Need Help Re: 12 Volt Motor Speed Controller

[snub]

Hopefully this is the right place to post this.I want to use a 12 Volt motor to drive the power feed on my lathe/mill combo unit. I have the motor, pulleys and belts to reduce the speed of the motor down to about 100 rpm. Most of the time the feed 'screw' is turning at less than 40 rpm, but I would like to be able to turn it much,much faster to return it for the next cut. I found this bi-directional controller but it is only rated at 5 amps. I believe the motor I have draws more than that. Here is a screen cap:




They say it can handle more amps than 5 amps, but I am not following what they are saying about this. They also have a single direction controller that is rated at 15 amps. Pic here:






So I am wondering why this single direction controller couldn't be wired up as shown in my diagram below. There might be a good reason for this. Plan C would be to cut the speed controller out of the circuit completely, for the reverse mode ( at 100 rpm ).




I see that these pictures have been reduced and may not be easy to view. Here are links to the originals:


http://www.electronickits.com/kit/complete/motor/k166.htm


http://www.electronickits.com/kit/complete/motor/CKMX033.htm

[snub]

So I poured another drink and decided to have a look at the PDF instructions for the bi-directional controller. Seems like my idea for the DPDT switch wasn't hair brained after all. Just need to use common sense when operating ( NO DRINKING ). Here is a highlight:







And here is a link to the rest, if you're interested:


http://www.electronickits.com/kit/complete/motor/k166.pdf

[andyf]

Hi Snub,

For another $5, the same people do a uni-directional controller for 30A:
 http://www.electronickits.com/kit/complete/motor/CKMX066.htm
But if your lathe is a small one, do you need a motor big enough to draw more than 5A when under fairly light loads? If you are gearing it down to 40RPM during cuts and 100RPM on the return, the motor won't have to produce much torque. Have a look here for an example on a mini-lathe:
 http://mikesworkshop.weebly.com/leadscrew-motor.html
and here for the control circuit:
 http://mikesworkshop.weebly.com/control-circuits.html

The first circuit diagram on the second of those pages shows how a reversing switch should be wired; your diagram wouldn't work.

Andy

[kwackers]

More expensive, but have you considered a stepper motor and driver?
Google ELS or electronic lead screw for some idea of what is capable.

Alternatively a simple controller would allow variable speed and allow precision end stops, so for example a single button press could feed to a point and then return quickly.

You could start off simply with the stepper and driver, driven from a simple 555 based astable to provide speed control and a fwd/bwd switch wired to the direction input of the driver.
That could be later replaced with either a custom microcontroller based driver or something along the lines of the ELS.

Just a thought.

[andyf]

Snub, here's your diagram reworked to show the switch wiring correctly



Andy

[kwackers]

Andy, both yours and snubs reversing switches are correct.

If you look you'll see the difference is that you've taken the motor feed off the middle and he's taken it off the 'outside'. Either method will work fine.

[andyf]

Andy, both yours and snubs reversing switches are correct.

If you look you'll see the difference is that you've taken the motor feed off the middle and he's taken it off the 'outside'. Either method will work fine.

You're right, Kwackers. Sorry for doubting your pic, Snub

Andy

[websterz]

Don't waste your time/money on the 15 amp unit. I did it and the thing lasted less than a month. Go for the 30 amp and use a DPDT switch between the controller and motor for reversing. Mine is over a year old and going strong.

[snub]

Thanks to all for your info and input. I ordered up a couple of the 30 amp controllers ( I'm sure I will have a use for the second one someday).

[Sorekiwi]

Sorry to chime in on this thread so late.

I am using the Bi-directional speed controller you show first in your post to control a right angle gear motor (a power window motor) as a power feed on my mini-mill.  Its powered by a modified computer power supply.

It works great, and has been trouble free for 4 years now.  I dont use the power feed for the big hogging cuts, but I do use it a lot for finishing cuts and almost always for flycutting.

Assembly was straight forward (even for an electronics novice like me), and I'm happy with the whole setup.