Shaded pole motor.

[Martaine2005]

Hi all,
I am making miniature electrical tools like table saws, sliding mitre saws, drill press, bench grinder etc. Some of the tools use food stick blender motors and others use the 775 dc motors. (Always open to suggestions).
I have a wide and varied amount of cheap Ebay motor controllers. I have several fans with shaded pole motors and would like to know the best way of speed controlling them. I tried triac based controllers but they don’t seem to work. I also tried direct voltage control which does work. However, the torque drops significantly too. VFD is beyond my knowledge but any help would be great. But finding a cheap 240v single phase output is really hard. I understand that AC is rectified to DC and back to AC. As I said, beyond my knowledge. So an easy way to control the speed of a shaded pole motor?.
This will be for a miniature drum sander. So torque is quite important. Thanks in advance for any help and also any ideas you may have.

Martin

 

[Alec_t]

So an easy way to control the speed of a shaded pole motor?.

I don't think there is an easy way without sacrificing torque. Can't you use a DC motor?

 

[WHONOES]

Main problems with shaded pole motors are low starting torque and poor efficiency of around 25%. You would be better of using dc motors and PWM controllers.
Incidentally I built a small pillar drill for making holes in PCB's. It uses a 30watt dc motor. The only speed control it has is pulleys of different diameters.
See photo attachment.

 

[Martaine2005]

Can't you use a DC motor?

Thanks @Alec_t . Yes I can. I am just playing with what I have. Some of these motors do have a tap for medium and low. I was just enquiring whether there was other ways.

Martin

 

[Martaine2005]

@WHONOES That looks great. A little on the big side for my miniatures. BTW, why pulleys instead of PWM?.
I am curious to the motor you used.

Martin

 

[WHONOES]

It's not as big as it might look. It is 500mm to the top of the column. The base is 200mm square whilst the table is 150mm square.
The reason for using pulleys was simply for torque multiplication for larger holes or speed ditto for smaller holes.
The motor is one that I got from Ebay. It is labelled "Gebr.Buhler Nacht. GMBH. C4705-60073. I comes with an optical feedback attachment that I don't use.
The motor is rated at 19.1V. I use it at either 12V or 24V depending on how much grunt I need.
The whole thing took about 6 weeks to make.

 

[Martaine2005]

That really is a nice build. My initial intention was to control these motors (cheaply).
I live in a throw away area, every winter there are dozens of fans thrown away. I keep some for future projects.
My sliding mitre saw uses 10mm rods and 10mm linear bearings. It was all an idea from 3D printing supplies.

Martin

 

[WHONOES]

Thanks for the compliments. I like making things.

PWM works well on dc motors and is simple to realise.

 

[Minder]

As mentioned, the shaded pole motor is only really useful for fans etc, that use a triac for speed control.
Also you cannot reverse them, electrically, anyway.
You can make a simple small DC PWM/Mosfet combo using a 555.
Lots of circuits out there.
I just picked up some very nice automotive DC motors from a local surplus dealer, brand new, including a worm and pinion seat motors..
Also auto wreckers are a source.
Most mains powered hand tools and equipment use a Universal motor, good torque and Very high RPM.
Also easy to triac control
M.

 

[Bluejets]

@WHONOES That looks great. A little on the big side for my miniatures. BTW, why pulleys instead of PWM?.
I am curious to the motor you used.

Martin

If you intend going miniature, you could give a thought to brushless motors from any of the r/c aircraft, drones etc.
Tons of torque and speed controlled via cheap esc controller and an equally cheap servo tester.
Can be battery powered or via old pc power supply or plug pack.

https://www.ebay.com.au/itm/New-30A...669650?hash=item23d32b0e52:g:2ZQAAOSwxVteb0QM

https://www.banggood.com/Racerstar-...-p-1114329.html?rmmds=search&cur_warehouse=CN

Sensitive drill below is for carby jets (20 thou bits) 200mm high rear support shaft, driven by high speed 12v slot car motor and pwm control.
Almost completed.......vice to come

 

[Martaine2005]

Thanks chaps, I gave up with the shaded pole motors and put the fans back together. More useful!.
I got hold of some car windscreen wiper motors which I stripped down for the gearbox. It works great for moving the main spindle motor up and down giving a nice oscillating action. I’ll just continue with DC motors for now.
Thanks for all the advice.

Martin