# Changing from AC to variable speed DC motor



## Foozer (Feb 17, 2009)

Being as I dislike cold, anything below 50 F the fingers refuse to do as directed, what should be a day project is now hit and miss.

Changing over the AC motor to a treadmill variable speed DC motor, we hope. Not a great wiz at electrics other than its like water thru a pipe. I always start out reminding myself; Do not stick your finger into anything than has a cord attached. Do not power up anything electrical until it has been triple checked, if you dont know ASK someone.

So got this 2hp DC motor from a treadmill, controller and supply of tubing, If I can avoid the smoke test it just may work








Now there no reverse built in to this thing as received so of course the first try was just reverse the input, ah no, that doest work, never can be that easy. Time to map the motor and reverse switch wires out and I see that I have in the motor 2 big wires, 2 little wires and 1 green wire. As the green is attached to the motor frame it must be ground, gotta keep that one in play. The 2 big wires end up as such, into one side of the armature, out the other, into one end of the field and out the other. Hmm must be a series system whatever that is. The reverse switch is native to the lathe and its mapping is, well I dont know what its called. Flip it one way and some contacts make while others break and so on. 

From forum searching the solution to getting the motor to reverse was found

Reverse the direction in which the coils are energized and the motor reverses.
http://www.homemodelenginemachinist.com/index.php?topic=2740.msg25008#msg25008

So I dig into the motor and split the armature to field wire, splicing in extra wires (soldered and double shrink wrap) so I end up with 2 circuits as seen in view B






Ol Dukie giving his approval so I must be OK so far







. With this and the mapping of the FWD/REV switch its time to see if I can wire it up.
Got the plan mapped out






And the actual (the motions getting to this step are dull, cut and solder, wire ties are your friend) 






Disconnected the motor power wires from the controller to allow testing with a small battery, Dont want to smoke the board. Hooked it up and ran the FWDREV switch thru its paces and YeeHaw, it rotates forward and reverse. Now its just mount it, dress it and use it.

Have to talk to that cat, seems even though the motor does the FWD/Rev bit it is stuck on slow speed. The controller does not alter the speed at all. So whats up with that? Back to the original motor wiring seems that the arm and field in series mean something, dont know what but shouldnt be hard to reconfigure the FWD/REV switch to alter the field polarity while leaving it in series with the armature rather than parallel as it now is.






Shorten the story of the last 2 months tinker it actually works as intended.
The 2 small wires mentioned earlier are for some sort of speed sensor attached to the motors armature, this in conjunction to a magnetic switch pulsed from a small magnet encased within the driven pulley (can see its wires in the shot) I guess regulate the controller read out. Mounted the original controller to the right side of the bench and with a push of a button (will grab a shot after I get the bench re-bolted to the floor) I can change speed at will. Ok so it reads in MPH, some Excel work as in =SUM((((4*(300/B9))*3.141)/12)*0.01136)*1.5 (1.5 is just a random pulley step up number, subject to change as experiments go on) may get me to the MPH to FPM realm for different materials and diameters, ya Im bored. Still have to get within the infield of the speed controller to pulley relationship, but for now 0.5 MPH and I can count the spindle revolutions, At 10 MPH, well its a lot faster than Im comfortable with, Good thing it will be bolted down to the floor.

Things to change, Motor brushes are mounted offset of centerline. Seems that its designed to favor one direction for brush life? To agree with the design need to remount motor 180 degrees. Can see why preferred method is mounting motor above lathe, chips dont fall up as well as they fall down. Have to fabricate some sort of guard for that. Figure out the speed pulley relationship for the controller and dump the multi-step to a single. Actually make something other than modifications.

And No Honey, I dont know what happen to your Tupperware


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## Kermit (Feb 17, 2009)

Slow and easy. Think it through, then think it through again.

You done good figuring out the wiring without the tedious tech schooling. 

This proves that electrical work can be done by amateurs with proper caution and lots of safety checks by just knowing the basics of Ohms law and the mechanics of how switches work.

I started out about 7 or 8 years old, -after I was shocked the first time I just HAD to find out what that stuff was all about. ;D

Way to go Foozer,
Kermit


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## Kludge (Feb 17, 2009)

Foozer  said:
			
		

> From forum searching the solution to getting the motor to reverse was found



I'm glad my writeup helped, Foozer. That's a good part of why it was written. (The other part is that I'm a writeaholic.) IF you have any questions, please feel free to ask. I'm sure I can come up with something that almost sounds plausable. 



