Lathe Motor Variable Speed Controller

[jdrichard]

I have beed trying to get a good foot operated variable speed controller for my new Lathe motor. Here is the problem. The hand controller works great and the motor seem to like it. I then purchased a Foredom Foot operated speed controller (FCT) , see photo. Upon using it, i noticed that the motor was pulsating a bit more and thus vibrating more (not as smooth). So is this normal and will it damage the motor?

 

Is their a better foot controller? I can always gift the Foredom controller to my kids?

 

 

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[oldhippy]

I really can’t help with this I’m no electrical engineer. The lathe I had was fitted with a foot control and I never knew what it was like before the conversion.   

[jdrichard]

I really can’t help with this I’m no electrical engineer. The lathe I had was fitted with a foot control and I never knew what it was like before the conversion.   

 

I am an Electrical Engineer and I think that the AC signal goes through an A to D converter and then it is digitally regulated and then out an inverter. And the frequency out of the inverter is pulsing slower than the Input frequency causing the motor to pulse a bit and then causing the burping.

 

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[jdrichard]

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[oldhippy]

I don’t understand any of that.

Wouldn’t all foot controllers be the same?

[jdrichard]

I don’t understand any of that.
Wouldn’t all foot controllers be the same?

Depends on the circuit.


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[measuretwice]

You're the sparky, but I'd say the top block diagram you put up is of a VFD, and a VFD will only work on three phase afaik (which is in itself a really convenient way to get variable speed, just use a 3P motor and VFD).  Bottom is a triac universal motor controller.   Is the bottom circuit what you have?  The SR foredoms are universal motors and the larger X are DC where the controller is PWM I believe.    Grasping at straws a bit, it shouldn't matter which controller if the motor is universal.  The motor is definitely universal?  I'm thinking it has to be, but you know what happens when one assumes. 

Have you checked the brushes?   if they are worn and not making good contact, it can show up as pulsating at different speeds.  

 

Edited October 28, 2017 by measuretwice

[vinn3]

all foot controlers are not the same.  dosen't the UK have 50 cycle current?  the US has 60 cycle current.  check out Granny's  sewing machine.  its GOOD  to have a   "double E" in the in the forum !!  vin

[oldhippy]

I was referring to the UK.

[jdrichard]

all foot controlers are not the same.  dosen't the UK have 50 cycle current?  the US has 60 cycle current.  check out Granny's  sewing machine.  its GOOD  to have a   "double E" in the in the forum !!  vin

Thats Me, JD the EE. (1983). I actually did micro electronics and hated machines: should hav paid attention in class. So dont think it is Pulse Code/Wave Modulated. These old watchmakers motors have to be three big magnets and three large coils.

 

 

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[jdrichard]

all foot controlers are not the same.  dosen't the UK have 50 cycle current?  the US has 60 cycle current.  check out Granny's  sewing machine.  its GOOD  to have a   "double E" in the in the forum !!  vin

They are at 50 cycles. Is this motor a European build? Funny it works with the other speed controllers, just works trough with the Foredom

 

 

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[vinn3]

my point is;  a speed controler  on ebay might be made where the current is 60 cycles and when attached to a motor that is 50 cycles --?  ka boom ?  and several kinds of moters (some without brushed or magnets).  i am happy to be a machinist and un lucky with electricity.  vin

[jdrichard]

Here is the guts of this controller. Looks like a simple part that may have some connection options to properly marry up with the lathe motor ??


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[vinn3]

no comprendp  vin

[jdrichard]

Problem solved i think. I landed three sewing machine motors and a singer foot pedal from a local sewing business that also does repairs. The maintenance guy had a large box of motors and gave me three. I have figured out how to hook up the motor to a transfer pulley and then to the lathe. Just need a few more brackets to attach the motor and i am done. Need to hook the pedal up as well, although i do have a Lowboy pedal in the mail that should work: in line with the power cord.


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[jdrichard]

I am now the proud owner of five sewing machine motors. I added the plugs and tested them all and they worked fine. The PCM of the SCR component on the Foredom and Lowboy pedals cause a bit more slight roughness than a analogue plain resistor type pedal, however, they will not damage the motor and work fine. Here are the last three motors


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[jdrichard]

Here is the guts of this controller. Looks like a simple part that may have some connection options to properly marry up with the lathe motor ??


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Turns out that the small orange screw is used to set the level the plunger on the component goes it before the switch and power control turns on: and thus the amount you need to push on the pedal before it starts the motor.


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