D.C motor controller

[swarfmacdaddy]

I recently picked up a treadmill for free as i need a motor to drive a reciprocating lapping table im building. The motor label reads" permanent magnet dc motor. Treadmill duty voltage and power- 90 vdc 1h.p.scr controller-115vdc,1.25 h.p.pwm controller.The electronics are a power supply, scr controller,and a destroyed digital console. Question is,should i throw out all the electronics and buy a controller or can someone tell me if its worth the time to salvage. Also what is the difference between a scr and a pwm controller? Is one any better than the other? If i buy one, what specs should i look for? Im going to be running it fairly slow. It has a 5/8 shaft that will be driving a 16 inch disk @ 60 rpm. There are tons of ways to gear that. So will it run more efficent slower or faster? Thanks in advance for any input guys! i have included a zip file of a block diagram that i scanned from the treadmill.

[MikeAber]

I don't know what your time is worth. I would purchase a KB electronics KBIC-125 DC or Minarik motor speed controller or equivalent as these are very common and inexpensive. $50.00 or less on eBay or the surplus stores. They are SCR controllers that use PWM to change 120VAC to 0-130VDC and will run your motor without any additional power supply. http://www.surpluscenter.com/item.as...tname=electric

Information in these posts also may be of interest to you on the same subject.
http://www.cnczone.com/forums/showpo...8&postcount=97
http://www.cnczone.com/forums/showpo...&postcount=115
http://www.cnczone.com/forums/showpo...&postcount=142
The motor will require a cooling fan if one is not attached for continued use over 30 minutes or so and these motors typically do not have low speed torque and usually are 2000 rpm or higher motors. Speed reduction gearing should work well for your application. These motors are available for $20.00 or so and are a great bargan for the power available.

[swarfmacdaddy]

Thanks alot Mike!! Your the first one to steer me in the right direction.Asked at Radio Shack(i knew better) they said "Duh,I dont know ,if we dont have it on the shelf then i dont know. Whats a scr?)

[Mariss Freimanis]

I guess no one excersises any more; there seems to be a glut of these motors on the surplus market. People have converted some of the better examples of these motors to servos by mounting encoders on them. Good way to tell if you have one that's suitable is to run it at a very low speed (use an old PC power supply's 5VDC output). If the motor turns smoothly without cogging at 30 RPM or so, it may be a servo motor candidate. I heard some Pacific Scientific motors fit the bill; they can't seem to build a bad motor even when they try.:-)

Mariss

[MikeAber]

I'm using these motors and motor controllers to run my R8 spindle, band saw and drill press, they work great! No more belt changing. Leave the belts on the slowest speed position and you have variable speed with lots of power!

I wish I could find some of the Pacific Scientific 1-2 hp motors at a good price, most people know what they are worth. They have high torque at slow speeds that make them excellent motors of outstanding quality for use in bench top lathes and mills. I agree with Mariss ; I believe they can’t make a cheap motor.

I have some AMTEK 4" diameter 6" long, 50 VDC 16 amp motors I'm going to use as servos for my gear head mill CNC conversion, they run beautify at 5VDC with tremendous torque. I'll use 500cpr encoders mounted on 5tpi ball screws with 2:1 timing belt drive reduction for that project.

[2muchstuff]

Amtek motors are also a very good quality motor. They can be found on Ebay, the prices are not too bad either. The guys who build those power generating windmills like to use them.

[ozzie34231]

Hi Mike and All,
I realize this thread has been dead for a long time, but here goes.
There are still lots of treadmill motors around, very cheap; but the KB controllers are a bit harder to come by, at least at a cheap price.

Now don't laugh, I'm electronically disadvantaged.
What would happen if I used one of the cheap Harbor Freight speed contollers, coupled to a rectifier?

Jerry "Ozzie" Pryor
Old Curmudgeon

[Al_The_Man]

The advantage of going with the higher end KB or repackaged in Baldor and others, is that the controller can be set for current limit to match the motor,
Also there are max min speed and accel adjustments on board.
If you are patient they seem to come up regularly on Ebay.
They also have the option of 120v or 240v in to tailor the controller to the motor.
If you get the 4 quadrant controller, they have braking and very fast reverse, also they take a ±10v signal for reversing without a relay or switch.
Al.

[ozzie34231]

Thanks for the quick answer Al,
I know the controllers do come up, but they usually go for $60-$100 and up plus $15 or more for shipping, and I have aquired 2, a KBPB 125 and a 240 volt model, (can't remember the model). I intend to use one on a new milling machine I'm getting together.
But I have some other uses in mind that I'd really like to do on the cheap.
So will my scheme work or will some thing burn up? I can monitor the voltage.

Another question:
The KBPB doesn't seem to have a place for control voltage input. Can the type board used for contorl voltage (Peter Homan) be hooked into the pins normally connected to the 5k pot?
Jerry

[Al_The_Man]

The poteniometer input is usually where you input the analogue voltage, you just use two terminals instead of three, but according to the manufacturer of most of the SCR DC drive, the input should be isolated.
Al.