DC conversion on lathe.

This forum is dedicated to those hobbyists with the 3-in-1 metalworking machines. Mill-Drill-Lathes. Tips, techniques, modification and use of these machines is topical.

Moderator: Harold_V

User avatar
SteveHGraham
Posts: 7788
Joined: Sat Jan 17, 2009 7:55 pm
Location: Florida

Re: DC conversion on lathe.

Post by SteveHGraham »

You're positive the aluminum extrusion on the controller was grounded?

Here is what another forum member told me, after I grounded my chassis and fried several components.

http://www.chaski.org/homemachinist/vie ... 24#p328931
Every hard-fried egg began life sunny-side up.
User avatar
LX Kid
Posts: 213
Joined: Fri Jan 07, 2011 3:33 pm
Location: Tampa, Fl

Re: DC conversion on lathe.

Post by LX Kid »

It was screwed right to the frame along with the grounds to the frame. But caution being the rule I don't think I'll ground the aluminum heat sink.

(At least I "think" that's the way I remember it!)
User avatar
LX Kid
Posts: 213
Joined: Fri Jan 07, 2011 3:33 pm
Location: Tampa, Fl

Re: DC conversion on lathe.

Post by LX Kid »

Sooo little expertise and soooo many questions! :roll: Now that I have the motor running I'll have to do some research, ask for suggestions, on how to make it all work on the lathe. Questions to think about would be mounting, keep or lose the flywheel, pulleys, electronic box material and where to mount to name just a few. I noticed that the variable pot was a 10K instead of the suggested 5k pot. Should I go and get a 5k pot?

One day I'm going to have to learn to use my equipment instead of playing with all the mods! But that seems to be just as much fun as "actually" making something! :lol:
Torch
Posts: 1684
Joined: Wed Mar 17, 2010 7:58 am
Location: Muskoka

Re: DC conversion on lathe.

Post by Torch »

You need to use whatever value pot is specified for the controller you are using. 5K is a common value, but yours might well be spec'd for 10K. That said, a 10K pot in place of a 5K would probably make it more difficult to make fine adjustments to the speed, as each degree of rotation would produce a greater difference in the resistance of a 10K than with a 5K. Another thing to know about potentiometers is that they come in two flavours: logarithmic vs linear. The rate of change in resistance of a logarithmic pot increases as you turn the knob. The rate of change in resistance of a linear pot is constant thoughout it's range of rotation. Logarithmic pots are often used for volume control, but a linear pot is probably a better choice in this application.

In the interest of complete information: For really fine speed control you could use a multi-turn pot, but that would be over-kill in this application. In a multi-turn pot, the range of adjustment is spread over many full revolutions (eg: 10 full turns) rather than the 300 or so degrees of a regular pot.
User avatar
LX Kid
Posts: 213
Joined: Fri Jan 07, 2011 3:33 pm
Location: Tampa, Fl

Re: DC conversion on lathe.

Post by LX Kid »

SteveHGraham wrote:You're positive the aluminum extrusion on the controller was grounded?
Here is what another forum member told me, after I grounded my chassis and fried several components.
http://www.chaski.org/homemachinist/vie ... 24#p328931

That was a very interesting read. :idea: You've been down that road I'm now traveling. What is with the need cutting the PSR-1 out of the circuit?
User avatar
LX Kid
Posts: 213
Joined: Fri Jan 07, 2011 3:33 pm
Location: Tampa, Fl

Re: DC conversion on lathe.

Post by LX Kid »

SteveHGraham wrote:Wonderful. Now whatever you do, don't ground the aluminum.
Sorry Steve but I guess I forgot about the ground on the aluminum chassis. Ever since I first started messing around with this little project it was grounded the whole time including after your help with getting it running. Had no issues at all though but will not ground in the future. Will mount everything on a 1/4" plywood, including choke, with ventilated grounded metal cage around everything. (Like you were suggesting on one of your other post.)
User avatar
LX Kid
Posts: 213
Joined: Fri Jan 07, 2011 3:33 pm
Location: Tampa, Fl

Re: DC conversion on lathe.

Post by LX Kid »

Torch wrote:You need to use whatever value pot is specified for the controller you are using. 5K is a common value, but yours might well be spec'd for 10K. That said, a 10K pot in place of a 5K would probably make it more difficult to make fine adjustments to the speed, as each degree of rotation would produce a greater difference in the resistance of a 10K than with a 5K. Another thing to know about potentiometers is that they come in two flavours: logarithmic vs linear. The rate of change in resistance of a logarithmic pot increases as you turn the knob. The rate of change in resistance of a linear pot is constant thoughout it's range of rotation. Logarithmic pots are often used for volume control, but a linear pot is probably a better choice in this application.

In the interest of complete information: For really fine speed control you could use a multi-turn pot, but that would be over-kill in this application. In a multi-turn pot, the range of adjustment is spread over many full revolutions (eg: 10 full turns) rather than the 300 or so degrees of a regular pot.
Thanks Torch. I used the 10k pot that came with the PWM I bought as I didn't have any other pots on hand. I like the idea of using a multi-turn pot to bring speeds up a little slower and making fine adjustments. I'll probably look on eBad for 5K pot to purchase. Thanks
User avatar
SteveHGraham
Posts: 7788
Joined: Sat Jan 17, 2009 7:55 pm
Location: Florida

Re: DC conversion on lathe.

Post by SteveHGraham »

I don't know the purpose of the resistor. I don't remember. I do know that before I clipped it, the motor was either on or off, with no adjustment possible. I didn't really need 5000 RPM.
Every hard-fried egg began life sunny-side up.
User avatar
LX Kid
Posts: 213
Joined: Fri Jan 07, 2011 3:33 pm
Location: Tampa, Fl

Re: DC conversion on lathe.

Post by LX Kid »

SteveHGraham wrote:I don't know the purpose of the resistor. I don't remember. I do know that before I clipped it, the motor was either on or off, with no adjustment possible. I didn't really need 5000 RPM.

Mine regulates just fine so I think I'll forego the removal for now.
User avatar
LX Kid
Posts: 213
Joined: Fri Jan 07, 2011 3:33 pm
Location: Tampa, Fl

Re: DC conversion on lathe.

Post by LX Kid »

I think I'll take the DC voltage out of the MC-60? card and go into the -/+ of the PWM controller and hook up the motor to the PWM and see how that works. I'll put the pot, on the MC-60? card, max voltage and regulate with the PWM pot. Does anyone think this will cause any damage? Good, bad or don't know? Anyone
Torch
Posts: 1684
Joined: Wed Mar 17, 2010 7:58 am
Location: Muskoka

Re: DC conversion on lathe.

Post by Torch »

I think it should work, but I would disable the IR Comp feature on the SCR controller. Let the PWM controller handle the load compensation otherwise the SCR controller will be varying the output based on what the PWM is trying to draw and that may cause problems.
User avatar
LX Kid
Posts: 213
Joined: Fri Jan 07, 2011 3:33 pm
Location: Tampa, Fl

Re: DC conversion on lathe.

Post by LX Kid »

Torch wrote:I think it should work, but I would disable the IR Comp feature on the SCR controller. Let the PWM controller handle the load compensation otherwise the SCR controller will be varying the output based on what the PWM is trying to draw and that may cause problems.
Thanks Torch. How would I go about doing that? Do I remove the IR pot or adjust it?
Post Reply