> And No Honey, I dont know what happen to your Tupperware



When it's no longer fit for the kitchen, it goes to the shop. When it's no longer fit for the shop then it gets cut up for patterns. What's left gets recycled. Repurposing at its finest. 

BEst regards,

Kludge


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## Bernd (Feb 17, 2009)

Interesting. All the tread mill motors I have have permanet magnets in them. Must be the newer motors they're using today.

Bernd


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## Foozer (Feb 17, 2009)

Finally all back together, dog approves but its just a neighbor mutt over to steal another ball.







Back in its home all bolted to the floor, Kid tried to get me to place the controller on the left side, we had a bit of a discussion about rotating objects and arms getting not so gently removed. The right side position does block the tool board a bit. However it will soon enough be grown accustom to. Small learning curve is well worth keeping the body parts intact.







To those to whom within their prior postings, have taken the time to explain details of the various niches surrounding metalworking Much Thanks. 

Now to work on the MPH to FPM math


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## Kludge (Feb 17, 2009)

Bernd  said:
			
		

> Interesting. All the tread mill motors I have have permanet magnets in them. Must be the newer motors they're using today.



Well, universal motors are easy and cheap to produce and, as a rule, tread mills only go one direction so they are a logical choice. A PM motor has the advantage of a fixed field where the universal motor's changes with the power supplied to the motor and the load. Increasing the load increases the current demand which, in turn, increases the field strength (Good old ampere-turns at work!) which with the increased armature current (more ampere-turns) should maintain a more or less constant speed. 

Ah, but then there's the speed control which will sense the decreased voltage drop which also occurs (along with the actual shaft speed most likely) and should bump the voltage up to everything's all happy and the sun is chirping and the birds are shining. 

The speed control on a PM motor should work the same way with the main difference being in what's it's driving and the details of how it does the sensing majique. 

Best regards,

Kludge


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## Foozer (Feb 19, 2009)

So after playing with the little lathe with its newly adopted variable DC drive a few items have come up.

From the link to the Siemens site http://www.homemodelenginemachinist.com/index.php?topic=4213.msg43734#msg43734

It is mentioned that series wound motors (which this one is) are not so stable at slow speed. Now this gizmos control head is equipped with a clock, so counting the tics against the second hand gives about 100 RRM spindle as the slowest obtainable stable speed. But after chucking 3 truck loads of stuff to the dump being bombarded by that little birds voice saying Get a Tach I looked at what other features the original treadmill had. Ah a heart rate monitor, now theres possibilities. All I need to do is make a heart beat. OK. Took a piece of vacuum tubing, plugged one end with a shot from the hot glue gun, filled it with water and hot glued the other end. Stuck it in a tool holder in such a way that the face plate dog would give it a whack each revolution.






Clipped the earlobe monitor to the other end and let it go round. Repurpose as it has been said






Its Alive

We have a pulse and at 102 compared to my 100 count I call it good. Did the repeatable test a few times and it came to the same speed +/- 2 RPM







Scaling up till the pulse monitor gave up counting (about 190 beats) the relationship between RPM and MPH seemed linear. Doesnt mater much as the metal tells what it likes. 

Total time of testing 43 minutes 05 seconds, Clock has got to go, if the bride knew how much time I spend on my pride watching shinny things . . .


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## Kludge (Feb 20, 2009)

Foozer  said:
			
		

> Finally all back together, dog approves but its just a neighbor mutt over to steal another ball.



That he's comfy there says a lot about you - all good. Dogs are excellent judges of character. 

Best regards,

Kludge


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## Kludge (Feb 20, 2009)

Foozer  said:
			
		

> It is mentioned that series wound motors (which this one is) are not so stable at slow speed.



This is true which is one reason why separating the field and armature windings is a Good Thing. Feed the armature with a steady current and vary the armature voltage to control the speed for a lot smoother operation. This is pretty much the same as a PM motor (but with a controllable magnetic field) and will improve low end performance. 

BEst regards,

Kludge


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## Noitoen (Feb 20, 2009)

One easy way to reverse a dc series motor by just reversing the input polarity is to install a full bridge rectifier to supply the field. 

