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Lathe DC controller/switch

AaronHG

Aluminum
Joined
Mar 2, 2005
Location
So Cal
One of my current projects is converting my Sheldon cone drive lathe to a under cabinet DC drive. I have a nice NOS 2 hp shunt wound motor and a really nice DC speed controller having main breakers, speed control, and reverse, stop, forward positions, contained in a NEMA type enclosure.
My design question is based on the ease of use with the old reverse/foreward rotor switch that is on the original motor. It is sooo comfortable "driving" the lathe (in its limited speed range) with one hand on the "tap". I now am thinking of relocating the speed pot and Rev/stop/Fwd switch to a remote box closer to the originals position. Fine I can do that. But the ergonomics (and rewiring of my brain) leads me to ask how have other dealt with this design and use issue?
Just realized I could replace the 3 position Fwd/stop/Rvs switct with a 3 position rotor switch...it could help.
I also want to add a large emergency stop switch, I'm not sure how to implement this yet.
 
The best design will depend on exactly what you are working with. It sounds like your DC supply has provision for a remote speed control via a pot. You can work with that. What other features does it have? Any connections for a remote, low voltage direction control? Otr energency stop? Or does the remote speed control also reverse direction? Is there any braking circuit or does it stop by simply removing power from the motor?

If the speed control can bring the speed down to zero, then a switch could be added to the pot to either short or open circuit it to that condition. Additional micro switches on an emergency stop bar could be wired in parallel or series with that added switch to allow stopping from there. But if there is a braking circuit, you may want to work with that for a faster stop in an emergency.

As for reverse, if it can be done with a low voltage circuit attached to the power supply, then that would be best. If not, you will need a DPDT (double pole, double throw) switch that is rated for the DC voltage and current your motor uses. Be sure to use at least double the motor's ratings as startup and stopping Vs and Is can spike. Ideally, it should also have a delay feature to prevent applying reverse voltage to the motor too quickly.

Paul A.
 








 
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