Constant speed controller for Universal Motor

[leaveme]

My routers spinddle is a universal AC motor (single phase brushed motor) and I was searching for a constant speed controller. I got a schematic yesterday from one of my friends. Taking a look on the schematic seems it's a chopper circuit and has feedback from the load. I would like to have some comments from electronics-guru's about this schematic -

1. do you think motor speed will be constant regardless of load?
2. can I isolate the circuit from the mains if I provide isolated 5-6V?

Thank you buddy.

[Sun_rise_pt]

Hi Leaveme,

If you wish a good speed control (near perfect) the best are a specialized IC controled by a tachometer.

www.classiccmp.org/rtellason/chipdata/tda1085.pdf

Some industrial machines are using this IC.

Good work!

[leaveme]

Thanks buddy!

Actually I did explore of the datasheet earlier but I discovered that TDA1085 doesn't work with >15k RPM (tacho input).

My posted schematic is much simpler. Just some of the points are not clear to me, i.e. R9 is the speed controller here but what R10 is doing. Appreciate if you can guess.

Seems I need to build it to check the result...

[pickit2]

R10 is a level shifter T1 and components are in feedback loop, and monitors the current of the motor.