly to the relay? Would there be any problems? Would the VFD and the Gecko have to share a common ground? Would try this, but I'm scared to blow something up and release the magic smoke. Any comments would be appreciated.

[Al_The_Man]

It might be best to draw up the circuit you intend to use in order to make a true assessment of it.
According to the G540 pdf, the output 1&2 are probably solid state outputs that sink to common, unfortunately they do not show the exact configuration because if they are open collector devices you would only need to take the G540 common to the VFD common and the outputs 1 & 2 to the fwd rev inputs on the VFD, the VFD would supply the + voltage for the open collectors.
If you can find out the nature of the outputs, they may be able to be used in the way you wish.
Al.