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phase drive control
« on: August 31, 2007, 10:41:52 PM »
Hi everyone, ¿what are the advantages and disadvantages of the phase drive control? ¿Why Mach3 doesn’t include this type of motor control?

          Jovimon

Offline jimpinder

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Re: phase drive control
« Reply #1 on: September 01, 2007, 04:03:53 AM »
Do you mean frequency control of a three phase AC motor for your spindle - or what ????

If that IS what you mean, then frequency control of a three phase electric motor means you can have seamless control of the motor speed from very slow to its maximum ( and a bit over maximum if you are lucky). Wiring is very simple, and with a modern single phase to three phase inverter merely involves connecting the motor to the controller.

The controller electronically changes the frequency of the output to control the motor. There are many different makes and models on the market, and probably many available second hand.

Mach3 can control them - if the inverter you choose has the electronics to do it - (NOT Mach3). Mine does not, but I can get M3,M4 and M5 without trouble and I am working on a servo control to control the speed.

The disadvantage is that at lower speeds, you do loose some torque, so if you do a lot of low speed work, a pulley system would still be of advantage, so you could still get maximum  torque at the spindle. My motor is twice the power of the original for this reason, and I haven't as yet resorted to a pulley change.

If you are NOT talking about this - ignore it !!!
Not me driving the engine - I'm better looking.
Re: phase drive control
« Reply #2 on: September 01, 2007, 03:36:46 PM »
Do you mean frequency control of a three phase AC motor for your spindle - or what ????

If that IS what you mean, then frequency control of a three phase electric motor means you can have seamless control of the motor speed from very slow to its maximum ( and a bit over maximum if you are lucky). Wiring is very simple, and with a modern single phase to three phase inverter merely involves connecting the motor to the controller.





The controller electronically changes the frequency of the output to control the motor. There are many different makes and models on the market, and probably many available second hand.

Mach3 can control them - if the inverter you choose has the electronics to do it - (NOT Mach3). Mine does not, but I can get M3,M4 and M5 without trouble and I am working on a servo control to control the speed.

The disadvantage is that at lower speeds, you do loose some torque, so if you do a lot of low speed work, a pulley system would still be of advantage, so you could still get maximum torque at the spindle. My motor is twice the power of the original for this reason, and I haven't as yet resorted to a pulley change.

If you are NOT talking about this - ignore it !!!


Hi Jimpinder: what I´m talking is to control step motors from a PC parallel port, generating pulses from the PC directly to the phases of motors, instead of a external driver control to generates step-directions. TurboCNC does it.

     Jovimon
« Last Edit: September 01, 2007, 03:41:18 PM by jovimon »

Offline jimpinder

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Re: phase drive control
« Reply #3 on: September 02, 2007, 02:37:35 AM »
Yes, it is possible to drive stepper motors direct from a PC or a programmable PIC chip. I have done it myself on a PIC chip development board. You merely have to switch on  each segment of the motor in turn, in the correct order for forward or reverse. You will still need some interfacing for the electronics. Computers work on 3.5 or 6 volts - steppers (to be of any use in CNC) need 24 volts at least, plus a current of about 2.5amps.

You would then have to be fairly competant at programming (with a suitable program and knowledge of PC output ports) to get all the requisite functions of a stepper motor driver board.

I can't therefore, see why you would want to do it - unless you have a cheap, cheap supply of components and copper clad to use up. The time alone to design it would be more costly than the board is worth.

I consider the stepper boards as bought ( mine are from Stepmaster) to be good value. They are competantly built, faultless in operation, and three wires gives me all the control I need. The have overvoltage protection, adjustable current provision and various switches to use virtually any type of motor.

Mine cost about £30 per motor - three hours work each - 9 hours altogether. I couldn't build an interface in that time, let alone program the computer.
Not me driving the engine - I'm better looking.
Re: phase drive control
« Reply #4 on: September 03, 2007, 12:53:21 PM »
Yes, it is possible to drive stepper motors direct from a PC or a programmable PIC chip. I have done it myself on a PIC chip development board. You merely have to switch on each segment of the motor in turn, in the correct order for forward or reverse. You will still need some interfacing for the electronics. Computers work on 3.5 or 6 volts - steppers (to be of any use in CNC) need 24 volts at least, plus a current of about 2.5amps.

You would then have to be fairly competant at programming (with a suitable program and knowledge of PC output ports) to get all the requisite functions of a stepper motor driver board.

I can't therefore, see why you would want to do it - unless you have a cheap, cheap supply of components and copper clad to use up. The time alone to design it would be more costly than the board is worth.

I consider the stepper boards as bought ( mine are from Stepmaster) to be good value. They are competantly built, faultless in operation, and three wires gives me all the control I need. The have overvoltage protection, adjustable current provision and various switches to use virtually any type of motor.