View attachment Field.bmp


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## Foozer (Feb 20, 2009)

Kludge  said:
			
		

> This is true which is one reason why separating the field and armature windings is a Good Thing. Feed the armature with a steady current and vary the armature voltage to control the speed for a lot smoother operation. This is pretty much the same as a PM motor (but with a controllable magnetic field) and will improve low end performance.



Got a PM motor 1hp to try first but it looked just to dinky, the treadmill was cheap and with it having a 2hp motor (at least it looks substantial) I figured it would dump the slow speed heat better. Slowest stable is around 650 motor RPM with a 100 RPM spindle rate. Dug into that hunk of steel perty good, lot more than the tailstock liked, to test it out, 'round .100 @ .002 pre rev. 

So a bit more fooling around with the pulley ratios to find a comfortable motor speed that is stable (stable being constant RPM holding capacity and sufficient rotation for its cooling fan to function while maintaining enough top end for small dia soft metals) It still has the back gears for low end but that brings into play the overpowered question. Hmm perhaps I should just quit thinking about it and run 'er. 



			
				Kludge said:
			
		

> That he's comfy there says a lot about you - all good. Dogs are excellent judges of character.



Ya he found a sucker, I go to the thrift store and get a box of old soccer balls, I buy em and he eats em. Leaves me thank you's hiding in the grass for my soles to find. Something wrong with that equation

Care


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## Foozer (Feb 20, 2009)

Noitoen  said:
			
		

> One easy way to reverse a dc series motor by just reversing the input polarity is to install a full bridge rectifier to supply the field.



I think I will go introduce my head to the business end of the wall for not thinking of that, should be less of a headache than it was trying to wire the FWD/REV switch. I like it.

Care


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## Stan (Feb 20, 2009)

> Got a PM motor 1hp to try first but it looked just to dinky,



I don't know what size of lathe you are working with but I have a 10" Logan that I drive with a 1/2 HP Boston DC motor driven by a Boston Ratiotrol.

I run the lathe between 2 and 2000 RPM and never run out of power. Your 1 HP PM motor should be more than adequate for most home shop lathes although a PM motor is not as versatile as a shunt wound motor.


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## Foozer (Feb 20, 2009)

Stan  said:
			
		

> I don't know what size of lathe you are working with but I have a 10" Logan that I drive with a 1/2 HP Boston DC motor driven by a Boston Ratiotrol.
> 
> I run the lathe between 2 and 2000 RPM and never run out of power. Your 1 HP PM motor should be more than adequate for most home shop lathes although a PM motor is not as versatile as a shunt wound motor.



Its only a little Atlas/Craftsman 109 6", older than dirt and for what I have spent on getting it usable, well that does seem to be a habit, taking the long way around the fence. Its so cute tho.

The 1 hp would of run it, but for the price of a controller I picked up the working treadmill complete for $50 bucks. Yes it is overpowered and the thought of some sort of shear pin in the pulley drive has crossed my mind. Off the cuff thinking is a 1/16 inch soft al pin might do. Need to cut a pulley anyway so just might travel down that road and see what happens. I don't know what if any torque control mechanisms are used in small machines other than bust a plastic gear or belt slip. 

Care


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## Kludge (Feb 21, 2009)

Foozer  said:
			
		

> Got a PM motor 1hp to try first but it looked just to dinky, the treadmill was cheap and with it having a 2hp motor (at least it looks substantial) I figured it would dump the slow speed heat better. Slowest stable is around 650 motor RPM with a 100 RPM spindle rate. Dug into that hunk of steel perty good, lot more than the tailstock liked, to test it out, 'round .100 @ .002 pre rev.



Stan has the right of it; 1 hp would easily be enough to turn your 109. So, since you don't want to use it, how about tossing it my way to put on my Taig. ;D



> Ya he found a sucker, I go to the thrift store and get a box of old soccer balls, I buy em and he eats em. Leaves me thank you's hiding in the grass for my soles to find. Something wrong with that equation



So what started this, him chewing the balls or you buying them for him? If it were really all that bad, you'd quit buying the soccer balls so his presence can't be all bad. But then, I'm a dog person in an apartment where I'm not allowed pets. That is frustrating so I "adopt" any dog I come across for a few minutes just to get a "canine fix".

