# Two-for-One VFD



## Hawkeye (Jan 24, 2012)

I've hinted that I was working on a VFD project. Well, it's up and running. The main difference with this one is that I'm running both my mill and lathe off one VFD. Since I'm the only one using the shop, there's no problem with only powering up one machine at a time. If one is running and I flip the switch over to the other one, nothing changes. The drive has to be stopped to switch.

The relays for the interlock system cost more than either 3 phase motor. This interlock is based on something I designed for some mining trucks in southern Africa. They wanted to make the driver put on the parking brake to shift ranges on the rear end, so they wouldn't do it on the fly. These were 80 kph mining trucks.

Here's the VFD unit with the remote panel in the foreground. I can swing it over to whichever machine I'm running. It also telescopes to get it out of the way or position it at the best location.





The enclosure houses the VFD, interlock relays, 3-pole output relay and a 12VDC power supply to run the relays and a cooling fan above the VFD. The thick white thing on the bottom of the box is an air filter from a Ford Taurus. Lots of air flow.



Here's the control box positioned for the mill and the lathe. The space at the top left corner is for a MachTach Tachometer. I'm still waiting for Guy to answer my email so I can get one. Until then, I'll make do with the laser tach. Controls include FWD/OFF/REV, speed pot and an emergency stop button.




The Teco/Westinghouse FM-50 VFD is, I believe, a discontinued model that can still be found here and there. This one is rated to 2 HP and can run off single phase. The lower and upper frequencies can be set from 0 to 200 Hz.


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## 12bolts (Jan 24, 2012)

Mike, that is an excellent idea, and well set up.
Get ready for some brain picking.

Cheers Phil


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## Hawkeye (Jan 24, 2012)

The day I bought the relays, I found a local ad for an older VFD for $20. I might still get it. I can't find any mention of it on the internet.


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## sic semper tyrannis (Jan 25, 2012)

Wow that is a cool set up.

Never thought about sharing a VFD.

Could you go cheap and simply use a plug on each machine that would plug into one outlet controlled by the VFD?  You could use a locking 30 amp connector to get 4 leads and enough current.

By only having one outlet you ensure only one machine is plugged in at a time.  Sort of a pain in the... but I ususally unplug the tools anyways.

Although I do love your set up I think it may be beyond me!


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## Hawkeye (Jan 25, 2012)

Yeah, Ed. I thought someone would comment on the temporary labeling. It will do until I get something better.

Sic, the original plan was to do the 3-phase plug routine. Those items are quite expensive, so I went with hard-wire and relays. By the time I found out the cost, I was committed. At least this way, I don't have to power down the system to switch machines.


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## Hawkeye (Feb 11, 2012)

*Adding the Tach*

I got the tach installed this week. I'll post the tach build (MachTach kit) in a separate thread. This is one sweet installation. The tach display changes to reflect the selected machine. You can also choose between RPM and SFM, which is great.




It's a bit tricky finding a place to put the sensor on a Hercus lathe (s/a SB9), since you want it on the spindle itself, not on the spindle pulley. I had originally mounted the optical sensor just behind the 'front' bearing, with 6 reflective patches spaced around the spindle. Worked great until I pulled out the pin to try back gear speeds. The (now longer) pin broke the sensor in half.  I decided to use a Hall Effect sensor and magnets instead, but where to put them?



I stuck them around the spindle nut with bits of carpet tape. (Yeah, I know the magnets will stick to the nut - the tape was to keep them from moving sideways when I wrapped them up.) The Hall sensor is mounted on a bracket to the rear.



On the mill, I made up a plastic ring with 6 magnets pressed in and screwed to the bottom of the spindle pulley.



The sensor for this one was bolted under the pulley. The cable just looks like it's rubbing against the pulley. It's held down by a P-clip hidden by the belt.



With the belts set in middlish positions, I get speeds from 126 - 1145 RPM on the mill and 14 - 133 (back gear) and 90 - 720 RPM on the lathe without moving belts. By changing belts, I can expand the ranges considerably. The tach reads within 1 or 2 RPM of my laser tach.


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## bcall2043 (Feb 11, 2012)

Hawkeye said:


> I got the tach installed this week. I'll post the tach build (MachTach kit) in a separate thread. This is one sweet installation. The tach display changes to reflect the selected machine. You can also choose between RPM and SFM, which is great.



Hawkeye,

Great build and install. I'm looking forward to the Tach build thread. Will it include enough detail for others to do one of their own?

Benny


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## 8ntsane (Feb 11, 2012)

Mike
I like the outside the box way of thinking. Speaking of box, I like the idea you come up with for the air filter! Good stuff, thanks for sharing.

Paul


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## Hawkeye (Feb 11, 2012)

Yeah, I had a filter left over after I sold the car. Since there is a lot of metallic dust in the shop, it made sense to use it.

If I had another VFD multi to build, I'd use the cheaper PCB-mounted relays for the logic portion. Could have saved a lot over using the industrial type.


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