Mine cost about £30 per motor - three hours work each - 9 hours altogether. I couldn't build an interface in that time, let alone program the computer.

Hi Jimpinder: I´m sorry, probably I´m misexplanning what I want to say or there is something that I really don´t understand (I´m just a hobbyst, not skilful on electronics). The point is that there is a shareware software (TurboCNC), that gives you two options to drive unipolar step motors (and probably many others): one is “Step-Dir” (which requires an external pulse generator)and the other is “Phase” (makes the PC generates the pulses directly). So the big question is ¿Why Mach 2/3/4 doesn´t have those options, since Mach seems to me a more robust software.

      Thanks   Jovimon
« Last Edit: September 03, 2007, 01:05:49 PM by jovimon »
Re: phase drive control
« Reply #5 on: September 04, 2007, 05:20:27 PM »
Step/Dir control is acceptable not only for drivers for steppers, but for drivers for brush/brushless motors also. That allows to use the same controller for any type/power of motors.
The term "phase drive" control has other purpose in control theory.
Where you find this term? 
« Last Edit: September 04, 2007, 05:22:04 PM by LeGa »

Offline jimpinder

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Re: phase drive control
« Reply #6 on: September 05, 2007, 07:30:08 AM »
 I think Art tried to make the interface as easy as possible - and it is all designed to run via a 25 pin printer port. The outputs and inputs to that port are limited - I just forget the actual numbers but there are something like 14 output lines and 5 input lines. The other six are common return wires.

They are arranged in three seperate addresses in the computer, one with 8 lines, one with 6 lines and one with 5 lines.

If you use an external stepper driver board, each motor only requires two wires and a return, so using the eight line address you can drive four motors which are three axis and maybe a rotary table or someother equipment.
You would like to run the spindle motor M3 M4 and M5 (forward, backwards and stop) which takes two wires of the second address, and maybe the coolant which takes another two wires.
On the input side you need limit switches, homing switches and motor speed reading wires.

I don't mean to be unkind to Art, but the programming is also easier if you only have to put out step and direction pulses, and as has been said, step and direction are a standard which can be used by other applications

If you think of it that way, the 25 wires of the printer port are soon taken up.

If you are driving motors direct from the printer port (apart from needing some sort of interface because the port is not powerful enough to do it directly) you need 4, 6 or 8 wires to drive one motor. You run out of wires very quickly - you would need 12 just to drive three axis, which would only leave you 2 to drive all the other things you might want.

Since you need some sort of power amplifier anyway, you might as well get a driver board, which has all the on board electronics in it to control current, shut down if over heated, drive different types of motor etc. It will not cost any more - and only uses two wires per motor !!


Not me driving the engine - I'm better looking.
Re: phase drive control
« Reply #7 on: September 06, 2007, 12:40:11 PM »
I think Art tried to make the interface as easy as possible - and it is all designed to run via a 25 pin printer port. The outputs and inputs to that port are limited - I just forget the actual numbers but there are something like 14 output lines and 5 input lines. The other six are common return wires.

They are arranged in three seperate addresses in the computer, one with 8 lines, one with 6 lines and one with 5 lines.

If you use an external stepper driver board, each motor only requires two wires and a return, so using the eight line address you can drive four motors which are three axis and maybe a rotary table or someother equipment.
You would like to run the spindle motor M3 M4 and M5 (forward, backwards and stop) which takes two wires of the second address, and maybe the coolant which takes another two wires.
On the input side you need limit switches, homing switches and motor speed reading wires.

I don't mean to be unkind to Art, but the programming is also easier if you only have to put out step and direction pulses, and as has been said, step and direction are a standard which can be used by other applications

If you think of it that way, the 25 wires of the printer port are soon taken up.

If you are driving motors direct from the printer port (apart from needing some sort of interface because the port is not powerful enough to do it directly) you need 4, 6 or 8 wires to drive one motor. You run out of wires very quickly - you would need 12 just to drive three axis, which would only leave you 2 to drive all the other things you might want.

Since you need some sort of power amplifier anyway, you might as well get a driver board, which has all the on board electronics in it to control current, shut down if over heated, drive different types of motor etc. It will not cost any more - and only uses two wires per motor !!



Hi Jimpinder, you gave an excellent explanation. Sometimes some of us (Hobbysts) want to make things always from scratch, make tools usable for everything, a so on.

      Many Thanks for your attention      Jovimon
Re: phase drive control
« Reply #8 on: September 06, 2007, 12:41:55 PM »
Step/Dir control is acceptable not only for drivers for steppers, but for drivers for brush/brushless motors also. That allows to use the same controller for any type/power of motors.
The term "phase drive" control has other purpose in control theory.
Where you find this term?

Hi Lega. I guess the two posts above are self-explanatory.

                   Thanks    Jovimon