Best regards,

Kludge ... *woof*


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## Foozer (Feb 21, 2009)

Kludge  said:
			
		

> Stan has the right of it; 1 hp would easily be enough to turn your 109. So, since you don't want to use it, how about tossing it my way to put on my Taig. ;D


I got a 1/2 hp PM motor sitting right here doing nothing



> So what started this, him chewing the balls or you buying them for him? If it were really all that bad, you'd quit buying the soccer balls so his presence can't be all bad. But then, I'm a dog person in an apartment where I'm not allowed pets. That is frustrating so I "adopt" any dog I come across for a few minutes just to get a "canine fix".



Have 2 of my own both named Sh$t Head, at least they, like me answer to it, both Shepard/Lab mixes. Good rodent hunters and too big, 90+ lbs for them overgrown flying chickens (Eagles) to cart off.






I'll PM you the little motor specs


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## RICHARDDV (Feb 21, 2009)

hi there--i am new to this group but i have been running my 109 with a pm treadmill motor for several years now with excellent results . i used the complete wiring from my donor treadmill to utilize the pm motor since the pm motors need some feedback to stabilize the speed and torque .this way the speed encoders on the treadmill are used to sense speed and the pulse modulation is increased or decreased as needed. another advantage is i kept the safety interlocks intact so the machine can be shut down immediately and it cannot be started at speed --everyone has their own methods so think the problem and make it work--   richarddv


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## Foozer (Feb 21, 2009)

RICHARDDV  said:
			
		

> another advantage is i kept the safety interlocks intact so the machine can be shut down immediately and it cannot be started at speed --everyone has their own methods so think the problem and make it work--  richarddv



Found that out quick enough, it will start at speed and rather abruptly at that. Getting the arm accustom to the new motion of hitting the pause button will cure that. I take the safety interlock key out to insure my fingers always stay connected to the end of my hands when fiddling around with the 109


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## Stan (Feb 21, 2009)

The 1/2 HP PM motor would do great on your 109. 

Motor controls are always on ebay. I have never had to pay more than $30.00 for a good one. Sometimes you have to be patient if there are a lot of bidders out there.
Something like this one has all the features you could possibly need on a lathe motor.

http://cgi.ebay.com/New-Beel-DC-Mot...ryZ97184QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

If that long link doesn't work, just search ebay for DC motor control and it is on the first page. HTH Stan


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## Kermit (Feb 21, 2009)

http://www.electronickits.com/kit/complete/motor/ck1400.htm


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## Kludge (Feb 21, 2009)

Foozer  said:
			
		

> I got a 1/2 hp PM motor sitting right here doing nothing



Got the specs & I'll be off to respond in a bit.



> Shepard/Lab mixes. Good rodent hunters and too big, 90+ lbs for them overgrown flying chickens (Eagles) to cart off.



Had a pair like that - mother was a Springer & father was the neighborhood. Not quite 90# each but close enough. Nothing I did could convince them they weren't lap dogs so I guess I should be happy I had a big lap. Thunderstorms were especially exciting because they both wanted to be on my lap at the same time. 

They were great watch dogs. They'd watch anything that happened aboard the boat. "Ooooh, there goes the TV ... and the microwave ... and the coffee maker ... Wait. Coffee maker. Better stop this action or daddy's gonna be highly provoked!"

BEst regards,

Kludge


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## Kludge (Feb 21, 2009)

Kermit  said:
			
		

> http://www.electronickits.com/kit/complete/motor/ck1400.htm



Okay, I'd seen that and totally forgot about it. Thanks, Kermit!

BEst regards,

Kludge


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## Stan (Feb 21, 2009)

> http://www.electronickits.com/kit/complete/motor/ck1400.htm



That is a good toy for the student in school but not much help if you are powering machine tools. Running 12 volt motors at 100 amps isn't going to be done with the electronic kit. In addition it provides no control over min and max speeds, no current limiting and no acceleration control. These features are all standard on the type I referenced in an earlier post.


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## Kermit (Feb 21, 2009)

Stan  said:
			
		

> That is a good toy for the student in school but not much help if you are powering machine tools. Running 12 volt motors at 100 amps isn't going to be done with the electronic kit. In addition it provides no control over min and max speeds, no current limiting and no acceleration control. These features are all standard on the type I referenced in an earlier post.



Would you prefer a link to multi hundred dollar controller?

I can do that too!


Can't make everyone happy, so I just settle for having fun pissing off the ones with short fuses. ;D


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## Kludge (Feb 22, 2009)

Stan  said:
			
		

> That is a good toy for the student in school but not much help if you are powering machine tools.



That depends on the application, doesn't it? For what you prefer, the one you spec'd is good. But the one Kermit indicated will handle just light of 1 HP out of the box and can be made to handle more with not a lot of effort. 

The difference is I can buy the one Kermit pointed to any time and modify it to suit my needs without a whole lot of added expense, dependent on what's in my junk box ... er, spare parts supply at the time. The one you indicated shows up periodically and is snapped up by people who need heavier controllers without taking the time to assemble and customize them. 

Some of us are very strange and like to solder and tinker with circuits as well as machines. Buying a kit and making it sit up & dance (which is significantly more than I can do ... dance, that it) suits us and we're happy. Plug and play suits you and you're happy. So everyone's happy and we can all sit back and enjoy our machines. 

BEst regards,

KLudge


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## Stan (Feb 22, 2009)

Kludge: I may have missed something on that link as I just took a quick look, but this is what caught my eye



> # This DC Motor controller can handle up to 16Amps, but PCB trace capacity would have to be beefed up with some hookup wire where DC motor current runs through the Printed Circuit Board.
> # Requires operating voltage of 9 - 18 VDC.



If you have a 18 volt motor and a power supply to drive the controller, you can get a maximum of 288 watts if you jumper the traces on the pc board. 1/4 HP will do fine on your small lathes but it it is not just a plug and play controller.


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## Kermit (Feb 22, 2009)

Another link to cuss, or is it discuss?
http://www.reliance.com/mtr/mtrthrmn.htm
Be prepared, this one will be to complicated for most but will be elementary to others. 



Who will I piss off next?, Tune in tomorrow and see 
Kermit


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## Stan (Feb 22, 2009)

If anyone is serious about DC motor controllers. take a look at this ebay ad, ending soon.

http://cgi.ebay.com/DANFOSS-Penta-K...ryZ71393QQssPageNameZWDVWQQrdZ1QQcmdZViewItem


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## Kermit (Feb 22, 2009)

If anyone is serious about steam engines.

They can buy one too!


I thought the point of this topic was ideas, not who is more "serious" than the other?

Doing it yourself is what makes these types of hobbies fun for some of us. If you don't like tinkering with circuits the by all means PURCHASE what you need. If you DO like to tinker with circuits then... ;D


My way or the Highway sucks, there's alot of lanes on this road. Change lanes or pass or take an exit, just stay off my assbumper,
Kermit


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## Foozer (Feb 22, 2009)

Kermit  said:
			
		

> Another link to cuss, or is it discuss?
> http://www.reliance.com/mtr/mtrthrmn.htm
> Be prepared, this one will be to complicated for most but will be elementary to others.



Good link, not to bad a read. Does answer at least to my level of understanding why the brushes on my doner motor are off center


> One method of reducing the arcing due to non-linear commutation is to shift the brushes away from the geometrical neutral position.


 Motor is designed to favor one rotational direction, so I better get my rump out and walk the talk, remount the motor to agree with its build design.Fortunately its supplied mounting system makes this an easy change.

All these links for DC Power supplies have there merits, and I can see the 12/24v 15amp unit as a controller for say a windshield wiper motor powered hacksaw controller for those who just like to be a tad off the bubble.

I made the switch from the original AC driven system 'cause I'm lazy. Switching belts around gets tiresome in a hurry and I avoid using the backgears, if I bust em replacements are hard to find. DC drive therefore sounds like the solution.

What do I want this conversion to do?

Make the wheels on the bus go round and round. Problem Stated

Considerations
1. I'm clueless
2. I'm cheap
3. Minimal thinking
4. Easily available
5. Skill level
6. Not burn the Barn Down!

1. Clueless and Cheap, searching around for the results of others who have tackled this conversion bring up as a common denominator, Treadmill Motors

2. Minimal thinking and availability, Treadmills are designed is as many shapes and sizes as a womens dress, finding one that is suitable just a metter as lookin over the racks (E-bay, Craigslist, local thrift stores) till one jumps out and says Howdy.

3. Skill level, I have seen items on this board that in my wildest dreams I could never match with my stone axe and hammer view of the world. As much a bolt on operation as possible for this thick head.

 "Treadmill" motor is there, pulleys are there, mounting brackets, controller and various pieces of stock all in one package. All for under a C-note, or rather 69 GBP, 125CAD, 154AUD.

As reported by the ol Kill-A-Watt meter the converted unit draws around 5 amps, well within the components capacity. All wires securely attached and a new GFI in the wall plug circuit. All in all pleased with the conversion. Room for improvement, sure, will it happen, maybe. Its functional, does what is asked of it.

But whitout post such as 





> [author=Kermit link=topic=4210.msg44098#msg44098 date=1235313068]


 I would not have gained further insight into the working of DC motors.


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## Kludge (Feb 22, 2009)

Stan  said:
			
		

> Kludge: I may have missed something on that link as I just took a quick look, but this is what caught my eye
> 
> If you have a 18 volt motor and a power supply to drive the controller, you can get a maximum of 288 watts if you jumper the traces on the pc board. 1/4 HP will do fine on your small lathes but it it is not just a plug and play controller.



Up toward the top they mention handling a 100v @ 7a load which works out to a wiggle under 1 hp. Without looking at the spec sheet, I'm guessing this hits the transistor's power limits while the 16 amps bumps up against the current limits. I'd have to look at the wee beastie's curves to give a more definite answer. With a little added circuitry, two of the power transistors could be operated in parallel which would increase the power handling capability as would changing to a meatier single transistor.

You're right. This is not a plug and play solution. It's for tinkerers like me who love the smell of solder in the morning (or any other time) and accept the risks of letting the smoke out at inopportune times. The kit mentioned is fairly basic yet it can be made to do everything a commercial speed control does with some "judicious adjustment".

The plug and play units I meant are the ones you mentioned - prebuilt and ready to rock 'n roll as is. (Actually, being an old school solder jockey, I'd probably find "improvements" to make in them as well. ) As a rule, they are fatter but they are also intended for different (heavier) applications than the kits are.

This is a one size doesn't fit all situation of which life presents many. That's part of what makes it so much fun!

BEst regards,

Kludge


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## Kludge (Feb 22, 2009)

Kermit  said:
			
		

> Another link to cuss, or is it discuss?
> http://www.reliance.com/mtr/mtrthrmn.htm
> Be prepared, this one will be to complicated for most but will be elementary to others.



This is beautiful plus gives me ideas how to rework series wound motors to do muchly moreso cleverer thingies. I like doing muchly moreso cleverer thingies. 



> Who will I piss off next?, Tune in tomorrow and see



As long as it's not Pele, ainokea. 

BEst regards,

Kludge


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## Kludge (Feb 22, 2009)

Foozer  said:
			
		

> Considerations
> 1. I'm clueless
> 2. I'm cheap
> 3. Minimal thinking
> ...



1. Disproven already.
2. This is a bad thing?
3. Thinking leads to brainaches. They are bad things. 
3a. OTOH, Danica McKellar on hand to help with the math would be nice. 
4. Reflects back to 2.
5. "Fine adjust with a 6# sledge" works nicely.
6. No sense of adventure, huh?

BEst regards,

Kludge


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## Andrew_D (Feb 23, 2009)

Stan  said:
			
		

> If anyone is serious about DC motor controllers. take a look at this ebay ad, ending soon.
> 
> http://cgi.ebay.com/DANFOSS-Penta-K...ryZ71393QQssPageNameZWDVWQQrdZ1QQcmdZViewItem



Be aware...I bought one of these controllers from the same seller. 

The one I got was NOT a Cycletrol C2000, even though the case sticker says it is. Once I opened it up, I found that the circuit board was not the same as the C2000 info I had downloaded.

More digging produced the manual for the VariSpeed A2000, also from Danfoss (although the line has since been sold to Graham Motors). The board was similar to the A2000, enough that I got it working. Plus, the A2000 can run up to 3HP motors!!! ;D

There isn't much info out there on the A2000. If anyone buys one of these and needs help, drop me a message...

The seller has been informed of this, but I don't know if they will change the listings. My best guess is that the original owner upgraded the boards at some point, but kept the original cases.

Andrew


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